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TDA7000 FM Radio Receiver With LM386 Amplifier
Posted on Tuesday, June 7, 2022   •   Category: FM Radio / Receivers

TDA7000 FM Radio Receiver With LM386 Amplifier

Simple circuit and easy to assemble DIY TDA7000 FM radio receiver with LM386 amplifier chip. Assembling an FM radio is always something interesting to the electronics enthusiast. TDA7000 which integrates a mono FM radio all the way from the aerial input to the audio output. Outside of the TDA7000 IC there is only one tunable LC circuit for the local oscillator, a few inexpensive ceramic capacitors and one resistor. The TDA7000 dramatically reduces assembly and post production alignment costs because only the oscillator circuit needs adjustment during manufacture to set the limits of the tuned frequency band. The complete FM radio can be made small enough to fit inside a calculator, cigarette lighter, key-ring fob or even a slim watch. The TDA7000 can also be used as receiver in equipment such as cordless telephones, CB radios, radio-controlled models, paging systems, the sound channel of a TV set or other FM demodulating systems.




BA1404 Stereo FM Transmitter With Booster
Posted on Wednesday, May 4, 2022   •   Category: FM Transmitters

BA1404 Stereo FM Transmitter With Booster

Build your own fairly simple high quality stereo FM transmitter circuit as shown in the photo. The circuit is based on the BA1404 chip from ROHM Semiconductors and S9018 amplifier for extending tansmitter's range. BA1404 is a monolithic FM stereo modulator that has built in stereo modulator, FM modulator, RF amplifier circuits. The FM modulator can be operated from 76 to 108MHz and the power supply for the circuit can be anything between 6 to 12 volts.




Portable Variable Bench Power Supply 1-32V 0-5A
Posted on Wednesday, April 13, 2022   •   Category: Power Supplies

Portable Variable Bench Power Supply 1-32V 0-5A

I have gone without a variable lab bench power supply for too long now. The power supply that I have been using to power most of my projects has been shorted out too many times. I have actually killed 2 by accident and needed a replacement. I had many 18650 lipo batteries lying around my workshop so I decided to use them to build a portable variable bench power supply that could be easily moved around and used on the go. The power supply consists of DC-DC step up power module, voltage and current display, a switch, standard size 10K trim pots, XT-60 and a balance connector for charging an array of 8x4 18650 batteries.




1 Watt FM Transmitter Booster
Posted on Wednesday, March 30, 2022   •   Category: FM Transmitters

1 Watt FM Transmitter Booster

1 Watt FM Transmitter amplifier with a reasonably balanced design specified to boost a RF frequency in the 88 – 108 MHz spectrum. It may be considered a fairly sensitive configuration when used with quality RF power amplifier transistors, trimmers and inductors. It involves a power amplification factor of 9 to 12 dB (9 to 15 times). At an input power of 0.1W the output may be well over 1W. It's advisable to choose T1 transistor on the basis of the input voltage. For 12V voltage it is recommended to use transistors such as 2N4427, KT920A, KT934A, KT904, BLX65, 2SC1970, BLY87. For 18-24V voltage may may want to use transistors such as 2N3866, 2N3553, KT922A, BLY91, BLX92A. You may also consider using 2N2219 with 12V input voltage however that would only produce an output power of around 0.4W.




Arduino DCC Decoder
Posted on Monday, March 14, 2022   •   Category: Miscellaneous

Arduino DCC Decoder

Modern model railroads are digitally controlled using a Digital Command Control (DCC) protocol similar to network packets. These data packets contain device address and instruction set that is embedded in the form of AC voltage and fed to train track to control locomotives. The great advantage of DCC over analog DC control is that you can independently control the speed and direction of many locomotives on the same train track as well as control many other lights and accessories using that same signal and voltage. Commercial DCC decoders are available on the market however their cost can add up pretty quickly if you have a lot of devices to control. Luckily you can build a simple Arduino DCC decoder yourself to decode DCC signal and control up to 17 LEDs / accessories per each DCC decoder.




Simplest FM Receiver
Posted on Tuesday, February 1, 2022   •   Category: FM Radio / Receivers

Simplest FM Receiver

This is perhaps one of the simplest and smallest FM receivers for receiving local FM stations. It's simple design makes it ideal for a pocket sized FM receiver. The audio output of the receiver is amplified through LM386 amplifier chip that can drive a small speaker or headphones. The circuit is powered by three AAA or AA battery cells. FM receiver section uses two RF transistors for converting frequency modulated signals to audio. L1 coil and variable capacitor form a tuned tank circuit that is used for tuning to any available FM stations.




7W FM Transmitter
Posted on Thursday, January 20, 2022   •   Category: FM Transmitters

7W FM Transmitter

This a build of a well known FM transmitter called Veronica. Transmitter was built on two separate boards. The first board (pictured above) is the Veronica transmitter itself with output power of 600mW when powered by 12V voltage or 1W when powered by 16V voltage. The second board is an RF power amplifier that uses 2SC1971 transistor to amplify Veronica's output signal to around 7 Watts. Although transmitter can be powered with 9-16V voltage, it is recommended that both transmitter and amplifier is powered by 12V voltage as 600mW is an upper limit for driving 2SC1971 transistor.




Simple Stereo FM Transmitter Using An AVR Microcontroller
Posted on Tuesday, January 4, 2022   •   Category: FM Transmitters

Simple Stereo FM Transmitter Using An AVR Microcontroller

I had been fascinated with the idea of making simple stereo encoder for building Stereo FM Transmitter. Not that stereo means much to me away from the computer. I use an FM broadcast transmitter to relay the output of my computers to FM radios in the kitchen, the bedroom, the driveway, and out in the garden. Under those circumstances, I find that mono is plenty, whether it is music or radio programs from over the internet, since I am primarily occupied with something else anyway. When on my hands and knees in the garden, all the way up to my elbows in planting a bush, the music really does not seem any more sweet when its stereo. But that did not stop me from being fascinated with the idea of making a stereo encoder. Stereo always seemed like a lot of circuitry and bother for the slight benefit that came with it. That is, until a few weeks ago.




Stereo FM Receiver
Posted on Friday, December 24, 2021   •   Category: FM Radio / Receivers

Stereo FM Receiver

High sensitivity TEA5711 receiver allows the reception of distant stations from over 150 miles (240 km) away. Good selectivity is obtained with narrow bandwidth ceramic filters. AFC automatic frequency control locks on stations for drift-free reception. Stereo separation which depends on signal strength is very apparent on strong signals. And with high quality headphones, the sound is rich with deep base and high treble, for hours of enjoyable stereo music.




Simple DIY FM Transmitter
Posted on Friday, October 1, 2021   •   Category: FM Transmitters

Simple DIY FM Transmitter

Ever wondered how come you can just simply tune in to your favorite FM Radio Channel. Moreover, ever had the curiosity of making your own FM Station on a specific frequency? Well if the answer is Yes to any of those questions then you are at the right place!. We are going to look into making small FM Transmitter for Hobby Purposes with a really basic component guide and components that are readily available off the shelf.




50W Power Amplifier With LM3886
Posted on Tuesday, August 31, 2021   •   Category: Amplifiers

50W Power Amplifier With LM3886

This is my second encounter with LM3886. I was pleased with the sound this chip produced the first time, so I decided to make another amplifier with it. The schematic is based on the schematic in the datasheet of the chip with minor changes. I removed the time delay capacitor connected to MUTE pin, because it’s better to use separate DC protection schematic which has similar functionality. I made the output inductance L1 by winding 15 turns of enameled wire around the resistor R7. The diameter of the wire must be minimum 0.4mm. The whole was wrapped with heat shrink. I used 47uF/63V non polarized capacitor for C2. It can be regular electrolytic capacitor, but it’s better to use non-polarized or bipolar.




BLF147 150W VHF Amplifier
Posted on Tuesday, June 29, 2021   •   Category: FM Transmitters

BLF147 150W VHF Amplifier

One of the very latest developments here is 150W VHF transmitter amplifier with BLF147 power transistor. Results are very impressive with well over 150W across the band with 10W input and 24 VDC supply. Over 200W is achieved at 28 VDC, and over 250W with a hot bias 4-5A quiescent. PCB is teflon glass board with printed transmission lines and porcelain caps. No external harmonic filter is needed, as the filtering is built into the matching network.




Fully Adjustable Power Supply
Posted on Wednesday, May 26, 2021   •   Category: Power Supplies

Fully Adjustable Power Supply

This circuit uses an LM317 regulator, chosen because of its built-in over-current and over-temperature protection. Its output is boosted up to 5A by the MJ2955 transistor. The output voltage is varied by adjusting VR1 potentiometer. Adjustable current limiting from 60mA to 5A is provided by op amp TL071 IC that is used as a comparator which monitors the voltage across the 0.1 Ohm current sensing resistors.




Stereo FM Transmitter With BA1404 IC
Posted on Monday, April 12, 2021   •   Category: FM Transmitters

Stereo FM Transmitter With BA1404 IC

There are many applications for an FM transmitter, particularly if it can broadcast in stereo. You can broadcast stereo signals from your CD player or any other source to an FM tuner or radio. This FM Transmitter uses a single BA1404 IC and a few other components. It broadcasts on the 88-108MHz FM band so that it can be received by any standard FM tuner or portable radio. Transmitter runs from a 5V supply and can drive a dipole antenna for improved range.




High Performance Stereo Audio Amplifier Using LM3886
Posted on Monday, February 22, 2021   •   Category: Amplifiers

High Performance Stereo Audio Amplifier Using LM3886

The LM3886 is a high-performance audio power amplifier capable of delivering 68W of continuous average power to a 4? load and 38W into 8? with 0.1% THD+N from 20Hz–20kHz. The performance of the LM3886, utilizing its Self Peak Instantaneous Temperature SPiKe protection circuitry, puts it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area. SPiKe protection means that these parts are completely safeguarded at the output against over voltage, under voltage, overloads, including shorts to the supplies, thermal runaway, and instantaneous temperature peaks. The LM3886 maintains an excellent signal-to-noise ratio of greater than 92dB. It exhibits extremely low THD+N values of 0.03% at the rated output into the rated load over the audio spectrum, and provides excellent linearity with an IMD typical rating of 0.004%.




1Km FM Transmitter With UA741 Opamp
Posted on Wednesday, February 10, 2021   •   Category: FM Transmitters

1Km FM Transmitter With UA741 Opamp

This project is the construction of FM transmitter circuit for commercial radio frequencies between 88 MHz and 108 MHz. The transmitter is easy to build and offers good frequency stability through the usage of UA741 oamp. 1Km range can be achieved when powered by 9V battery with 30cm long telescopic antenna.




Easy Crystal Locked FM Transmitter
Posted on Tuesday, November 24, 2020   •   Category: FM Transmitters

Easy Crystal Locked FM Transmitter

The circuit presented here uses a crystal oscillator and frequency multiplier to generate a highly-stable carrier signal frequency of 96MHz. It can be used to transmit voice or music up to hundred meters. The circuit is built around 9018 transistor, 24MHz crystal, air coil and a few other basic components.




Adjustable Delay Circuit
Posted on Wednesday, November 18, 2020   •   Category: Miscellaneous

Adjustable Delay Circuit

Build an adjustable auto power On Off delay timer circuit using CD4541 timer. This electronic timer circuit is helpful when you need to power On/Off any AC Appliances after a pre-defined duration. Delay time it can be adjusted from about 2 to 120 seconds.




DIY Adjustable Bench Power Supply
Posted on Monday, October 5, 2020   •   Category: Power Supplies

DIY Adjustable Bench Power Supply

Every electronics hobbyist needs at least one bench power supply in his house for tinkering with some weekend projects. This small power supply was built with an old 19V 3A laptop charger and buck-boost converter. Output voltage is continuously adjustable from 1.25V to 33V with up to 3A current. I have been using it for 3 weeks now and have realized that I am using it more than I thought I would.




BA1404 FM Stereo Transmitter With Amplifier
Posted on Tuesday, June 2, 2020   •   Category: FM Transmitters

BA1404 FM Stereo Transmitter With Amplifier

This is a classic low-cost stereo FM transmitter that can send your signal to a FM receiver within 500 meter range. This transmitter uses the famous BA1404 all-in-one chip and operates from 5v power supply. Stereo channel separation is excellent. You can even use this as a front-end stereo RF signal generator for a large FM transmitter setup; by adding step-by-step RF amplifier. A few inch long copper wire can be soldered at the PCB to use as an antenna. The gang-condenser can be used to adjust frequency output. You can use this with your iPod or other audio source, inside your home or car on in an outdoor garden party or wherever you use.




LM350 3A Adjustable Voltage Regulator
Posted on Monday, May 4, 2020   •   Category: Power Supplies

LM350 3A Adjustable Voltage Regulator

The LM350 is a tried and true 3A adjustable voltage regulator. It accepts an input voltage up to 35V and can deliver an output voltage between 1.25 and 33V. It is rugged beyond belief. Where fairly beefy step-down converters go up in smoke, the LM350 just takes a nap. And a nap is infinitely better than a plume of smoke. LM350 can also be used to limit current though that requires a separate LM350/LM317 in series with our voltage regulator.




1 Watt FM Amplifier
Posted on Tuesday, April 14, 2020   •   Category: FM Transmitters

1 Watt FM Amplifier

This is 1 Watt FM amplifier with a good design that can be used to amplify RF signal of low power FM Transmitters in the 88 – 108 MHz band. It is very sensitive if you use good RF power amplifier transistors, trimmers and coils. It has a power amplification factor of 9 to 12 dB (9 to 15 times). At an input power of 0.1W the output will be 1W. You must choose T1 depending on applied voltage. If you have a 12V power supply then use transistors like: 2N4427, KT920A, KT934A, KT904, BLX65, 2SC1970, BLY87. At 18 to 24V power supply you must use transistors like: 2N3866, 2N3553, KT922A, BLY91, BLX92A. You may use 2N2219 at 12V but you will get maximum output power of 0.4W.




TDA2050 Stereo Audio Power Amplifier
Posted on Monday, March 23, 2020   •   Category: Amplifiers

TDA2050 Stereo Audio Power Amplifier

This is 2x30W audio amplifier based on TDA2050 and LM1875. Amplifier PCB is suitable for both TDA2050 and LM1875 chips. Amplifier has all the necessary circuitry on board – power supply, speaker protection, delayed turn-on and fast turn-off. This is achieved using the convenient uPC1237 IC. TDA2050 and LM1875 are pin to pin compatible, the differences in their schematics are the values of a couple resistors and one capacitor. All this allows to make an universal circuit board, suitable for any of these two ICs.




DIY Walkie Talkie
Posted on Monday, March 2, 2020   •   Category: FM Transmitters

DIY Walkie Talkie

RF projects are always special and I am confident that almost every engineer or enthusiast want to try building a RF project. Because of this we have put together a guide for building a super cool Walkie Talkie project. Walkie Talkie is a half duplex wireless communication device that is capable of establishing communication within short range. Half Duplex means only one user can speak or send his message at a time and communication cannot happen simultaneously. These devices are widely used by Security Personal, Industrial workers and so on. Of course it can make a great toy as well. This guide explains about a Walkie Talkie circuit that allows user to establish communication with another identical device within a range of 30m.




5km FM Transmitter
Posted on Tuesday, February 11, 2020   •   Category: FM Transmitters

5km FM Transmitter

This is a good quality FM transmitter with 5km range and stable frequency brought by the modified oscillator, which is actually two oscillators built around Q2 and Q3 working at around 50MHz in anti-phase. The output is taken at the two collectors, where the frequencies of the two oscillators combine to form FM signal. This will provide a greater stability than normal single ended oscillators.




Bench Lab Power Supply 0-50V 0-5A
Posted on Sunday, February 2, 2020   •   Category: FM Transmitters

Bench Lab Power Supply 0-50V 0-5A

Every laboratory needs a few critical devices, the most important of which is a power supply for powering the projects. But as demand grows and the projects get bigger a professional and adjustable power supply becomes a necessity. Here is an adjustable 50V/5A power supply with a variable output from 0V to 50V and adjustable current limiting from 0A to 5A. Most simple power supplies cant get the output to come down to exactly 0V or 0A. But in this circuit, the differential amplifiers have a negative power supply rail at (-3V), which can pull the output down to exactly zero.




Tiny FM Transmitter
Posted on Wednesday, January 22, 2020   •   Category: FM Transmitters

Tiny FM Transmitter

This tiny FM transmitter can be used for varierty of applications such as monitoring, running your own radio station, etc. It can run on a voltage between 3 and 13 volts, draws 2-3 milliamps and has a theoretical output power of 3 milliamps although you could easily increase that by adding an RF amplifier.




3V One Transistor FM Transmitter
Posted on Tuesday, January 7, 2020   •   Category: FM Transmitters

3V One Transistor FM Transmitter

The above wireless FM transmitter circuit is basically a small RF transmitter built around a single transistor. The circuit functions quite like a Colpitts oscillator incorporating a tank circuit for the generation of the required oscillations. The frequency mainly depends on the positioning and the values of the inductor, C1, C2 and C3. The coil turn distance and diameter may be manipulated a little for optimizing best response over the FM receiver. A small antenna in the form of a 3 inches wire may be attached at the shown point for making the “bug” highly responsive and generates distortion free signals.




FM Music Transmitter
Posted on Tuesday, December 10, 2019   •   Category: FM Transmitters

FM Music Transmitter

If you want your tiny FM transmitter circuit to transmit music instead of spying or eavesdropping, you would probably find the following design interesting. The proposed FM transmitter will allow combining a stereo input simultaneously from the source so that the info contained inside both the channels get into the air for an optimal reception. The stability of the transmitter is improved by tapping the antenna from one top turn of the coil as shown in the above circuit.




Simple and Small Temperature Fan Controll
Posted on Thursday, November 28, 2019   •   Category: Motor Controllers

Simple and Small Temperature Fan Controll

I published this schematic long ago in this article: Adjustable power supply and since then I made some improvements in PCB to make the board as small as possible. The idea is to be easy to attach the whole board to the heat sink which we want to monitor. The board is only 27mm x 27mm.




Easy to Build FM Transmitter
Posted on Monday, July 22, 2019   •   Category: FM Transmitters

Easy to Build FM Transmitter

Learn to build your own mini FM transmitter. This fun project will show you how to build a mini broadcasting device that can transmit an audio signal up to a quarter mile to any FM receiver. It's easy to build and a good learning experience.




Broadcasting FM Transmitter
Posted on Tuesday, June 18, 2019   •   Category: FM Transmitters

Broadcasting FM Transmitter

With this three stage transistor transmitter we can create and broadcast our mini radio station. We using S9018 transistor because it can handle very high frequencies, up to and including the VHF band. The first transistor on the left is a microphone audio amplifier for modulation. The gain can be adjusted with the potentiometer. The second transistor is the oscillator with a range of 80 to 103 MHz. The frequency can be changed with the upper coil 4T5 by pulling it slightly apart. The signal from the oscillator is very small, so that still needs to be amplified. The right most transistor is therefore an RF amplifier. This amplifies the signal from the oscillator to feed to the antenna. This transistor also immediately provides more stability, because the oscillator is not directly connected to the antenna.




Arduino Soil Moisture Sensor
Posted on Friday, June 14, 2019   •   Category: Miscellaneous

Arduino Soil Moisture Sensor

This is a simple arduino project for a soil moisture sensor that will light up a LED at a certain moisture level. It uses Arduino Duemilanove microcontroller board. Two wires placed in the soil pot form a variable resistor, whose resistance varies depending on soil moisture. This variable resistor is connected in a voltage divider configuration, and Arduino collects a voltage proportional to resistance between the 2 wires.




2KM FM Transmitter
Posted on Tuesday, June 4, 2019   •   Category: FM Transmitters

2KM FM Transmitter

With a matching antenna, the FM transmitter circuit shown here can transmit signals up to 2 kilometers. The transistor Q1 and Q2 forms a classic high sensitive preamplifier stage. The audio signal to be transmitted is coupled to the base of Q1 through capacitor C2. R1, R3, R4, R6, R5 and R9 are the biasing resistors for the preamplifier stage comprising of Q1 and Q2. Transistor Q3 performs the collective job of oscillator, mixer and final power amplifier. C9 and L1 forms the tank circuit which is essential for creating oscillations. Inductor L2 couples the FM signal to the antenna.




Portable Tube Headphone Amp
Posted on Monday, April 15, 2019   •   Category: Headphone Amplifiers

Portable Tube Headphone Amp

This little tube amplifier is easy to build and will fit into a small metal Altoids box and can be carried around. It can be build with few common parts, that should be readily available. Amplifier works with many tubes like 6DJ8, ECC88, 6922, 12AT7, 12AX7, DAF96, 1T4, etc. It is powered by 12V supply and power consumption may be optimized to allow for small rechargeable battery packs.




Adjustable Lab Power Supply 0-30V 0-3A
Posted on Monday, February 25, 2019   •   Category: Power Supplies

Adjustable Lab Power Supply 0-30V 0-3A

Presented here is a Laboratory Power Supply with 0-30V voltage and 0-3A current regulation. The schematic is pretty straightforward, it uses standard dual opamps such as TL082, TL062, TL072, NE5532, RC4558 and MC34072. The trimmer P3 adjusts the minimum current limit. P4 adjusts the maximum output voltage. After the final adjustment you may replace the trimmers with standard resistors. Power transistor dissipates quite a bit of heat and thus require a heatsink with optional fan. We may use two or tree transistors in parallel with emitter resistors to achieve more power. The transformer must be 100-120W with 27-30VAC output voltage.




28W Power RF Amplifier for FM Broadcast 88-108 MHz 2SC1946
Posted on Friday, February 1, 2019   •   Category: FM Transmitters

28W Power RF Amplifier for FM Broadcast 88-108 MHz 2SC1946

This RF Amplifier designed for FM broadcast using a single 2SC1946 VHF Power Transistor. This 10-30W RF amplifier circuit provides an appropriate power boost with an input of 1-3 watt. Tower are 30 meters high will send signal surrounding air should be around 15 km.




BF494 Micro FM Transmitter
Posted on Tuesday, January 22, 2019   •   Category: FM Transmitters

BF494 Micro FM Transmitter

That small circuit transmitter it is ideal for ready espionage for strip from radio Fm or receiver of VHF. Of course the recreational purpose also exists and the children will adore to have a transmitter that allows to speak for a radio FM placed at distant place and like this pretend the secret agent.




1W 87-110MHz FM Transmitter with 2N3886 Amplifier
Posted on Wednesday, November 14, 2018   •   Category: FM Transmitters

1W 87-110MHz FM Transmitter with 2N3886 Amplifier

Powerful microtransmitter that can cover 3km range. To amplify the signal, a 2N3866A transistor is used that can provide up to 1W with gain > 10dB (24Volt). In our case the output power is about 100mW depending on the input power of 10mW and 9V battery power supply. The transistor Q1 must be mounted with a heatsink, the heatsink must have small dimensions (cylindrical) in order not to increase the parasitic capacitance. The trimmer R2 serves to adjust the bias of the transistor, start with the trimmer fully open and close by measuring the current absorbed by the 9V, in my case you get 100mW at the output with a current of 50mA not increase this value as you only increase the absorption by heating the transistor without increasing output power, because the input power is too low. Clearly the 9V battery will be able to provide 50mA only for a few hours, if necessary have greater autonomy should be used a larger battery, but it is no longer a bug but simply an FM transmitter.




Spy Bug FM Transmitter
Posted on Monday, October 29, 2018   •   Category: FM Transmitters

Spy Bug FM Transmitter

This tiny 88-108Mhz FM transmitter bug measures just 10mm x 17mm in size and as you can see in the photos the biggest components are just the microphone and the battery. You can use a small microphone from an older cell phones, they are small in size and have an excellent sensitivity. For an effective power supply the 9V battery (Duracell) is excellent and allows several hours of battery life, but if you want to have a smaller size it is better to use 2 or 3 lithium cells like the 2032 used in PCs. The circuit works well from 3 to 12V, the maximum range is obtained with 12V and a piece of 40-60cm cable as an antenna.




Simple FM Radio Bug
Posted on Monday, September 10, 2018   •   Category: FM Transmitters

Simple FM Radio Bug

In the mid 1970s large numbers of small FM transmitters, operating in the FM radio broadcast band (88-108 MHz) appeared on the market. It started with a self-build kit from the Danish manufacturer Jostykit that allowed everyone to build a small FM transmitter for a few Euros. Such transmitters generally consist of a single transistor oscillator with a simple resonance circuit, sometimes with an extra transistor that is used as audio pre-amplifier. The image shows a few examples that were available in European electronics shops in the mid 1970s. The transmitter shown here was built in the mid-1970s and measures just 1 x 2 cm. When properly built, it may have a range of several kilometers.




1 Watt FM Transmitter
Posted on Wednesday, July 11, 2018   •   Category: FM Transmitters

1 Watt FM Transmitter

This is a simple, portable transmitter operating in the 88-108 MHz FM band. You may use it to run your own private neighborhood radio, just replacing the microphone capsule with a male audio jack connected to your pc or MP3 player. You may also use this as a spy transmitter, but be reasonable in that case. It's rated for 1 Watt, so you can listen to it even from a few kilometers, with a good antenna and not too much obstacles in the way.




PCM2707 USB DAC Soundcard
Posted on Tuesday, June 19, 2018   •   Category: Audio DAC

PCM2707 USB DAC Soundcard

The following is a simple USB DAC Soundcard. It uses PCM2707 that incorporates USB interface to communicate with the computer and audio DAC all in one chip.




Dual Adjustable Power Supply
Posted on Saturday, May 26, 2018   •   Category: Power Supplies

Dual Adjustable Power Supply

This project is a solution to power up most of devices or projects requiring dual (+/-) adjustable power supply. The circuit is based on LM317 positive and LM337 negative voltage regulators. LM317 series of adjustable 3 terminal regulator is capable of supplying in excess of 1.5A over a 1.2V to 30V DC output range, due to TO3 package of IC and large heat sink the power supply can handle maximum load current.




Stable FM Transmitter
Posted on Wednesday, May 2, 2018   •   Category: FM Transmitters

Stable FM Transmitter

FM transmitter circuit projects are indeed quite popular among electronics hobbyists / students. But the frustrating part is most transmitters refuses to work at all, and secondly the internet is full of crappy transmitter circuits. Designing a stable FM transmitter circuit is rather a difficult job, many calculations are involved their. There are also some construction error and component value tolerance. Here you can find a reasonably stable and well tested transmitter that actually works.




15W FM Transmitter
Posted on Monday, March 19, 2018   •   Category: FM Transmitters

15W FM Transmitter

This FM Transmitter is stable and has output power of 15-18 watts. You don't have to understand the precise working of the transmitter to build it. But some basic information won't harm. A transmitter alone is, as you probably know, is not enough to start your radio station. In the simplest form you need 4 things. First an input device such as an amplifier you also use with your home stereo. You need a regulated power supply. In this case a 14-18 Volts 2.5-3.5 Ampere. One of the most influential things you need is antenna and coax cable. And finally the transmitter itself. Transmitter is divided into two main parts; the oscillator and the amplifier. The oscillator converts electric sound information into electromagnetic waves. The amplifier gives these waves a bigger amplitude.




LM317 Constant Current Source Circuit Design
Posted on Monday, November 13, 2017   •   Category: Power Supplies

LM317 Constant Current Source Circuit Design

A constant current source source can supply a fixed current to a load regardless of input voltage or load change. LM317 / LM350 / LM338 constant current source is one of the simplest design. The LM317 is quite useful as a constant current source, works on a wide input voltage range, from 3V up to 40V. So, here’s the LM317 based constant current source, it’s design and a little about it’s working principle.




2SC9018 FM Transmitter
Posted on Monday, October 16, 2017   •   Category: FM Transmitters

2SC9018 FM Transmitter

This FM transmitter circuit is a quite fun project for electronics beginners, so here’s a circuit with the 2SC9018 transistor. It uses the 2SC9018 high frequency transistor, based on a different spin of the common base Collpit’s oscillator. The circuit is rather simple, uses only one transistor and few passive components and performs well in terms of frequency stability, almost zero drifting after about 4 hours of continuous operation.




5 Km Long Range FM Transmitter
Posted on Monday, August 7, 2017   •   Category: FM Transmitters

5 Km Long Range FM Transmitter

Here we are presenting a long range FM transmitter that can cover a reasonable distance of 5 kilometers / 3 miles and beyond with a one watt RF power with full circuit details, bill of material and testing procedure. With 12 volt DC it will deliver 1 watt RF power. With Yagi antenna, looking like early days of TV antenna with aluminum pipes at both at transmitter and receiver end looking each other at line of sight distance, the range can be up to 5 km / 3 miles.




One Transistor FM Transmitter
Posted on Wednesday, June 21, 2017   •   Category: FM Transmitters

One Transistor FM Transmitter

This circuit is basically an oscillator which runs at around 100 MHz. The most important parts of the oscillator are the transistor Q1 and the tuned circuit, which comprises the inductor Ll and the variable capacitor CV1. When the battery is first connected, a brief surge of current flows from the collector to the emitter of Q1, causing an oscillating (i.e: alternating) current to flow back and forth between Ll and CV1. An oscillating voltage therefore appears at the junction of Ll and CV1. The frequency of the oscillation depends on the values of Ll and CV1, so that varying the value of CV1 tunes the oscillations to the exact frequency required.




Using RF 433MHz Transmitter / Receiver Modules With Arduino
Posted on Wednesday, June 14, 2017   •   Category: Arduino

Using RF 433MHz Transmitter / Receiver Modules With Arduino

This post aims to be a complete guide for the popular RF 433MHz Transmitter/Receiver modules. I’ll explain how it works, show some features and share an Arduino project example that you can take and apply to your own projects.




4 Watt FM Transmitter
Posted on Wednesday, March 22, 2017   •   Category: FM Transmitters

4 Watt FM Transmitter

The following is a simple yet powerful 4W FM transmitter which is tunable to 88-108MHz frequency. Connect to your ipod/computer, etc. When this was first made, I only had a 2N2219A on hand, which resulted in a lower RF output. I have since swapped out the transistor for a 2N3866 for full 4W output at around 15VDC supply. In order to achieve a high output level, you will need a well tuned antenna, and a large heatsink to dissipate the heat from T2 transistor. Transmitter was mounted in metal enclosure and works extremely well.




Analog Capacitor ESR Tester
Posted on Wednesday, November 16, 2016   •   Category: Test and Measurement

Analog Capacitor ESR Tester

I finally got round to making my capacitor ESR tester this week after finding a nice simple 5 transistor version. Unfortunately, for me, the design was only SMD so, I decided to replicate his schematic in Eagle PCB using a through hole component design. I will not be going into much detail regarding ESR or Equivalent Series Resistance Meters as, there is already plenty of other sources of information on the subject. Yet, every tinkering knows capacitors are guilty of a lot of sins in electronics. Capacitors love to throw red herrings! They can appear physically fine (no bulge), show good capacitance and hide in circuit, standing to attention like the Queens Guards hiding shorts and high resistance under their big hats. This is where the ESR tester can be a saviour, with the ability to test for "out of specification" high resistance, within the capacitor. They can also be used to test "in circuit", without the need to remove every capacitor in the circuit.




300mW FM Transmitter with 2SC2538
Posted on Sunday, October 30, 2016   •   Category: FM Transmitters

300mW FM Transmitter with 2SC2538

The above FM transmitter has RF output power of 300 mW and covers more than one kilometer distance. Frequency adjustment is accomplished with MV2105 varactor diode and R7 10K potentiometer. 2SC2538 is a class C 300mW amplifier.




500mW FM / VHF Transmitter Amplifier / Booster
Posted on Monday, October 24, 2016   •   Category: FM Transmitters

500mW FM / VHF Transmitter Amplifier / Booster

High performance low noise 500mW amplifier / booster for all low power FM transmitters such as BA1404, BH1417, BH1415, 433MHz transmitter modules, etc. The amplifier chip is an integrated circuit containing multiple transistor stages and all other parts conveniently within a single small package. Boosting your FM transmitter has never been easier and the output signal can also directly drive 2n4427 or 2n3866 transistors for 1W or 5W of RF output power.




15W Transmitter Power Amplifier 88-108MHz
Posted on Friday, October 21, 2016   •   Category: FM Transmitters

15W Transmitter Power Amplifier 88-108MHz

The power amplifier boosts 88-108MHZ 1-2W FM transmitter's power to 15 W. It includes multi-level low pass filter and has a high conversion efficiency with strong Yi-wave suppression. With good antena expected transmission coverage is at least 15Km. It uses high power 175 MHZ 4A 25W 2SC1972 RF transistor that must to be mounted to heatsink for proper heat dissipation.




DIY USB 5V Solar Power Pack
Posted on Friday, September 30, 2016   •   Category: Power Supplies

DIY USB 5V Solar Power Pack

Solar energy is renewable, free, widely available and clean form of energy. It is considered as a serious source of energy for many years because of the vast amounts of energy that is made freely available, if harnessed by modern technology. Many people are familiar with so-called photovoltaic cells, or solar panels, found on things like spacecraft, rooftops, and handheld calculators. The cells are made of semiconductor materials like those found in computer chips. When sunlight hits the cells, it knocks electrons loose from their atoms. As the electrons flow through the cell, they generate electricity. In this project, we are building a power bank which harvests energy by using a solar panel. The energy gained by the solar panel is stored in a LiPo battery. Then the battery is used to supply a stable 5V which is used by USB gadgets. The power bank can also be charged by an external 5V source. The best thing for this power bank during day that you don’t need to remember to charge it. It charges itself by using the sunlight and you don’t come up with an empty bank.




ICL8038 Function Generator
Posted on Thursday, June 30, 2016   •   Category: Frequency Wave Generators

ICL8038 Function Generator

Function generator with adjustable frequency from 0 Hz to over 400 kHz, adjustable amplitude, DC offset, duty, and of course the function selection – square, triangle, and sine. Generator based on good old ICL8038 integrated chip generator that gives pretty good shaped signals as for amateur purposes. This circuit has been designed a little differently than ICL’s note or other similar circuits are suggesting. I tested a bunch of different configurations with different peripherals and chosen the best – so to get good waveshape at 400kHz. I got rid of some of the elements, I added my own solutions. The two ICL chips that i have can oscillate around up to 420-430kHz, and practically we can get good waveforms up to that frequency.




2-5 Km Long Range FM Transmitter
Posted on Friday, June 24, 2016   •   Category: FM Transmitters

2-5 Km Long Range FM Transmitter

The proposed long range transmitter circuit really is very steady, harmonic free design which you can use with standard fm frequencies between 88 and 108 MHz. This will likely encompass 5km spectrum (long range). It includes an extremely consistent oscillator for the reason that you employ LM7809 stabilizer that is a 9V stabilized power source for T1 transistor and for frequency realignment that may be reached by means of the 10K linear potentiometer. The output strength of this long range rf transmitter is approximately 1W. Transistor T1 is employed as an oscillator stage to present a small power steady frequency. To fine-tune the freq. apply the 10k linear potentiometer this way: should you moderate, in the direction of ground, the freq. would probably decrease but when you fine-tune it in direction of + it would climb. Essentially the potentiometer is needed just as a flexible power source for the a pair of MV2019 varicap diodes. Both of these diodes function as a changeable capacitor whilst you regulate the pot. By tweaking the diode capacitance the L1 + diodes circuit renders a resonance circuit for T1. Feel free to employ transistors similar to BF199, BF214 however be careful not to use BCs. At this point you don’t receive yet the long range fm wireless transmitter due to the fact that the electric power is fairly reduced, a maximum of 0.5 mW.




0-30V Mini Bench Power Supply
Posted on Thursday, June 2, 2016   •   Category: Power Supplies

0-30V Mini Bench Power Supply

After many years of employing this ugly and clumsy bench power supply, I decided it was time to build something better, smaller and nice looking. It began as a variable power supply based on an LM338 5A voltage regulator and external power adapter. LM338's Data Sheet has several very helpful application notes and circuits. I chose one that illustrated variable output and included protection diodes. Diodes are included to protect the regulator from damage in case the input is accidentally shorted to ground. This is a distinct possibility if using jumpers to attach it to the power supply. Also the output of station supply may be shorted if some other device fails. Without the diodes, if this happens, the capacitors will dump their charge back through the regulator. Since the current spike may be many amps, the regulator may fail. The diodes steer the current around the regulator and into ground, thereby protecting it from damage. With adequate input the LM338 makes a fabulous variable power supply. This small supply is user friendly and fits nicely on my cluttered bench.




Pen FM Transmitter Bug
Posted on Friday, May 20, 2016   •   Category: FM Transmitters

Pen FM Transmitter Bug

Pen FM Transmitter bug projects have been very popular. The idea of being able to hide a transmitter in a pen is very appealing. In an effort to reduce the size of this design, we have used surface-mount components. Firstly, the thought of using the coil in the tank circuit for transmitting RF was a little far fetched, but we used it as an example for those who were interested in experimenting with our circuits. Now we have gone back to a conventional antenna, the whip. The whip or straight-line antenna can be coiled, wound longitudinally or folded. The way it is wound makes a big difference to its effectiveness, but when you are limited in space, you have to accept these limitations. Even though we have used this antenna set up in our previous pen bugs we have considerably improved the circuit to the point were it has low battery consumption, but high RF output. The size of this design has been reduced considerably by using surface-mount components.




76MHz - 110MHz FM Transmitter with Booster
Posted on Monday, May 16, 2016   •   Category: FM Transmitters

76MHz - 110MHz FM Transmitter with Booster

Three stage FM transmitter with an on board signal booster for increased transmitting range. It broadcasts audio on 76MHz - 110MHz FM frequency via included on board microphone or from MP3 player, Phone, iPod, Computer, Laptop, CD Player, TV, Satellite Receiver via on board 3.5mm connector. It transmit sound with excellent clarity throughout your home, office, yard, camp ground, etc. Transmitter is supplied by 3-12V DC voltage and uses one 2SC9014 and two 2SC9018 low noise RF transistors.




Simple Miniature FM Transmitter
Posted on Saturday, April 16, 2016   •   Category: FM Transmitters

Simple Miniature FM Transmitter

I found this FM transmitter circuit on the internet, it works very well and it is very simple to build, even for amateurs. I managed to squeeze all the parts on small 1.5 x 2 cm PCB. When using small wire antenna and 3V power the range is 50m. The coil has 10 turns on a 3 mm diameter and is wound with 0.3 mm copper wire. The microphone is an electret type. Transmitting frequency is changed by stretching or compressing the coil. Furthermore, we can change the frequency by changing C2 capacitor (10pF capacitor with a frequency of about 88MHz, with 8.2pF 95Mhz and 6.8pF 104Mhz). Further tuning to the correct frequency is done through the coil. Transmitter can be powered by 3V button battery.




FM Stereo Transmitter using BA1404
Posted on Sunday, April 3, 2016   •   Category: FM Transmitters

FM Stereo Transmitter using BA1404

This easy to build transmitter transmits high quality stereo sound from your MP3 player, computer, walkman or discman to any FM radio or car radio. The circuit is designed around the BA1404 single chip FM stereo transmitter from ROHM. The IC requires only a small number of external parts so it is well suited for hobbyist projects. The chip features excellent frequency stability, low power consumption & good channel separation. The transmitting RF frequency can be set by adjusting the coil (Lx). This 2 turn coils is paired with a 39 pF capacitor (Cx) to give a frequency range from 87 MHz - 106 MHz.




250mW FM VHF Transmitter
Posted on Sunday, March 20, 2016   •   Category: FM Transmitters

250mW FM VHF Transmitter

This FM VHF transmitter will output approximately 250mW of RF power using a 2N3866 output transistor and can operate between 75MHz and 146MHz. It utilities a variable high gain audio pre-amplifier which can detect voices 40 feet away using an electret microphone. Using a NBFM scanner, ranges over 5KM have been achieved using a 48cm wire antenna. Coils are 22SWG 7mm air core. L1 and L2 should be 6 turns for 75MHz to 85MHz, 4 turns for 85MHz to 100MHz and 3 turns for 100 to 146MHz. For frequencies over 100MHz the Crystal will be higher than 20MHz hence the base emitter capacitor should be 47pF. L3 is a 4.7uH choke. It is ideal to tune up this circuit using a wave detector meter placed a few inches away from the transmitter.




Mini FM Radio Broadcast Transmitter
Posted on Tuesday, February 23, 2016   •   Category: FM Transmitters

Mini FM Radio Broadcast Transmitter

Have you ever wanted to broadcast your own radio station within your neighborhood? This small and simple 87-108MHz FM transmitter is the toy that geeks have always wanted. This tutorial includes the PCB layout and the schematics. It has a range of up to 1/4 mile or more. It's great for room monitoring, baby listening and nature research.




30V/4A Adjustable Bench Power Supply
Posted on Tuesday, February 16, 2016   •   Category: Power Supplies

30V/4A Adjustable Bench Power Supply

This is a high quality bench power supply with adjustable output voltage from 0 to 30V and adjustable output current from few miliamperes to 4 amperes. Built-in electronic output current limiter that effectively controls the output current makes this power supply indispensable in the experimenters laboratory as it is possible to limit the current to the typical maximum that a circuit under test may require, and power it up then, without any fear that it may be damaged if something goes wrong. There is also a visual indication that the current limiter is in operation so that you can see at a glance that your circuit is exceeding or not its preset limits.




Super Simple iPod FM Transmitter
Posted on Wednesday, February 3, 2016   •   Category: FM Transmitters

Super Simple iPod FM Transmitter

FM transmitters can be complicated to build, but not this one — this iPod FM transmitter about the easiest you can possibly make. And though the science of radio is well understood, there’s a magical, emotional quality about it that we don’t often stop to appreciate. You will not forget the first time you pick up a transmission broadcast from a device you soldered together, yourself, from a few bits of copper, carbon, plastic, and wire.




VHF FM Transmitter
Posted on Monday, January 18, 2016   •   Category: FM Transmitters

VHF FM Transmitter

The circuit is a simple 88-108 MHz VHF FM transmitter circuit. It is basically a VHF Colpitts oscillator capable of transmitting sound or music to any standard FM receiver. The circuit is powered by 9V battery which makes it easily portable. It also has a capacitor microphone which picks up very weak sound signals. The output frequency can be easily adjusted by potentiometer thanks to onboard MV2109 varicap diode and the frequency stability is quite good. The range of this transmitter is 100 meters.




BA1404 3V Stereo FM Transmitter
Posted on Friday, December 18, 2015   •   Category: FM Transmitters

BA1404 3V Stereo FM Transmitter

This simple circuit is based on BA1404 FM Transmitter, works with two AA batteries and can drive a 300W dipole antenna for improved range. There are many applications for an FM transmitter, particularly if it can broadcast in stereo. You can broadcast stereo signals from your CD player or any other source to an FM tuner or radio. The transmitter uses a single IC and a few other components. It broadcasts on the FM band (88-108MHz) so that it can be received by any standard FM tuner or portable radio.




Basic FM Transmitter
Posted on Thursday, December 3, 2015   •   Category: FM Transmitters

Basic FM Transmitter

This basic RF oscillator circuit is easy to build and the components are not critical. Most of them can be found in your junk parts box. The circuit operated with 9V DC power supply. The L1 antenna coil can be made by close winding 8 to 10 turns of 22 gauge insulted magnetic wire around 1/4 inch form such as a pencil. You can experiment with the size of the coil and the number of turns to see how it affects the frequency and signal output of the oscillator. You should be able to pick up its signal with standard FM radio receiver. Signal In to any audio player through 0.1uF capacitor.




7 Watt FM Transmitter
Posted on Thursday, November 26, 2015   •   Category: FM Transmitters

7 Watt FM Transmitter

This 7 Watt FM Transmitter was originally a 200mW unit, without the universal power stage added. Together with the power amp 2SC1971 / MRF237 / NTE342 it then became a 7W unit. I used this transmitter with a half-wave open-end dipole in a vertical position 50 feet above ground. Together with about 70 feet of coax, this transmitter delivered great audio at a distance of 10 miles ... overall distance was 17 miles, but the audio signal was weak. I had no equipment, other than a watt meter to measure it's power and a digital FM tuner with a 5-LED Signal Strength Bargraph display to use as capturing the main oscillating frequency, which was right at 87.5 MHz. This circuit worked well for me, as I had experimented with it for nearly a year. Of course, one would be better off with more equipment than I have had to capture the main oscillating frequency. That was, by far, one of the hardest things to capture. It was thru trial and error, with the FM tuner, in finally finding out how to grab the right frequency. When I finally did get used to find out where my 'main' frequency was, the unit performed extremely well. Like I had said above, right at 10 miles, the unit was at its best giving clear audible audio into the speakers of my car. With the transmitting antenna at 50 feet above ground, I decided to see how well I could receive the transmitter signal from an overpass than is exactly 15 miles from the transmitter. When I got to the top of the overpass in my car, the audio signal came in as 'clear as a bell'. I now understand what is meant when one says FM signal travels best in a line of sight. Well, being on that overpass, if I had a strong telescope with me, I am sure I could see the 50 foot antenna in my oak tree. So with the overpass being right around 50 feet in height also, the transmitter surpassed my judgement call on its signal. I surrender this circuit to anyone who likes to experiment in things like this. Enjoy!




Simple FM Radio
Posted on Friday, October 9, 2015   •   Category: FM Radio / Receivers

Simple FM Radio

This is one of my favorite radio builds just because of how simple it is and how well it is able to pick up a lot of FM radio stations. I have browsed the world in search of a one transistor FM receiver. I have seen a couple but they were always attached to some sort of added device, such as another IC or another transistor for amplification in the receiver itself. Through my continued quest of searching for that too good to be true one transistor, I happened to run across a super-regenerative receiver, by Charles Kitchin, famous for his vast knowledge of regenerative designs. I printed out the schematic and made it. It turned out extremely well.




The Simplest FM Transmitter Ever Made
Posted on Friday, September 25, 2015   •   Category: FM Transmitters

The Simplest FM Transmitter Ever Made

This is the most simple and cheap FM transmitter you can ever find. This circuit is really cool. This runs at very low voltage, by a CR2025 3V battery, current consumption is also low.And the total size of this FM transmitter (including battery, excluding antenna) is less than that of a matchbox. The circuit has a central RF oscillator NPN transistor BF494 (substitute: BF199). A coil takes care of the output frequency. It consists of 36SWG wire 2.5 turns only in 5mm diameter ferrite rod. Keep the circuit as small as possible. Try to use no wires in the main functional area (transistor and coil). The input from the audio output of computer / PMP / mobile is given to the biased base of the transistor. The transistor gives a RF humming accordingly to the audio input, and the FM wave is spread by the external antenna. By using a standard TV antenna, the range of this transmitter can go up to 1KM radius, using small (15-20cm) Ariel, it can work up to around 50M range. This circuit is most suitable for miniature FM transmitter for use in computer, mobile etc to send music to home theater system without wires, and in homemade wireless walky-talkies.




Aircraft Transmission Receiver
Posted on Tuesday, August 25, 2015   •   Category: FM Radio / Receivers

Aircraft Transmission Receiver

This passive airband receiver is basically an amplified "crystal radio" designed to receive nearby aircraft transmissions on 121 - 133 MHz frequency. Useful for listening to the pilot transmissions. The input tuned cct 'L' is a 2 turn loop, with 30mm diameter measured at 0.15uH on my LC Meter which intercepts RF directly as opposed to an LC cct fed with external aerial. Tuning capacitor is a 30pF Philips Beehive trimmer, with a short length of plastic tube glued - as a tuning shaft. Capacitance runs from 28 to 7pF; which by formula gives a frequency range of 77 - 155MHz. Detector uses a biased 1N5711 (or similar) schottky diode with lowest forward-biassed voltage drop. The two 10M resistors bias the detector diode and the op-amp input near mid-rail for better detector efficiency. LM358 dual op-amp draws less than 1 ma so the battery drain is minimal. Insertion of earphones plug completes supply circuit and acts as an on/off switch. 9V battery fits neatly inside a 30mm x 130mm long PVC tube.




Simple AM Transmitter
Posted on Friday, August 21, 2015   •   Category: AM Radio

Simple AM Transmitter

There are not many AM transmitters that are easier to build than this one because the inductor is not tapped and has a single winding. There is no need to wind the inductor as it is a readily available RF choke. To make the circuit as small as possible, the conventional tuning capacitor has been dispensed with and fixed 220pF capacitors used instead. To tune it to a particular frequency, reduce one or both of the 220pF capacitors to raise the frequency or add capacitance in parallel to lower the frequency. Q1 is biased with a 1MO resistor to give a high input impedance and this allows the use of a crystal ear piece as a low cost microphone.




50W LM3886 Power Amplifier
Posted on Sunday, August 16, 2015   •   Category: Amplifiers

50W LM3886 Power Amplifier

This is a second revision of 50W LM3886 power amplifier that is used to power two bookshelf speakers. The sound produced by LM3886 chip is excellent so I decided to make another amplifier with it. The schematic is based on the schematic in the datasheet of the chip with minor changes. I removed the time delay capacitor connected to MUTE pin, because it's better to use separate DC protection schematic which has similar functionality. I made the output inductance L1 by winding 15 turns of enameled wire around the resistor R7. The diameter of the wire must be minimum 0.4mm. The whole was wrapped with heat shrink.




The Simplest FM Transmitter
Posted on Thursday, July 2, 2015   •   Category: FM Transmitters

The Simplest FM Transmitter

This is the most simple and cheap FM transmitter you can ever find. It's powered by CR2025 3V battery and current consumption is very low. The total size of this FM transmitter is less than that of a matchbox. The circuit has a central RF oscillator NPN transistor BF494. A coil takes care of the output frequency. The coil consists of 36SWG wire 2.5 turns in 5mm diameter ferrite rod. Keep the circuit as small as possible. By using a standard TV antenna, the range of this transmitter can go up to 1KM radius, using small 15-20cm wire, it can work up to around 50M range. This circuit is most suitable for miniature FM transmitter for use in computer, mobile etc to send music to home theater system without wires, and in homemade wireless walky-talkies.




1Hz to 1MHz XR2206 Function Generator
Posted on Sunday, June 28, 2015   •   Category: Frequency Wave Generators

1Hz to 1MHz XR2206 Function Generator

When i was using operational amplifiers at school lab i wanted a function generator at home to play with and work on circuits with Op Amps for better understanding. So i found on the internet a free function generator circuit which uses the IC XR-2206, i printed the PCB with my UV exposure box, i bought an enclosure box, i put everything inside and here is the result. The function generator can generate Square, TTL, Sine and Triangle waveforms from 1Hz to 1Mhz with Voltage regulation to Square Sine and Triangle waveforms.




Single Transistor VCO FM Transmitter
Posted on Thursday, May 28, 2015   •   Category: FM Transmitters

Single Transistor VCO FM Transmitter

This simple transmitter allows you to broadcast on FM radio band 87.5 - 108 MHz. It consists of a simple oscillator with silicon planar RF PNP transistor. Directly to the oscillator an antenna is connected. Due to the large amplitude of RF voltage is sufficient antenna length of about 5-10 cm. I used insulated 7cm long copper wire 1mm diameter. I eliminated the tuning capacitor, which is usual for most bugs and miniature transmitters, because this greatly complicates the tuning. From my own experience I know that if you get closer to such capacitor, the operating frequency is changed. That's why I chose to use the voltage tuning using the Voltage Controlled Oscillator (VCO). Instead of tuning capacitor the varicap (capacitance diode) is used, which changes its capacity by changing the reverse DC voltage. We can tune the operating frequency by changing the DC voltage using the trimmer P1. Varicap also provides frequency modulation.




400mW VCO FM Transmitter
Posted on Sunday, May 24, 2015   •   Category: FM Transmitters

400mW VCO FM Transmitter

This simple 400mW transmitter broadcasts audio on 87.5 - 108 MHz FM radio band. With good dipole antenna transmission range up to 4km is possible. Frequency is selected by adjusting R1 potentiometer. Transmitter should be powered by regulated 12-14V power supply with at least 100mA current rating.




Simple Audio FM Transmitter
Posted on Thursday, April 23, 2015   •   Category: FM Transmitters

Simple Audio FM Transmitter

FM transmitters can be complicated to build, but not this one it’s about the easiest you can possibly make. And though the science of radio is well understood, there’s a magical, emotional quality about it that we don’t often stop to appreciate. You will not forget the first time you pick up a transmission broadcast from a device you soldered together, yourself, from a few bits of copper, carbon, plastic, and wire.




Stereo FM Transmitter
Posted on Thursday, March 12, 2015   •   Category: FM Transmitters

Stereo FM Transmitter

This is a small stereo FM transmitter. Output can be tuned from 88 to 108Mhz and the transmitter can be battery powered or be used with presented low voltage power supply. This circuit is based on the Rhom BA1404 datasheet. The maximum voltage should not exceed 3V. The IC can be driven from a 7805 Regulator with a couple of 1N4001 diodes to reduce the supply voltage to about 2.8 Volts. RF output power is typically 500mW but range depends upon antenna coupling and efficiency, environment and size of antenna. A small telescopic whip has an expected range of at leaset 100 metres or more.




Arduino Prototype
Posted on Monday, March 2, 2015   •   Category: Arduino

Arduino Prototype

Arduino Prototype is a spectacular development board fully compatible with Arduino Pro. It's breadboard compatible so it can be plugged into a breadboard for quick prototyping, and it has VCC & GND power pins available on both sides of PCB. It's small, power efficient, yet customizable through onboard 2 x 7 perfboard that can be used for connecting various sensors and connectors. Arduino Prototype uses all standard through-hole components for easy construction, two of which are hidden underneath IC socket. Board features 28-PIN DIP IC socket, user replaceable ATmega328 microcontroller flashed with Arduino bootloader, 16MHz crystal resonator and a reset switch. It has 14 digital input/output pins (0-13) of which 6 can be used as PWM outputs and 6 analog inputs (A0-A5). Arduino sketches are uploaded through any USB-Serial adapter connected to 6-PIN ICSP female header. Board is supplied by 2-5V voltage and may be powered by a battery such as Lithium Ion cell, two AA cells, external power supply or USB power adapter.




76-110MHz FM Radio Transmitter
Posted on Tuesday, December 30, 2014   •   Category: FM Transmitters

76-110MHz FM Radio Transmitter

Here is a simple 76-110MHz FM transmitter that can transmit your voice or audio over an ordinary FM radio within the FM broadcast band. It can transmit both voice using microphone and music from any music player. Frequency is changed by adjusting 5.5 turn inductor coil. Transmitter is powered by 9V battery or 3V-9V power adapter. Transmission range is 100 meters but can be increased with better antenna or RF amplifier.




Super Simple FM Transmitter
Posted on Wednesday, December 10, 2014   •   Category: FM Transmitters

Super Simple FM Transmitter

FM transmitters can be complicated to build, but not this one. It’s about the easiest you can possibly make. And though the science of radio is well understood, there’s a magical, emotional quality about it that we don’t often stop to appreciate. You will not forget the first time you pick up a transmission broadcast from a device you soldered together, yourself, from a few bits of copper, carbon, plastic, and wire.




Driving CDROM Stepper Motor with Arduino
Posted on Saturday, October 25, 2014   •   Category: Stepper Motors

Driving CDROM Stepper Motor with Arduino

H-bridge is frequently used to control DC motors and stepper motors. When controlling a bipolar stepper motor, two full H-bridges are needed. There are many H-bridge ICs (like L298, MPC17529 and SN754410 which is a quad half H-bridge) for just that purpose. But if you are on a budget, you may want to consider building a dual H-bridge yourself. The following schematic shows a simple dual H-bridge using eight general purpose transistors (2N3904 and 2N3906). Given the maximum current of roughly 200mA, this circuit can be used to drive a small bipolar stepper motor operating between 5V and 12V, such as the stepper motors found in most floppy drives and CD / DVD drives.




6W FM Transmitter 88-108 MHz
Posted on Tuesday, August 26, 2014   •   Category: FM Transmitters

6W FM Transmitter 88-108 MHz

Presented FM transmitter is built around low power PLL transmitter and amplifier that boosts its signal all the way up to 6 Watts. The signal is amplified by three RF stages of amplification. In the first and second stages of the transmitter one of the best driver transistors were used 2SC2053. You can use the other transistors but only up to 500mW of power. In the third stage 2SC1971 RF transistor was used to achieve 6W of power. For making any RF transmitter circuit at least two meters are necessary, one is frequency counter and the other is RF field strength meter for which the schematic is provided.




Battery Powered Amplifier
Posted on Friday, August 22, 2014   •   Category: Amplifiers

Battery Powered Amplifier

This is battery powered amplifier based on LM386 chip and has an input buffer that is feeding the inverting input. The input buffer helps to retain treble details going into the LM386 chip. It is powered from a single 9V battery.




12V Fluorescent Light Inverter
Posted on Sunday, August 17, 2014   •   Category: Miscellaneous

12V Fluorescent Light Inverter

This is a low voltage 12V fluorescent inverter for powering two 20W or single 40W fluorescent tube. It's a circuit you can put together from junk box components and is a very simple to build. The transformer is hand-wound on a ferrite rod from an old transistor radio and the winding wire can be salvaged from an old transformer. The cost of powering the circuit is about 22 watts and this will produce the same light output as 60 watt incandescent light bulb.




Easy FM Transmitter
Posted on Sunday, August 3, 2014   •   Category: FM Transmitters

Easy FM Transmitter

The figure shows a schematic of an easy to build FM transmitter circuit. Mostly all FM transmitter circuits you will find online or in books require some kind of hand build inductor/coil and after building the transmitter you have to adjust that coil and trimmer capacitor a little to adjust the transmitter to transmit on your desired frequency. If you are looking for an easy or simple FM transmitter circuit in which you don't have to make a coil with your hand then the circuit given here is ideal for you. The circuit is using a ready made 1uH inductor which can be purchased from an electronic components store. These inductors are mostly look like resistors. The circuit also does not require a trimmer capacitor, because we have used a fixed value of 39pF capacitor in the place of trimmer capacitor. We have already calculated and used the values of coil and capacitors of oscillator to broadcast on FM band, so you don't have to do any further adjustments and tuning after building the circuit. The circuit can be operated with 9 to 12 volt DC. For antenna use a 12 inch wire or for maximum range use a 30 inch wire and make it vertical.




Curious C-Beeper
Posted on Monday, July 28, 2014   •   Category: Test and Measurement

Curious C-Beeper

Curious C-Beeper is a fun to build little probe that can be used to quickly detect the capacity of capacitors in pF nF range, test their stability with temperature changes, find broken wires, locate wires, trace wires on PCBs, and to locate live wires behind the walls without touching them. The circuit uses three transistors to make a most unusual capacitance beeper probe. When a capacitor is touched to the probe, the probe beeps at a frequency that varies with capacitance. The frequency change is so steep with capacitance that tiny capacitors may be precisely matched or an exact fixed value may be selected to replace a trimmer in a prototype. If the user has reasonably moist skin, simply holding one lead of the capacitor to be tested while touching the other lead to the probe is all that is necessary. The user's body forms the other connection through the beeper's metal case. When the beeper is properly adjusted it draws only 10 uA with nothing touching the probe - no power switch is required. This design is optimized for capacitors less than about 0.1 uF (100 nF). Large capacitors give a low frequency "clicking" sound and small capacitors sound a tone that increases as the capacitance decreases. Many decades of frequency change occur over the beeper's range giving even the more tone-deaf among us sufficient change to discern slight differences in capacitance. The entire device is powered by two CR2032 lithium cells that fit into TicTac box. The use of power switch is unnecessary since the circuit consumes almost no power when not being used.




Automatic Night Light
Posted on Thursday, July 24, 2014   •   Category: Miscellaneous

Automatic Night Light

This circuit automatically turns on the light through a relay when daylight intensity falls below a preset level on the Light Dependent Resistor (LDR).




LM386 Utility Amplifier
Posted on Tuesday, July 1, 2014   •   Category: Amplifiers

LM386 Utility Amplifier

It's always handy to have a little amp kicking around to trace audio signals, test mics, CD tape and TV audio outputs. You know, something that doesn't weigh a lot and isn't clumsy. There are tons of uses for this little circuit. There are a couple of versions of this amplifier chip. Both are 8 pin DIP packages and the difference between the two are apparent by their part numbers. Either are suited for this circuit provided the supply voltage does not exceed the recommended 5 to 12 volt DC range. Power output can range from about 325 mW to about 750 mW within this supply range when using an 8 ohm speaker. Power it with batteries or a small DC supply...why not solar cells or a little windmill generator?




Mini FM Transmitter
Posted on Friday, June 27, 2014   •   Category: FM Transmitters

Mini FM Transmitter

Here's how to build your own mini FM transmitter. It transmits FM waves so you could easily receive the signals on your mobile phone, radios, etc. As the name and the picture indicates it is very small and is approximately the size of a 9v battery clip. With this FM transmitter you could start your own mini FM station. The circuit uses BC547 transistor to amplify the signal and then frequency modulate it. It uses "frequency modulation" most commonly known as FM, the same principal to transmit audio signals captured by the microphone.




Automatic Garden Light
Posted on Sunday, June 22, 2014   •   Category: Miscellaneous

Automatic Garden Light

This circuit automatically turns on and illuminates the LEDs when the solar panel does not detect any light. It switches off when the solar panel produces more than 1v and charges the battery when the panel produces more than 1.5v + 0.6v = 2.1v.




USB Battery Pack
Posted on Friday, June 20, 2014   •   Category: USB Circuts

USB Battery Pack

This project is able to power a USB device using two standard AA batteries and an electronics circuit. The circuit is based on LT1073 DC/DC converter to convert the 3V to 5V needed by USB. In that way it can power the USB device on the go.




Phone Transmitter
Posted on Sunday, June 15, 2014   •   Category: FM Transmitters

Phone Transmitter

This small phone transmitter will transmit a phone conversation to an FM radio on the 88-108MHz band. It uses energy from the phone line to transmit the signal about 100 meters away. It uses the phone wire as the antenna and is activated when the phone is picked up. Transmitter components are mounted on a small PC board. PC layout is included.




27MHz Walkie Talkie
Posted on Friday, June 6, 2014   •   Category: FM Transmitters

27MHz Walkie Talkie

This classic walkie talkie consists of both 27MHz transmitter and receiver all in one circuit. Nearly all the components in the 4-transistor circuit are used for both transmitting and receiving making it simple to build and economical at the same time. The frequency-generating stage only needs 27MHz crystal to be removed and it becomes a receiver. Next is a three transistor audio amplifier with very high gain. The first transistor is a pre-amplifier and the next two are wired as a super-alpha pair, commonly called a Darlington pair to drive the speaker that is also used as a microphone. The use of telescopic antenna will provide better reception and transmitting range. Use two identical walkie talkie circuits for two way communication.




Plant Water Alarm
Posted on Sunday, June 1, 2014   •   Category: Miscellaneous

Plant Water Alarm

This simple plant water alarm circuit indicates when the soil is dry and the plant needs watering. The circuit does not have a current-limiting resistor because the base resistor is very high and the current through the transistor is only 2mA. Replacing 220K resistor with 1M potentiometer will provide adjustment when the alarm should be triggered depending on the moisture left in the soil.




4km FM Transmitter
Posted on Friday, May 16, 2014   •   Category: FM Transmitters

4km FM Transmitter

This is a VCO FM Transmitter. With good antenna (dipole placed outdoor and high) the transmitter has very good coverage range about 500 meters, the maximal coverage range is up to 4 km. To calibrate for maximum power connect 6 V / 0,1 light bulb to the output and use R1 to tune the right frequency, adjust L1 coil if necesary. Then use C14 and C15 to adjust the highest power (the highest light of the bulb). Then you can connect antenna and audio signal. Adjust R2 until the audio sounds as loud as the other stations.




1 Watt FM Transmitter Amplifier
Posted on Thursday, May 15, 2014   •   Category: FM Transmitters

1 Watt FM Transmitter Amplifier

This is a 1 Watt FM Transmitter amplifier with a good design that can be used to amplify a RF signal in the 88 – 108 MHz band. It is very sensitive if you use good RF power amplifier transistors, trimmers and coils. It has a power amplification factor of 9 to 12 dB (9 to 15 times). At an input power of 0.1W the output will be 1W. You must choose T1 transistor depending on applied voltage. If you have a 12V power supply then use transistors like: 2N4427, KT920A, KT934A, KT904, BLX65, 2SC1970, BLY87. At 18 to 24V power supply you must use transistors like: 2N3866, 2N3553, KT922A, BLY91, BLX92A. You may use 2N2219 at 12V but you will get an output power of 0.4W maximum.




Simple MOSFET Switch
Posted on Tuesday, May 13, 2014   •   Category: Miscellaneous

Simple MOSFET Switch

Constructing a MOSFET switch is one of the basic level electronics projects and could be useful for beginners to get a hang of the various FET transistors. The aim of this project is to make control a heavy duty DC load by constructing a simple switch. MOSFET transistors are capable of handling a large voltage and current. It is because of this feature that it is being much sought after for connecting heavy loads to a circuit or a microcontroller.




AM Radio Transmitter Using 555 Chip
Posted on Friday, April 25, 2014   •   Category: AM Radio

AM Radio Transmitter Using 555 Chip

This project shows how to build a simple AM radio transmitter based on 555 timer IC. The circuit parts are: the 555 timer IC, a NPN transistor three caps, three resistors and a potentiometer. The circuit is able to generate an amplitude modulation signal at 600Khz and you are able to receive it using a plain AM receiver. The range is about 30-40 feet.




Adjustable Bench Power Supply
Posted on Tuesday, April 22, 2014   •   Category: Power Supplies

Adjustable Bench Power Supply

If you are starting to learn electronics variable bench power supply is the first thing you should build to power your projects. This simple power supply is built around the LM317/LM338/LM350 linear voltage regulator. The LM317 is one of the most popular voltage regulators on the market, and for good reason. It is very simple to use and requires very few external components. LM317/LM338/LM350 regulators provide a stable and reliable output voltage adjustable between 1.25V and 37V. The short circuit protection is also built right in the voltage regulator.




Arduino RF link using 433MHz Transmitter / Receiver modules
Posted on Monday, April 14, 2014   •   Category: Arduino

Arduino RF link using 433MHz Transmitter / Receiver modules

If you are looking into wireless communication between two Arduino modules, this project might be helpful. It uses low costs RF transmitter and receiver from Electronics-DIY.com to establish radio link between two Arduino boards up to 500 ft. Data can be transferred serially at the maximum rate of 2400 bps. The schematic shows how receiver and transmitter is hooked up to two different Arduino boards. When wiring the receiver / transmitter you only need to give them power / ground and then a pin for the TX (serial transmit) or RX (serial receive) pin. I also wired a button to the Arduino doing the transmitting, and used the LED on pin 13 that is built into my Arduino boards on the receiver so I could test this setup. The test app just flashes LED on the receiving board when a button is pressed on the transmitting board.




MAX038 Generator
Posted on Tuesday, April 1, 2014   •   Category: Frequency Wave Generators

MAX038 Generator

This is simple MAX038 generator. It produces sine, triangle and square waves from 1Hz up to 22MHz. The Amplitude, offset and duty cycle are adjustable to offer wide range of generated signals. Frequency adjustment is made as a rotary switch S8 with a capacitor bank and variable resistor P7. Amplitude, offset and duty-cycle are performed via variable resistors. Switch S5 selects generated waveform.




Adjustable Constant Current Load
Posted on Sunday, March 9, 2014   •   Category: Test and Measurement

Adjustable Constant Current Load

An adjustable power load is a piece of test equipment that often comes handy in the development of a certain electronics projects. For example, when you are building a power supply, it will come a time when you need to "simulate" a load to see how well your design performs as the load varies. Adding power resistors to the output can sometimes do in a pinch, but often you will not have the right resistor value handy with the right power rating for the test. This is where an adjustable electronic load comes handy. In this article, I'll show how you can build one using common components available to the electronics hobbyist.




68W LM3886 Amplifier
Posted on Thursday, February 27, 2014   •   Category: Amplifiers

68W LM3886 Amplifier

LM3886 is a high-fidelity audio power amplifier IC capable of delivering 68W of continuous power using 4 Ohm speakers. LM3886 provides excellent S/N ratio of 92dB and above as well as extremely low total harmonic distortion over the audio spectrum. LM3886 comes equipped with Self Peak Instantaneous Temperature Protection Circuitry (SPiKE) that makes it a class above other discrete and hybrid amplifiers. SPiKe Protection makes LM3886 amplifier safe against problems like over voltage, under voltage, overloads, shorts to the supplies, thermal runaway, and temperature peaks.




18W FM Transmitter
Posted on Tuesday, February 18, 2014   •   Category: FM Transmitters

18W FM Transmitter

Here's FM transmitter for commercial FM band that provides 18 watts of power. Since the electronic diagram is too large we decided to divide it into two parts. The first part is the actual FM transmitter while the second part is 18W RF amplifier. The circuit should be built on an epoxy printed circuit board with the upper face components reserved for interconnecting tracks and the bottom solder to the ground plane. If powered by 14V and 2.5A transmitter outputs 15W of power, whereas 18V and 3.5A will provide 18W. BB110 variable capacitor connected to the collector of transistor BF199 adjusts the transmission frequency of the circuit. 2K2 potentiometer serves as fine tuning. Once the output frequency is adjusted amplifier variable capacitors must be adjusted for maximum output power one stage at a time. All adjustments must be made with 50 Ohm dummy load connected to the output of transmitter.




Solar Charger for USB Devices
Posted on Friday, February 14, 2014   •   Category: Solar Circuits

Solar Charger for USB Devices

As the world around us becomes more and more environmentally conscious, alternative energies such as solar power are becoming more and more popular. The following solar charger is very simple and inexpensive to build and could be used to charge cellphones, tablets and other USB devices. 6V solar panel could be easily salvaged from outdoor garden lights. Solar charger uses REG113-5 efficient low dropout regulator that only loses 250mv of forward voltage. Linear style regulators such as a LM7805 or LM317 type voltage regulators lose as much as 2-3V and can not be used in this application. Optionally you may also add four-resistor voltage divider to charge an iPhone or iPad.




500W Modified Sine Wave Inverter
Posted on Tuesday, January 28, 2014   •   Category: AC / DC Innveters

500W Modified Sine Wave Inverter

Here is a simple but powerful, stable and efficient schematic diagram for a 500W modified sine wave inverter circuit. Originally I used a 555 timer and a CD4017 decade counter to produce the modified sine wave, but then I thought a simple PIC micro controller with its internal clock would produce a stable 50Hz/60Hz frequency without the need for two ICs. As you can see its a very simple circuit. 220V transformer should be used for 220V voltage output. For 110V voltage output use transformer with 110V rating.




3.3V and 5V Power Supply
Posted on Wednesday, January 22, 2014   •   Category: Power Supplies

3.3V and 5V Power Supply

I normally use a USB port as power supply for my projects but some ICs need 3.3V instead of 5V. Therefore I decided to build this small dual power supply. Power supply uses two low dropout voltage regulators that provide up to 800mA of output current and come in TO-220 package. LD1117V33 is used for 3.3V and LD1117V50 for 5V. Input voltage is 6V-15V and both regulators can be switched on/off individually.




Veronica 1W FM Transmitter
Posted on Sunday, December 29, 2013   •   Category: FM Transmitters

Veronica 1W FM Transmitter

Veronica 1W FM transmitter is an easy to build transmitter. Veronica is also known for frequency stability, clean FM signal and uses no integrated circuit. The Veronica oscillator is actually formed from 2 oscillators which operates somewhere around 50 MHz in anti phase and the 2 signals are combined to form 100MHz FM radio signal. This kind of circuit design is stable and is amplified up to 1W by 2n4427 transistor. Veronica transmitter is equipped with a mini-mixer and so you may forget an external mixer. This consist from T1 transistor which amplifies the microphone signal before it is combined with cd-player audio or PC signal. R1 and R2 are potentiometers (variable resistors) used to adjust the audio level. The component between R8 and C21 represents the oscillator wich generates radio signal. D1 is a varicap diode (like a variable capacitor or trimmer) controlled by audio signal. C12, C13 and L1 determines the frequency.




Transformerless Joule Thief
Posted on Sunday, December 29, 2013   •   Category: LED

Transformerless Joule Thief

The "Joule Thief" circuit that does not use a transformer to power LED from a single 1.5V battery cell. The circuit consists of two bipolar transistors, coil, two resistors and capacitor to generate higher voltage through 50KHz frequency to power an ordinary LED. Entire circuit draws only about 15 milliamps.




1W PLL Transmitter with MC145152
Posted on Wednesday, December 18, 2013   •   Category: FM Transmitters

1W PLL Transmitter with MC145152

Following 1W PLL transmitter exciter provides stable, low noise operation. Transmitter uses a PLL frequency synthesizer built with MC145152 which covers the FM band in 100kHz steps. The VCO uses MV2109 varicap diode to automatically tune to selected frequency via SW1 dip switch. output stage uses 2N4417 RF power transistor and provides 1W of RF power. With good antenna expected transmission range is 2km. Transmitter may be built on a double sided PCB, with top side copper left mostly undisturbed as a ground plane. The copper is removed only around non-grounded pins. The ground connections can be soldered on the top side, so it’s not necessary to have plated-through holes.




Eliminating LED Christmas Lights Flicker
Posted on Friday, December 13, 2013   •   Category: LED

Eliminating LED Christmas Lights Flicker

I like the idea of using LED Christmas lights because they look cool and consume very small amount of electricity, but the flicker drives me crazy! That's because they are powered directly from 110V AC voltage instead DC voltage which makes them flicker 60 times per second. Here is a simple circuit that will completely eliminate LED Christmas lights flicker. The solution is to convert AC to DC voltage with resistor, rectifier diode and capacitor. Using 470 ohm - 1K resistor is very essential because it limits the current to 20mA and minimizes the voltage to about 80 volts. If we didn't use the resistor LEDs would be powered by over 50mA of current which is much more than what they need and that would definitely shorten their life. Note that lowering voltage does not reduce the brightness of the LEDs because when powered by DC voltage they are always on.




100m Simple FM Transmitter
Posted on Thursday, December 12, 2013   •   Category: FM Transmitters

100m Simple FM Transmitter

Here is a very interesting and simple FM transmitter used to transmit audio in the wide range up to 100M using only one transistor. The entire circuit of FM transmitter is divided into three major stages oscillator, modulator and amplifier. The transmitting frequency of 88-108 MHz is generated by adjusting VC1. The input audio generated by microphone is changed into electric signal and is given to base of transistor T1. Transistor T1 is used as oscillator which oscillates the frequency of 88-108 MHz. The oscillated frequency depends upon the value R2, C2, L2 and L3. Transmitted audio from FM transmitter circuit can be received by standard FM receiver.




PCM5102 Burr-Brown DAC with DIR9001 SPDIF Receiver
Posted on Monday, December 9, 2013   •   Category: Audio DAC

PCM5102 Burr-Brown DAC with DIR9001 SPDIF Receiver

This DAC is based on latest 32bit/384K PCM5102 DAC chip and DIR9001 from Texas Instruments. Sound quality produced by PCM5102 DAC is surprisingly good, very smooth and airy, with great dynamics and excellent soundstage. It features both S/PDIF and optical inputs connected to DIR9001 low jitter digital receiver. PCM5102 uses a next generation architecture based on the PCM1792/4 TI's flagship DACs. It has 112dB SNR, with an integrated negative rail charge pump and line driver, so you don't need no opamps at the end or dual split supplies. Just a simple RC low pass filter is all that is needed. In addition, there's a fancy PLL involved that will autodetect I2S rate, configure the device, and generate it's own internal master clock so no need for external clock. Entire DAC is powered by only 3.3V from 1117-33 regulator and consumes only 20mA of power. Although PCM5102 DAC can be powered by 4-12V DC voltage, it's recommended to power it from a single 3.7V LIPO battery to achieve the best performance.




Simple FM Transmitter with BC549
Posted on Thursday, November 21, 2013   •   Category: FM Transmitters

Simple FM Transmitter with BC549

This is simple FM transmitter for FM broadcast band in 88-108 MHz. BC 549 is small signal transistor for wide applications, but usually for AF. You can build simple FM transmitter with one BC549 transistor and several other component parts. Simple FM transmitter with only one transistor is often called “bug”. This project is suitable for beginners in radio amateur, education, or hobbies. As an antenna you can connect 150cm of copper wire.




Simple MP3 FM Transmitter
Posted on Wednesday, October 16, 2013   •   Category: FM Transmitters

Simple MP3 FM Transmitter

A simple MP3 FM transmitter circuit shown here can be built easily in few minutes if all parts are available to you. All the components used in this transmitter circuit are general purpose and low cost. The circuit will work as a best FM transmitter for simply broadcasting your music around your house and yard, and can be used to broadcast the output of any equipment like mp3 player, ipod, satellite, etc.




Infrared Remote Control with Microcontroller
Posted on Sunday, October 6, 2013   •   Category: Remote Control

Infrared Remote Control with Microcontroller

This little project will demonstrate how you can use NEC IR protocol based TV, DVD or VCR remote control to control you home appliances like fan bulb or virtually anything. There are lots of projects out there to accomplish this task but i have to write my own code because of too many requests on IR infrared Remote Control Relay Board with PIC12F675 Microcontroller. There are a number of consumer Infrared protocols out there and they have been used for every single purpose possible, like PDA laptops and other consumer appliances. RC-5 & RC-6 by Phillips, RCA are few examples of consumer IR protocols.




Simple FM Radio Receiver
Posted on Thursday, September 26, 2013   •   Category: FM Radio / Receivers

Simple FM Radio Receiver

This FM radio receiver circuit is very simple to build and is powered by just a single 1.5V battery cell. Receiver consists of a regenerative rf stage, TR1, followed by a two of three-stage audio amplifier, TR2 to TR4. In some areas 3 stages of audio amplification may not be necessary, in which case TR3 and its associated components can be omitted and the free end of capacitor C5 connected to the collector of TR2. The critical part of the fm radio receiver is the first stage, TR1/VC1, where the wirings must be kept as short as possible. Coil L1 is formed by winding 8 turns of 1mm (20 swg) enamelled copper wire on a 6 mm diameter former, which is then removed. After that L1 should be stretched carefully and evenly to a length of about 13mm.




1 Watt PLL FM Broadcast Transmitter
Posted on Monday, September 23, 2013   •   Category: FM Transmitters

1 Watt PLL FM Broadcast Transmitter

This is a 1 Watt PLL FM broadcast transmitter. The RF output varies from 500mW to about 1.2W depending on the frequency selected and RF output transistor used. Motorola 2N4427 always seems to work well. Transmitter uses CMOS PLL VCO that prevents the frequency drifts. The frequency is selected via DIP switches. The transmitter is supplied by 12V DC and can also be powered from the battery.




Two Wire I2C Arduino LCD Display
Posted on Friday, September 20, 2013   •   Category: Arduino

Two Wire I2C Arduino LCD Display

In this tutorial you will learn how to build a simple serial 16x2 LCD display that is controlled via Arduino board by only two wires. The magic behind is done by the PCF8574 chip, an I/O expander that communicates with the micro-controller by using I2C protocol. The PCF8574 is a quick and easy solution to extending and adding output/input ports to Arduino. The chip connects to a standard I2C bus and adds an additional 8 output ports. A total of 8 LCD displays can be connected to the same two wire I2C bus with each board having a different address.




Simple FM Transmitter
Posted on Friday, September 13, 2013   •   Category: FM Transmitters

Simple FM Transmitter

This FM transmitter is about the simplest and most basic FM transmitter it is possible to build and have a useful transmitting range. It is surprisingly powerful despite its small component count and 3V operating voltage. It will easily penetrate over three floors of an apartment building and go over 300 meters in the open air. The circuit we use is based on a proven Australian design. It may be tuned anywhere in the FM band. Or it may be tuned outside the commercial M band for greater privacy. (Of course this means you must modify your FM radio to be able to receive the transmission or have a broad-band FM receiver.) The output power of this FM Tx is below the legal limits of many countries (eg, USA and Australia). However, some countries may ban ALL wireless transmissions without a license. It is the responsibility of the builder to check the legal requirements for the operation of this circuit and to obey them.




Portable FM Transmitter
Posted on Sunday, September 1, 2013   •   Category: FM Transmitters

Portable FM Transmitter

This portable FM Transmitter is easy to build. I have used a pair of BC548 transistors in this circuit. Although not strictly RF transistors, they still give good range. Transmitter is powered by 9V battery. The coil L1 consists of 7 turns on a quarter inch plastic former with a tuning slug. The tuning slug is adjusted to tune the transmitter. Actual range on my prototype tuned from 70MHz to around 120MHz. The aerial is a few inches of wire. Lengths of antenna wire should be 1 - 2 feet. The circuit is basically a radio frequency (RF) oscillator that operates around 70-120 MHz. Audio from audio jack is fed into the audio amplifier stage built around the first transistor. Output from the collector is fed into the base of the second transistor where it modulates the resonant frequency of the tank circuit by varying the junction capacitance of the transistor. Junction capacitance is a function of the potential difference applied to the base of the transistor. The tank circuit is connected in a Colpitts oscillator circuit.




4 Transistor FM Transmitter
Posted on Friday, July 19, 2013   •   Category: FM Transmitters

4 Transistor FM Transmitter

This circuit provides an FM modulated signal with an output power of around 500mW. The input microphone pre-amp is built around a couple of 2N3904 transistors (Q1/Q2), and audio gain is limited by the 5k preset trim potentiometer. The oscillator is a colpitt stage, frequency of oscillation governed by the tank circuit made from two 5pF ceramic capacitors and the L2 inductor. The output stage operates as a 'Class D' amplifier, no direct bias is applied but the RF signal developed across the 3.9uH inductor is sufficient to drive this stage. The emitter resistor and 1k base resistor prevent instability and thermal runaway in this stage.




Low Power FM Transmitter
Posted on Sunday, May 19, 2013   •   Category: FM Transmitters

Low Power FM Transmitter

This low power fm transmitter is designed to use an input from another sound source and transmits on the commercial FM band. This low power fm radio transmitter it is actually quite powerful. The first stage is the oscillator, and is tuned with the variable capacitor. Select an unused frequency, and carefully adjust C3 until the background noise is removed.




FM Broadcast Receiver
Posted on Wednesday, May 15, 2013   •   Category: FM Radio / Receivers

FM Broadcast Receiver

Here's a portable FM broadcast radio receiver for reception of FM broadcast band based around FET transistor. The topology is a classic grounded-gate FET VHF Hartley oscillator. The drain resonator inductance is centre-tapped with feedback to the source through a small capacitance. By tapping down towards the cold-end of the coil the feedback isn't as critical as your usual source-drain capacitor feedback and it tends to be far less difficult to get to work across a broad range of frequencies. The RFC to an RC source circuit to implement self-quenching is very traditional for super-regenerative detectors. The quench gets frequency-modulated somewhat by the drain current, so it varies with signal strength and the recovered modulation, this is typical for self-quenched circuits.




Building Simple FM Transmitter
Posted on Saturday, May 11, 2013   •   Category: FM Transmitters

Building Simple FM Transmitter

This article shows you how to build a very simple FM transmitter from thirteen components, a Printed Circuit Board (PCB) and a 9v battery. This project was designed to be mounted on a PCB, however you don’t have to. You could construct the project on Vero board (strip board) or any other 0.1” pitch style of project board. If you just want to experiment with this circuit, you don’t even need a board; you can just solder the component s together and let the completed project just rest on the work top. No matter which style you choose, try to keep all component leads nice and short. You could also make the PCB much smaller than the one shown here which is approx. 3 cm square. This is a good size to keep the unit small but nicer to work on for beginners. If you wanted to make one really small, you could use all SMT parts.




Park Assist Circuit
Posted on Thursday, May 9, 2013   •   Category: Sensors

Park Assist Circuit

Park Assist circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when approaching too close to the wall. All distances mentioned before can vary, depending on infra-red transmitting and receiving LEDs used and are mostly affected by the color of the reflecting surface. Black surfaces lower greatly the device sensitivity. Obviously, you can use this circuit in other applications like liquids level detection, proximity devices etc.




ESR Meter / Transistor Tester
Posted on Monday, May 6, 2013   •   Category: Test and Measurement

ESR Meter / Transistor Tester

ESR Meter is an irreplaceable tool for troubleshooting and repairing electronic equipment by determining performance and health of electrolytic capacitors. Unlike other ESR Meters that only measure ESR value this one measures capacitor's ESR value as well as its capacitance all at the same time. Additionally, ESR Meter also tests and identifies PINs of all transistors such as Bipolar (NPN, PNP), FETs, MOSFETs (N-Channel, P-Channel, enhancement-mode and depletion-mode MOSFETs), Thyristors, SCRs and Triacs. Tests and identifies PINs and voltage of diodes, dual diodes, varicap diodes (and their capacity), zener diodes (test voltage up to 5V) and LEDs. It measures resistance of resistors, power resistors, coils starting from just 0.1Ω up to 20MΩ.




IR Remote Control Extender
Posted on Thursday, May 2, 2013   •   Category: Remote Control

IR Remote Control Extender

If you want control the DVD or TV/AV system that located in your living room via the remote control when you sleeping in your Bedroom. this IR extender will achieve this for you. Basically, it works as a repeater that moves the IR signal to a different location. This is an improved IR remote control extender circuit. It has high noise immunity, is resistant to ambient and reflected light and has an increased range from remote control to the extender circuit of about 7 meters. It should work with any domestic apparatus that use 36-38kHz for the IR carrier frequency.




Repairing Switching Power Supply
Posted on Friday, April 26, 2013   •   Category: Power Supplies

Repairing Switching Power Supply

Modern power supplies are known as "switching regulator power supplies." In most switching supplies, the 110 volt AC input is first rectified by two diodes and filtered by a pair of capacitors. This creates two high- voltage sources; one positive and the other negative. A pair of transistors is then used to switch these high voltage supplies across the primary winding of a transformer. This switching action is very fast. A typical switching speed is around 40,000 cycles per second or 40KHz. An integrated circuit is commonly used to control the transistors. This IC not only controls the speed at which the transistors are switched, but also controls the amount of time that each transistor is energized. The output voltage of the power supply is determined by the "on" time of the transistors. If the transistors are keep on for a longer period of time, the output voltage of the supply will rise, while shorter times lower the output voltage. This is known as "pulse-width modulation."




1000W AC Motor Speed Controller
Posted on Sunday, April 21, 2013   •   Category: Motor Controllers

1000W AC Motor Speed Controller

This triac based AC motor speed controller circuit is designed for controlling the speed of AC motors like drill machines, fans, vacuums, etc. The speed of the motor can be controlled by changing the setting of P1 potentiometer. The setting of P1 determines the phase of the trigger pulse that fires the triac. The circuit incorporates a self-stabilizing technique that maintains the speed of the motor even when it is loaded.




1W Long Range FM Transmitter
Posted on Tuesday, April 16, 2013   •   Category: FM Transmitters

1W Long Range FM Transmitter

Long range, very stable, harmonic free, FM transmitter circuit which can be used for FM frequencies between 88 and 108 MHz. With good antenna transmitter can cover 5km range. It has a very stable oscillator because it uses LM7809 voltage regulator which is a 9V stabilized power supply for T1 transistor. Frequency adjustment is achieved by using the 10K linear potentiometer. The output power of this long range RF transmitter is around 1W but can be higher if you use transistors like KT920A, BLX65, BLY81, 2N3553, 2SC1970 or 2SC1971.




40 Watt FM Transmitter Amplifier
Posted on Friday, April 12, 2013   •   Category: FM Transmitters

40 Watt FM Transmitter Amplifier

Building two stage 40 Watt FM Transmitter Amplifier. RF input power should be between 0.5 and 1 watt. Amplifier is powered by 28V power supply. The diagram shows a 2N3375 driving a 2N5643 but there are many other transistors that will work. I used these two transistors just because they were cheap at the time. If any of the variable capacitors are at full capacitance you can pad them out with a fixed ceramic capacitor of suitable value. Extra capacitance also might be needed on the base of the transistors (i had to add 3 100pF capacitors on the base of the 2N5643). The transistors are bolted to a piece of right angle aluminum which is fixed to the metal chassis to dissipate heat effectively.




XR2206 Function Generator
Posted on Thursday, April 4, 2013   •   Category: Frequency Wave Generators

XR2206  Function Generator

Presented here is XR2206 function generator with multiple waveform selection and a frequency readout display. The diagram on the right shows the internal workings of the XR2206 in the form of a block diagram. Essentially the chip contains A VCO (voltage controller oscillator), wave shaper and buffer. The XR2206 frequency generator diagram frequency of the VCO is set with a capacitor and a resistor. The capacitor sets the frequency range whilst a variable resistor can be used to vary the frequency in the set range. The frequency is defined by ƒ = 1/(RC). For a starting point for the design of the frequency generator I used the test circuit from the XR2206 datasheet. I built this on bread board and experimented with the timing resistor and capacitor and managed to get the frequency up to 4MHz.




150W FM Transmitter Amplifier
Posted on Saturday, March 30, 2013   •   Category: FM Transmitters

150W FM Transmitter Amplifier

This is 150W FM transmitter amplifier for 88-108MHz band. The amplifier has two stages using BLF244 mosfet transistor for the first stage which requires 0.5 - 1Watt of RF input to get about 20watts to drive the final stage SD1407 which can push nearly 200 Watts on this design. This design is more or less broadband however I added two variable capacitors after each stage for optimum matching and power output. Make sure the trimmer and the capacitors after the final stage SD1407 are a high voltage types with at least 200V rating. The power on this amplifier can be varied by adjusting the bias voltage using the white pot to the BLF244 mosfet. I added a zener diode onto the bias supply to protect the transistor from too much bias voltage.




LM317 Adjustable Power Supply
Posted on Sunday, March 24, 2013   •   Category: Power Supplies

LM317 Adjustable Power Supply

Here's how to build your own adjustable power supply based on LM317. The IC LM317 is so versatile that an almost unlimited number of different, small, high grade power supply circuits can be built using it. The configurations can be introduced for different applications for upgrading an existing unit with features that would virtually make it indestructible. A few useful application circuits using IC LM317, collected from National Semiconductor's PDF datasheet are meticulously explained in this section with the help of the relevant circuit diagrams. All the circuits discussed below require an unregulated input voltage (max. 35 Volts) from any standard transformer/bridge/capacitor network.




How to Make FM Transmitter
Posted on Wednesday, March 20, 2013   •   Category: FM Transmitters

How to Make FM Transmitter

This tutorial is for making simplest FM transmitter using only one transistor. VC1 is a small, screw-adjustable, trimmer capacitor and its rating should be around 10-100pF. Set your FM receiver for a clear, blank station. Then, with a non-conductive tool, adjust the capacitor for the clearest reception, rotate it till the receiver receives a sound from the microphone of transmitter. Use the following formula for determining the frequency.




VHF FM Aircraft Receiver
Posted on Friday, March 15, 2013   •   Category: AM Radio

VHF FM Aircraft Receiver

VHF FM Aircraft Receiver is a superregenative receiver developed for listening to FM transmitters but also tunes the aircraft band and the top portion of the FM broadcast band. Receives both AM and FM (107mHz to 135 MHz). You can use this receiver with the any FM transmitter. The receiver is amazingly simple using only one transistor for the receiver section and one IC for the audio section. This circuit is a self-quenching regenerative RF receiver also known as a superregenerative receiver. A superregenerative receiver performs two basic functions. First it feeds back a portion of the received signal from it’s output in phase to its input; and second a super audible quenching oscillator drives the amplifier through the point of oscillation and maximum sensitivity and then quenches the oscillation repeatedly. This keeps the feedback from driving the circuit into self-oscillation and allows the signal to be regenerated over and over again. In this version of the circuit, both functions are performed by the circuitry associated with Q1. The rest of the circuit, shown to the right of L3 in the schematic, comprise the audio amplification circuit and are centered on the LM386 Audio Amp IC. In this configuration the LM386 is set at a gain of 200 and feeds it’s output to a standard 1/8-inch diameter stereo phone jack. The audio can then be heard by plugging any standard stereo headset into the jack.




Simple Coil Less FM Transmitter
Posted on Monday, February 25, 2013   •   Category: FM Transmitters

Simple Coil Less FM Transmitter

For months I’ve been looking for a simple FM BUG project, the ones online require inductors which you either have to acquire or build, if you don’t have a LCR meter it becomes rather hard to get the circuit working, specially if you’re a beginner without an oscilloscope! – Sometimes they don’t even tell you which inductance is required and you have to calculate an estimate, which is the main reason why many high frequency RF projects fail in the first place. This circuit on the other hand performs pretty well, even if you’re manipulating the board or touching the coax it will stay within the tuned frequency (unless you touch the transistor or timing capacitor!).




3V FM Transmitter
Posted on Saturday, February 16, 2013   •   Category: FM Transmitters

3V FM Transmitter

The objective of this 3V FM Transmitter design is to provide a simple low-power transmitter solution for broadcasting audio from various audio sources. This transmitter transmits audio using small sensitive microphone. Transmitter's frequency, as built is tunable via 15pF trimmer to the desired frequency, and the coil is embedded on the circuit board. This implementation is adapted to rebroadcast the output of a CD player, television receiver, or radio receiver. I use this transmitter so that I can move about the house and listen to my favorite programs without disturbing others. Within and the house, I find that I can get 50 to 100 meters away from the transmitter with the small pocket FM receiver I carry in my shirt pocket.




500mW Broadcast FM Transmitter
Posted on Sunday, February 10, 2013   •   Category: FM Transmitters

500mW Broadcast FM Transmitter

This little broadcast FM transmitter has 500mW of RF output power and runs of 12-15V battery or power supply. DC whose signal modulated by FM using four transistors. Transmitter includes four transmitter stages and draws around 100-150mA of current. Using the values of the circuit components, the frequency will be around 100 MHz but can be changed via coil. Through the 5 pF capacitor and 10K ohm resistor, the modulation of audio signal is supplied to the tank circuit. The amount of modulation is being managed by the 1N4002, a general purpose rectifier diode. FM Transmitter's output stage is functioning as a class D amplifier where the output transistors act as a switch.




Function Generator using XR2206
Posted on Tuesday, January 29, 2013   •   Category: Test and Measurement

Function Generator using XR2206

This is high quality function generator system using the XR2206 chip. Waveform function generator capable of producing AM/FM modulated sine wave outputs find a wide range of applications in electrical measurement and laboratory instrumentation. This application note describes the design, construction and the performance of such a complete function generator system suitable for laboratory usage or hobbyist applications. The entire function generator is comprised of a single XR2206 monolithic IC and a limited number of passive circuit components. It provides the engineer, student, or hobbyist with highly versatile laboratory instrument for waveform generation at a very small fraction of the cost of conventional function generators available today.




1.2-36V 5A Adjustable Power Supply with LM317
Posted on Thursday, January 24, 2013   •   Category: Power Supplies

1.2-36V 5A Adjustable Power Supply with LM317

This is very simple 1.2 - 36V adjustable bench power supply with 5A of output current. Max input voltage is 37V and output is adjustable via potentiometer between 1.2 up to 36 volts. TIP147 PNP darlington transistor boosts the current of LM317 from 100mA to 5A. LM317 is the most useful and inexpensive adjustable regulator and for this circuit you can also use LM317L that can give 100mA, that's enough for transistor bias. D1 and D2 are protection diodes because when you turn the circuit off the output capacitors are discharging and can damage the transistor or regulator. 100nf capacitors are in parallel with electrolytic capacitors to remove high frequency noise because large value electrolytic have large ESR and ESL and can't remove high frequency noise.




Solar Powered Long Range FM Transmitter
Posted on Wednesday, January 16, 2013   •   Category: FM Transmitters

Solar Powered Long Range FM Transmitter

There are many miniature FM transmitter bug circuits online, this one is unique in that it runs completely on solar power. No battery is required. As long as the sun is shining on the PV panel, the transmitter will transmit. The transmitter bug is useful as a "remote ear", and can be used for anything from listening birds to surveillance work. The mic preamp and oscillator circuits were borrowed from a common circuit found around the Internet, a regulated solar power supply and an RF amp that extends the range of transmitter and improves frequency stability were added.




12V Dual Power Supply
Posted on Sunday, January 6, 2013   •   Category: Power Supplies

12V Dual Power Supply

12V dual power supply has symmetrical voltage output +12V and -12V with limited current to 100mA. It has been built to power three OPA627 opamps of Audio DAC I am building with PCM1792 & PCM1794 chips. Circuit has on the primary side only fuse. I couldn't find smaller than 50mA. We can connect power cord directly to the X1 connector or via power switch on the chassis. On the secondary side of transformer are connected two fuses 100mA and after them is bridge rectifier. For filtering of rectified voltage there are C1 and C2. Next are positive and negative voltage regulators 78L12 and 79L12 with decoupling capacitors C3 to C6 close to regulators. Next are small filter capacitors and also signaling LEDs connected via resistors. Output voltages are connected to 3 pin connector. For signaling of presence of voltage is enough only one LED. We can also use 2 pin connectors for LED connecting.




Mini FM Broadcast Transmitter
Posted on Sunday, December 23, 2012   •   Category: FM Transmitters

Mini FM Broadcast Transmitter

Build your own simple mini FM transmitter. This fun project will show you how to build a mini broadcasting transmitter that can transmit an audio signal up to a quarter mile to any FM receiver. It's easy to build and a good learning experience. It serves as a hands-on learning tool for students or anybody interested in electronics. Having a range of up to a quarter mile, it's great for a house security system, baby monitoring device or simply a listening gadget that you can place anywhere!




2km Long Range FM Transmitter
Posted on Tuesday, December 4, 2012   •   Category: FM Transmitters

2km Long Range FM Transmitter

The power output of many transmitter circuits are very low because no power amplifier stages are incorporated. The transmitter circuit described here has an extra RF power amplifier stage using 2N3866 RF power transistor after the oscillator stage to increase output power to 250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometers. Transmitter's oscillator is built around BF494 transistor T1. It is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to tune the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. 2N3866 transistor T2 forms a VHF-class A power amplifier. It boosts the oscillator signal power four to five times. Thus 250mW of power is generated at the collector of transistor T2.




30V Volt Meter with PIC16F676
Posted on Friday, November 30, 2012   •   Category: Test and Measurement

30V Volt Meter with PIC16F676

This is a simple 30V volt meter using PIC16F676 micro controller with 10-bit ADC (analog to digital converter) and three 7 segment LED displays. You can use this circuit to measure up to 30V DC. The possible applications are on bench power supply or as a digital panel meter in various systems. PIC16F676 is the heart and brain of this circuit. The internal adc of the mcu with a resistor network voltage divider is used to measure the input voltage. Then 3 digits of comm anode 7 segment display is used to display final converted voltage. As you can see in the schematic the displays are multiplexed with each other. It means we switch on one display and put the corresponding digit on this while other two displays are off this cycle goes for each of the displays.




Micro Transmitter Bug
Posted on Sunday, November 18, 2012   •   Category: FM Transmitters

Micro Transmitter Bug

Presented FM transmitter bug is built using BF414 / BF324 / BF606 transistor. The 30cm antenna has a range of about 30m in the building, more in the open field. Power supply 2x AAA batteries have been used with voltage of 2.75 V. I added resistor 10K in parallel with 1.5pF capacitor so that the system works well when connected to an external source (mp3 player / computer). On the computer I had to reduce sound to about 35% of capacity, so that I do not have clipping. I managed to improve transmitter stability with simple shielding. The coil is 5 turns of enameled copper wire wound on 1 mm ø = 5 mm.




How Do Lead Acid Batteries Work
Posted on Wednesday, November 7, 2012   •   Category: Battery Chargers

How Do Lead Acid Batteries Work

Lead Acid batteries have changed little since the 1880's although improvements in materials and manufacturing methods continue to bring improvements in energy density, life and reliability. All lead acid batteries consist of flat lead plates immersed in a pool of electrolyte. Regular water addition is required for most types of lead acid batteries although low-maintenance types come with excess electrolyte calculated to compensate for water loss during a normal lifetime. Lead acid batteries used in the RV and Marine Industries usually consist of two 6-volt batteries in series, or a single 12-volt battery. These batteries are constructed of several single cells connected in series each cell produces approximately 2.1 volts. A six-volt battery has three single cells, which when fully charged produce an output voltage of 6.3 volts. A twelve-volt battery has six single cells in series producing a fully charged output voltage of 12.6 volts.




BA1404 Transmitter with UPC1651RF Amplifier
Posted on Friday, October 26, 2012   •   Category: FM Transmitters

BA1404 Transmitter with UPC1651RF Amplifier

BA1404 transmitter includes onboard RF amplifier for increased transmitting range. Operating voltage range is 1-3V, the circuit contains FM stereo mixer, 38KHZ oscillator, FM modulator and high-frequency amplifier monolithic integrated circuit. As the "electronic newspaper" BBS there are many users requiring detailed information on the FM stereo transmitter, so I re-collect the relevant information on the simple discrete, merge, integrated FM stereo transmitter experiment, that BA1404 with μpc1651 mix of the most easy to make and debug, and very high frequency stability (relative to the previous circuit BA1404), transmission power is increased by UPC1651RF amplifier.




Simple EMF Probe
Posted on Tuesday, October 16, 2012   •   Category: Test and Measurement

Simple EMF Probe

There's something fascinating about electromagnetic fields. Thanks to the modern world and the prevalence of electronics and electricity, they're all around us these days. But because of the extremely limited array of senses that we humans have, we spend most of the time completely oblivious of them. Wouldn't it be cool to make something simple that could not just detect them, but would allow you look at the waveforms on an oscilloscope. An EMF probe in other words.




Stereo FM Transmitter Using BA1404
Posted on Sunday, October 7, 2012   •   Category: FM Transmitters

Stereo FM Transmitter Using BA1404

A high quality stereo FM transmitter circuit is shown here. The circuit is based on the IC BA1404 from ROHM Semiconductors. BA1404 is a monolithic FM stereo modulator that has built in stereo modulator, FM modulator, RF amplifier circuitry. BA1404 FM transmitter can be operated from 76 to 108MHz and power supply for the circuit can be anything between 1.25 to 3 volts.




VHF FM Antenna Booster
Posted on Tuesday, October 2, 2012   •   Category: Antennas

VHF FM Antenna Booster

Together with a good directional antenna this high performance two-stage antenna amplifier for the VHF FM broadcast band will enable you to receive distant radio stations. VHF FM Antenna booster will also drastically improve reception of FM signals you’ve come to accept as marginal and noisy in your area. Antenna booster is also great for extending transmission range of low power VHF / FM transmitters.




USB FM Transmitter
Posted on Sunday, September 16, 2012   •   Category: FM Transmitters

USB FM Transmitter

Here is a simple USB FM transmitter that could be used to play audio files from an MP3 player or computer on a standard VHF FM radio by connecting it to an USB port. The circuit use no coils that have to be wound. This USB transmitter can be used to listen to your own music throughout your home. To keep the fm transmitter circuit simple as well as compact, it was decided to use a chip made by Maxim Integrated Products, the MAX2606. This IC from the MAX2605-MAX2609 series has been specifically designed for low-noise RF applications with a fixed frequency. The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit. The variable-capacitance (varicap) diode and feedback capacitors for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency.




Sensitive FM Transmitter Bug
Posted on Monday, August 20, 2012   •   Category: FM Transmitters

Sensitive FM Transmitter Bug

This easy to build FM transmitter bug can transmit voice to exceptionally good range. Tune trimmer to hear the signal to your near radio. Transmitter frequency range is 88-108 MHz. Max current consumption is 30mA. You can power the fm transmitter bug with a 9Volt Battery, or you can plug a power supply to feed in 9-12 Volts. That bug will pick even a low whisper or even the sound of a breath well far from the microphone. Great spy transmitter equipment.




6 Watt FM Transmitter Amplifier
Posted on Saturday, June 23, 2012   •   Category: FM Transmitters

6 Watt FM Transmitter Amplifier

After building FM transmitter I decided to build a 6W RF Transmitter amplifier for the FM band to get more power and we chose to copy a 6 Watt design built around 2SC1971 RF power transistor. We were not satisfied with finished result and decided to replace the fixed capacitors around the pcb inductors with variable capacitors, this is much better and possible to tune to your transmitter frequency.




Wideband DTV UHF Antenna TV Amplifier
Posted on Friday, June 15, 2012   •   Category: Antennas

Wideband DTV UHF Antenna TV Amplifier

This HD TV UHF wideband amplifier(Ultra High Frequency amplifier) has a total gain of 10 to 15 dB in the 400 – 850 MHz domain frequency so it can be used where the tv signal is weak. For this UHF antenna tv amplifier to work correctly you need to cut the components pins as short as possible. C1, C2, C6, C7 are SMD type ( surface mounted ). This antenna tv amplifier or uhf wideband amplifier need to be build inside of a metal box and then connected close to the tv antenna.




KT88 Tube Power Amplifier Class A
Posted on Sunday, June 10, 2012   •   Category: Amplifiers

KT88 Tube Power Amplifier Class A

Single Ended Valve Triode Amplifier has not same tone with Push Psu Amplifier. Over 90% of Amplifiers are push pull, and push pull amplifier does not 2nd harmonic and off course does not get 2nd 4th, 6th harmonic vs SE has 2nd, 4th, 6th harmonic. Push pull has minor distortion than SE Amplifier.2nd harmonic is make good tone for Music.not too much and not less than.feel good sound get from Single Ended Amplifiers with high efficiency speakers from 88dB/m to 100dB/m. I means Single Ended Amplifier is almost Single Ended Triode Amplifier.or Penthode but wired Triode. Tone is Different.good for Jazz and small room Classic.




1 Watt QRP Power Transmitter
Posted on Friday, June 8, 2012   •   Category: FM Transmitters

1 Watt QRP Power Transmitter

The 1 watt 20 meter QRP transmitter with VXO. This is a nice QRP transmitter that can be used in combination of one of the simple receivers. Normally these designs have only two transistors: one is the X-tal oscillator and the second the final amplifier. A good example is my first QRP rig that is also described somewhere on this site. Here the VXO (Variabele X-tal Oscillator) has a tuning range of 16 kHz. This VXO is buffered with an extra driver stage for a better frequency stability and a varicap diode is used instead of a variabele capacitor. An extra transistor is added for keying the transmitter with a low keying current. What you can do with such a simple 1 watt QRP power transmitter. This is a real low power transmitter, so do not expect that you can do everything with it but... When conditions are normal, you can easily make many QSO's during one afternoon with stations with distances upto 2000 km with a simple inverted V wire dipole antenna! From Europe, I did even make QSO's across the Ocean!




500mW PLL FM Transmitter 88-108MHz
Posted on Tuesday, May 29, 2012   •   Category: FM Transmitters

500mW PLL FM Transmitter 88-108MHz

This PLL transmitter is controlled and the frequency is very stable and can be programmed digitally. Transmitter will work 88-108 MHz and output power up to 500mW. With a small change can set the frequency of 50-150 MHz. The output power is often set to several watts with transistors. So therefore I decided to build a simple transmitter with great performances. The frequency of this transmitter can easily be changed by software and space / compress air coil. This transmitter is the oscillator colpitts. Oscillator is a VCO (voltage controlled oscillator) which is set by the PLL circuit and PIC micro controller. This oscillator is called the Colpitts oscillator and voltage controlled to achieve the FM (frequency modulation) and PLL control.




Wideband RF Field Strength Meter
Posted on Wednesday, May 23, 2012   •   Category: Test and Measurement

Wideband RF Field Strength Meter

Field strength meter is extremely useful when working with RF devices. It can be used to quickly diagnose whether a transmitter circuit is working, and can be used to detect RF signals in the environment. The simplest field strength meter could be built with a tuned LC circuit and a germanium diode, just like the way of a building a crystal radio except replacing the ear piece with a high sensitivity current meter. While this approach fits the needs of most simple applications, it has a pretty narrow frequency range (~100 MHz) and requires tuning the LC circuit to the correct frequency before measurements can be made and the design can become complicated if wider frequency range tuning is desired.




50V Bench Power Supply
Posted on Monday, May 21, 2012   •   Category: Power Supplies

50V Bench Power Supply

An 50v bench power supply can be made using electronic diagram below which is designed using LM10 op amp and 2n3055 transistors. This LM10 2n3055 50v bench power supply allows an output voltage regulation in a range between 0 and 50 volts and the output current can be limited to a maximum of 2A. Output voltage increases linearly with the amount of resistance potentiometer P1, while the current can be adjusted linear using potentiometer P3. Potentiometer P2 serves to regulate maximum output current (maximum value is 2A).




Class-A Mosfet Headphone Amplifier
Posted on Wednesday, May 16, 2012   •   Category: Amplifiers

Class-A Mosfet Headphone Amplifier

Not thrilled with how a computer soundcard drove my 32ohm headphones so I decided to build myself class-A mosfet headphone amplifier. As with most of my projects, the goal was to keep it simple, keep cost down and try use some salvaged parts. This is a simple do-it-yourself (DIY) headphone amplifier project that is fashioned primarily after the Class A MOSFET Headphone Driver project by Greg Szekeres and to some extent Mark's DIY Class A 2SK1058 MOSFET Amplifier Project. The amplifier concept is simple and follows a typical single-ended class A circuit utilizing an active constant current source (CCS) in place of a passive resistor. A CCS doubles the efficiency of the circuit over that where a passive load resistor is used, bringing it to a maximum of 25%.




1.5V - 30V 1.5A LM317 Variable Power Supply
Posted on Sunday, May 13, 2012   •   Category: Power Supplies

1.5V - 30V 1.5A LM317 Variable Power Supply

This is a basic universal variable Power Supply voltage regulator circuit using an LM317, 3-terminal regulator in a TO-220package. The Universal Power Supply output voltage can be set to anywhere in the range 1.5V to 30V by selecting two resistances. By using a potentiometer, R2, as one of the resistors you can dial up the output voltage wanted. Either AC or DC input can be supplied to the PCB via a socket or terminal block. Connection can be either way around. This is because we have provided a bridge rectifier on board. The input DC voltage to the regulator must be at least 2.5V above the required output voltage. An off/on switch is provided. For many applications (say 12V at 60mA) a heat sink will not be necessary. The LM317 will provide slightly higher output voltages than 30 volts. However, for most hobbyists over 30V will not be needed. So to make a small PCB we have used some electrolytic capacitors rated to 35 volts. To be safe for continuous operation the maximun input DC voltage to the regulator should not be over 33V. With a 2.5V to 3.0V drop across the regulator this will give a regulated output of 30V. You can draw up to 1.5A from the LM317. If you need higher then use an LM338T rated to 5A.




12AU7 Tube Preamplifier
Posted on Tuesday, May 8, 2012   •   Category: Amplifiers

12AU7 Tube Preamplifier

I'm not sure what motivated me to decide on building a high-gain tube preamp of this sort. Maybe it was the tube computer sound card idea I have seen, or the fact that I have enough junk to fill a dump truck. What ever it was, it all started with a cute little plastic Hammond enclosure that had been on my shelf for a couple of years. I originally thought I might use it for a tube headphone amp, but in the end realized there would not be enough space for the three tubes needed to make a head amp. This is a high gain preamplifier that is suitable for use where a lot of gain is required - to drive a power amplifier that needs plenty of gain or perhaps for use with instruments, like a guitar or microphone. If you need less gain, take a look at the RCA 12AU7 / ECC82 Cathode Follower Tube Preamp Schematic which has a gain of about 8.




3 Watt FM Transmitter
Posted on Wednesday, May 2, 2012   •   Category: FM Transmitters

3 Watt FM Transmitter

This is the schematic for an FM transmitter with 3 to 3.5 W output power that can be used between 90 and 110 MHz. Stability of this transmitter is not bad and PLL circuit can be added on. This is a circuit that I've build a few years ago for a friend, who used it in combination with the BLY88 amplifier to obtain 20 W output power. From the notes that I made at the original schematic, it worked fine with a SWR of 1 : 1.05 (quite normal at my place with my antenna).




Class-A 12AU7 Tube Headphone Amplifier
Posted on Friday, April 27, 2012   •   Category: Headphone Amplifiers

Class-A 12AU7 Tube Headphone Amplifier

This is simple to build audiophile class-A tube headphone amplifier. It is based around 12AU7 / ECC82 audiophile vacuum tube that provides warm, rich and smooth sound expected from audiophile amplifiers. The 12AU7 (ECC82) is a Twin Triode vacuum tube, it is very popular in the audio world because it is rather rugged and can be operated at lower voltages. Headphone amplifier and 12AU7 tube is powered by just 12V DC voltage. This is great news for those new to vacuum tubes that want experience and learn more about them. Typically vacuum tubes operate at high and dangerous voltages so you must have some experience and know what you are doing. On the other hand this headphone amplifier operates at low 12V voltage so it is safe to build and experiment.




Hybrid Headphone Amplifier
Posted on Monday, April 16, 2012   •   Category: Headphone Amplifiers

Hybrid Headphone Amplifier

Simple Hybrid Headphone Amplifier DIY Audio Project. Rogers has put together a very simple hybrid headphone amplifier. The head amp uses a 12AU7/ECC82 vacuum tube for voltage gain stage and a IRF612 MOSFET follower biased in Class A with a passive CCS. What is nice about the project is that both the tube and MOSFET operate off of a 24V external switch mode power supply. Read on for more details about 12AU7 Tube / IRF610 MOSFET Hybrid Headphone Amplifier.




Portable Headphone Amplifier
Posted on Sunday, April 15, 2012   •   Category: Headphone Amplifiers

Portable Headphone Amplifier

Portable Headphone Amplifier powered by just 3 Volts. Notes: * Can be directly connected to CD players, tuners and tape recorders. * Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohm. * Schematic shows left channel only. * B1, SW1, J1 & C3 are common to both channels. * R3 value was calculated for headphone impedance up to 300 Ohm. Using 600 Ohm loads or higher, change R3 value to 100K.




Class-A Push-Pull Tube Power Amplifier
Posted on Tuesday, April 10, 2012   •   Category: Amplifiers

Class-A Push-Pull Tube Power Amplifier

This Class-A Push-Pull Tube Power Amplifier uses a Pair of Push-Pull Class A, Ultra Linear Mono Block Tube Amplifiers that can be used with several different vacuum tubes including KT77 / 6L6GC / KT88 with a 12SL7 driver and 6NO30 tubes. The amplifier stage is based on the Compact Hi-Fi Power Amplifier. One thing about DIY audio is that it is a journey, not a destination, it never ends. One project leads to another. The only limits are time and money. DIY audio is a lot about perfection. While I was quite happy with my previous tube amplifier projects, I felt there was room to improve (here comes the journey again). I like to be involved in the music. If anything sticks out, it will degrade the experience. So I tend to like smooth response, lots of detail, wide soundstage and full spectrum of sound. These amps deliver all that in quantity. Regardless of what tubes I used for outputs, the sound is "silky" and refined.




200mW FM Broadcast Transmitter
Posted on Sunday, April 1, 2012   •   Category: FM Transmitters

200mW FM Broadcast Transmitter

A simple 200mW FM Transmitter circuit which covers frequencies from 88 to 108 MHz. It is built with 3 transistors: BC109, BFR91A and BFR96S. It is quite stable and the output power is around 200mW. The first stage of transmitter is a mic amplifier but if you connect this radio transmitter directly to an audio source you can remove this stage and connect the audio signal to R5. U1, 1PH51C can be replaced with LM7805. You must use a stabilized power source for oscillator stage to prevent frequency variation. You can remove C7 and use a linear potentiometer instead of R6 with the median connector to C4, one pin to ground and the other one to +. FM Transmitter uses MV2109 varicap diode and C7 for frequency tuning.




General Purpose 2 Watt Stereo Power Amplifier
Posted on Saturday, March 31, 2012   •   Category: Amplifiers

General Purpose 2 Watt Stereo Power Amplifier

A general purpose audio power amplifier is a must have for the electronics amateur. It's not a good thing to use your HiFi set for an experiment, when there's a risk of blowing it's transistor out. Amplifier for your experiments should be simple in construction, durable, and easy to repair. Also a portable, low power consumption and battery powered. Taking the considerations above, I gave you the PCB design for the TBA820M based amplifier. It is rated for 2Watts of RMS power output (16W PMPO) but gives even two times more if you cool it well by some tricks. I've been using this circuit for over ten years and personally still surprised by it's durability, thinking of how many short circuits and overdrives it is subjected.




Zener Diode Meter 1V to 50V
Posted on Friday, March 23, 2012   •   Category: Test and Measurement

Zener Diode Meter 1V to 50V

Presented here is zener diode meter for testing voltage value of an unknown zener diode. The zener diode or diode voltage regulator is a special diode, Unlike normal diodes these diodes are intended to work in the breakdown voltage and an essential part of the voltage regulator circuits. These components maintain constant voltage at its terminals suffer variations even when substantial current, its connection with reverse bias is normal also to work in the zener voltage of the source Vs must be greater than the rupture Vz, as always condition using a resistance Rs in series to limit current to a value always less than its maximum power.




Coilless FM Transmitter
Posted on Tuesday, March 20, 2012   •   Category: FM Transmitters

Coilless FM Transmitter

The RF oscillator using the inverter N2 and 10.7Mhz ceramic filter is driving the parallel combination of N4 to N6 through N3.Since these inverters are in parallel the output impedance will be low so that it can directly drive an aerial of 1/4th wavelength. Since the output of N4-N6 is square wave there will be a lot of harmonics in it. The 9th harmonics of 10.7Mhz (96.3Mhz) will hence be at the center of the FM band. N1 is working as an audio amplifier. The audio signals from the microphone are amplified and fed to the varicap diode. The signal varies the capacitance of the varicap and hence varies the oscillator frequency which produce Frequency Modulation.




Split Laboratory Power Supply
Posted on Monday, February 20, 2012   •   Category: Power Supplies

Split Laboratory Power Supply

Split power supply provides a stable regulated bipolar voltage in the range ±1.5V to ±17V. It is based on LM317/LM337 linear voltage regulators that also have a short circuit protection. Most parts are easily accessible, including a 6"x3"x2" project box, 12V 1.2A center tap transformer, pots, knobs, etc. Power supply schematic shows how to wire LM317/LM337 to get +/- split voltage output.




1.5V Tracking Transmitter
Posted on Wednesday, February 15, 2012   •   Category: FM Transmitters

1.5V Tracking Transmitter

With this circuit you can build a very small tracking transmitter that can be tracked using a FM broadcast band radio receiver. The transmitter can be powered from any 1.5V volt battery or power supply. Transmitter has a range up to 1 mile depending on battery voltage, height above ground, receiver sensitivity, and antenna length. Under certain conditions distances of 1 mile have been achieved. It is recommended that this transmitter be used with FM radios that can tune continuously across the dial. The better the receiver and receiver antenna system the greater the practical range of the transmitter, however good functionality can be achieved with the least expensive radios and using only the standard telescoping antenna included with most radios.




Portable USB Charger
Posted on Tuesday, February 14, 2012   •   Category: Battery Chargers

Portable USB Charger

Portable USB Charger is a device that will charge things like Ipods, PDAs, that accepts charge from a USB port. It runs off a 9-V battery, and through the simple circuit, out comes a regulated 5-V perfect for a USB port. Portable USB chargers will always be handy, lets face it these days every gadget around us has USB charging capabilities. This is a very basic and simple project, and cheap too. Maybe its time for you to build your own diy portable USB charger.




BH1417 USB FM Transmitter
Posted on Tuesday, February 7, 2012   •   Category: FM Transmitters

BH1417 USB FM Transmitter

Here's BH1417 USB FM Transmitter with built-in PLL circuit. Its low-frequency signal is converted into high-frequency, which can take any audio device with FM radio (stereo, car CD, MP3, DVD player, etc.), as a normal radio station. Transmitter power is sufficient for reliable reception of its signal within a few tens of meters. The basis of the device is a chip BH1417F, included in a typical scheme. This device contains all the necessary circuitry to generate a composite stereo signal c of the pilot tone, the RF generator with PLL and power amplifier. A detailed description is given in.




300mW FM Transmitter
Posted on Wednesday, February 1, 2012   •   Category: FM Transmitters

300mW FM Transmitter

Here's a long range 300mW FM Transmitter for the 88MHz to 108MHz band. This particular TX is of special interest to those wishing to build low power Power Amplifiers for the VHF bands since it used impedance matching, power amplifier and antenna filtering, all of which should be used by radio constructors, whether it be for amateur radio or any other form of radio. The features of this project are: Higher output power - 150mW min (at 9v) and 300mW+ (at 12.5v). Very pure output signal due to careful design and filtering. VARICAP modulation - possibility to add a synthesizer. Single sided Printed Circuit Board, only 40mm x 72mm. Covers the domestic FM band - 88MHz to 108MHz. Easy to build, but coil winding experience IS required




555 LED Pulsing Breathing Circuit
Posted on Tuesday, January 24, 2012   •   Category: LED

555 LED Pulsing Breathing Circuit

Here is a circuit for simulating breathing / pulsing LED with the 555 timer chip. It became very popular and i received many comments and emails with people that made this circuit and worked fine, as well as comments with people that had troubles converting it to operate at 12 volts supply. It was designed to operate with 5 volts, because i plan to use it for a future PC mod. Since the PC power supply has 5 volts output, and since the LEDs that i plan to use require 3.8 volts to operate, choosing 5 volts for supply was the best choice to minimize power dissipation on the transistor.




1.5V FM Broadcast Transmitter
Posted on Tuesday, January 17, 2012   •   Category: FM Transmitters

1.5V FM Broadcast Transmitter

The objective of this 1.5V FM Broadcast Transmitter design is to provide a simple low-power transmitter solution for broadcasting audio from various audio sources. This transmitter accepts stereo input via two 470K resistors. Since there is no audio level control on the input, the audio level out from the source needs to be adjusted. Or, you can just add a 10k as an input level control. Transmitter's frequency, as built is tunable via spreading or compressing the coil to the desired frequency, and the coil can be glued down. If you want to make one that's tunable, it might be easiest to reduce the 18 pf capacitor and put a small trimmer capacitor in parallel with the inductor (across the reduced value capacitor). Voltage variable capacitors would be an nice alternative to a mechanical variable capacitor but they don't offer much tuning range with only a 1.5V power supply.




FM Broadcast Transmitter
Posted on Sunday, January 8, 2012   •   Category: FM Transmitters

FM Broadcast Transmitter

This FM Broadcast Transmitter circuit will transmit a continuous audio tone on the FM broadcast band (88-108 MHz) which could used for remote control or security purposes. Circuit draws about 30 mA from a 6-9 volt battery and can be received to about 100 yards. A 555 timer is used to produce the tone (about 600 Hz) which frequency modulates a Hartley oscillator. A second JFET transistor buffer stage is used to isolate the oscillator from the antenna so that the antenna position and length has less effect on the frequency. Fine frequency adjustment can be made by adjusting the 200 ohm resistor in series with the battery. Oscillator frequency is set by a 5 turn tapped inductor and 13 pF capacitor.




TV Transmitter Circuit
Posted on Wednesday, January 4, 2012   •   Category: TV Transmitters

TV Transmitter Circuit

This is a small TV transmitter circuit which transmits in VHF band, negative sound modulation and PAL video modulation. It is suitable in countries where the B and G system is used.




Capacitance Meter
Posted on Tuesday, January 3, 2012   •   Category: Test and Measurement

Capacitance Meter

RF laboratory often requires capacitance meter for small capacitors in pF range. Such a device can easily be built by yourself. Here, a measurement converter for PC serial port is presented. The frequency of an oscillator is reduced by the target and measured on a PC. The appropriate conversion then allows the direct display of the capacity. The input uses a short and low capacitance probe tip. The opposite pole is clamped to ground cable with a crocodile. The NE555 precision timer receives its operating voltage directly from the serial interface and produces a measurement object without C is a square wave with a frequency of 3.5 kHz. The signal is processed via the CTS input of the interface.




Function Generator XR2206
Posted on Saturday, December 31, 2011   •   Category: Test and Measurement

Function Generator XR2206

For measurement purposes in the electronics laboratory is needed again and again signals of different frequency and waveforms. A common function generator provides sine, for example, triangular and square waves. The frequency must be adjustable and at least cover the low frequency range. The low-cost IC XR2206 provides a very simple function generator with only a few external components. XR2206 data sheet provides complete basic circuit for a simple function generator. It requires an operating voltage of 12 V and delivers sine and square wave signals. Instead of the sine wave output is obtained after opening of S1 a triangular output wave. XR2206 IC contains an internal VCO (Voltage Controlled Oscillator, Voltage Controlled Oscillator) with triangular and rectangular output. The capacitor C and the power to determine the frequency at pin 7. With a pot of 2 megohms and a fixed resistor of 1 kOhm variation gives a ratio of 1 to 2000 and may include a range of 10 Hz to 20 kHz sweep.




Phone Spy Transmitter
Posted on Friday, December 30, 2011   •   Category: FM Transmitters

Phone Spy Transmitter

Here is a very simple telephone broadcaster transmitter which can be used to eavesdrop on a telephone conversation. The circuit can also be used as a wireless telephone amplifier. One important feature of this phone transmitter is that the circuit derives its power directly from the active telephone lines, and thus avoids use of any external battery or other power supplies.




1Watt AM CW Transmitter for 10 Meterband
Posted on Wednesday, December 28, 2011   •   Category: FM Transmitters

1Watt AM CW Transmitter for 10 Meterband

In this project, you will make a simple 3-stage low-power broadcast-type circuit, using a crystal oscillator integrated circuit and an a collector modulated AM oscillator with amplifier. You can connect the circuit to the an electred microphone or amplified dynamic microphone. Using an electred microphone is shown (in gray) in the diagram below. (no amplified dynamic microphone has a to low output voltage to work. at least 100mv is needed). You could also add a LF preamp stage of one transistor to allow connecting a dynamic microphone directly. You'll see that you can receive the signal through the air with almost any AM radio receiver. Although the circuits used in radio stations for AM receiving are far more complicated, this nevertheless gives a basic idea of the concept behind a principle transmitter. Plus it is a lot of fun when you actually have it working! Remember that transmitting on the 10 meter band you'll need a valid radioamateur license!! A wide range of different circuits have been used for AM, but one of the simplest circuits uses collector modulation applied via (for example) a transformer, while it is perfectly possible to create good designs using solid-state electronics as I applied here (T1 BC557). The transmitter is build as a Colpitts Oscillator with a BSX20 transistor. HF-output of the oscillator is approx. 50 mW, depending on the supply voltage of 6 to 15 Volts. This is amplified by the BD135 and brings the power up to approx. 1 watt @ 12volts. The transmit frequency is stabilized with the 28Mhz crystal. A slight detuning of approx 1kc is possible when using a 120pF trimmer capacitor for C8. The oscillator signal is taken from the collector of T2 and guided to the input of T3 which output is lead via an L-filter and low-pass PII filter circuit cleaning up the signal pretty good and ensuring spectral purity. The oscillator is keyed by T1 and the morse key (S). By keying the morse-key T1 is not been used for modulation and is biased, hence lets T2 freely oscillate.




500W 12V to 220V Inverter
Posted on Friday, December 23, 2011   •   Category: AC / DC Innveters

500W 12V to 220V Inverter

This is a 500W DC-to-AC inverter circuit diagram which produces an AC output at line frequency and voltage. 12VDC to 220V 50Hz inverter circuit will power 220V or 110V appliances from 12V car battery. The circuit is easy to make and is low cost. Use proper transformer. The output (in watts) is up to you by selecting different power rating transformer and power transistor rating. If you load electronic device which require 120V AC, then use transformer with 120V in output.




Relay Timer with PIC16F628
Posted on Monday, December 19, 2011   •   Category: PIC

Relay Timer with PIC16F628

Here is 0 to 99 minutes relay timer using PIC16F628 microcontroller and 16 character LCD display. The microcontroller is PIC16F628A running at 4.0 MHz clock using an external crystal. An HD44780 based 16×2 character LCD is the main display unit of the project where you can watch and set the timer duration using tact switch inputs. There are three tact switches connected to RB0 (Start/Stop), RB1 (Unit), and RB2 (Ten) pins. You can select the timer interval from 0-99 min using Unit and Ten minute switches. The Start/Stop switch is for toggling the timer ON and OFF. When the timer gets ON, a logic high signal appears on the RA3 pin, which can be used to switch on a Relay. The circuit diagram of this project is described below.




Mini FM Radio Transmitter
Posted on Thursday, December 15, 2011   •   Category: FM Transmitters

Mini FM Radio Transmitter

This small FM transmitter with a range of about 50 meters designed for hoby. With lots of mini-transmitters then you have a comprehensive, action-packed radio program. Due to the power supply via the USB port of a high frequency stability is achieved. Alternatively, the receiver, a battery 5 to 12 volts to operate.




PIR Motion Detector
Posted on Monday, December 12, 2011   •   Category: Sensors

PIR Motion Detector

Presented schematic shows how to build simple PIR motion detector sensor. PIR sensors allow you to sense motion, almost always used to detect whether a human has moved in or out of the sensors range. They are small, inexpensive, low-power, easy to use and don't wear out. For that reason they are commonly found in appliances and gadgets used in homes or businesses. They are often referred to as PIR, "Passive Infrared", "Pyroelectric", or "IR motion" sensors. PIRs are basically made of a pyroelectric sensor (which you can see above as the round metal can with a rectangular crystal in the center), which can detect levels of infrared radiation. Everything emits some low level radiation, and the hotter something is, the more radiation is emitted. The sensor in a motion detector is actually split in two halves. The reason for that is that we are looking to detect motion (change) not average IR levels. The two halves are wired up so that they cancel each other out. If one half sees more or less IR radiation than the other, the output will swing high or low.




iPod FM Transmitter
Posted on Tuesday, December 6, 2011   •   Category: FM Transmitters

iPod FM Transmitter

Here are instructions for building your own ipod FM radio transmitter. It works quite easy, there is a power switch on the bottom to turn it on and tune your radio and transmitter to the right frequency. For the antenna you can use a copper wire of 70 cm. The range of this FM transmitter is about 100 to 150 meters (500 feet). With R5 you can adjust the input signal and with C6 you can tune your frequency. Transmitter is supplied by 9V battery.




Stereo FM Transmitter with BA1404
Posted on Friday, December 2, 2011   •   Category: FM Transmitters

Stereo FM Transmitter with BA1404

With this Stereo FM Transmitter with BA1404 you will be able to create a mini stereo FM station and broadcast to your entire home, a simple way to have an audio link wireless with ease. With the FM transmitter BA1404 Hifi Stereo you can stream your music from your iPod MP3, satellite receiver, computer, DVD player, Mobile Phone, MP4 player and MP3 and other audio source directly to an FM receiver with crystal clear sound.




150W LM3886 Power Amplifier
Posted on Monday, November 28, 2011   •   Category: Amplifiers

150W LM3886 Power Amplifier

LM3886 power amplifier with 150W audio output power. Three LM3886 amplifiers are bridged together to achieve 150W. Power supply is +/- 30V. LM3886 amplifier maintains an excellent signal-to-noise ratio of greater than 92dB with a typical low noise floor of 2.0µV. It exhibits extremely low THD+N values of 0.03% at the rated output into the rated load over the audio spectrum, and provides excellent linearity with an IMD (SMPTE) typical rating of 0.004%




FM Transmitter with 2N2218
Posted on Friday, November 18, 2011   •   Category: FM Transmitters

FM Transmitter with 2N2218

Here's simple FM transmitter circuit using medium power 2N2218 transistor. Micropohone is of electret type that connects to two input terminals and the antenna should be a copper wire from 15 to 40 cm. Below is schematic circuit of the fm transmitter.




AM Radio built around LM555
Posted on Sunday, November 13, 2011   •   Category: AM Radio

AM Radio built around LM555

AM radio built around 555 timer chip. The only active device (silicon, germanium, or otherwise) is the LM555. The tuning is accomplished with an inductor and a capacitor, and the LM555 acts as an AM demodulator and class-D power amplifier to drive the speaker. You may be wondering how all this is accomplished with a 555. Here’s how the circuit works: The AM radio signal is tuned by inductor L, which is 300 turns of wire on a 1/2 inch diameter cardboard tube made out of a paper roll, along with the 100pF variable capacitor. One end of the parallel configuration of L and C connects to an antenna (surprisingly long!) and the other end connects to a ground wire which is tied to the AC outlet ground (old books tell you to ground it to a water pipe). So far this is exactly like an AM crystal radio. The 555 timer is configured as a pulse width modulator in a non-traditional configuration. If I used the standard approach and connected the input to the CV pin, the low impedance of the pin would prevent the circuit from receiving any radio signals. I had to invert the circuit and tie both high impedance analog pins, Threshold and Trigger to the radio signal input. This is the reason why the CMOS version of the 555 timer performs much better than the standard bipolar, which has higher input bias current.




Active FM Antenna Booster
Posted on Friday, November 4, 2011   •   Category: Antennas

Active FM Antenna Booster

This is a simple active antenna booster. This amplifier will pull in all distant FM stations clearly. The circuits is configured as a common-emitter tuned RF preamplifier wired around VHF/UHF transistor Q1. Input coil L1 consists of four turns of 20SWG enameled copper wire (slightly space wound) over 5mm diameter former. It is tapped at the first turn from ground lead side. Coil L2 is similar to L1, but has only three turns. Pin configuration of transistor 2SC2570 is shown in the fm antenna booster schematic. Adjust input/output trimmers (VC1/VC2) for maximum gain.




Low Power Stereo Amplifier with TDA2822
Posted on Friday, November 4, 2011   •   Category: Amplifiers

Low Power Stereo Amplifier with TDA2822

Here's low power stereo amplifier built around TDA2822 chip. Many people may have heard of the TDA2822 before, but for those who haven't, it is a small power amplifier that will drive two channels. It is usually in an 8-pin DIL package, but older versions I have seen are 14-pin or similar (there are datasheets for both variants). For simplicity though, my circuits show schematics for the 8-pin DIL package. The datasheet is here, provided by ST. This article is based along the usage of the TDA2822M variant of the chip series as it is commonly available. The TDA2822 is similar, but has slightly more pins so is less used.




1W Linear FM Transmitter Booster with 2N4427
Posted on Friday, October 28, 2011   •   Category: FM Transmitters

1W Linear FM Transmitter Booster with 2N4427

Here's 1W RF Amplifier is for boosting small fm transmitters and bugs. It use two Philips 2N4427 and its power is about 1Watt. At the output you can drive any linear with BGY133 or BLY87 and so on. Its power supply has to give 500mA current at 12 Volts. More voltage can boost the distance but the transistors will be burned much earlier than usual.! In any case do not exceed the 15Volts. The Amp offers 15 dB in the area of 80Mhz to 110 Mhz. L4, L5, and L6 are 5mm diameter air coils, 8 turns, with wire 1mm wire diameter.An easy project, with great results.




Stereo Audio Amplifier with TDA2616
Posted on Thursday, October 27, 2011   •   Category: Amplifiers

Stereo Audio Amplifier with TDA2616

I built my first power amplifier when I was still in secondary school. The circuit was made of transistors, didn't provide much power and had an ugly PCB. Around the same time I got access to a datasheet of TDA1524, a tone/volume control circuit, and I decided to use it to build a pre-amplifier, to improve the quality of the sound coming out of the amplifer. Both circuits worked well for almost a decade but the old amplifier was never up to my expectations. In 2006 I decided that it was time to build a real power amplifier, this time based on an integrated circuit to reduce the number of external components and cost.




Stereo FM Transmitter with BA1404
Posted on Sunday, October 23, 2011   •   Category: FM Transmitters

Stereo FM Transmitter with BA1404

A high quality stereo FM transmitter circuit is shown here. The circuit is based on the IC BA1404 from ROHM Semiconductors. BA1404 is a monolithic FM stereo modulator that has built in stereo modulator, FM modulator and RF amplifier. The FM modulator can be operated from 76 to 108MHz and power supply for the circuit can be anything between 1.25 to 3 volts. In the circuit R7, C16, C14 and R6, C15, C13 forms the pre-emphasis network for the right and left channels respectively. This is done for matching the frequency response of the FM transmitter with the FM receiver. Inductor L1 and capacitor C5 is used to set the oscillator frequency. Network C9,C10, R4,R5 improves the channel separation. 38kHz crystal X1 is connected between pins 5 and 6 of the IC. Composite stereo signal is created by the stereo modulator circuit using the 38kHz quartz controlled frequency.




LM317 Overvoltage Protection
Posted on Sunday, October 23, 2011   •   Category: Power Supplies

LM317 Overvoltage Protection

This is an add-on over voltage protection circuit for LM317 voltage regulator. It is a voltage regulator that allows a 6V portable supply to be derived from the 12V car battery. You can add a 6.2V zener diode and a LED to warn you when the input supply is overvoltage. If you could find a relay that would operate from 6.2V right up to 12v that you could connect in such a way that if over voltage occurred, then the relay would automatically switch off the output preventing damage to any connected equipment. Such a relay would be quite difficult to find, so I designed this, it is a simple two transistor circuit which will switch off the output should the voltage raise above 6.2v this can be changed by selecting a different value of zener diode.




Simplest FM Transmitter
Posted on Tuesday, October 18, 2011   •   Category: FM Transmitters

Simplest FM Transmitter

This simple FM Transmitter takes audio input through a 1/4" phono jack and, constructed as shown, without the optional antenna connections, will broadcast an FM radio signal about 30 feet. This is the standard model of simplest FM transmitters includes a trim capacitor to adjust the transmitting frequency. It can be powered by a 9V battery and uses a hand-turned copper coil. The circuit is extraordinarily simple and could be built on perfboard or on a panel almost as easily.




Simple FM Transmitter Bug
Posted on Wednesday, October 12, 2011   •   Category: FM Transmitters

Simple FM Transmitter Bug

This is a simple design of a small FM Transmitter Bug that's perfect for transmitting and eavesdropping purposes. Due to the high sensitivity, even the ticking of the clock to hear. The range is estimated at anything from 50 meters. With a small piece of wire as an antenna to get at least the whole house. L1 and L2 are two equal air pools. They each consist of 5 turns at a diameter of about 4 mm. The thickness of the wire does not matter, 0.5 mm works perfectly. C4 is the frequency adjustment. Tune an FM radio in an empty area of the FM band and C4 to turn your silence or hear a whistle. From what you can precisely adjust the radio and the transmitter installed in a room somewhere to intercept. Note: Because these transmitter bugs inherently unstable, you better read the short legs of the components keep the circuit mechanically tightly together up. Also placing a 1 nF capacitor (C6) will benefit stability. R1, R3, R4: 4K7 R2: 100K R5: 10K R6: 270 Ohms C1, C2: 10 uF C3, C6: 1 nF C4: 2-18 pF trimmer C5: 5.6 pF L1, L2: air puddle windings on May 4 mm in diameter (see text) T1, T2: 547 BC Condenser microphone Original Text: Ook het plaatsen van een 1 nF condensatortje (C6) over de voedingsaanluitingen komt de werking ten goede. [Origineel TinyCAD ontwerp] Show alternative translations




30V 10A Variable Bench Power Supply
Posted on Saturday, October 8, 2011   •   Category: Power Supplies

30V 10A Variable Bench Power Supply

Presented here is a circuit for 30V 10A variable bench power supply that offers variable voltage and current adjustment. Power supply is based around a LM723 voltage regulator chip and has current limiting. I often end up with the power clips shorting out on the bench and with no problems. I have had this circuit in use now for over 20 years and has never let me down and is one of the most handiest gadgets i have built. The 2N3055 transistors are a well proven high current transistor. More 2N3055 transistors can be connected together for more output current. The transistors will need to be mounted on a good size heatsink.




PLL Stereo FM Transmitter
Posted on Friday, September 23, 2011   •   Category: FM Transmitters

PLL Stereo FM Transmitter

The circuit shown here is of a good Stereo FM transmitter that can transmit high quality signals up to a range of 70 feet. The circuit is based on BH1417 PLL stereo transmitter IC from Rhom semiconductors. The IC has separate audio processing sections for the left and right channels, pre emphasis circuit for improving signal to noise ratio, crystal control circuitry for accurate frequency locking, multiplex circuit for making sum ( left plus right) and difference ( left minus right) {see this article for better understanding Stereo decoder circuit} etc. Another important feature of this IC is that the transmission frequency can be set using a 4 channel DIP switch. The IC can be powered from anything between 4 to 6V DC and has an output power around 20mW. At full output power the circuit consumes only 20mA and has a channel separation of 40dB.There are 14 possible preset transmission frequencies, starting from 88.7MHz and incrementing in steps of 0.2MHz that can be selected using the DIP switch. The PLL circuitry of the IC is so precise that there is practically no frequency drift.




USB Voltmeter
Posted on Sunday, September 11, 2011   •   Category: Test and Measurement

USB Voltmeter

USB Voltmeter is a PC based dual channel voltmeter built around PIC18F2455 / PIC18F2550 microcontroller that measures voltage from 0.00V up to 500.00V with 10mV resolution. USB Voltmeter sends measured data to PC via standard USB connection displaying data on a computer monitor. USB Voltmeter is self-powered drawing very little current from USB port. Voltage readings are displayed via included USB Voltmeter software.




Miniature FM Transmitter
Posted on Thursday, August 25, 2011   •   Category: FM Transmitters

Miniature FM Transmitter

This miniature transmitter is easy to construct and it's transmissions can be picked up on any standard FM receiver. It has a range of up to 1/4 of a mile or more. It is great for room monitoring, baby listening, nature research, etc. L1 is 8 to 10 turns of 22 gauge hookup wire close wound around a non-conductive 1/4 inch diameter form, such as a pencil. C4 is a small, screw-adjustable, trimmer capacitor. Set your FM receiver for a clear, blank space in the lower end of the band. Then, with a non-conductive tool, adjust this capacitor for the clearest reception. A little experimenting and patience may be in order. Most of the parts' values are not critical, so you can try adjusting them to see what happens.




LM3886 Amplifier Gainclone
Posted on Monday, August 22, 2011   •   Category: Amplifiers

LM3886 Amplifier Gainclone

Several years ago, National Semiconductor came up with some very high performance, easy to use audio power amplifier LM3886 circuits. I needed an extra amp so I can bi-amp some of my homemade electrostatic speakers so I tried the LM3886 chip. LM3886 amplifier was chosen because of ease of use, performance, low distortion and a built-in protection against short circuits and thermal instability. There is not much to remove a power amp, than asking. When driving electrostatic speakers, you can not be much protection. There are people who have “golden ears” and the feeling, provided that no application note scheme is never good enough for it to “Optimize” to “improvements” to make a claim. The problem is that most of them do not engineers and have no idea what the possible consequences of their “improvements” can be. For example, for a few years if these chips were popular with the audiophile crowd, it was all the rage at minimum power filter caps for “Best Sound” to use. We are talking about 500 uF on each power rail for each chip used LM3886 amplifier. This is clearly insufficient and leads to a distortion in the volume low enough that the power supply sags under load. The problem was that some of the golden ears of the large power supply rejection IC spec saw and thought it meant that the chip could tolerate the 10V power supply ripple. The pendulum has swung the other way, and now many music lovers are sufficient amounts of energy storage in the diet.




TV Audio Video Transmitter
Posted on Friday, August 12, 2011   •   Category: TV Transmitters

TV Audio Video Transmitter

This TV transmitter transmits audio and video signal from Camcoder Camera, DVD, VHS, Satellite, video game, etc. Playing them in a channel free from the strip of VHF. These signal can be radiated with a common antenna and captured in an it distances of until about 500 meters that it is the most appropriate for urban areas, reminding that and necessary to be a lot of caution and careful for not interfering in frequencies of other issuing, as well as to emergency services. Depending on the local conditions (existence or not of obstacles). Fed with tensions from 12 to 15 Volts, the circuit has excellent I carry out so much in the emission of monochrome signal, as in colors. An important point of this project ‚the easiness with that he can be set up and adjusted, since only two coils are used. Ideal to be used with surveillance cameras turning the without thread. As it Works the tv video and audio transmitter with lm1889n The heart of this circuit transmitter ‚is the integrated circuit LM1889N of National Semiconductor, that consists of a Modulator of Video for TV in an involucres of 18 pins DIL.




Digital Volt Ampere Meter
Posted on Wednesday, August 10, 2011   •   Category: Test and Measurement

Digital Volt Ampere Meter

Even if the digital multimeter have dominated in a lot of applications, in the measurement, exist the need for existence of instruments of clue in various appliances, voltage and current, as in power supply or elsewhere. The circuits that give make this precisely the work, measure the voltage in terminal a circuit and the current that passes in his. The circuit does not present particular difficulties for somebody that has a small experience. The two circuits are the himself, with a small difference only in their input, when they have they measure voltage or current and in connection that concern decimal point [ dp ]. In the department of input IC1 and IC3, exist the CA3161E, that is a A/D Converter for 3-Digit Display. In the drive of Display IC2 and IC4, exist CA3161E, that is a BCD the Seven Segment Decoder/ Driver. As it appear in Fig.1, that concern the voltmeter in input [ + IN ], exist in series a what resistor R1 in combination with the R3 create a voltage divider. On the contrary in the Fig.2 that it concern the ampere meter, this resistor does not exist, because the circuit is connected differently, thus the current pass through the R5, creating a fall of voltage, in her terminal, proportional current that it pass from this.




FM Transmitter Circuit
Posted on Monday, August 8, 2011   •   Category: FM Transmitters

FM Transmitter Circuit

Here is the circuit diagram of the simple FM transmitter using a transistor. Great performance or range is not guaranteed here, because this is an elementary design. General purpose radio frequency transistor BF 494 (Q1) is used here for obtaining FM modulation. A condenser mic is used here to pickup the sound.The condenser mic converts the sound to electrical variations and this variations are fed to the base of Q1 , which performs the amplification as well as modulation.The capacitor C2 and L1 determines the frequency of transmission.The circuit can be powered from a 9V transistor radio battery.




Digital AC Voltmeter
Posted on Saturday, August 6, 2011   •   Category: Test and Measurement

Digital AC Voltmeter

I wanted a digital AC voltmeter to measure the output range from 0 to 150VAC with reasonable accuracy. Sure I could buy some premade DVM packages or use a microcontroller with a built-in ADC, but I wanted to make one from scratch myself using readily available parts I had on hand. I aimed for reasonable accuracy so I chose to have a 2 and a half display for the voltage, meaning the meter reads from 000 to 199. Below is the schematic of the AC DVM.




80 MHz - 108 MHz FM Transmitter
Posted on Thursday, August 4, 2011   •   Category: FM Transmitters

80 MHz - 108 MHz FM Transmitter

FM transmitter or often called fm transmitter uses 2 transistors in this article uses 2 transistors 2n2222. If the fm transmitter is in use voltage supply of 9 volt battery and use an antenna whose length is less than 12 inches, then this fm transmitter will be within FCC limits. Signals from the microphone in the fm transmitter is reinforced by Q1, Q2 with carrier frequency generator is determined by the C5 and L1. The frequency of the FM transmitter is in the range 80 MHz - 108 MHz. L1 can be made ​​with as many as 24 e-mail wire wrap and 6 wrap. The following is a picture series for the fm transmitter fm transmitter referred to in article 2 of this transistor.




Single Chip FM Receiver TDA7012
Posted on Thursday, August 4, 2011   •   Category: FM Radio / Receivers

Single Chip FM Receiver TDA7012

FM Radio Receiver IC TDA 7012T is very simple, but Radio This FM receiver has good sensitivity and selectivity. Single Chip TDA 7012T FM Receiver is to build an FM receiver requires a few additional components. Feature contained in FM receiver IC TDA 7012T is quite tempting to an FM receiver. Among features an FM receiver TDA 7012T is a low-voltage applications micro affability arrangement (MTS), Frequency Locked Loop (PLL) to 76 KHz range and selectivity of FM receiver with RC Filter. In an article by FM Radio Receiver IC TDA 7012T can be seen in the FM receiver circuit which can be made​​.




Humidity Temperature Meter (Hygrometer)
Posted on Wednesday, August 3, 2011   •   Category: Test and Measurement

Humidity Temperature Meter (Hygrometer)

Here's hygrometer thermometer that simultaneously monitors both humidity and temperature on large LCD display which can be read from across the room. It's great for labs, chemical storage areas, clean rooms, stock rooms, warehouses, factories, greenhouses, and outdoors. Monitor humidity and temperature in your room, kitchen, desiccators, incubators, refrigerators, and fume hoods. Comes with AG13/LR44 battery. Temperature range -10 C to 50 C (14 F to 122 F). Humidity range 20% RH to 95% RH.




VHF FM Transmitter MAX2606
Posted on Monday, August 1, 2011   •   Category: FM Transmitters

VHF FM Transmitter MAX2606

If you want to be independent of the local radio stations for testing VHF receivers, you need a frequency-modulated oscillator that covers the range of 89.5 to 108 MHz — but building such an oscillator using discrete components is not that easy. Maxim now has available a series of five integrated oscillator building blocks in the MAX260x series which cover the frequency range between 45 and 650 MHz. The only other thing you need is a suitable external coil, dimensioned for the midrange frequency.




Rotary Encoder for ATS Transceivers
Posted on Saturday, July 30, 2011   •   Category: AVR

Rotary Encoder for ATS Transceivers

This equipment is dedicated for an easier control of the popular mini-transceiver AT Sprint known by ham radio operators as ATS (series ATS-2, ATS-3, A, B, B.1 compatible). Originally the ATS has just four push buttons on the top cover and in combination with the paddle it is possible to send all commands to ATS including the tuning, scanning etc. After connecting the rotary encoder accessory module an easy tune, scan and other functions are available as same as on the big size desktop transceivers. Comfort and operation is much higher even with this mini transceiver.




1W FM Transmitter
Posted on Wednesday, July 27, 2011   •   Category: FM Transmitters

1W FM Transmitter

A very good 1 watt fm transmitter circuit, very easy to build circuit. It has 4 transistors, one is a very stable oscillator, followed by a buffer stage to prevent frequency variation when you adjust the transmitter. Next is a resonance stage and the final stage built with a minimum 1W transistor which must have a heatsink. You must use a LM7805 stabilizer for the oscillator diodes and one LM7809 for powering up the T1 oscillator stage. This will give you a very stable transmitter frequency.




Small FM Receiver
Posted on Monday, July 25, 2011   •   Category: FM Radio / Receivers

Small FM Receiver

This is the most simple fm radio receiver with good performances that works great even if the sensitivity is not too high. The working principle of this fm receiver may seem a little unusual. It is made of an oscillator (T2 and T3) that is synchronized with the received frequency of T1. This transistor works as a broadband preamplifier in VHF range.




FM Radio Receiver
Posted on Friday, July 22, 2011   •   Category: FM Radio / Receivers

FM Radio Receiver

This simple fm radio receiver circuit consists of a regenerative rf stage, TR1, followed by a two of three-stage audio amplifier, TR2 to TR4. In some areas 3 stages of audio amplification may not be necessary, in which case TR3 and its associated components can be omitted and the free end of capacitor C5 connected to the collector of TR2.




FM Antenna Booster
Posted on Tuesday, July 19, 2011   •   Category: Antennas

FM Antenna Booster

This is a low cost fm antenna booster that can be used to listen to programs from distant FM radio stations clearly. The antenna fm booster circuit comprises a common-emitter tuned RF preamplifier wired around VHF/UHF transistor 2SC2570 (C2570). Assemble the circuit on a good-quality PCB (preferably, glass-epoxy). Adjust input/output trimmers (VC1/VC2) for maximum gain.




Flashing LED Circuit
Posted on Monday, July 18, 2011   •   Category: LED

Flashing LED Circuit

Here's a simple circuit that flashes an LED on and off. This circuit uses the 555 timer in an Astable operating mode which generates a continuous output via Pin 3 in the form of a square wave. This turns the LED (D1) on and off. The speed at which the LED (D1) is turned on and off is set by the values of R1 and R2.




2 Watt FM Transmitter
Posted on Monday, July 18, 2011   •   Category: FM Transmitters

2 Watt FM Transmitter

This 2 Watt FM transmitter will provide 10km range in good weather conditions. Use dipole antenna for maximum range. Transmitter can be tuned between 88-108 MHz with c5. BB204 could be replaced with conventional led (big) with reverse bias (no light given in correct polarity). 9v power for 2km transmission with good sound quality and up to 18v for 10km range. 2N3553 RF transistors may be replaced with 2N4427 or 2N3866.




Thermostat Controller with LCD
Posted on Monday, July 18, 2011   •   Category: AVR

Thermostat Controller with LCD

I wanted to share my project of modifying the temperature sensor project and turning it into a thermostat with ATmega168. I added a digital output to drive an LED to "warm" the temperature sensor when the current (actual) temperature falls below the desired temperature. Two push buttons come in as digital inputs one to ramp the desired temperature up and the other to ramp it down. The logic is simple bang-bang control to turn the LED on and off based on the relationship of actual temperature to desired temperature. It simulates a thermostat in heater mode. The LED is off when the current temperature is above the desired temperature and turns on once the current temperature falls below.




Radio Receiver Circuit
Posted on Monday, July 18, 2011   •   Category: FM Radio / Receivers

Radio Receiver Circuit

This radio works with solar batteries that provide voltages between 0.5 and 2V. Microphones should be magnetic, high impedance (2k or more). The coil is wrapped around a ferrite rod 1 cm in diameter with 28AWG wire.




Character LCD Displays
Posted on Monday, July 18, 2011   •   Category: Miscellaneous

Character LCD Displays

LCD character displays can be found in espresso machines, laser printers, children’s toys and maybe even the odd toaster. The Hitachi HD44780 controller has become an industry standard for these types of displays. This tutorial will teach you the basics of interfacing with a HD44780 compatible display using some DIP switches and a few other components.




USB AVR Programmer
Posted on Saturday, July 16, 2011   •   Category: AVR

USB AVR Programmer

USB AVR Programmer for Atmel AVR microcontrollers. USB AVR Programmer is made of an Atmega8 and few components. The programmer uses a firmware driver that makes this programmer attractive to many amateurs. Another thin why this programmer is so popular is because it is officially included and supported in WinAVR. Once again lets see what this programmer is made off and how to set it up. The core of USB AVR Programmer adapter is Atmega8 microcontroller clocked by 12MHz crystal. Soldered board is ready to be connected via simple USB cable with B type connector (Computer side needs A type of connector). Resistors R2 and R6 are current limiting resistors, that protect computer USB port. Resistor R7 helps computer to recognize device as LS (Low Speed). Diodes D1 and D2 indicates about data transfer. Header SV1 is compatible with STK200/300 just 4 and 6 pins are used for RXD and TXD (may be used for other purposes).




Adjustable Bench Power Supply
Posted on Friday, July 15, 2011   •   Category: Power Supplies

Adjustable Bench Power Supply

I’ve built myself my own universal, adjustable bench power supply. This isn’t strictly astro stuff but the main reason I built it is to experiment with TFT backlight panels that I use for my lightboxes. I needed 5V and 12V to play around with the inverter boards and figure out their pin-out. I considered buying a bench power supply. But prices were too high, especially for ones with adjustable voltages. So I decided to build my own. This one has 4 outputs. One 5Volt, one 12V and two individually adjustable outputs going from about 1.5V to 19.5V. Each can draw up to 1.5Amp with a total of 3.5A for all together. The input is a standard replacement laptop power supply 20V, 3.5A. With a stronger external power supply the total output current can be higher, up to 1.5A per output. But currently the 3.5A is more than enough. Each of the adjustable outputs has its own little voltmeter built in. The fixed voltage regulators are based on a 7805 for the 5V and a 7812 for 12V. The two adjustable regulators are based on one LM317 each.




28W FM Broadcast Transmitter Amplifier 88-108 MHz
Posted on Friday, July 15, 2011   •   Category: FM Transmitters

28W FM Broadcast Transmitter Amplifier 88-108 MHz

This RF Amplifier designed for FM broadcast using a single 2SC1946 VHF Power Transistor. This 10-30W RF amplifier circuit provides an appropriate power boost with an input of 1-3 watt. Tower are 30 meters high will send signal surrounding air should be around 15 km. The layout of the 2SC1946 28 Watts FM broadcast RF amplifier has been created with Eagle. The pcb outline is 100 x 50 mm (width x height), all bitmaps have a resolution of 600dpi.Use FR-4 single sided photoresist epoxy pcb material for best results.




Digital Barometer with Graphical LCD Display
Posted on Thursday, July 14, 2011   •   Category: PIC

Digital Barometer with Graphical LCD Display

Here's a digital barometer that uses Atmega8 microcontroller and graphical LCD display. This project uses SCP barometer pressure sensor graphical LCD display connected to Atmega8 microcontroller. Graphical LCD displays latest 128 readings while one reading occur once in 20 minutes. You can see information of about two last days. Provided C source code can be customized to your liking.




PIC Temperature Logger
Posted on Thursday, July 14, 2011   •   Category: PIC

PIC Temperature Logger

This project uses a Microchip PIC microcontroller, a serial EEPROM and a thermistor to create a temperature recorder. The temperature is measured and stored at user programmable intervals; this can be from 1 second to 256 seconds. The time interval is set by programming it and the start time into the EEPROM. Most of the time the PIC will be asleep and the EEPROM IC is inactive. This gives a very low current consumption of approximately 50 uA or about 1 mAh per day. The EEPROM used is 32kBytes which can store up to 32,000 measurements. This could be one measurement every 30 seconds for 11 days for example. The combination of thermistor and analogue circuit gives a range of between about -40 °C and +100 °C although the linear range is between about -10 °C and +40 °C.




5 Watt Transmitter
Posted on Thursday, July 14, 2011   •   Category: FM Transmitters

5 Watt Transmitter

This is a very simple 5 watt CW TX based upon a TTL logic chip. There is just one "tricky" component and this is Cx. This component should have an impedance of about 10 - 50 ohms at the frequency of interest. If you wish to reduce the transmitter power, increase the value of Cx. It is Cx which causes the square wave from the output transistor to approximate a sine waveform. The value of Cx is the price of simplicity in this TX.




Automatic Battery Charger
Posted on Wednesday, July 13, 2011   •   Category: Battery Chargers

Automatic Battery Charger

Automatic battery charger automatically starts the charging procedure when battery voltage drops below a certain predefined value and stops after the voltage has risen above the maximum allowed value. Setup can't be easier, just connect two alligator clips to battery terminals and plug the device in mains. This way it can stay connected for months and the battery will never overcharge. This comes very very handy when you have a scooter or a real motorcycle that you don't drive during the winter time. Because we all know what happens to a battery when not used and especially during the winter.




Power Supplies
Posted on Wednesday, July 13, 2011   •   Category: Power Supplies

Power Supplies

There are many types of power supply. Most are designed to convert high voltage AC mains electricity to a suitable low voltage supply for electronics circuits and other devices. A power supply can by broken down into a series of blocks, each of which performs a particular function. Each of the blocks is described in more detail below:

Transformer - steps down high voltage AC mains to low voltage AC.

Rectifier - converts AC to DC, but the DC output is varying.

Smoothing - smooths the DC from varying greatly to a small ripple.

Regulator - eliminates ripple by setting DC output to a fixed voltage.




Transistor Tester
Posted on Wednesday, July 13, 2011   •   Category: Test and Measurement

Transistor Tester

Here is a very simple circuit that can b e used to check the hfe of transistors. Both PNP and NPN transistors can be checked using this circuit. Hfe as high as 1000 can be measured by using this circuit.The circuit is based on two constant current sources build around transistors Q1 and Q2.The Q1 is a PNP transistor and the constant current flows in the emitter lead. The value of constant current can be given by the equation; (V D1 -0.6)/ (R2+R4).The POT R4 can be adjusted to get a constant current of 10uA.




DIY USB Power Supply
Posted on Tuesday, July 12, 2011   •   Category: Power Supplies

DIY USB Power Supply

Here is a quick and easy way to make an USB charger / power supply powered by the wall outlet. This can be used to charge / power a PSP, iPod or any other USB device. First you need to acquire a regulated 5 vdc wall wart rated at 500ma or higher. The one I used is from an IoMega Zip drive. It has a switching regulator with an output of 5vdc @ 1amp. This is a cool way of making an old wall-wart (plug in power supply) into a useful USB power supply and requires very few extra components.




Water Alarm
Posted on Tuesday, July 12, 2011   •   Category: Sensors

Water Alarm

This is a simple water alarm. At the heart of this circuit is a small water sensor. For fabricating this water sensor, you need two foils—an aluminium foil and a plastic foil. You can assemble the sensor by rolling aluminium and plastic foils in the shape of a concentric cylinder. Connect one end of the insulated flexible wire on the aluminium foil and the other end to resistor R2. Now mount this sensor inside the water tap such that water can flow through it uninterrupted. To complete the circuit, connect another wire from the junction of pins 2 and 6 of IC1 to the water pipeline or the water tap itself.




Wireless Microphone FM Transmitter
Posted on Monday, July 11, 2011   •   Category: FM Transmitters

Wireless Microphone FM Transmitter

This Wireless Microphone FM Transmitter has been a very popular project with beginners and experienced constructors alike. It has been used inside guitars and as the basis of a remote control system. I do however, receive many requests for a higher powered circuit and better microphone sensitivity. Now I can introduce the new FM Wireless Microphone, which also has a better frequency stability, over 1Km range (under ideal conditions) and is good on microphone sensitivity. This has been achieved by adding an RF amplifier buffer (with 10dB gain) and an AF preamplifier to boost the modulation a little.




Solar Recorder
Posted on Monday, July 11, 2011   •   Category: Sensors

Solar Recorder

Build a simple data recorder for solar energy lab. The Recorder uses a calculator solar cell as the input sensor and a Multimedia Memory Card for nonvolatile data storage. The device used for measuring daily insolation has been developed. The device was built with a PIC18F458 and the 128MB Multimedia Memory Card, MMC. The solar radiation is measured by a calculator solar cell. The PIC chip interfaces the MMC using SPI mode. The interval between samples is set to one minute. The firmware detects the memory card, assigns the file name and begins recording automatically. The LCD displays the file name, current sample and real-time ADC data. With the MMC flash technology and a cheap media card reader, the devices will be able to record huge amount of data and quick data uploading to the PC.




Clock Relay Controller
Posted on Saturday, July 9, 2011   •   Category: AVR

Clock Relay Controller

Build a digital clock that turns AC load on/off through relay with preset time. The clock is based around 7-segment LED display with multiplex connection and AT89C2051 microcontroller. It is nice to be used as the display for clock controller. So I spent my weekend built the board. Below are the pictures for outlook and internal. The board is quite small. The output has small relay for 0.5A AC load. The program clock.c was written in ‘C’ language and was complied by Micro-C Compiler from DunfiledDevelopment Systems. The memory model is TINY. The hex file of clock.c suitable for downloading by Easy-Downloaderis clock.hex.




Phone Audio Interface
Posted on Saturday, July 9, 2011   •   Category: Phone Circuits

Phone Audio Interface

I needed a way to extract audio from a phone line for my DTMF decoder. I found a site full of examples on how to do it, and I built an interface that suited my needs: RCA output, with a signal strong enough to be fed directly to an audio amplifier or line-in. The interface can stay connected on the line at anytime (no problems with the ring signal), and does not take of the hook. The interface must provide isolation from the line. I discovered that it can also be used to inject audio in the line.




PC LED Load
Posted on Saturday, July 9, 2011   •   Category: PC Circuits

PC LED Load

PC LED Load is a device and software designed to display many shades of colors from green to red on your computer case LED. Colors are controlled completely by software and can be updated in real-time. The PC LED Load circuit board is connected to one of the internal USB ports found on most newer motherboards. The only actual case modification required is in replacing the two (or more) front panel LEDs with tri-color versions. These are then connected to the PC LED Load circuit board.




40mW FM TRANSMITTER
Posted on Friday, July 8, 2011   •   Category: FM Transmitters

40mW FM TRANSMITTER

The transmitters on my homepage seem to be quite popular, especially those intended for the 88 - 108MHz FM band. I must really confess that I also favor this broadcast band, mainly because it is so easy to find signals on the workshop radio. Everyone has an FM radio, and it is fun to play with. Experimental antennas and the like can all be developed in this band since there are a huge range of "beacons" all transmitting just for my benefit :-). Basic oscillators also are easy to fault-find in this frequency band, and then later modified for other VHF bands. The V5 FM Wireless Microphone is a 10mW transmitter that featured a coil fabricated on the PCB itself. This made the project easy to duplicate and removed "microphony" (the ability of coils to act as a microphone with spring-line reverb). But as several people have already commented, although more stable than most other similar kits and projects, the frequency still does vary with battery voltage. In just one session it can vary by 200kHz when a cheap "Mighty Atom" battery falls to 8 volts.




Long Range FM Transmitter
Posted on Thursday, July 7, 2011   •   Category: FM Transmitters

Long Range FM Transmitter

Presented here is a Long Range FM Transmitter. This circuit is a super-sensitive, mini-powered FM transmitter consisting of a RF (radio Frequency) oscillator section interfaced with a high sensitivity, wide pass-band audio amplifier and capacitance mike with a built-in FET (Field Effect Transistor) that modulates the base of the RF oscillator transistor. Transistor Q1 forms a relatively stable RF oscillator whose frequency and is determined by the value of coil L1 and turning capacitor C4.




2km TV Transmitter
Posted on Wednesday, July 6, 2011   •   Category: TV Transmitters

2km TV Transmitter

Here is a simple TV transmitter. The circuit is simple and really quite crude, but it does include MONO sound. I have not shown the two regulators in the drawing. These are one 12v DC 1A series regulator chip, and one 8v DC 1A series regulator. I fed the 8v regulator from the output of the 12v regulator. The rest of the circuit looks like this. It is a free-running Variable Frequency Oscillator (VFO) using just one coil and one capacitor to determine the frequency. Change this as you will. The basic circuit uses a 150pf from the Base of the RF transistor to ground, so that TR2 operates as a "common-base mode" (grounded base) amplifier. The tuned circuit in the collector and the capacitor from collector to emitter provide tuning and feedback.




Camera VHF Video Transmitter
Posted on Wednesday, July 6, 2011   •   Category: TV Transmitters

Camera VHF Video Transmitter

This is a simple video transmitter that can transmit as far as 50 meters. This video transmitter can be used with the camera or other video sources. You can view them on VHF channel analog TV. Supply voltage to the video transmitter can use 9V battery. Transistor components that are used for a video transmitter is BC548 or you can use another type of transistor BF199. Meanwhile, other passive components used SMD type. For winding coil L1 is 5 Turns 8 mm in diameter and use wire AWG 0.3-0.5 mm.




AVR Programmer
Posted on Tuesday, July 5, 2011   •   Category: AVR

AVR Programmer

Here's AVR programmer for programming AVR microcontrollers such as the AT90S1200 via the parallel port. AVR programmer is extremely simple. IC1 provides buffering for the signals that travel from the parallel port to the microcontroller and vice versa. This is essentially everything that can be said about the circuit. The two box headers (K2 and K3) have the ‘standard’ ISP (in system programming) pinout for the AVR controllers. The manufacturer recommends these two pinouts in an attempt to create a kind of standard for the in-circuit programming of AVR microcontrollers. These connections can be found on many development boards for these controllers. The software of AVR programmer carries out the actual programming task.




RF Inductance Meter
Posted on Tuesday, July 5, 2011   •   Category: Test and Measurement

RF Inductance Meter

This RF inductance meter measures RF chokes in the 500 nH to 50 uH range. I needed a way to measure hand-wound RF inductors in my second lab, and since I would only be doing this occasionally, I didn't need anything fancy, and since once a friend finishes his AT90S1200-based design, I plan to make one myself, I figured I'd use this for less than a year, so I didn't want to invest a lot of time in making it . I had run across the forerunner of this circuit, one that is more sophisticated in that it has a zero adjustment and range switch, but it was limited to higher inductances. I adapted it to the components I had on hand and changed it so that it would work in the 500 nanohenry to 50 microhenry range.The original circuit was reportedly published a few years ago by the Amrican Radio Relay League, so it is with appreciation of the ARRL that I make this circuit available.




Hybrid Tube Headphone Amplifier
Posted on Monday, July 4, 2011   •   Category: Headphone Amplifiers

Hybrid Tube Headphone Amplifier

Here's a simple to build hybrid tube headphone amplifier built around 12AU7 / ECC82 vacuum tube. I have always been intrigued by tube amplifiers, but most DIY kits are very expensive and use very high voltage. So I decided to build an amplifier that would be inexpensive and had the least amount of parts necessary to drive a pair of 32 ohm Grado headphones. Having built several YAHA amps based on the fa-schmidt design, and a Szekeres Mosfet follower I wondered how the two would sound together. So I built the schematic into TINA-TI, a free spice based program to test circuits before the build, and the results were remarkable. Nearly 20dB of gain across 20Hz-100kHz from a 13VDC power supply. As you see in the schematic and parts list, there are less than 30 discrete components and most DIY'ers will have them as spares from other builds. I chose the 12AU7 / ECC82 vacuum tube because it can be driven with low voltage and the filament voltage is 12.6 volts, so there is no need to regulate the voltage any further. I used 1/4W resistors in the first stage and 2W in the second. The 2W resistors may be overkill but I did not want to change them later. The 20ohm resistor must be a minimum of 5W and do not use wire wound, as the inductive characteristics will distort the response curve.




Inductance Meter
Posted on Saturday, July 2, 2011   •   Category: Test and Measurement

Inductance Meter

This is inductance meter I built using 74HC14 IC. Initially I used a DMM as the display device, but on a whim I tried hooking up a moving-coil meter. To my surprise, it actually worked just fine, 1K in series was sufficient to allow a useful calibration and didn't overload the drive capabilities of the last gate in the package. I calibrated my unit for 0-100 uH, as this is the range I am generally most interested in, and it gives direct-readings on the uA scale of the meter. With the values as Dick specified, there is sufficient range to calibrate it from about 25 uH to 250 uH FSD.




100W Transmitter RF Power Amplifier 2SC2782
Posted on Thursday, June 30, 2011   •   Category: FM Transmitters

100W Transmitter RF Power Amplifier 2SC2782

This is a 6m band transmitter RF power amplifier (50 MHz) with 100W output. It used with my FT-736R and drive from 10W for the 6m SSB DX. The Building information comes from Japan CQ Magazine. The Toshiba RF bipolar power transistor is used in it. If you want to construct this rf amplifier, it's the better way if the double side PCB use for increase the grounding and current transfer. The TX power can be tune to 120W.




USB Sound Card with PCM2902
Posted on Thursday, June 30, 2011   •   Category: Audio DAC

USB Sound Card with PCM2902

This is USB sound card with PCM2902 chip. For the purpose of testing the D / A converters, I built a simple USB sound card with the circuit PCM2902. The card has analog input and output, an electrical S / PDIF output, galvanically separated input and optical input and output TOSLINK. The heart of USB sound card is PCM2902 it is a circuit connection, which is a complete USB codec. The circuit can handle up to 48kHz sampling frequency. The integrated circuit includes a USB controller for A / D and D / A converter, HID part for 3 buttons, volume control, custom converters and S / PDIF encoder and decoder.




200W Leach Amp
Posted on Wednesday, June 29, 2011   •   Category: Amplifiers

200W Leach Amp

This article describes how to build 200W Leach Amplifier from Mr. Marshall Leach known like “The Leach Amp”. Article about building of this amplifier I found later in journal A_Radio Praktická elektronika 11/2002. For many years I looked for construction of HiFi amplifier wit a good parameters, enough power reserve and simple construction. I built a couple of amplifiers with integrated circuits MBA810, TDA2005, LM3886, but I was disappointed by their output quality and noise. I decide to built a classic construction with discrete components and bipolar transistors. Construction from Mr. Dudek was interesting, but I didn’t like used components and complexity. All of my requirements satisfied construction of the Leach Amp. Circuit author publicates in a February 1976 in american journal. From these days circuit was not practically changed. Little changes are described on authors page. I succeeded to find almost all original components on our local market, which was a miracle. Only a bigger problem was a power transformer and filter capacitors. Recommended toroid transformer for power 200W to 4 ohms is 230V/2x 42V.




1.5 Watt FM Transmitter
Posted on Tuesday, June 28, 2011   •   Category: FM Transmitters

1.5 Watt FM Transmitter

Presented here is a 1.5 Watt FM Transmitter. A transmitter is an installation in which electrical oscillations are generated by an antenna as radio waves are emitted.Although there are a variety of channels exist in terms of size, application and frequency, each transmitter is an oscillator is present (usually crystal controlled) that an electric thrill, the carrier, with a constant frequency electricity.This is followed by one or more selective amplifier stages tuned oscillation circuits, which usually frequency multiplication is performed.Modulation can occur at low power, and even strengthening of the modulated signal to the power required to reach.Modulation can also occur at high power, when the carrier signal and separately reinforced.




Lipoly Low Battery Indicator
Posted on Tuesday, June 28, 2011   •   Category: Battery Chargers

Lipoly Low Battery Indicator

Lipoly batteries are great power source for our AEGs, they offer high current capacities and are available in different shapes and sizes that can fit virtually any AEG. But they have a downside, they are prone to failures when over discharged. Their nominal voltage is 3.7V (4.2V-full charge) but must not go below their critical voltage of 2.7V. New development in AEG electronics protect the battery from going too low by either cutting the power or an audible warning that indicates low battery voltage. While saving up for the "Panther" or "Cheetah" SW-COMP, here is a cheap and easy to construct 11.1V lipoly lo-batt indicator.




LM317 Variable Power Supply
Posted on Saturday, June 25, 2011   •   Category: Power Supplies

LM317 Variable Power Supply

Here's variable power supply voltage regulator circuit based around LM317 that provides fully regulated output voltage between 1.25 and 37v with current up to 1A. In many cases we can manage with a suitable fixed voltage regulator such as 5v or 12v, but occasionally we need a non-standard voltage. In these circumstances the LM317 range of regulators proves to be very useful.




Running LEDs with PIC 12F675
Posted on Friday, June 24, 2011   •   Category: LED

Running LEDs with PIC 12F675

Here's a simple running LEDs circuit based around PIC 12F675. I'm begin in developer with MCUs and recently i bought some eletronics components. Then i using Proteus for assembling the circuit and MikroC for developer MCU. I am making the leds blink using PIC12F675, 4 resistors 220 ohm and 4 leds.




LM3886 Power Amplifier 100W
Posted on Friday, June 24, 2011   •   Category: Amplifiers

LM3886 Power Amplifier 100W

This is 100W LM3886 power amplifier. Since my DIY speaker is 4-ohm and somewhat difficult to drive, I want to have a more powerful amplifier to match with it. Therefore I designed this amplifier which uses two LM3886 per channel, in parallel circuit. This amp can deliver about 50W into a 8-ohm speaker and 100W into a 4-ohm speaker. This is a stereo amplifier and therefore 4 LM3886s are used. The LM3886 circuit is in a non-inverted configuration, so the input impedance is determined by the input resistor R1, i.e. 47k. The 680 ohm and 470pF resistor capacitor filter network is used to filter out the high frequency noise at the RCA input. The 220pF C4 and C8 capacitors are used to shot out the high frequency noise at the LM3886 input pins. I used high quality audio grade capacitors at several locations: 1uF Auricap at the input for DC blocking, 100uF Blackgate for C2 and C6, and 1000uF Blackgate at the supply filter.




LIPO Battery Overvoltage Protection
Posted on Friday, June 24, 2011   •   Category: Battery Chargers

LIPO Battery Overvoltage Protection

Simple LIPO saver board to throw onto lithium based batteries for overvoltage protection. It consists of a TLV3012 comparator with onboard reference, an voltage divider, load resistors, indicator LED and a transistor. It should turn on the transistor, and load LIPO battery cell when its voltage is >4.25V Ive attached LIPO saver schematic. The diode represents the onboard reference in the comparator, eagle didn't have the device in its library.




LIPO Saver
Posted on Friday, June 24, 2011   •   Category: Battery Chargers

LIPO Saver

The presented battery saver or TL431 LiPo Saver is designed to prevent deep discharge of lithium polymer batteries. Decreases the cell voltage of a LiPo batteries below 2.4 volts will permanently damage the cell. When LIPO battery is about to reach the critical voltage a buzzer alarm is activated. I have built several of these for use as Tx alarm and they do SCREAM especially if you fit twin piezo sounders. TL431 is adjusted to sound off at pretty much any low voltage level you wish.




RF Field Strength Meter
Posted on Thursday, June 23, 2011   •   Category: FM Transmitters

RF Field Strength Meter

Most transmitter has several variable capacitors which are used to match impedance for transistors and antennas. I know people hate trimmers and so did I. The reason is that it is difficult to trim a system if you can't measure the performances. To trim a transmitter you need to measure the output power. Most transmitter are tuned with a dummy load of 50 ohm to substitute an antenna of 50 ohm. Not everyone has a power meter, and how can you know that the antenna you connect is purely 50 ohm. If not, the hole trimming is waste of time! What you would like to do is to measure the radiated power out from the antenna you actually are going to use. If you can measure the radiated energy field you can easy tune the system for max output field strength (max power). So, how can we measure the radiated energy field? The block diagram at right show you one easy way to measure the RF filed strength. To the left you find a dipole antenna. The antenna should be cut to match the receiving frequency ...




80W RF Amplifier 88-108 MHz
Posted on Wednesday, June 22, 2011   •   Category: FM Transmitters

80W RF Amplifier 88-108 MHz

This is 80W RF power amplifier that boosts FM Transmitter's power using 2SC2782 bipolar transistors in a tuned class C circuit. RF amplifier can be driven to full 80W power with less than 1 watt driving input power, so that a large gain margin results in this FM transmitter. To obtain stability in this RF amplifier, I employed several techniques, such as placing the resonances of base and collector chokes far apart, damping the chokes with resistors, using RC combinations for absorption of unwanted frequencies, using feed trough capacitors for bypassing on the board, etc. It took some tweaking, but the amplifier ended up unconditionally stable.




TV Video Transmitter
Posted on Monday, June 20, 2011   •   Category: TV Transmitters

TV Video Transmitter

This is a TV transmitter for transmitting video of various video sources such as video cameras, Satellite receivers, DVD players, game consoles, etc. TV transmitter's circuit is working on the 470-580 MHz frequency and can be received on UHF channels 21-34. TV Video transmitter can radiate as far as 300 meters by using a 10-20 cm wire antenna. TV transmitter requires voltage of 9-15 Volts. However, you can also use a 9v batteries. Oscillator is based around BF199 and BFR90 RF transistors. If needed the range of TV transmitter can be extended by replacing BFR90 with 2N3886 transistors.




Bootloader for 16F87x PIC Microcontrollers
Posted on Saturday, June 18, 2011   •   Category: PIC

Bootloader for 16F87x PIC Microcontrollers

A bootloader enables download of hex-files directly into the flash-memory of a PIC or other microcontroller. The bootloader receives the user program via the PIC's UART and writes it directly to the program memory (self programming). This feature greatly speeds up the development process, because the chip remains in the target circuit and need not be moved between the target circuit and the programmer. When no bootloader is installed, all memory in the PIC can be utilized for user programs. That is 4 K for the 16F873 (0x000 to 0xFFF). Installing a bootloader means, that some part of the memory is occupied by the bootloader. The user can download his program into the remaining memory space. The bootloader in figure 1 occupy 256 words (0xF00 to 0xFFF), that is 6 % of the memory in a 16F873. The disadvantage of loosing 6 % memory is little compared to the advantage of fast program download and more friendly development routines.




RF Field Strength Meter with Attenuator up to 200 MHz
Posted on Friday, June 17, 2011   •   Category: FM Transmitters

RF Field Strength Meter with Attenuator up to 200 MHz

RF Field Strength Meter with Attenuator up to 200 MHz The RF field meter unit is a great help to tune transmitters for best performance and output power. You can measure the radiated energy field and can easy tune the system for max output field strength maximum power. This field strength meter comes with selectable attenuator. You can use it for measuring the antenna gain and pattern, compare different magnetic field strengths. See the following RF field strength meter schematic.




8W Broadband FM RF Amplifier
Posted on Friday, June 17, 2011   •   Category: FM Transmitters

8W Broadband FM RF Amplifier

Here's 8W broadband FM RF amplifier using 2SC1971 VHF power transistor. The RF Amplifier PCB layout designed for FM broadband 88-108 MHz transmitters using microstripline technique. This 8W RF amplifier circuit provides an appropriate power boost for transmitters with an input of 500 mW.




LiPo Battery Charger
Posted on Wednesday, June 15, 2011   •   Category: Battery Chargers

LiPo Battery Charger

This is LiPo battery charger circuit based around the MAX1551 / MAX1555 chip from Maxim ICs. And it happens to be a very easy chip to use. I used the typical circuit from the datasheet and referred to the pin out to see which pin is what. I also used adapter board so that I could prototype the LiPo battery charger on a breadboard. The barrel plug towards the top goes into an LM7805 that can take 7-16V and regulates it down to 5V. Besides that, pretty simply stuff with only a handful of common components.




Super Spy Transmitter Bug
Posted on Tuesday, June 14, 2011   •   Category: FM Transmitters

Super Spy Transmitter Bug

A very small home made FM transmitter Bug using a single transistor and with a transmission range of 200 meters. This FM transmitter Bug is very easy to build. The size of the circuit board is ONLY 22mm x 10mm.




Building Simple FM Transmitter
Posted on Saturday, June 11, 2011   •   Category: FM Transmitters

Building Simple FM Transmitter

Here's how to build a simple FM Transmitter. This tiny transmitter has smaller radius of the service area, lower quality of the sounds and the relatively unstable frequency. These can be considered as a compromise to easily have your own transmitter for the time being or as a more positive choice. These "defects" are only from the perspective of conventional transmission such as "clear stereo sound to receive anywhere". Artist could change these to another directions. Whether or not, you can experience a convivial wireless imagination by this transmitter.




Micro Spy PLL FM Transmitter
Posted on Thursday, June 9, 2011   •   Category: FM Transmitters

Micro Spy PLL FM Transmitter

This micro spy PLL FM Transmitter transmits on the 160MHz frequency (if we use a 40MHz quartz) and therefore can be listened through a receiver tuned on this frequency. This circuit can be used to on various frequencies, for example on the FM band 88-108 just modifying some components, among which the quartz (25MHz). Voice is detected by an electret microphone, then it is amplified and filtered by U1 pass-band in order then to be modulated from the carrier section, where through the varicap diode it "mixes" with the frequency generated by the quartz, that guarantees an adapted stability. Practically the modulating voltage is obtained applying the audio signal to the resonating circuit varicap diode that determines the carrier oscillation. The carrier frequency (160 MHz) must be greater than the modulating frequency (300-3300 Hz) audio band. The transmission is on the fourth harmonic, therefore 160MHz, the oscillation frequency of the driver RF transistor Q1. A small calibration is allowed acting on the L1 inductance and the C1 Trimmer Capacitor.




PIC Controlled Relay Driver
Posted on Thursday, June 9, 2011   •   Category: PIC

PIC Controlled Relay Driver

We love to read emails from our visitors, Please let us know by clicking here if you find any kind of bug/error in our site. We will fix it as soon as possible. PIC Controlled Relay Driver This circuit is a relay driver that is based on a PIC16F84A microcontroller. The board includes four relays so this lets us to control four distinct electrical devices. The controlled device may be a heater, a lamp, a computer or a motor. To use this board in the industrial area, the supply part is designed more attentively. To minimize the effects of the ac line noises, a 1:1 line filter transformer is used.




Simple FM Transmitter
Posted on Wednesday, June 8, 2011   •   Category: FM Transmitters

Simple FM Transmitter

Mini FM transmitters take place as one of the standard circuit types in an amateur electronics fan's beginning steps. When done right, they provide very clear wireless sound transmission through an ordinary FM radio over a remarkable distance. I've seen lots of designs through the years, some of them were so simple, some of them were powerful, some of them were hard to build etc. Here is the last step of this evolution, the most stable, smallest, problem-less, and energy saving champion of this race. Circuit given below will serve as a durable and versatile FM transmitter till you break or crush it's PCB. Frequency is determined by a parallel L-C resonance circuit and shifts very slow as battery drains out.




100W Car Subwoofer Amplifier
Posted on Tuesday, June 7, 2011   •   Category: Amplifiers

100W Car Subwoofer Amplifier

Complete car amplifier for subwoofer based on TDA7294 amplifier chip. This is a much powerful than previous TDA1562 based version (LINK), but its based on push-pull converter so its more difficult to build. Build-in low-pass filter, all on one one-sided 75mm x 125mm dimension PCB.




Zen Headphone Amplifier
Posted on Monday, June 6, 2011   •   Category: Headphone Amplifiers

Zen Headphone Amplifier

This is a scaled-down version of Nelson Pass' Zen power amplifier for my headphones. For this use, the Zen topology is perfect excellent sound quality, simplicity, linearity and no multi-stage feedback. It is a single stage class A MOSFET design with the right gain and a low output impedance. Here we don't have the limitations of the Zen amps at least in the single-stage implementations regarding speaker compatibility. A single stage topology with correct interfacing values misses very few things in the original music message. The gain device in the original Zen amplifier is biased by fixed current source. For this amp, I employed an active current source described in Pass' patent no. 5,710,522 (see Zen Variations Part 2). The benefits of an active source include higher output current, lower distortion and 50% theoretical operating efficiency (compared to the 25% efficiency from a fixed source). This type of current source is featured in the Aleph power amplifiers from Pass Labs.




Class A Headphone Amplifier
Posted on Monday, June 6, 2011   •   Category: Headphone Amplifiers

Class A Headphone Amplifier

This class A headphone amplifier can output up to 0.5W into a 32-ohm headphones. I built this headphone amplifier for dynamic headphones based on my rules of proper audio design. People who know my designs will realize that this headphone amplifier is much more than just a headphone amp. It is a pure class A design containing a new never-before-seen servo loop that is not part of the audio signal chain in any way. The sound of this class A headphone amplifier is just amazing.




Building Noise Canceling Headphones
Posted on Saturday, June 4, 2011   •   Category: Headphone Amplifiers

Building Noise Canceling Headphones

In today’s hectic and noisy world, we are all searching for a little peace and quiet. Well, you might not be able to slip off to a tranquil forest for an hour or two, but you can block out background noise with the Noise-Canceling Headphones. The theory behind this project is that by picking up ambient sound with a microphone and reproducing it out of phase, we can actively cancel or "null" out background noise. In fact, several commercially available devices perform the same function. However, by building your own headset, you can add features not otherwise available and have fun while doing it! Along with noise-features, the Active Noise-Canceling Headphones let you mix in an auxiliary line-level signal from a CD or tape player. That allows you to minimize background noise while quietly listening to music. The project also has a phase switch that will let you keep the microphone signals in phase, thus amplifying background sound. In addition, the design of the Noise-Canceling Headphones lends itself to several other interesting functions, which we will look at later.




Big Ear Amplifier
Posted on Wednesday, June 1, 2011   •   Category: Amplifiers

Big Ear Amplifier

This circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume, avoiding to bother relatives and neighbors. Even if you have a faultless hearing, you may discover unexpected sounds using this device: a remote bird twittering will seem very close to you. Ear amplifier is powered by 1.5V battery and draws only 7.5mA of current. The heart of the circuit is a constant-volume control amplifier. All the signals picked-up by the microphone are amplified at a constant level of about 1 Volt peak to peak. In this manner very low amplitude audio signals are highly amplified and high amplitude ones are limited. This operation is accomplished by Q3, modifying the bias of Q1 (hence its AC gain) by means of R2.




Simple AVR Programmer
Posted on Wednesday, June 1, 2011   •   Category: AVR

Simple AVR Programmer

This is simple to build AVR programmer for Atmel microcontrollers from AVR family. The microcontrollers must support serial programming. AVR programmer is connected to a PC through the RS232 serial interface and can be used with the PonyProg or Avrdude software programmer. AVR programmer is quite simple and it is based on the SI-Prog from the author of PonyProg software. AVR programmer can be used for programming Attiny13, Attiny26, Attiny2313, Atmega48, Atmega88, Atmega168, Atmega16, Atmega8 and it works very well. I also use the programmer with desktop computer, laptop, with and wihout USB-to-RS232 adapter and it works in all cases.




Bass Treble Tone Control Circuit
Posted on Wednesday, June 1, 2011   •   Category: Amplifiers

Bass Treble Tone Control Circuit

This simple tone control (bass & treble control) can be used in may audio applications. It can be added to amplifiers, used as a stand alone control module, or even built into new and exciting instruments. It uses NE5532 IC but other ICs such as LF353 or 4558 could be used as well. It requires dual +12V,-12V power supply.




Wireless Security Alarm
Posted on Tuesday, May 31, 2011   •   Category: Miscellaneous

Wireless Security Alarm

Alarm circuit is functioning as a car wireless security alarm. Yes, this is an FM radio-controlled anti-theft alarm. This alarm can be used on any vehicle that has a DC power supply 6-12V. Alarm circuit system is divided into two parts, the transmitter unit and receiver unit. Transmitter unit is working on the range of VHF Band II, exactly at a frequency of 88-108 MHz. This transmitter is a miniature FM transmitter that is installed in vehicles at night while parked in the car porch or car park.




LM3886 Amplifier
Posted on Sunday, May 29, 2011   •   Category: Amplifiers

LM3886 Amplifier

Several years ago, National Semiconductor came out with some very high performance, easy to use audio power LM3886 amplifier ICs. I was in need of an extra amplifier so I could biamp some of my home-built electrostatic loudspeakers so I tried the LM3886 chip. LM3886 amplifier was chosen because of the ease of use, power output, turn-on and off thump suppression, low distortion, and built-in protection against shorts and thermal runaway. There isn't much more to ask of a power amp than that. When driving electrostatic speakers, you can't have too much protection.




Field Strength Meter
Posted on Saturday, May 28, 2011   •   Category: Test and Measurement

Field Strength Meter

This Field Strength Meter has been specially designed for our FM bugs. It is capable of detecting very low power transmitters and will assist enormously in peaking many of our FM transmitters that have a coil in the output stage that can be adjusted for optimum output. Up to now, field strength meters have only been able to detect transmitters with an output of 100 milliwatts or higher, and for an output such as this, a simple circuit such as a meter and a coil is sufficient. But when it comes to a low power device, a simple circuit, with no amplification, is not suitable. We spent more than 5 days building all the circuits we could find - that purported to be suitable for low-power transmitters, hoping to find one that would work. Unfortunately none came anywhere near good enough so we had to design our own. The circuit we came up with is shown above and it incorporates an RF amplifier, diode rectification, and a DC amplifier so that a movement from a multimeter (a movement is the 'meter' part of a multimeter) could be used as the readout. The heart of the design is a pair of diodes that are partially turned on via a resistor (the 100k sensitivity control) and this overcomes some of the .6v threshold of a diode. You may not think .6v is very much but when you are talking in millivolt terms, it is 600 millivolts. The signal we are attempting to pick up produces one or two millivolts on the receiving antenna and if you need 600 millivolts to turn a diode ON, the field strength meter becomes very insensitive.




Audio Volume Control Attenuator with IR Control
Posted on Saturday, May 28, 2011   •   Category: Amplifiers

Audio Volume Control Attenuator with IR Control

The circuit provides both audio volume and input channel selection. A stepwise volume control is implemented with a set of small relays and resistors. In a high-end audio system, a noticable sound improvement over potentiomeneters can be obtained, also over 'audio grade' potentiometers. Clearly, the IR remote control provides convenience over solutions with stepped attenuator rotary switches. The sealed relays will maintain contact quality over a practically endless lifetime.




75 Meter SSB Transceiver
Posted on Friday, May 27, 2011   •   Category: RF Radio Frequency

75 Meter SSB Transceiver

Here's 75 Meter QRP SSB Transceiver. In general, the transceiver switches the 4-element 1500 ohm xtal BPF ends between the inputs and outputs of the two SA602s to reverse the signal flow for R/T operation. Since no IF amplifier is used in the design, 20 dB of additional receiver gain is produced by the 2N2222 receiver RF amplifier, while automatic gain control (AGC) is produced by the peak DC swing of the LM386 output passed through a rectifier and filtered by a capacitor and fed to the gate of a BS170 enhancement mode FET acting as a variable resistor across the input of the LM386. Both receive and transmit band pass filtering are done by the same half-pi BPF. The diode pair in the mic circuit reduce the "chirp" that occurs during the R/T transition. Additional BS170s could easily be used to mute both the mic and audio instead of the R/T switch directly. These BS170s would be controlled by the +R and +T voltages on their gates while their drains would be tied to 1) the mic circuit between the two coupling capacitors and 2) pin number 1 (audio in) of the LM386 (BS170 sources to ground). Additional power output (perhaps 60 mW) could also be attained by connecting the RF output transistor's collector choke (10 uH) to a 9 V supply instead of the 5 V. Additional biasing current might also be required for this change.




8W PLL Stereo Transmitter with LCD
Posted on Friday, May 27, 2011   •   Category: FM Transmitters

8W PLL Stereo Transmitter with LCD

This is 8W PLL Stereo Transmitter with LCD. It is a stable PLL FM transmitter based on TSA5511 synthesizer. Frequency is performed with three buttons through PIC16F84 microcontroller. Frequency of the transmitter is displayed on 16x1 LCD. Transmitter oscillator is based around BF981, BFR91, BFR96 transistors. 2SC1971 RF power transistor can be replaced with 2N4427 or 2N3553 but they will provide less output power.




LM4780 Gainclone Amplifier
Posted on Thursday, May 26, 2011   •   Category: Amplifiers

LM4780 Gainclone Amplifier

LM4780 gainclone amplifier with a design similar to the National Semiconductor BPA-200 (Bridge/Parallel Amplifier) which uses 4x LM3886 per channel and an input buffer. The total effect is (2x LM3886's paralleled amplifiers) 2x Bridged and should give approx 225 watts into 8 ohm and 335 watts into 4 ohm speakers when used with a sufficient power supply.




LM3875 Gainclone Amplifier
Posted on Thursday, May 26, 2011   •   Category: Amplifiers

LM3875 Gainclone Amplifier

Gainclone amplifiers have very few components and this one is based on the National Semiconductor LM3875 IC. The PCBs and components are very simple and quick to make, only took about 20 mins to assemble both amps and rectifier board. DC offset was about 80mV on one channel and about 40mV on the other. I used the optional Ci capacitor in the national datasheet for the IC which reduced it to between 0-4mV: This is the capacitor I chose, its an Elna Starget (expensive). The case was MUCH more time consuming and difficult to make though. I bought all the aluminium from a scrap metal yard including the heatsink. I got my aluminium panels cut at a sheet metal shop as I cant make straight cuts with a hack saw.




1.5V LED Flasher
Posted on Wednesday, May 25, 2011   •   Category: LED

1.5V LED Flasher

The circuit is a LED flasher to light LED with single 1.5V battery is usually based on a blocking oscillator or a charge-pumped voltage doubler.This is another (but similar to charge pump) way to flash LED with 1.5V battery. The base-R voltage becomes nearly double the Vcc while making oscillation timing of astable multivibrator. LED can be flashed if it is attached aside. Since the LED discharges the C electricity, oscillator timing is shortened.




12V Power Supply - 30A
Posted on Wednesday, May 25, 2011   •   Category: Power Supplies

12V Power Supply - 30A

This is high current 12V power supply. Power supply uses LM7812 IC and can deliver up to 30A to the load by the help of the TIP2955 pass transistors. Each transistor can handle up to 5A and six of them result an total output current of 30A. You can increase or reduce the number of TIP2955s to get higher or lower current outputs. In this design the IC delivers about 800mA. A 1 amp fuse is connected after the LM7812 to protect the IC against high current transients. The transistors and the 12V regulator IC both require adequate heatsinking. When the load current is high, the power dissipation of each transistor also increases so excess heat may cause the transistors to fail. Then you will need a very large heatsink or fan cooling. 100Ω resistors are used for stability and prevent current swamping as the tolerances of dc current gain will be different for each transistor. The bridge rectifier diodes must be capable of passing at least 100 amps.




Arduino Sinewave Generator
Posted on Wednesday, May 25, 2011   •   Category: Arduino

Arduino Sinewave Generator

Arduino Sine wave Generator using the direct digital synthesis Method. Here we describe how to generate sine waves with an Arduino board in a very accurate way. Almost no additional hardware is required. The frequency range reaches form zero to 16 KHz with a resolution of a millionth part of one Hertz! Distortions can be kept less than one percent on frequencies up to 3 KHz. This technique is not only useful for music and sound generation another range of application is test equipment or measurement instrumentation. Also in telecommunication the DDS Method is useful for instance in frequency of phase modulation (FSK PSK).

The DDS Method (digital direct synthesis). To implement the DDS Method in software we need four components. An accumulator and a tuning word which are in our case just two long integer variables, a sinewave table as a list of numerical values of one sine period stored as constants, a digital analog converter which is provided by the PWM (analogWrite) unit, and a reference clock derived by a internal hardware timer in the atmega. To the accumulator , the tuning word is added, the most significant byte of the accu is taken as address of the sinetable where the value is fetched and outputted as analog value bye the PWM unit. The whole process is cycle timed by an interrupt process which acts as the reference clock. Further details of the DDS Method are described in web of course.




Arduino Battery Saver - Watchdog and Sleep Functions
Posted on Wednesday, May 25, 2011   •   Category: Arduino

Arduino Battery Saver - Watchdog and Sleep Functions

This example shows how to make use of the Watchdog and Sleep functions provided by the ATMEGA168 chip (decimila). These functions are useful if you want to build low power consuming devices operated by battery or solar power.

The reduced power consumption is achieved by through a intermittent operation of the system .In case of Arduino your main loop will be executed once before the system is put into the sleep mode. After a few seconds t the watchdog wakes the system up and the main loop is executed again. The ratio between main loop execution time and watchdog time determines the amount of power that will be saved.

When we assume that the time to measure a sensor and making some decisions will take 10 millisecond and the watchdog is set to 8 seconds the on/off ratio is 800 which extends the battery live time by this factor.




Horsepower Monitor
Posted on Tuesday, May 24, 2011   •   Category: Miscellaneous

Horsepower Monitor

This device is designed to measure the torque in an automobile drive shaft and provide an output to a vehicle data recording system or a portable computer via an RS-232 interface. The received data can then be combined with RPM measurements from the data recording system to calculate horsepower. It consists of the sensor unit, (Figure 1), which attaches to the driveshaft, and the receiver unit, , which provides the serial output signal. The sensor unit is battery powered and communicates with the receiver via a 433 Mhz RF data link.The receiver unit is powered by the vehicle electrical system. Circuit operation is shown in the diagram.




Laboratory Power Supply 0-30 Volt
Posted on Monday, May 23, 2011   •   Category: Power Supplies

Laboratory Power Supply 0-30 Volt

The linear laboratory power supply, shown in the schematic, provides 0-30 volts, at 1 amp current, using a discrete transistor regulator with op-amp feedback to control the output voltage. The supply was constructed in 1975 and has a constant current mode that can be used to recharge batteries. With reference to the schematic, lamp, LP2, is a power-on indicator. The other lamp (lower) lights when the unit reaches its preset current limit. R5, C2, and Q10 (TO-3 case) operate as a capacitor multiplier. The 36 volt zener across C2 limits the maximum supply voltage to the op-amps supply pins. D5, C4, C5, R15, and R16 provide a small amount of negative supply for the op-amps so that the op-amps can operate down to zero volts at the output pins (pins 6). A more modern design might eliminate these 4 components and use a CMOS rail-to-rail op-amp. Current limit is set by R3, D1, R4, R6, Q12, R10, and R13 providing a bias to U2 that partially turns off transistors Q9 and Q11 when the current limit is reached. R4 is a front panel potentiometer that sets the current limit, R22 is a front panel potentiometer that sets the output voltage (0-30 volts), and R11 is an internal trim-pot for calibration. The meter is a 1 milliamp meter with an internal resistance of 40 ohms. Switch S1 determines whether the meter reads 0-30 volts, or 0-1 amp.




USB Servo
Posted on Monday, May 23, 2011   •   Category: RC Servo Motors

USB Servo

The USB-Servo is a device to control a servo via USB. A servo is a motorized device that is commonly used in remote controlled cars and planes. I built this device to activate a toy puppet. The puppet has a button on its bottom, if you press the button the puppet collapses. When the computer is able to press the button, I can use the puppet to signal information like someone's online-state in the Jabber-network: when my friend goes online, the puppet stands up, when he logs off it collapses.

Servos are connected with three-wire-cables. A red and a black one for the power, and a yellow one for the signal. Power has to be between 4.8 and 6 volts, so the 5 volts from the USB-port is in the range. The signal doesn't take much current, so you can connect it directly to the controller. The angle of the servo is controlled with pulse width modulation (PWM). It gets a signal of about 50Hz (one pulse every 20ms), the length of the pulse tells the servo the angle to adjust.




PWM Motor Driver with MOSFET H-Bridge and AVR ATmega8
Posted on Sunday, May 22, 2011   •   Category: Motor Controllers

PWM Motor Driver with MOSFET H-Bridge and AVR ATmega8

Here is a very simple project of controlling a small DC-motor (taken from an old personal cassette player) with ATmega8. The ATmega8 is having three PWM channels, out of which two are used here. PWM waveforms are fed to MOSFET (RFD3055) H-bridge. Here, direction is controlled using a two-position toggle switch and speed of the motor is controlled by two push-buttons, one for increasing the speed and other for reducing. The schematic is geiven here (click on the image to enlarge): When switch SW1 is closed, OC1A channel is active which will feed the PWM signal to Q1 & Q4 MOSFETs. The OC1B pin will remain low keeping the Q3 & Q2 in OFF condition. When SW1 is toggled to open position, OC1A pin will become low, making Q1 & Q4 OFF and OC1B will feed the PWM signal to Q3 & Q2, resulting in the change in the direction of current flow through motor. Hence, motor rotation direction will change. The speed is controlled by Push-buttons S2 & S3. Pressing S2 will increase the speed in fixed steps. Similarly, pressing S3 will reduce the speed in fixed steps.




USB DAC PCM2906 with Headphone Amplifier
Posted on Sunday, May 22, 2011   •   Category: Audio DAC

USB DAC PCM2906 with Headphone Amplifier

Presented here is high quality USB DAC PCM2906 with built-in headphone amplifier. To see one or more of the same sound card than this is a compact device. That acts as the computer sound card is easy to use. Just plug into a USB port on your computer. It can be used immediately within an IC in PCM 2906 Burr Brown's brand of Neu hear all agree that the sound of course. Used to convert digital signals from the USB port can adjust volume and mute the signal with Noise from the hard drive or CD player can not come to interference. Because a separate circuit from the computer. Add power to drive headphones with a Single Supply OPA2353 Opamp serves as Headphone Amp that does not reconcile the external power supply. This may be an alternative for those who are looking for sound card priced tight, but the quality of glass.




Lightning Detector
Posted on Sunday, May 22, 2011   •   Category: Miscellaneous

Lightning Detector

This DIY lightning detector circuit is a very sensitive static electricity detector that can provide an early warning of approaching storms from inter-cloud discharge well before an earth-to-sky return strike takes place. An aerial (antenna) formed of a short length of wire detects storms within a two mile radius. The circuit emits an audible warning tone from a piezo buzzer, or flashes an LED for each discharge detected, giving you advance warning of impendig storms so that precautions may be observed.




68 Watts LM3886 Power Amplifier
Posted on Saturday, May 21, 2011   •   Category: Amplifiers

68 Watts LM3886 Power Amplifier

Presented is 68 watts LM3886 Power Amplifier with the use of popular LM3886 amplifier integrated circuit. Amplifier should be fed by source symmetrical good filtered of + 34 and – 34 volts. R2 and L1 is a resistor of 10 ohms / 2watt coiled with 10 to 12 you exhale of enameled thread AWG 20. The circuit integrated lm3886 is a component easy of being found at the electronics stores, for that he is used in several projects of potency audio, some exist circuits with linked lm3886 in bridges for power of up to 150 watts. For most information on the assembly of that circuit, I suggest that sees the datasheet of the lm3886 in the site of the national semiconductors. With the information of the leaf of data you can adapt the circuit with lm3886 your needs.




100KHz Crystal Oscillator
Posted on Saturday, May 21, 2011   •   Category: Oscillators

100KHz Crystal Oscillator

There is a great deal of old amateur gear which many amateurs have decided to restore and bring back to life. While much of the early amateur transceivers work just fine they usually lack a digital readout and must rely on analog dials for tuning. The problem of dial calibration is complicated by the non-linear effects of tuning capacitors. This month's circuit is a 100Khz crystal calibrator using an inexpensive microprocessor crystal and CMOS IC's which are readily available at Radio Shack. The main problem with building a 100Khz oscillator is the unavailability of 100Khz crystals. Even if you find a vendor willing to cut such a crystal for you, plan on paying $20 or more not including shipping charges. The circuit uses an inexpensive 8MHz microprocessor crystal which can be easily obtained from most parts suppliers. Using a 74HCT393 binary counter IC, we can easily divide down the 8 MHz signal from our crystal into 100Khz or almost any frequency we need.




Build A 9 dB, 70cm, Collinear Antenna From Coax
Posted on Saturday, May 21, 2011   •   Category: Antennas

Build A 9 dB, 70cm, Collinear Antenna From Coax

Recently the RASON technical committee was hard at work at the repeater site repairing our 2 meter repeater antenna. One of the members commented to me that I should write an article about collinear arrays so that we could all build our own. While it is not always feasible to home-brew a commercial quality antenna designed to take hurricane force winds, it is very feasible to built a collinear antenna for average use. This article describes a collinear antenna made from very inexpensive RG58/U coaxial cable and encased in PVC pipe. Before we start building we need to cover some ground about the characteristics of coaxial cable. First remember that there is something called the velocity factor for coaxial cable. For RG58/U coax it is typically .66. This means that when we calculate the length of ½ wavelength in free space we need to adjust its size by multiplying it by the velocity factory. Simply put, RF slows down by the velocity factor when traveling through coaxial cable. All that aside now, lets calculate the ½ wavelength of RG58/U coaxial cable with a frequency of 444 Megahertz.




Laboratory Power Supply 24V 4A
Posted on Saturday, May 21, 2011   •   Category: Power Supplies

Laboratory Power Supply 24V 4A

Here's a laboratory power supply with output voltage continuously adjustable from 0 V to 24 V DC, remote voltage sense capability (Sense internal/external), output current limit is continuously adjustable from 0.04 A to 4 A and output current can be limited continuously or output shut down (Limit/cut).

Remote sensing means there are two additional wires which sense the delivered voltage at the load and compensate for any voltage drop along the cables which carry the delivered current. This improves voltage regulation at the load considerably but requires two additional wires for the sensing. A switch allows internal sensing at the output terminals for simpler operation when remote sensing is not required.

I like to have a switch which lets me choose between limiting the output current continuously (useful for charging batteries), or shutting down the output if the current limit is reached (useful for protecting equipment being repaired).

Another thing I like to have in the power supplies I build is a push button switch which multiplies the current scale by a factor of 10. That way one can momentarily press the button and get a much more precise reading of current. By making the switch a push button one cannot forget to turn the function off and risk the instrument being damaged when a large current is put through it. In this case and for now I am not installing this function because I am using the instrument's shunt resistor to sense the current for the electronic control system and I would have to change several things. I might do this in the future.




Long Range FM Transmitter
Posted on Friday, May 20, 2011   •   Category: FM Transmitters

Long Range FM Transmitter

The power output of many transmitter circuits are very low because no power amplifier stages are incorporated. The transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres. The circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2 (2N3866) forms a VHF-class A power amplifier. It boosts the oscillator signal power four to five times. Thus, 200-250 milliwatts of power is generated at the collector of transistor T2.




Power LED Driver Circuit
Posted on Friday, May 20, 2011   •   Category: LED

Power LED Driver Circuit

Here's a really simple and inexpensive Power LED driver circuit. The circuit is a "constant current source", which means that it keeps the LED brightness constant no matter what power supply you use or surrounding environmental conditions you subject the LED's to. Or to put in another way: "this is better than using a resistor". It's more consistent, more efficient, and more flexible. It's ideal for High-power LED's especially, and can be used for any number and configuration of normal or high-power LED's with any type of power supply. As a simple project, i've built the driver circuit and connected it to a high-power LED and a power-brick, making a plug-in light. Power LED's are now around $3, so this is a very inexpensive project with many uses, and you can easily change it to use more LED's, batteries, etc.




Rotary Encoders
Posted on Friday, May 20, 2011   •   Category: PIC

Rotary Encoders

Rotary encoders are very versatile input devices for microcontroller projects. They are like potentiometers expect of digital nature and unlike analogue potentiometers they never wear down. Rotary encoders not only provide 360 degrees of rotational freedom they also allow digital positioning information to be gained without the use of analogue to digital converters (ADCs). When using rotational encoders in projects it's possible to use the same encoder to represent a number of different input types, however this requires some form of feedback display to let the user know what information he is inputting and the 'position' of the encoder. The project is based around a 24 position rotary encoder, 16 LEDs arranged in a circle around the encoder, an A6276 16 LED serial driver IC and the PIC182550 microcontroller. A rotary encoder has 3 pins usually called A, B and C. The C pin (which is normally the centre pin) should be grounded and both A and B should be connected to the microcontroller with individual pull-up resistors on each input. In this project I used RB4 and RB5 on the PIC to connect the encoder; this has 2 advantages, firstly you can use the PORTB internal weak pull-up (which means you do not need external resistors) and also the PIC provides an 'interrupt-on-change' which can be used to monitor the encoder.




Electronic Thermometer using LM35
Posted on Friday, May 20, 2011   •   Category: Sensors

Electronic Thermometer using LM35

As shown in the schematic, temperature sensor of our electronic thermometer is LM35DZ. There are some kinds of LM35 IC, since it is cheap and easy to find we used LM35DZ in our project. It measures from 0°C to 100°C with a very linear output graph.For one degree change, it increases its output 10mV. On the Electronic Thermometer Schematic other hand, this circuit measures temperature values only between +10°C and +39°C. 2 numbered (middle) pin of the sensor is connected to the 5 numbered pins of LM3914 ICs. So every IC determines how many leds of bargraph will bright due to the analog signal received from the sensor. 2.2 microfarad tantal capacitors are connected between the 2 and 3 numbered pins of LM3914. Resistors in the circuit have %1 tolerance values.




LM386 Audio Amplifier
Posted on Thursday, May 19, 2011   •   Category: Amplifiers

LM386 Audio Amplifier

This project shows how to build an Audio amplifier based on LM386 IC. The circuit is very simple and construction is easy on a breadboard. The LM386 IC is unique in that the gain can be modified by changing Resistor R2 and Capacitor C2. This configuration will give us a gain of 20. By removing R2 and connecting C2 across pins 1 and 8, we can increase the gain to 200. It is important to understand that increasing the gain does not increase the output power. The increased gain is only used when a very low input signal is to be amplified. In a previous article I discussed building audio amplifiers using discrete transistors. While it is possible to build good audio amplifiers from discrete transistors, they are no match for the many audio amp IC's available to us. IC's offer many advantages including high efficiency, high gain, low standby current, low component count, small size and ,of course, low cost. It is little wonder that audio amp IC's have replaced discrete transistors in most consumer electronic devices. While many experimenters have stayed away from these little black mysteries, I am going to uncover some of their secrets and demonstrate how easy they are to use.




LM4780 Power Amplifier
Posted on Thursday, May 19, 2011   •   Category: Amplifiers

LM4780 Power Amplifier

Having decided to build an ultra-compact design, using a spare LM4780 seemed like an obvious plan. Having said that, I might choose a different IC if I didn't already have one to hand. The LM4780 contains two LM3886 dies (reference) giving 60 watts per channel, which is rather more than required this application. National Semiconductor make an enormous range of IC's with differing power levels and configurations, and there are plenty of possible candidates for this application - after all, we only need a few watts as this amplifier will principally be driving small speakers on the computer desk.




USB LED Fader
Posted on Wednesday, May 18, 2011   •   Category: LED

USB LED Fader

The USB-LED-Fader is a device to control a number of LEDs via USB. I built it to display the online status of my internet connection, the recording status of my video recorder (VDR), and warnings if the available disk-space is low. You can imagine an endless number of applications for this. The LEDs are controlled with pulse width modulation (PWM). That way, they are not only on or off, it is possible to control the brightness. Included in the device are a number of 'waveforms' that can be displayed through the LEDs. That way, one LED can display some kind of a sine- or triangular wave without any interaction with the controlling host. Every LED can be controlled individually; each one can display its own waveforms.




Special Edition Accurate LC Meter Kit
Posted on Wednesday, May 18, 2011   •   Category: Test and Measurement

Special Edition Accurate LC Meter Kit

Build your own Special Edition Accurate LC Meter (Inductance Meter / Capacitance Meter) and start making custom made precision coils and inductors. Accurate LC Meter allows to measure incredibly small inductance making it perfect tool for making all types of RF coils and inductors. It can measure inductance starting from only 10nH - 1000nH, 1uH - 1000uH, 1mH up to 100mH and capacitance from 0.1pF up to 900nF.

Special Edition LC Meter includes top notch high precision components that are only found in premium quality kits. It includes high quality double-sided printed circuit board (PCB) with red solder mask and pre-soldered tracks for easier soldering, detachable LCD display with yellow-green LED backlight, programmed PIC16F628A microcontroller chip, high precision capacitors and inductor, 1% Metal Film resistors, Machined IC Sockets, gold plated header pins, LCD header connectors and all the other components that are needed to build a premium quality kit. Thanks to the use of LCD connectors LCD display can be detached from the main PCB board at any time even after the kit has been assembled. All components are through-hole and are easy to solder. Special Edition Accurate LC Meter is designed for professionals that require unprecedented measurement accuracy and offers great value at low cost.




ESR Meter / Low Resistance Meter
Posted on Tuesday, May 17, 2011   •   Category: Test and Measurement

ESR Meter / Low Resistance Meter

This ESR Meter is perfect for any electronics repair technicians, engineers or hobbyist. This handy ESR meter measures electrolytic capacitor equivalent series resistance (ESR) in the circuit. ESR is a very important characteristic of capacitors greater than 1 microfarad. This meter makes measurements which are often impossible to check with standard digital capacitance meters. This ESR meter is based around ICL7107, 4049, NE555 and TLC274 operational amplifier and can measure resistance from 0.01 Ohm up to 19.99 Ohm. ESR value is displayed in Ohm on four digit LED display . The power consumption is only 8mA using 12V battery. ESR Meter offers very simple design and is easy to assemble.




FM Radio Receiver using TDA7088
Posted on Tuesday, May 17, 2011   •   Category: FM Radio / Receivers

FM Radio Receiver using TDA7088

This tiny receiver is not much bigger than an AA cell. It is powered off two LR44 button cells, which are expensive and I assume wouldn't last terribly long. I'll be on the lookout for LR44's at the markets and $2 shops now that I've got this radio! As with all these sorts of radios, the headphone lead functions as the aerial. Supplied with this receiver were a pair of those awful "in-the-ear" type of miniature type earphones. Apart from the appalling sound quality, they are insensitive, unhygenic and dirty, fragile, and do not block out external sounds. So, I use the normal kind of headphones instead. The enclosure is all clipped together, and once I'd opened it, sure enough, a TDA7088T was visible. The audio amp appears to be one transistor; ie. single ended class A. I don't know what current it's drawing so I can't say whether it's consuming much more battery current than a class B amp would. In any case I would prefer AAA cells rather than the LR44's.




Soft Start for Power Supply
Posted on Tuesday, May 17, 2011   •   Category: Power Supplies

Soft Start for Power Supply

The circuit will limit the current through the supply wires to 5.5A for about 1.5sec. After that time the relay will close and the current flow won't be restricted anymore. This is a very interesting circuit if you have a large toroid with big electrolytic caps connected to the power supply, since these will act like short circuits for a small amount of time if they start charging. This unit is a delay unit that can be connected directly to the mains power supply. It´s not obligatory to use one but it is a good idea, specially if you have a big toroidal transformer larger than 300 VA. This unit has a delay circuit and for the delayed time the mains power is supplied through power resistors minimizing in this way the big inrush current due to big capacitors and big toroidal transformers in the power supply. When everything is stable it shorts the power resistors and supplies the mains power directly.




FM Radio with TDA7000
Posted on Tuesday, May 17, 2011   •   Category: FM Radio / Receivers

FM Radio with TDA7000

This project is a FM Radio based on TDA7000 and LM386 integrated circuits. What is unusual about TDA7000 IC is how it operates. It is a proper FM superhet receiver, with the usual local oscillator, mixer, IF amplifier, limiter, and phase detector. The difference is that there's only one tuned circuit; the local oscillator. Like the Pulse Counting Receiver, the TDA7000 relies on a low IF so that ordinary Op Amp circuitry can take care of the gain and bandpass characteristics. Only 70Kc/s is used with the TDA7000. Now, you might remember that the deviation of a broadcast FM signal is +/- 75Kc/s. A fully modulated signal would therefore sound rather distorted. So, how can this IC work? It's quite simple in that there is what Philips call a Frequency Locked Loop. Basically, the local oscillator is shifted in response to detector output so that the bandwidth of the mixer output is never more than +/- 15Kc/s. It is actually compressing the frequency range of the modulated signal. The muting or squelch feature is novel to say the least. Although it performs as any other muting circuit does, the TDA7000 provides an artificial noise generator so that the receiver still sounds alive while tuned off station. If you don't need that feature, just remove the .022uF condenser at pin 3. Not all Philips data sheets show it, but connecting a 10K resistor from the supply to pin 1 will disable the squelch.




Class A Amplifier 8W
Posted on Monday, May 16, 2011   •   Category: Amplifiers

Class A Amplifier 8W

This is 8W Class A Amplifier I recently built. I am very pleased with the sonic results of this amplifier. It really does not disappoint. Even using fairly standard 3 way speakers in a large room, surprisingly there is ample power. What strikes me the most is the ability of this amplifier to differentiate between instruments and noises in the sound stage. This clarity is what I like most and I think this is achieved by deceptively simple and pure circuit topology. I used the original board layout, transistors and JFETs, and made some modifications. Heat sinking was increased to approximately triple the amount recommended. Instead of using the standard bridge rectifier, capacitor bank and battery setup, I opted for a fully regulated supply with a total of 127,0000 uF capacitance per channel and a 500 VA toroid transformer.




Automatic Battery Charger
Posted on Sunday, May 15, 2011   •   Category: Battery Chargers

Automatic Battery Charger

Here is a simple battery charger circuit intended for 12 Volt gell-type battery. Current is limited by the 7805 regulator IC and the limiting resistor (62 ohms) to approximately 250 milliamperes, anyway most small sized gell-type battery capacities ranges from 2.5AH to 7.5AH so charging time should take several hours. When the battery is full, the regulator adjust its voltage output from 15 volts down to 5 volts automatically terminate the charging process.




Solar Battery Charger with LM317
Posted on Saturday, May 14, 2011   •   Category: Battery Chargers

Solar Battery Charger with LM317

This is a solar panel battery charger schematic for AA and AAA rechargeable batteries. A small solar panel would be very good as a source of voltage charger. Building a solar AA battery charger only requires a few components and a simple construction. Solar panels should be well adapted to the battery to be charged or the battery may be overcharged. If you want to charge batteries with different capacities, then you need to change the solar panels. Since this is a simple solar battery charger that does not automatically turn off when the battery is full. So we need to maintain the charging current is low enough that will not damage the battery even when they are fully charged. An LM317T voltage regulator chip that can be used with a suitable resistor to regulate current. See solar AA battery charger




Light / Dark Relay Switch
Posted on Friday, May 13, 2011   •   Category: Sensors

Light / Dark Relay Switch

A simple light / dark activated relay switch circuit, suitable for many applications like the automatic switching of the lights in a shop window or a room according to the ambient light level. The circuit uses a light dependent resistor (LDR). A light/dark option has been incorporated. The term 'light/dark' is used because the circuit has a PCB-mounted switch on board. In one switch position a light-to-dark transition will activate the relay. In the other position a dark-to-light transition is required. So you can use the falling light on the detector to switch on a normally off circuit or switch off a normally on circuit. The relay is on when LDR uncovered and relay off when LDR covered. Adjust VR1 for light sensitivity. LED will turn on at the same time with relay.




DTMF Decoder Using MT8870
Posted on Thursday, May 12, 2011   •   Category: Phone Circuits

DTMF Decoder Using MT8870

This circuit detects the dial tone from a telephone line and decodes the keypad pressed on the remote telephone. The dial tone we heard when we pick up the phone set is call Dual Tone Multi-Frequency, DTMF in short. The name was given because the tone that we heard over the phone is actually make up of two distinct frequency tone, hence the name dual tone. The DTMF tone is a form of one way communication between the dialer and the telephone exchange. A complete communication consist of the tone generator and the tone decoder. In this article, we are use the IC MT8870DE, the main component to decode the input dial tone to 5 digital output. These digital bits can be interface to a computer or microcontroller for further application eg. remote control, phone line transfer operation, LEDs, etc...




Transformerless Power Supply
Posted on Thursday, May 12, 2011   •   Category: Power Supplies

Transformerless Power Supply

Simple, low cost and easy to build power supply. Ideal for applications that doesn’t require too much power. It can provide power to circuit that uses less than 100mA without any problem. The disadvantage of this circuit is the danger of an electrical shock, so it cannot be used if the circuit is in contact with the user. The voltage supplied by this is determined by the zener diode.




HI-FI Valve Amplifier
Posted on Wednesday, May 11, 2011   •   Category: Amplifiers

HI-FI Valve Amplifier

I wanted to make this HI-FI Valve Amplifier so that MCS can be considered a classic brand like a lot, but my hand veteran tuner anfimden kopamıyordum transistor amplifier at the end of this one day I decided to take it in my hand as long as I have somehow amplifier kurtulamayacaktım air after breakfast and drinking my tea I gave trying to check if the decision is correct Cry with her ​​almost 15 years we have not shared this with less than animism, but cherish her ​​love of rock music by pressing the send us compelled to take this tube amplifier device bitirebilecektim yes, I was sure before I took a friend who wants to 3 months without music ... without it stood late Tagged with kamçılandım ITSELF HERE:)




Arduino AVR In System Programmer
Posted on Tuesday, May 10, 2011   •   Category: Arduino

Arduino AVR In System Programmer

Randall converted an Arduino into AVR chip programming hardware for use with AVRDude. The project programs AVR tiny13 and other tiny AVR chips using an Arduino. He provides code and instructions to implement the Atmel AVR910 In System Programming protocol. I ported the Atmel AVR910 In System Programmer protocol to the Arduino. Now I can write programs to my ATtiny2313 and tiny13 chips. The Arduino sketch is available for download here. It works with the AVRDude programming software. This article will show how to use the Arduino to upload a program to the tiny13. The first step is to download the zip, extract the .pde file, then load it into the Arduino IDE, and write it to the Arduino. Next we can hook up the tiny13 chip.




PIC based Spectrum Analyser for PC
Posted on Tuesday, May 10, 2011   •   Category: Test and Measurement

PIC based Spectrum Analyser for PC

This is PIC18F2550 based Spectrum analyzer mod for PC. It uses WG24064A 240x64 graphical LCD with T6963 controller to display the result.




AVR ISP Programmer (In-Sytem programmer) for ATMEL
Posted on Tuesday, May 10, 2011   •   Category: AVR

AVR ISP Programmer (In-Sytem programmer) for ATMEL

This AVR ISP original by ATMEL you can found on "AVR software and technical Library - April 2003" CD-rom. It small component count I design new PCB and change some component that easy to build small PCB. The new firmware was writen by John Samperi for AT90S2313. This code can program more devices.




5 Watts FM RF Amplifier
Posted on Monday, May 9, 2011   •   Category: FM Transmitters

5 Watts FM RF Amplifier

This fm rf amplifier uses 2SC1971 transistor to provide 5 watts of output. Output matching is adjusted via the two 40pF trimmer capacitors likewise also to the input. Note that the emitter of this transistor is directly grounded on the heat sink and should have a good thermal transfer. Driving power of 100 to 200mW can be applied in order to provide 5watts of output. Use a dummy load to tune this amplifier and remember that the transistor is biased in Class C, sufficient filtering should be followed after the output to minimize all the harmonics. Use ground plane construction technique in the PCB lay-out for best result, the more the grounding the better. If you have hard time finding the 10uH rf choke, try to wind 1/2 meter of 0.2mm enamel wire over a 33K 1/2 watt resistor and solder the coil ends to the legs of the resistor.




Simple AVR Programmer
Posted on Monday, May 9, 2011   •   Category: AVR

Simple AVR Programmer

This is a very simple and easy to build programmer for Atmel microcontrollers from AVR family. The microcontrollers must support serial programming. This programmer is connected to a PC through the RS232 serial interface and can be used with the PonyProg or Avrdude software programmer. The programmer is quite simple and it is based on the SI-Prog from the author of PonyProg software. The Zener diodes D2, D3 with the resistors R2, R3 reduce the voltage from the ouput pins DTR, RTS on the serial port to around 5V which is suitable for microcontroller (MOSI, SCK). MISO signal is connected directly to the input CTS pin. The Zener diode D1 with the resistor R1 drive the NPN transistor T1, which controls RESET signal. The AVR microcontrollers are in reset when the signal has low level. The resistor R5 works as a pull-up for reset signal. The resistor R4 helps to close the transistor T1. The programmer has standard 10 pins header.




FM Transmitter with Varactor Diode Tuning
Posted on Monday, May 9, 2011   •   Category: FM Transmitters

FM Transmitter with Varactor Diode Tuning

Presented here is a low-power FM transmitter with varactor diode tuning using surface-mount devices (SMD) that will be received with a standard FM radio. Soldering surface mounted devices is not so hard and actually is quite easy. There are many designs for small FM transmitters but they have some problems. First, you need an audio amplifier to get enough modulation. Second, the antenna is attached directly to the collector. Third, the coil L must be wound by hand and adjusted by stretching. It all ads with a weak signal that tends to drift in frequency. In contrast the transmitter schematic we present here eliminates some of those problems, using varactor diode for tuning and modulation, givin great sensitivity without an audio amplifier.




100W Transmitter Amplifier for 2200m
Posted on Sunday, May 8, 2011   •   Category: FM Transmitters

100W Transmitter Amplifier for 2200m

This particular transmitter was later shipped up to VY1JA in the Yukon where, thanks to Jay's excellent antenna system, it was heard in Europe as well as in New Zealand during one of the Trans-Pacific Tests! Running 24 volts on the final will produce 100 watts into a 50 ohm load. The transmitter utilizes a 4060 binary counter IC chip as both the crystal oscillator and frequency divider. I used a 2200 kHz crystal along with the 'divide-by' sixteen output to produce a signal at 137.5 kHz. Other combinations of crystal frequencies and 'divide-by' combinations may also be used since the 4060 features divided outputs for f/32 (pin 5) and f/64 (pin 4), among others. You may have a 4MHz crystal or an 8MHz crystal in your junk box that will put you in the band using these output pins.




8 Channel IR Remote Control
Posted on Sunday, May 8, 2011   •   Category: Remote Control

8 Channel IR Remote Control

This IR remote control that you can use to control other devices or circuits up to 8 devices. The control codes are sent in RC5 format modulated to about 38 kHz carrier frequency.The IR transmitter powered by the CR2016 which is a 3V button Cells Battery CR2016.To extend the life of the battery this is done by putting the CPU into SLEEP mode for most of the time and wake-up only when a key is pressed. PIC16F630 is the heart of the transmitter used to send IR command to receiver.It also generate 38KHz carrier frequency.The CR2016 is 3V battery which is supply for the circuit. When any key not pressed the CPU work in SLEEP mode to reduce baterry power consumption and wake-up only when any key pressed. To wake-up the CPU from SLEEP mode the CPU use interrupt on change feature which interrupted when the state on PORTA change then the program execution after an interrupt is at the interrupt vector, if the global interrupt is not enabled, the program starts executing the first line of code right after the SLEEP instruction.In the interrupt service routine the software will scan the key that pressed and send IR command appropriate with key pressed.




8 Channel RF Remote Control
Posted on Saturday, May 7, 2011   •   Category: Remote Control

8 Channel RF Remote Control

This is a 8 channel RF remote control project. The transmitter powered by 5V.the RF module I used had long start-up and power down period after receiving a high pulse. To counter all of this I kept the receiver in constant standby mode, but sending a information all the time. That way the noise is flooded out, and the receiver will always respond. I had been trying all sorts of error detection methods and different ways of encoding the bytes, when I just gave up. Since the link is so noisy I decided to cut out all of the error detection methods and just make it accept anything it receives, and see what happened from there. But what do you know, it worked!




LM4780 2x60W Power Amplifier
Posted on Friday, May 6, 2011   •   Category: Amplifiers

LM4780 2x60W Power Amplifier

Here's a 2x60W LM4780 Power Amplifier. LM3886 is very interested in our project was the first project, and were acclaimed. But the feedback we receive from you, from scratch, we knew we should make a complete device. One reason for that, but hard to find and the LM3886 integrated into the original cost of a fact to be taken into consideration. In this project, in which hosts two LM3886 LM4780 integrated with Integration, ie, making a complete amplifier. Advantageous LM4780 is an integrated, cost of both purchase price aşacağından sahtesinin made ​​of forged-not-at least we do not see, but also would have received only two LM3886 price, or even more cheaply. We mean the complete amplifier, pre-amplifier, power amplifier and power supply hosts, ready for use, kutulayıp living room you can put the head in a corner of the device. If your hand if you have preamps or power amplifier, may be helpful in other projects.




10 Flashing LEDs using CD4017
Posted on Friday, May 6, 2011   •   Category: LED

10 Flashing LEDs using CD4017

This the circuit light led flashing ,with show of 10 LED. By use integrated number circuit CD4017 perform be Decade Counter/Divider with 10 Decoded Outputs. Which it is integrated digital circuit CMOS then use the power supply about 9VDC. For a signal input continue the circuit can produce general frequency may use IC NE555 all right.




LM317 Power Supply Circuit
Posted on Friday, May 6, 2011   •   Category: Power Supplies

LM317 Power Supply Circuit

This is a DC power supply circuit using the LM317T voltage regulator IC, which is the IC of this type is very popular among electronics hobby. Parameter to regulate the output DC voltage carried by the LM317 circuit with a maximum current of 1A. LM317 output voltage of this circuit is 6V DC, source from the stress out of the 12V CT AC transformer, and then converted to DC half-wave voltage by diodes D1-D2, and filtered by C1 capacitor. The transformer is used should be about 1-2A. Output voltage of 6V DC power supply circuit is determined by the value of R1 and R2. Diodes D3-D4 on the LM317 voltage current circuit to protect poor return for LM317 circuit IC. As for the other capacitors C3-C4 is used to refine the output voltage, and complete power supply circuits.




ESR Meter
Posted on Friday, May 6, 2011   •   Category: Test and Measurement

ESR Meter

"ESR" stands for equivalent series resistance. ESR is one of the characteristics that defines the performance of an electrolytic capacitor. Low ESR is highly desirable in a capacitor as any ripple current through the capacitor causes the capacitor to heat up due to the resistive loses. This heating accelerates the demise of the capacitor by drying out the electrolyte at an ever increasing rate. Over the lifetime of a capacitor, it is not uncommon for the ESR to increase by a factor of 10 to 30 times or even go open circuit. Typical lifetime ratings for electrolytics are 2000-15000 hours and are very dependant on ambient operating temperature. As the ESR increases, the filtering operation of the capacitor becomes impaired and eventually the circuit fails to operate correctly.

Why are ESR Meters so Useful?
A typical capacitor checker measures the capacity (usually in micro farads) of the test capacitor. Some advanced units also test for leakage current. Most of these testers require that the capacitor be removed from the circuit. Unless the capacitor has totally failed, they will not detect a high ESR value. In a typical circuit, there may be 10's or 100's of capacitors. Having to remove each one for testing is very tedious and there is a great risk of damaging circuit boards. This tester uses a low voltage ( 250mv ) high frequency (150khz) A/C current to read the ESR of a capacitor in the circuit. The in circuit testing is possible because of the low voltage used for obtaining the measurement. The voltage is low enough that solid state devices in the surrounding circuitry are not activated and do not affect the low resistance reading we are attempting to obtain. A lot of capacitor checkers will be damaged if you happen to test a charged capacitor. This circuit is A/C coupled and will withstand up to 400vdc of charge on a capacitor (but watch your fingers!). The ESR checker will not detect shorted capacitors as they will read with a very low ESR value. If you are trouble shooting a circuit, you will have to use several instruments including your nose, voltmeter and oscilloscope to locate all the possible failure modes. My experience has found that the ESR meter catches about 95% of capacitor problems and potential problems.




Stepper Motor Driver
Posted on Thursday, May 5, 2011   •   Category: Stepper Motors

 Stepper Motor Driver

Stepper motors are everywhere in electronics these days. There are two main types of stepper motors: 1. Bipolar motors. These have two coils and are controlled by changing the direction of the current flow through the coils in the proper sequence. These motors have only four wires and cannot be connected to this kit. See our Kit 1406 for a Bipolar Stepper driver Kit. 2. Unipolar motors. These have two center-tapped coils which are treated as four coils. These motors can have five, six or eight wires. Five-wire motors have the two center-taps commoned internally and brought out as one wire (Fig 1). Six-wire motors bring out each center-tap separately. The two center-taps need to be commoned externally (Fig 2). Eight-wire motors bring out both ends of each coil. The four “center-taps” are joined externally to form one wire. In each case the center-tap(s) are connected to a positive motor power supply. Unipolar motors may be connect as bipolar ones by not using the ‘+’ wires. A stepper motor has no brushes or contacts. It is basically a synchronous motor with the magnetic field electronically switched to rotate the armature magnet around. The Internet is where to get all the explanation about steppers. Just google ‘stepper motor’ and you will find tens of sites. In particular, look for ‘Jones on Stepper motors’ (it comes up top of the list when I did it just now) and read it. If you look at the other references you will find that the circuit in this kit has been around for many years in various forms. The latest publication was in Silicon Chip, 5/2002, and I have based this circuit on it.




Stereo Headphone Amplifier Adapter
Posted on Thursday, May 5, 2011   •   Category: Headphone Amplifiers

Stereo Headphone Amplifier Adapter

If you built our 20W Class-A Stereo Amplifier described last year, you will be aware that it lacks a headphone socket. Similarly, many hifi valve amplifiers also lack a headphone socket, the assumption being that a true hifi enthusiast will want to listen via good-quality loudspeakers. A headphone output was not included in the Class-A Stereo Amplifier because it would degrade its superb audio performance. Both the wiring paths and the general circuit layout are critical factors in the design and any changes, however slight, can cause big changes in the signal-to-noise ratio and harmonic distortion figures of the amplifier. Click for larger image Fig.1: the Stereo Headphone Adaptor connects between your stereo amplifier and the loud-speakers and can drive two pairs of headphones. If you do want to listen via headphones, a far better option is to build the simple Stereo Headphone Adaptor presented here. It connects directly to the amplifier’s speaker terminals and switches the loudspeakers and stereo headphone sockets using two DPDT (double-pole, double-throw) relays, so there’s no chance of it degrading the audio performance.




Digital Thermostat with LED Temperature Display
Posted on Thursday, May 5, 2011   •   Category: Sensors

 Digital Thermostat with LED Temperature Display

I needed to replace two old, unreliable thermostats for controlling the heating and cooling for a large garden shed. Commercial basic digital thermostats are available quite cheaply, but some lack the ability to control heavy loads or have the extra features that I require for saving energy when the door is often left open or to indicate temperature being out of range etc. I like the PIC18F1320 microcontroller used in my previous project - so decided to use it again in a very similar design to drive three multiplexed LED displays and read the temperature from a Dallas/Maxim DS18x20 "1-Wire" digital sensor.




60 Minute Countdown Timer
Posted on Wednesday, May 4, 2011   •   Category: Timer Circuits

60 Minute Countdown Timer

Here is a 60 minute countdown timer that can be used as an exposure timer for UV light boxes, photography, egg timer, and many other projects where counting or delay is necessary. The heart of the countdown timer is PIC16F84A chip and 4 digit character LED display. The relay is energized after the count down timer goes down from specified minute and second until zero, and can both turn devices on or off. See the link for details and schematic.




Homemade Metal Detector
Posted on Wednesday, May 4, 2011   •   Category: Sensors

Homemade Metal Detector

Nowadays, metal detection has become a hobby of many people. Besides as a funny and interesting hobby for them, they also wished indeed a treasure that is embedded in the soil when excavated. For this one hobby, you have to have a tool known as a metal detector. To undergo this hobby is quite expensive to buy. But for those of you who want to try to make yourself a metal detector, the following will be presented a simple schematic that relates to metal detection. The operation of metal detector is based on superheterodying principle, which is generally used in a heterodyne receiver. This circuit uses two RF oscillators. Both oscillator frequency is fixed at 5.5 MHz. The first RF oscillator comprises transistor T1 (BF 494) and 5.5 MHz ceramic filter commonly used in TV sound-IF section. The second oscillator is an oscillator Colpitt realization with the help of the transistor T3 (BF494) and inductor L1 (follow the details of construction) was driven by trimmer capacitor VC1.




Studio Stereo Headphone Amplifier
Posted on Tuesday, May 3, 2011   •   Category: Headphone Amplifiers

Studio Stereo Headphone Amplifier

This is a dual/stereo headphone amplifier with high quality audio built around OPA2134. This headphone amplifier can drive high or low impedance phones with low noise and distortion. When used with line level signals from CD/MP3 players, etc., requiring only a power supply and volume potentiometer. Many high-power amplifier audio designs have already provided an output for headphones. To support simple headphones, additional circuitry is required by adding only two resistors in series with the loudspeaker output to limit the drive current and protects the phone that in terms of reinforcing failure. Considering its simplicity, this scheme works well resistive limit, although it will cause distortion if the load is non-linear - a prospect that may be most headphones. In addition to eliminating potential sources of distortion, there are a number of other reasons why you might consider to build a separate headphone amplifier.




ESR & Low Resistance Test Meter
Posted on Monday, May 2, 2011   •   Category: Test and Measurement

ESR & Low Resistance Test Meter

As electrolytic capacitors age, their internal resistance, also known as "equivalent series resistance" (ESR), gradually increases. This can eventually lead to equipment failure. Using this design, you can measure the ESR of suspect capacitors as well as other small resistances. Basically, the circuit generates a low-voltage 100kHz test signal, which is applied to the capacitor via a pair of probes. An op amp then amplifies the voltage dropped across the capacitor’s series resistance and this can be displayed on a standard multimeter. In more detail, inverter IC1d is configured as a 200kHz oscillator. Its output drives a 4027 J-K flipflop, which divides the oscillator signal in half to ensure an equal mark/space ratio. Two elements of a 4066 quad bilateral switch (IC3c & IC3d) are alternately switched on by the complementary outputs of the J-K flipflop. One switch input (pin 11) is connected to +5V, whereas the other (pin 8) is connected to -5V. The outputs (pins 9 & 10) of these two switches are connected together, with the result being a ±5V 100kHz square wave. Series resistance is included to current-limit the signal before it is applied to the capacitor under test via a pair of test probes. Diodes D1 and D2 limit the signal swing and protect the 4066 outputs in case the capacitor is charged.




RF Control for Home Appliance
Posted on Monday, May 2, 2011   •   Category: Remote Control

RF Control for Home Appliance

This circuit consists of Transmitter and Receiver section. The circuit can be used to control home appliances within a range of 30 meters. In open area, you can expect a range of 100 meters. The circuit comprises HT12 Encoder and Decode IC's. HT12 Encoder is used in the transmitter (remote) circuit where as HT12E is used in receiver circuit. The Encode IC encodes the 4 bits of data and transmit it serially to to RF Transmitter module. These 433Mhz transmitter and receiver modules operate using ASK Modulation.




Light RF Remote Control
Posted on Sunday, May 1, 2011   •   Category: Remote Control

Light RF Remote Control

This is another remote control for my RF light switch. Pretty much the same as before but on a smaller PCB. Also ended up putting it in an old Maxim sample box. I found a couple of button nubs in my junk box so decided to go with those. Even so I had to raise the buttons with pieces of rubber. A piece of tape keeps the buttons from falling out when the box is opened and also adds some tolerance for misalignment.




Simple IR Remote Receiver with Decoder
Posted on Saturday, April 30, 2011   •   Category: Remote Control

Simple IR Remote Receiver with Decoder

The function of the device is very simple. Any IR remote than can be programmed to use the Sony protocol will work. The module outputs the device code (TV/VCR/DVD/AUX) and the button pressed, so the device can be used on as many different projects as your remote has devices (usually four). The numeric keys output the number of the key (0 outputs a 0, etc.). The function keys all output unique numbers. Note that not all buttons are available depending on which device you have selected. The VCR setting seems to use most of the keys on the remote. Also note that the first key pressed after the device is powered up does not output what it should. All subsequent numbers are correct. Luckily, all of the numbers so generated make a number different than any of the key codes, so it doesn't cause any problem. This could even be used to let the device know if it has just been powered up or rebooted. I have no idea why it does this.




100W HI-FI MOSFET Amplifier
Posted on Friday, April 29, 2011   •   Category: Headphone Amplifiers

100W HI-FI MOSFET Amplifier

Here is a simple 100W HI-FI MOSFET Amplifier. The main feature of this amplifier is a simple design and assembly. Simplicity of the circuit by looking at the circuit you expect amplifier to be simple. It should be noted that many hi-end amplifiers have a very simple but good quality designs. General technological theory is due to fewer parts, fewer problems. Additionally power to supplement your system is quite effective. Power supply transformer is very important. 8 Ohm output for a 35 - 0 to 35 V and at least 3 amps per power amplifier is recommended that a transformer can be transferred. Naturally, the two substations will be required for stereo use.




LM386 Audio Probe Amplifier
Posted on Thursday, April 28, 2011   •   Category: Test and Measurement

LM386 Audio Probe Amplifier

LM386 audio probe amplifier is an essential tool for troubleshooting audio stages in audio related circuits such as amplifiers, oscillators, function generators, phone circuits, radios and lots of our other projects. It is a very handy piece of test equipment that can be built on pre-drilled board and will make a perfect addition to your electronic collection. There are lots of things that can go wrong with an audio stage. It can produce distortion or a “hollow” sound, go weak or simply fail altogether. Likewise tone circuits can present a number of faults and it is very handy to be able to “hear” what is going wrong. It is not sufficient to measure the DC voltages on these stages. This only gives a partial picture of the conditions and does not tell you the quality of the audio being processed. To determine this you need a piece of test equipment that will let you see or hear what is being processed. Some of the projects you can test with the Mini Bench Amplifier are tone circuits while others are audio circuits. Tone circuits and audio stages are surprisingly difficult to test unless you have an audio probe or a oscilloscope. Oscilloscope is an ideal piece of equipment but if your budget does not extend this far, the next best thing is an audio probe.




High Power FM Wireless Microphone
Posted on Thursday, April 28, 2011   •   Category: FM Transmitters

High Power FM Wireless Microphone

This FM Wireless Microphone has been a very popular project with beginners and experienced constructors alike. It has been used inside guitars and as the basis of a remote control system. I do however, receive many requests for a higher powered circuit and better microphone sensitivity. This High Power FM Wireless Microphone has a better frequency stability, over 1 Km range and is good on microphone sensitivity. This has been achieved by adding an RF amplifier buffer (with 10dB gain) and an AF preamplifier to boost the modulation a little.




BA1404 HI-FI Stereo FM Transmitter
Posted on Thursday, April 28, 2011   •   Category: FM Transmitters

BA1404 HI-FI Stereo FM Transmitter

This FM transmitter design is a result of many hours of testing and tweaking. The goal was simple; to test many existing BA1404 transmitter designs, compare their performance, identify weaknesses and come up with a new BA1404 transmitter design that improves sound quality, has very good frequency stability, maximizes transmitter's range, and is fairly simple for everyone to build. We are happy to announce that this goal and expectations have been met and even exceeded. The transmitter can work from a single 1.5V cell battery and provide excellent crystal clear stereo sound. It can also be supplied from two 1.5V battery cells to provide the maximum range. One of the qualities of BA1404 FM transmitter is excellent frequency stability. This is mainly due to a use of high quality 3.5 turn variable coil. Tunable RF coils are ideal for precise frequency tuning because their magnet wire is halfway embedded within the plastic, which minimizes frequency drifts. Regular air coils are not preferred for professional broadcasting because the coil expands and contracts with temperature changes. That's the very reason why variable coil was chosen as a substitution for an air coil and a variable capacitor.




Telephone Conversation Recorder
Posted on Thursday, April 28, 2011   •   Category: Phone Circuits

Telephone Conversation Recorder

This circuit enables automatic switching-on of the tape recorder when the handset is lifted. The tape recorder gets switched off when the handset is replaced. The signals are suitably attenuated to a level at which they can be recorded using the ‘MICIN’ socket of the tape recorder. Points X and Y in the circuit are connected to the telephone lines. Resistors R1 and R2 act as a voltage divider. The voltage appearing across R2 is fed to the ‘MIC-IN’ socket of the tape recorder. The values of R1 and R2 may be changed depending on the input impedance of the tape recorder’s ‘MIC-IN’ terminals. Capacitor C1 is used for blocking the flow of DC. The second part of the circuit controls relay RL1, which is used to switch on/off the tape recorder. A voltage of 48 volts appears across the telephone lines in on-hook condition. This voltage drops to about 9 volts when the handset is lifted. Diodes D1 through D4 constitute a bridge rectifier/polarity guard. This ensures that transistor T1 gets voltage of proper polarity, irrespective of the polarity of the telephone lines.




Temperature Control using a DS1621 Sensor and a ATtiny 2313 Micrcontroller
Posted on Thursday, April 28, 2011   •   Category: Sensors

Temperature Control using a DS1621 Sensor and a ATtiny 2313 Micrcontroller

This circuit uses a Dallas DS1621 temperature sensor which indicates the temperature of the device. The temperature sensor has an thermal alarm output, which becomes high when the temperature of the device exceeds a user defined value. When the temperature drops below a user defined value, the alarm output becomes low. In this way any amount of hysteresis can be programmed. The values are stored in a special register of the device that is nonvolatile. The signal of the alarm output is amplified by a BC557 PNP transistor, that drives a relay that can switch a heater element or a blower on or off. The temperature settings and readings are communicated to/from the device over a simple 2-wire serial interface. An ATMEL 90S2313 microcontroller controls the serial communication to/from the DS1621.The microcontroller also controls three LED, only one of the LED's is on when the temperature is within a certain range. The range of the temperature in which the LED's are on can be set by the user in the program code. The circuit needs to be powered by a 5V power supply, which can be obtained from a wall-wart.




Thermostat Controller with Relay using LM35 and TL431
Posted on Tuesday, April 26, 2011   •   Category: Sensors

Thermostat Controller with Relay using LM35 and TL431

Here is a simple yet highly accurate thermal control circuit which can be used in applications where automatic temperature control is needed. The circuit switches a miniature relay ON or OFF according to the temperature detected by the single chip temperature sensor LM35DZ. When the LM35DZ detects a temperature higher than the preset level (set by VR1), the relay is actuated. When the temperature falls below the preset temperature, relay is de-energized. The circuit can be powered by any AC or DC 12V supply or battery (100mA min.)




Automatic Fan Controller Circuit
Posted on Monday, April 25, 2011   •   Category: Sensors

Automatic Fan Controller Circuit

This circuit will turn on/off 12V DC fan or CPU fan when temperature above normal temperature.You can set turn on temperature by adjust VR1. This circuit use an NTC (Negative temperature coefficient)which is a thermistor is one in which the zero-power resistance decreases with an increase in temperature. So If temperature increase the voltage at pin 3 on LM311 will decreased .The resistance of NTC is about 10K at 25'c.




Simple XR2206 Function Generator
Posted on Thursday, April 21, 2011   •   Category: Test and Measurement

Simple XR2206 Function Generator

The generator was build using XR-2206 function generator IC, which is capable to generate sine, square, ramp and pulse waveforms in frequency range of 0.01Hz to 1MHz. The amplitude and frequency is modulated by voltage (potentiometers). The example circuit from datasheet worked well.




USB Powered PC Headphone Amplifier
Posted on Thursday, April 21, 2011   •   Category: Headphone Amplifiers

USB Powered PC Headphone Amplifier

This audio amplifier uses TDA7053 which is an integrated class-B stereo power amplifier in a 16-lead dual-in-line (DIL) plastic package. Which requires minimal amount of external parts. This might be good solution to all of those who have PC with integrated sound card into motherboard. The main problem is that outputs of such sound cards are for active acoustic systems, this means that speakers must have power amplifier built in. If you decide to connect a headphones sometimes it might be not enough to provide required sound level.




AVR ISP Programmer
Posted on Thursday, April 21, 2011   •   Category: AVR

AVR ISP Programmer

This is an AVR ISP Programmer which is controlled via COM port. Signal levels of the RS-232C line is converted to the target level, so that target device can operate in entire range of the VCC. And also it can be used as an communication cable to communicate between host PC and target program (this is explained in the following section). This ISP adapter is sufficient to develop most of the AVR applications.




DIY 4 x 22W Car Audio Amplifier Based on TDA7384
Posted on Wednesday, April 20, 2011   •   Category: Amplifiers

DIY 4 x 22W Car Audio Amplifier Based on TDA7384

So this time I decided to make pretty simple but powerful enough car audio amplifier. For this I’ve chosen quad bridge car audio amplifier TDA7384 which has four input and four output channels with power capability of 4x35W. As datasheets of TDA7384 says it is low distortion, low output noise, low external component count. Also has Stand-By function and Mute function. It has several protections like from output short circuit to GND or to Vs, capable to handle very inductive loads, thermal limiter, load dump voltage. TDA7384 is an AB power amplifier cased in flexiwatt25 (eagle library is included in project archive) package witch is designed for high end car radio applications. It allows rail to rail output voltage swing with no need of boot-strap capacitors.




Oscilloscope Probes for Accurate Signal Measurements
Posted on Wednesday, April 20, 2011   •   Category: Oscilloscopes

Oscilloscope Probes for Accurate Signal Measurements

On the following article learn about Oscilloscope probes, their basic characteristics and proper calibration. Measuring signals with oscilloscopes may be challenging task especially high frequency ones. Without proper oscilloscope probes correct measurement of high speed time domain signals wouldn’t be possible. For high speed measurement you should consider signal parameters like amplitude, source impedance, rise time and bandwidth.




Temperature Controlled Fan
Posted on Tuesday, April 19, 2011   •   Category: Sensors

Temperature Controlled Fan

With this simple circuit you will be able to control the speed of a DC fan according to temperature measured by a temp sensor. It’s an ideal add-on for your PC cooling fans to eliminate produced noise. Requested by some correspondents, this simple design allows an accurate speed control of 12V dc fan motors, proportional to temperature. A n.t.c. Thermistor (R1) is used as temperature sensor, driving two directly coupled complementary transistors wired in a dc feedback circuit. An optional circuitry was added to remotely monitor fan operation and to allow some sort of rough speed indication by means of the increasing brightness of a LED.




Four Channel Power Amplifier
Posted on Monday, April 18, 2011   •   Category: Amplifiers

Four Channel Power Amplifier

I am a big fan of surround sound. Up until the moment I finished this amp, I was using two two-channel amplifiers to power four speakers. This was very annoying, because it meant I had two volume controls. This invariably meant that the balance between front and rear was off. Added to this, was that the amplifier for the rear speakers was not very good. It produced too much noise, and allowed clicks and pops from the power grid through, to be amplified and heard. I decided I was going to build a four channel power amplifier, and later a pre-amplifier to feed it. You might wonder why I didn't choose to make a five channel one instead. This is because I don't see the use of the center channel. I will probably write an article detailing why, but for now, suffice it to say that four channels is enough for 2 dimensional sound, which is what 5.1 is as well.




1KM Power FM Transmitter
Posted on Sunday, April 17, 2011   •   Category: FM Transmitters

1KM Power FM Transmitter

This small power FM transmitter can transmit more than 1 km in good conditions. The modulation can be made so much with a microphone or audio source. Circuit of power fm transmitter is built around 2n2218 transistor. Transmitter coil is 5 turns of enameled 22 AWG wire, with diameter of 1 cm without nucleus. Look at the capacitors that it should be ceramic. The antenna should possess from 15 to 40 cm. For transmission it ties a receiver of FM (radio) in the proximity to half volume in a free frequency (that there is not any radio operating), with a wood or plastic key, rotate the screw of CV to capture the frequency of the transmitter.




Digital ON-OFF Tactile Button Relay Switch
Posted on Saturday, April 16, 2011   •   Category: Miscellaneous

Digital ON-OFF Tactile Button Relay Switch

Small circuit, with which we can use to get rid of the standard switch and operate any type of load with a push of a tactile button. Voltage between 5 and 18 V DC ( depends on the operating voltage of the relay coil ) in terminal CN1. Output Current is 10A ( depends on relay contacts ) in terminal CN3 activated by external positive pulse or short-circuiting the terminal CN2. Circuit is protected against double pulses and rebounds.




1.5V Battery Operated Rebroadcast FM Transmitter
Posted on Friday, April 15, 2011   •   Category: FM Transmitters

1.5V Battery Operated Rebroadcast FM Transmitter

This implementation is adapted to rebroadcast the output of a CD player, television receiver, or radio receiver. I use it so that I can move about the house and listen to my favorite programs without disturbing others. Within and the house, I find that I can get 10 to 20 meters away from the transmitter with the small pocket FM receiver I carry in my shirt pocket. Your mileage may vary. The transmitter as built and pictured below (the transmitter is in the blob of hot melt glue on the end of the battery holder) does not have an on-off switch. I put a 1.5 AA cell that was run down too far to run my CD player in this transmitter and it ran for over a month before I replaced it. The one in the transmitter at this moment has been running it continuously for over three months. Current draw is only about a milliamp with a new battery (assuming you don't have a super-high beta transistor in which case the theoretical limit is about 2.5 ma). An on-off swich is not necessary, though it may satisfy an emotional need.




Mini FM Transmitter
Posted on Thursday, April 14, 2011   •   Category: FM Transmitters

Mini FM Transmitter

9 Volt battery operated simple Mini FM Transmitter. FM Transmitter is very simple, compact, and has transmission signal with a range of 100-150m, good sensitivity and low current consumption. Transmitter's schematic consists of a bass amplifier for the first transistor and the proper frequency generator in the second. FM Transmitter divided transitional capacitor that allows you to set up a cascade separately.




Broadcast FM Transmitter
Posted on Tuesday, April 12, 2011   •   Category: FM Transmitters

Broadcast FM Transmitter

Here's a nice AC mains powered FM Broadcast Audio Transmitter with pre-emphasis, audio level control, and tuning control. The circuit consists of a frequency modulated oscillator, an audio preamplifier with pre emphasis to supply the frequency modulating signal, and a buffer amplifier to drive the antenna connector. Oscillator's frequency is determined by L1 resonating with the 10 pf capacitor and the total capacitance across it. The collector-base capacitance of the transistors Q3, Q4, and Q5 is a function of their revers bias. This is basically a poor man's (or lazy man's) varactor. The voltage across Q3 is set by a voltage divider and is then modulated by an Ac coupled audio signal from the pre amp, causing the reverse bias to vary with the audio signal, which changes the resonant frequency of L1's circuit, causing the frequency of the oscillator to vary with the audio signal. The capacitance of Q4 and Q5 is adjusted by DC bias from the tuning adjustment potentiometer, and this capacitance sets the center frequency of the oscillator. All of the transistors in the oscillator -Q1 through Q5, are 2N4401. The purpose of the buffer is to minimize frequency shift as loading on the antenna is changed. It was specifically designed to reduce the signal amplitude to the antenna. Transmitters should not use any more power than is necessary to achieve the task at hand, and lightly coupling the RF into the buffer's base with a gimmick capacitor did the trick. The transistor is an MPSH34.




1.5V to 5V/12V DC/DC Converter with LT1073
Posted on Monday, April 11, 2011   •   Category: AC / DC Innveters

1.5V to 5V/12V DC/DC Converter with LT1073

Small 1.5V to 5V or 12V DC/DC converter with LT1073 chip. The IC is available in three different versions, depending on output voltage. Two with fixed output voltage of 5V and 12V, and the most interesting that can be adjusted. The adjustment is done through a voltage divider with two resistors, of mass, output and Terminal 8, internally connected to the voltage comparator IC, which is responsible for stabilizing the output voltage.




RF Remote Control Light Switch
Posted on Sunday, April 10, 2011   •   Category: Remote Control

RF Remote Control Light Switch

This is a remote controllable light switch that comes with an RF remote. The only light switch is across the room from my PC and it's a pretty large room. (The building's basically a 1-room apartment) so this works out great with the remote. Of course since I'm using the remote to cut the lights when I go to bed I'm basically using the remote from two places which brings with it the unavoidable annoyance of the remote being in the wrong place all the time. Which means I have to get up and look for it which is effectively as much of an annoyance as it was meant to solve. So I wanted a second controller that would basically be a stationary switch by my bed so I could leave the portable remote around the desk.




1.5V Spy FM Transmitter Bug
Posted on Saturday, April 9, 2011   •   Category: FM Transmitters

1.5V Spy FM Transmitter Bug

Here's a tiny one transistor spy FM transmitter bug that operates from a single 1.5V AA battery. Main advantage of this circuit is that power supply is a 1.5 Volts cell (any size) which makes it possible to fix PCB and the battery into very tight places. Transmitter even runs with standard NiCd rechargeable cells, for example a 750mAh AA size battery runs it about 500 hours (while it draws 1.4mA at 1.24V) which equals to 20 days. This way circuit especially valuable in amateur spy operations. Mini FM transmitters take place as one of the standard circuit types in an amateur electronics fan's beginning steps. When done right, they provide very clear wireless sound transmission through an ordinary FM radio over a remarkable distance. I've seen lots of designs through the years, some of them were so simple, some of them were powerful, some of them were hard to build etc.




Solid State Relay
Posted on Friday, April 8, 2011   •   Category: Miscellaneous

Solid State Relay

Solid state relay is a hybrid circuit, normally composed of an optocoupler which isolates the input, a trigger circuit that detects the zero crossing of the line current and a triac or similar device that acts as a circuit breaker. Its name comes from the similarity presents an electromechanical relay, this device is generally used for applications which has a continuous use of the contacts of the relay compared to a conventional relay generate a serious mechanical wear, besides being able to switch high amperage in the case of electromechanical relays in a short time would destroy the contacts. These relays allow switching speeds much higher than the electromechanical relays.




300m FM Transmitter
Posted on Thursday, April 7, 2011   •   Category: FM Transmitters

300m FM Transmitter

This FM transmitter is about the simplest and most basic FM transmitter it is possible to build and have a useful transmitting range. It is surprisingly powerful despite its small component count and 3V operating voltage. It will easily transmit over 300 meters in the open air and even more with higher voltage supply. The circuit we use is based on a proven Australian design. It may be tuned anywhere in the FM band. Or it may be tuned outside the commercial M band for greater privacy. Of course this means you must modify your FM radio to be able to receive the transmission or have a broad-band FM receiver. The output power of FM transmitter is within the legal limits of many countries. However, some countries may ban all wireless FM transmitters without a license. It is your responsibility to check the legal requirements for the operation and to obey them. FM transmitter is constructed on a single-sided printed circuit board PCB.




Power RGB LED Controller
Posted on Wednesday, April 6, 2011   •   Category: LED

Power RGB LED Controller

Power RGB LED Controller is the extension of tiny RGB to drive high power LED’s. For this project I used a 3 x 1W common Anode RGB LED. Q1 to Q3 are N-Channel HEXFet Mosfet’s with logic level drive and a RDSon at about 50mOhms. R1 to R3 are at about 2k2, R4 to R6 at about 15k and R7 to R9 depend on the LED used and VCC. If you use FET’s with higher RDSon you have to consider RDS in your calculation!




Lithium Ion Battery Charger with Microchip MCP73831
Posted on Wednesday, April 6, 2011   •   Category: Battery Chargers

Lithium Ion Battery Charger with Microchip MCP73831

Here's a simple and inexpensive compact lithium ion / polymer battery charger based on Microchip's MCP73831 IC. It features adjustable current charging from 15mA up to 500mA for single cell lipo batteries. With this lipo charger just a few external components are needed. Constant voltage power supply of 5 ~ 6V is needed. Power can also be drawn from USB port. When USB power is 150mA charge current should not be higher. Charge current can be adjusted with external resistors. External LED provides status when lipo battery is fully charged. The LED lights when battery is fully charged. The maximum charging voltage is selectable from 4.2 to 4.5. This has to be chosen at the time of purchase. Typically 4.2V is a standard charging voltage. MCP73831-2 <- 4.2V, MCP73831-3 <- 4.3V, MCP73831-4 <- 4.4V, MCP73831-5 <- 4.5V.




24V to 12V 400W DC Inverter
Posted on Wednesday, April 6, 2011   •   Category: AC / DC Innveters

24V to 12V 400W DC Inverter

24V to 12V 20A 400W DC to DC Inverter. Does little to change my PV system 12v 24v me the problem arose of what to do with investors who already had 12V. I was looking for a pattern online and found several schemes with linear regulators 20A, this solution although quite simple, due to the huge losses they have is not advisable. Ideally, a converter switched, high-performance. At the end I found nothing I liked and decided to design my own. Circuit characteristics: Output current: 20A at 12V (15A continuous and 30A Momentary), Input voltage: 18 to 30V DC, Output voltage: 5 to 20V, Operating Frequency: 70kHz, Effectiveness: 95%, 400W maximum power, Protections: Above current (30A) in the F1 circuit, D1 and F1 polarity in the circuit.




PLL FM Transmitter using LMX1601, ATtiny2313 AT90S2313
Posted on Tuesday, April 5, 2011   •   Category: FM Transmitters

PLL FM Transmitter using LMX1601, ATtiny2313 AT90S2313

Here's a PLL FM Transmitter using LMX1601, ATtiny2313 or AT90S2313 microcontrollers. The common characteristic of all of the previous low power FM transmitters I've built over the decades, is that their operating frequency is determined by an LC resonant circuit. Some of them had excellent stability, some of them didn't, but I had always wanted to make one that is crystal controlled. Various schemes had been considered from time-to-time, including the direct approach of modulating the load capacitance of a a crystal oscillator, a whimsical phase modulation scheme involving a phase shifter, some balanced modulators, and limiting amplifiers, and at times, the down-to-earth and sober approach of modulating a VCO within a phase locked loop (PLL). While browsing Digikey's online catalog, I found the LMX1601 frequency synthesizer chip and thought: "Just maybe, the PLL approach is finally within my grasp." The LMX1601, which apparently was designed for use in cell phones, includes everything need to make two phase locked loops except for the VCOs. More importantly, one of the PLLs, specifically the "AUX" PLL, is specified to work in the FM broadcast band. The LMX1600 and the LMX1602 were also considered, but the LMX1601 was selected because it has a "500 MHz option", meaning that it can work down to about 50 MHz.




USB Relay Board
Posted on Tuesday, April 5, 2011   •   Category: USB Interface Adapters

USB Relay Board

Here's the new 6 channel USB relay card for switching different appliances, lamps or motors by a computer program via the USB interface. There are certain switching sequences can be programmed via computer. The card was dispensed on SMD technology and is thus the ideal craft project for beginners and novices. Those who do not always wanted with his computer what Steruern. This can be done with the help of a web application even over the Internet. About the SPI connector could even imagine the relay card to cascade with other relay boards. The relays max. 250V AC and have a switching current of 8A (depending on the used relay). Furthermore also 4 inputs, which are separated optocouplers, and monitors can be queried. AVR simulates a USB RS 232 interface can thus this relay, the card without problems using a terminal program or other software to be easily addressed. The USB driver in the AVR firmware was developed by Objective Development ( http://www.obdev.at/products/avrusb/projects-de.html ) and under the GPL2. Through this USB driver could have very special devices and SMD technology abandon. Her come out is a very compact board with dimensions of 100mm x 85mm. The setting of the simulated serial port is: 9600 baud, 8Datenbits, no parity and 1 stop bit further handshaking. To power supply reaches a normal 9 - 12V power supply.




Driving N-Channel MOSFETs with a Microcontroller
Posted on Monday, April 4, 2011   •   Category: Miscellaneous

Driving N-Channel MOSFETs with a Microcontroller

MOSFET transistors are excellent choice for driving high current devices such as motors or high power RGB LEDs. They offer very low switching resistance and very small heat dissipation compared to bipolar transistors. This guide is designed to explain how to drive N-Channel MOSFETs with a microcontroller such as PIC or ATMEGA. Transistors heat up when driving large loads because they have a voltage dropped over them (Vce), and Heat (Watts) = Voltage * Current. This leads to thermal runaway within the transistor, eventually driving the device to destruction if not handled carefully. FET's are like digital switches, capable of turning on and off between the Drain and Source via a voltage potential at the Gate. When a FET is on, it usually has a resistance of less than 0.01 ohm, and when off, its like an open circuit. Because of the low resistance during the FET's on state, it can allow large amounts of current to pass through it without heating up. FET's turn on by voltage potential, not an electric current, and in return they have a very high input impedance. With this in mind, you only need a voltage to turn them on, perfect for digital electronics.




Microphone Amplifier with TDA7050 IC
Posted on Monday, April 4, 2011   •   Category: Miscellaneous

Microphone Amplifier with TDA7050 IC

Here's a simple microphone amplifier based around TDA7050 IC. There are many schematics, the choice fell on the amplifier chip TDA7050, the only downside was it that it was not appointed to the microphone. By adding a resistor R1 in the scheme by 4,7 kOhm - amplifier can no longer work with conventional condenser microphones. If you remove the resistor R3 - the alarm will be put on a small speaker with an impedance of winding 32 Om'a. Voltage amplifier is powered by 3 - 5 volts, but as the amplifier must be nourished from 12 in the scheme of linear stabilizer was added at 5 V. This scheme was checked with headphones (current consumption was 50 mA) and connect to the line input of your TV.




LM3875 Power Amplifier
Posted on Sunday, April 3, 2011   •   Category: Amplifiers

LM3875 Power Amplifier

The amp described on this page, is a very simple poweramp based on the National Semiconductor chip LM3875. According to National it's a chip meant for TVs, compact stereos etc. But many people claim that these chips are great high-end amps... So I decided to try building one. The "design" work was quickly done, as I just used the guidelines and sample circuit of the datasheet. I designed a small PCB for the amp (I'm lazy), and I made it double sided to make it easier to keep all the ground lines separate, as recommended by National. The prototype board can be seen below with a 100VA toroid I used for testing.




Class A Headphone Amplifier
Posted on Sunday, April 3, 2011   •   Category: Headphone Amplifiers

Class A Headphone Amplifier

Presented here is a Class A headphone amplifier built around OPA134 opamp and IRF510 MOSFET power transistor as output stage and current driver. Quality, sound engineering applications, the most important criterion. Although many criteria used in the definition of quality for Class A amplifier. The most important feature, new crossover and work conditions and very low intermodulation distortion characteristics of a sound is very close to nature. Audio gurus know very well that the sound of a class A amplifier is the best one you can ever get.




DIY Power Supply for Home Server
Posted on Saturday, April 2, 2011   •   Category: Power Supplies

DIY Power Supply for Home Server

I'm replacing my old power-hog home server with a new one based on the Intel D945GSEJT mainboard. This board is essentially a netbook platform that's been "desktopified". Among it's weirder points are that it uses the Mobile 945GSE chipset, SODIMM ram, 44PIN IDE, and that it runs off a single 12V supply. The reason I chose this board is that it consumes 13W in idle and 18W under full CPU and GPU load which is pretty much the lowest power consumption one can get with an Atom system (excluding some server-specific boards that were beyond my budget). Not wanting to use an ATX PSU I've decided to build a completely new power supply for the board. Not having to bother with all the voltages needed for ATX makes this a lot easier. I've decided to make a high-amp 12V supply, and a 5V supply capable of driving two HDDs.




200W MOSFET Power Amplifier
Posted on Wednesday, March 30, 2011   •   Category: Amplifiers

200W MOSFET Power Amplifier

This 200W MOSFET Power amplifier is suitable for many applications such as Guitar Ampplifier, Mic or Home theater. As many people prefer because of its legendary robustness of MOSFET transistors. MOSFET amplifier is rated at 200W power with 4Ω speakers. It has good frequency range of 1 dB 20Hz up to 80kHz. THD is less than 0.1% at full power and signal to noise ratio when compared to 200W is better than -100 dB unweighted.




LM3886 Gainclone 2x68 Watt Power Amplifier
Posted on Sunday, March 27, 2011   •   Category: Amplifiers

LM3886 Gainclone 2x68 Watt Power Amplifier

In this application, we are building a gaincard like amplifier. This application type is named gainclone in the audio world. To take a satisfactory audio response, we are adding equalizer to the feedback line and adding bass compensation also. We are using LM3886 which is the revised version of its brother LM3875. These are the parameters that we are interested in. Honestly this values are much more better than many of HI-FI amplifiers sold in the market. Especially it is hard to find 110dB signal to noise ratio. And another property is, when there is no input, this amplifier is quite like a dead. It is nearly impossible to hear any noise when you stick your ear to the speakers.




USB RGB LED Controller
Posted on Saturday, March 26, 2011   •   Category: LED

USB RGB LED Controller

This is great LED-controller board with lots of handy features. USB interface allows selecting operating modes directly on your PC screen without need additional input devices on boars. Project has preprogrammed several modes including slow and fast color change, temperature base color ,where color depends on temperature measured from temperature sensor (DS1821). Other modes include constant colors that can be configured with C# Win application. Actually there are more possibilities of usage especially when USB is used. Write your own or use PC application that would represent CPU load or other content with RGB colors. Project is built around PIC18F2550 microcontroller which comes along with USB interface. So USB requires couple elements what allows focusing on other parts of circuitry.




Driving P-Channel MOSFETs with a Microcontroller
Posted on Saturday, March 26, 2011   •   Category: Miscellaneous

Driving P-Channel MOSFETs with a Microcontroller

MOSFET transistors are excellent choice for driving high current devices such as motors or high power RGB LEDs. They offer very low switching resistance and very small heat dissipation compared to bipolar transistors. This guide is designed to explain how to drive P-Channel MOSFETs with a microcontroller such as PIC or ATMEGA. There are a couple of tricks to remember when using them. P-Channel MOSFETs are useful for switching positive supply of a target circuit on and off. Particular attention must be placed to the target circuit if the supply voltage is greater then the micro controller's logic voltages. If for example, your target device is being powered by 12 volts, and your logic high state from the micro controller is 5 volts, then the MOSFET will never turn off, as voltage will either be -12V or -7V (remember that this guide is designed for logic level MOSFETs). Anything over -3 volts will generally drive the logic level MOSFET on (varies between types of LL MOSFETs).




DS18S20 Dual Temperature Meter
Posted on Friday, March 25, 2011   •   Category: Test and Measurement

DS18S20 Dual Temperature Meter

DS18S20 dual temperature meter uses two very exciting DS18S20 digital temperature sensors that come in convenient TO92 package. Unlike regular sensors where temperature readings are passed as varying voltage, DS18S20 passes temperature information in a digital format as data. This brings many new possibilities and enables to pass temperature information over much longer distances just over a two wire cable. With this capability temperature can be measured in different locations at the same time away from the main circuit board. With regular temperature sensors that rely on the voltage cables must be as short as possible because longer wire lengths introduce stray resistance and bring unreliable readings. Another great feature of DS18S20 sensor is that it doesn't require any calibration at all, while providing 100% accuracy out of the box. That means that you just plug it in and there's no need spending time recalibrating temperature readings. This is all due thanks to the nature of sending information in a digital format. In fact DS18S20 is just like a computer connected to the network that has a unique serial number identifier similar to an IP address. Multiple DS18S20 sensors can send information simultaneously, even over the same two wire bus cable. The two wires provide 3-5V voltage supply to the sensors and they are also used to pass data in two different directions. If wires are very long so that voltage on DS18S20 sensors drops below 3V external 5V voltage supply can be used with 1K resistor to power the sensors. Once PIC microcontroller receives temperature information it converts it into both Celsius and Fahrenheit values so that they can be displayed on LCD display. DS18S20 dual temperature meter is capable of measuring temperatures from -55 to 125 °C degrees Celsius (-67 to 257 °F Fahrenheit) with 0.5 °C / 1 °F accuracy. If you just need to measure temperature in one location you may just use one DS18S20 sensor and PIC16F628 microcontroller will use just one sensor.




4-CH RF Remote Control
Posted on Friday, March 25, 2011   •   Category: Remote Control

4-CH RF Remote Control

Having the ability to control various appliances inside or outside of your house wirelessly is a huge convenience, and can make your life much easier and fun. RF remote control provides long range of up to 200m / 650ft and it works even through the walls. You can control many low voltage gadgets including motors, RC cars, robotic devices, amplifiers or 110V/220V appliances through relays such as lights, fans, AC systems, home appliances, garage doors, security systems, motor-driven curtains, motorized window blinds, door locks, sprinklers, motorized projection screens and anything else you can think of. 4-CH RF remote control is used to turn ON / OFF four different devices independently. Any of the four outputs can be configured to work independently in either toggle or momentary mode. Outputs are buffered by BC549 NPN transistors and can drive low voltage devices directly such us motors or be connected to either 5V or 12V relays to control appliances that use 110V / 220V mains voltage or any voltage of your choice. Multiple remote systems can be used independently to control more than four appliances in the same location by changing the address code on 433MHz receiver and remote. It is also possible to use several remotes to control the same appliance such as garage door.




USB IO Board PIC18F2455 / PIC18F2550
Posted on Friday, March 25, 2011   •   Category: USB Circuts

USB IO Board PIC18F2455 / PIC18F2550

USB Input / Output Board is a spectacular little development board / parallel port replacement featuring PIC18F2455 / PIC18F2550 microcontroller. USB IO Board is compatible with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB Input / Output Board is self-powered by USB port and can provide up to 500mA for electronic projects. USB IO Board is breadboard compatible. Simply solder included 12-PIN & 8-PIN headers on the bottom side of the PCB and the board can be plugged into a breadboard for quick prototyping.




RGB LED Strip with 12 Ultra Bright LEDs
Posted on Friday, March 25, 2011   •   Category: LED

RGB LED Strip with 12 Ultra Bright LEDs

These flexible waterproof RGB LED strips contain 12 Ultra Bright RGB LEDs on 30cm strip. RGB LEDs can produce Ultra Bright White, Red, Green, Blue, Violet, Cyan & Yellow light. LED strips have durable and waterproof design and can be used for cars, trucks, motorcycles, garden decoration, cabinets, Audio / Video systems, home theaters, computer, etc. They include double-sided self-adhesive tape that can be used to attach to cabinets and other surfaces. RGB LED strip includes 4-PIN female connector at each end and one 4-PIN male connector to connect multiple RGB LED strips together (no soldering is required). Simply connect 12V DC power supply and you are ready to go.




ESR Meter
Posted on Thursday, March 24, 2011   •   Category: Test and Measurement

ESR Meter

The ESR Meter is basically an AC Ohmmeter with special scales and protective circuitry. It provides a continuous reading of series resistance in electrolytic capacitors. It operates at 100 kHz to keep the capacitive reactance factor near zero. The remaining series resistance is due to the electrolyte between the capacitor plates and indicates the state of dryness. Capacitor termination problems also show up plainly due to the continuous ohmic reading. The ESR meter uses 8 operational amplifiers. An op-amp is an idealized basic amplifier with two inputs. The non-inverting input (+) has an in-phase relationship with the op-amp output, and the inverting input (-) an out-of-phase relationship. Op-amps are usually used with negative feedback and reach a stable operating condition when their two inputs are equal in voltage. Op-amps IA & 1B form a regenerative 100 kHz oscillator circuit. Capacitor C1 is the basic timing capacitor and RI is selected to set frequency. Diodes D2 & D3 clip the bottom and top of the output waveform so that the output level and frequency are resistant to battery voltage changes.




FM Telephone Transmitter
Posted on Thursday, March 24, 2011   •   Category: FM Transmitters

FM Telephone Transmitter

The FM telephone circuit is built on a PC board that is so small it can easily be fitted inside the housing of a telephone making it an instant pseudo-speak earphone. This FM transmitter circuit connects in series with telephone line, steals power from it, and transmits both sides of the conversation to an FM radio tuned between 90 and 95 MHz.




Digital Potentiometer with Memory
Posted on Wednesday, March 23, 2011   •   Category: Audio Attenuators

Digital Potentiometer with Memory

Digital potentiometer with memory is a built around PIC 16F819 microcontroller that reads analog resistances, records them to memory and plays them back via digital potentiometer DS1267 chip. The memory buffer size and the playback speed can be adjusted.




Simple 300W Lamp Dimmer
Posted on Wednesday, March 23, 2011   •   Category: Miscellaneous

Simple 300W Lamp Dimmer

This simple lamp dimmer uses only a Triac, a Diac and some other passive components to achieve power control on lamp . It is suitable for 230V incandescent lamps with a total power of up to 300 Watts. At first triac TR1 is not conducting; C1 is charged through R1/P1 until the trigger level of diac D1 is reached. When the diac trigger level is reached (about 30 V), D1 fires and Triac TR1 is switched on. The triac will remain in conductive mode until the mains current is lower than the triac hold current at the end of the half mains period. This works for both the negative and positive mains period because both the triac and the diac are bi-directional. R1 is added to protect the potentiometer in the case of a short circuit. The fuse is absolutely mandatory as the discharge arc in a failing incandescent lamp is virtually a short circuit.




DIY USB to RS232 Adapter
Posted on Wednesday, March 23, 2011   •   Category: USB Circuts

DIY USB to RS232 Adapter

Sometimes you just need to connect some device to COM port, but computer don’t have one especially laptop. There are two ways – go and buy USB – COM adapter or build one. So if you decided to build USB to COM(RS232) adapter, there is one of solutions. This adapter is very easy to build as there is single chip USB to UART bridge (CP2102) used. This chip from Silicon Labs support USB2.0 full speed, has internal Resistors required for USB interface, integrated clock, internal 1024 -byte EEPROM for vendor ID, Product ID serial number, power descriptor and other information. SP2102 USART part support almost all standard features of RS232 communication including handshaking, Databits (5, 6, 7 and 8); 1 or 2 stop bits; odd, even, mark, space and no parities; baud rate from 300bps to 1Mbits. Device is powered from USB port and requires about 10mA. Chip drivers enable to connect this adapter to most of Operation systems like Win98, Win2000, WinXP, Linux.




USB Switch
Posted on Tuesday, March 22, 2011   •   Category: USB Circuts

USB Switch

USB switch is used to share USB devices such as printers, scanners, hard drivers, etc. between two computers. Just connect the two computers on a network device and say the printer as shared. This method however requires the continued operation of the computer we plugged the printer. Solution to above problem is to give the circuit that we present, and has the potential to be transferred to the printer on whichever computer we want, because the printer is connected to one of two computers, but in construction.




2 Channel RF AVR Remote Control
Posted on Monday, March 21, 2011   •   Category: Remote Control

2 Channel RF AVR Remote Control

There are lot of remote controls like infrared, RF, SMS (like my other circuit) and more. The basic small-range remote controls are 2, Infrared and RF (Radio Frequency). One of the weaks of Infrared is that the signal can not pass the walls. So, if you want to control your garage door, the only way is to use some RF remote control. The circuit (transmitter and receiver) use few components and ordinary (I love few component circuits) . Its easy to build it because you don't have to tune-up any coil or variable capacitor. The RF modules are fix to work in 418MHz area.




High Power RGB LED Lamp
Posted on Monday, March 21, 2011   •   Category: LED

High Power RGB LED Lamp

In this page we will introduce a great project designed by Toon Beerten. This project can become a very interesting add-on for your room that's absolutely sure it will impress everyone. As you can see on the photos, we talk about a color fading lamp, that looks amazing! The purpose of this page is to try to give some hints building it successful. This high power led mood light is based on PIC16F628 and the ability of this mcu to produce PWM pulses. Varying pulse width we can produce millions of color combinations using only the three basic colors. So only one RGB (Red-Green-Blue) led is capable producing a rainbow of fading colors. With the help of four switches we can handle all functions of the lamp. We can choose fading or jumping between colors, we can select a rainbow style or a random color changing behavior, we can choose slow or fast changing of colors and we can pause on a desired color. Finally we will make some power dissipation measurements to help us select an appropriate power supply unit.




MAX16834 High Power LED Driver
Posted on Monday, March 21, 2011   •   Category: LED

MAX16834 High Power LED Driver

There is a major advantage to using LEDs for lighting: various dimming techniques allow seamless control of the light output from the LED source. While LEDs are efficient light sources, the dimming feature also allows for considerable power savings. Control over the light output also helps to set the desired ambience. PWM dimming is preferred to analog dimming for several reasons. For many applications PWM dimming maintains the color of the light output regardless of the dim level. For circuit design, PWM control is more immune to noise; the control signal need not be accurate in both voltage levels and dimming frequency; and the driver circuit design is less complex. PWM dimming usually requires a control line that carries the PWM dimming signal, in addition to the two power-supply lines. This standard configuration is, however, a drawback for applications that use common dimming for a large number of lights; the configuration also makes it difficult to replace the incandescent light installations with two-wire supply lines that depend on supply chopping for dimming control. Traditional, crude LED driver circuits that work with power-supply dimming are problematic. Those drivers turn off power to the LEDs gradually as the input filter capacitors discharge to the minimum operating voltage of the driver. That process can cause the input and output filter capacitors to discharge to low levels. Then when the supply is turned back on, a huge surge of current flows to replenish the capacitor charge, thus causing EMI issues and premature dimmer damage. To prevent these various issues, those circuits use large inductor filters that increase cost. The LED driver reference design described here addresses this basic design challenge with PWM dimming. This LED driver implements PWM dimming based on supply chopping; it does not cause any supply current overshoot. The design provides up to 90% efficiency while operating from a 24V supply. It allows a unidirectional supply input with an efficient semi-MOSFET bridge rectifier at the input. Figure 1 shows the top view of the design board.




X10 Remote Temperature
Posted on Monday, March 21, 2011   •   Category: Miscellaneous

X10 Remote Temperature

I became interested in the ATtiny85 processor recently. Up till now, my projects were based on the ATmega328 or the ATmega644. The ATtiny85 is just that, tiny - only 8 pins vs. 28 on the ATmega328. The photo on the left shows the new X10 temperature transmitter, with the DS1621 temperature chip on the left and the ATtiny85 on the right.




Stereo FM Transmitter with BA1404
Posted on Friday, March 18, 2011   •   Category: FM Transmitters

Stereo FM Transmitter with BA1404

Circuit of stereo FM transmitter of of high quality using integrated circuit ba1404 for mp3, mp4, ipod, computer, radio of the car. Transmit of your equipment of portable audio for the radio of your car, transmitters of fm of low potency are the ideal for transmission wireless of audio sign for fm receivers. Mainly in that case that is treated of transmitter of FM stereo with ba1404. The heart of that circuit is the circuit integrated ba1404, that is a mini fm transmitter, that already counts with the necessary internal circuits for transmission in fm. just being necessary to increase some components discman or any other audio source turning the wireless. If you already set up other transmitters of transistorized fm it will see that when setting up that with having integrated BA1404, that the quality of the sound and the frequency stability is excellent. Besides the but it presents easy assembly.




100W LM3886 Parallel Stereo Power Amplifier
Posted on Wednesday, March 16, 2011   •   Category: Amplifiers

100W LM3886 Parallel Stereo Power Amplifier

This amplifier is based on the PA100 parallel amplifier detailed in National Semiconductor's application note - AN1192. Since my DIY speaker is 4-ohm and somewhat difficult to drive, I want to have a more powerful amplifier to match with it. Therefore I designed this amplifier which uses two LM3886 per channel, in parallel circuit. This amp can deliver about 50W into a 8-ohm speaker and 100W into a 4-ohm speaker. This is a stereo amplifier and therefore 4 LM3886s are used. The LM3886 circuit is in a non-inverted configuration, so the input impedance is determined by the input resistor R1, i.e. 47k. The 680 ohm and 470pF resistor capacitor filter network is used to filter out the high frequency noise at the RCA input. The 220pF C4 and C8 capacitors are used to shot out the high frequency noise at the LM3886 input pins. I used high quality audio grade capacitors at several locations: 1uF Auricap at the input for DC blocking, 100uF Blackgate for C2 and C6, and 1000uF Blackgate at the supply filter.




LM386 Amplifier
Posted on Wednesday, March 16, 2011   •   Category: Amplifiers

LM386 Amplifier

This amplifier is very easy to make and very compact, works with a single power source whose value can be between 4V and 12V.It is based on the use of a type LM386 amplifier, capable alone to issue a power of several hundreds of milliwatts to a load (HP) of 8 ohms, while consuming only a few mA at rest. Ideal for make a small portable battery powered amp. The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.




DIY Water Usage Meter
Posted on Tuesday, March 15, 2011   •   Category: Miscellaneous

DIY Water Usage Meter

Working with the interaction design team, a bunch of us at Teague have been tinkering with measuring water, analyzing usage data in realtime to affect behaviors, and storing it to see patterns over time. At the heart of the exploration was a need to cheaply measure water from the tap. Water meters vary quite drastically in price (from $250+ for industrial grade sensors to $6 for garden hose attachments that limit total usage based on rough estimates). We settled on a $20 water meter used for PC cooling systems (the INS-FM17N by Koolance) due to its accuracy, low price, small size, and electronic sensing method that could be easily measured by a microcontroller (such as an Arduino).




Motion Activated Camera
Posted on Tuesday, March 15, 2011   •   Category: Miscellaneous

Motion Activated Camera

I made a relatively simple attachment to my Canon SLR to create a motion activated camera using Arduino. A lot of this was based on and inspired by the intervalometer project at The Honey Jar. I made some changes to his circuit to use a 4N35 optocoupler instead of reed relays.




Sine Wave Synthesizer
Posted on Tuesday, March 15, 2011   •   Category: Miscellaneous

Sine Wave Synthesizer

Every group wants their final project to be something that will be remembered long after they're gone. Some do highly sophisticated and complex projects that entail upwards of a hundred hours to complete. Yet others go out of their way to develop something 'cool' and 'fun'. Luke and I decided that we wanted to be in this second category, because developing something that's 'cool' would also be fun to do. So in deciding what to design we tried to think of something that would catch the attention of the people in the lab. The easiest way of doing this is to create something that would make noise or play music so everyone in the lab could enjoy it. Realizing this would be the best way to go, we decided to create a synthesizer that could record and playback notes, 'teach' the user how to play a simple melody, and also play some prerecorded tunes. After all, don't you think being remembered as the group that played back the Imperial March theme from Star Wars is cooler than a paper tape reader? (no offense to those groups doing paper tape readers)




Microchip's Li-ion battery charger MCP73831 IC
Posted on Friday, March 11, 2011   •   Category: Battery Chargers

Microchip

Microchip announced the expansion of its analog power-management family with the MCP73831 battery charger, a fully-integrated, single-cell, Li-ion/Li-Polymer charge-management controller. Tiny 500mA linear charge management controller can be powered directly from the USB port. Includes integrated pass transistor, current sense and reverse-discharge protection, the MCP73831 charger reduces the number of components needed for battery-charger designs. Its highly accurate, pre-set voltage regulation (maximum accuracy 0.5 per cent to 0.75 per cent) results in more fully charged batteries and extended battery life. Since the MCP73831 charge-management controller includes a pass transistor, current sense and reverse-discharge protection on a single chip, it reduces the number of system components needed for battery-charger designs, which, added Microchip, lowers overall system costs.




20 Watt Stereo Amplifier with TDA2005
Posted on Friday, March 11, 2011   •   Category: Amplifiers

20 Watt Stereo Amplifier with TDA2005

20W TDA2005 stereo amplifier for all suitable applications like amplifying medium power speakers. It is suitable for car use but before, the power supply must be choked with at least 150mH and it must give up to approximately 6 to 7 amps during the upstream performance.




RGB LED Controller with PIC12F675
Posted on Tuesday, March 8, 2011   •   Category: LED

RGB LED Controller with PIC12F675

This code is for a simple RGB LED controller for 1 RGB LED using a PIC12F675 (or PIC12F629). The pattern is determined by the data in the EEPROM. When the PIC needs a new target for the PWM, it loads it from EEPROM. Pin 4 (GP3) is pulled high because it is used to switch between displays. Please see the source code for more information; the structure and design is commented. The operation of the controller is very simple and so is the wiring.




200W Leach Amplifier
Posted on Monday, March 7, 2011   •   Category: Amplifiers

200W Leach Amplifier

Article about building Marshall 200W Leach Amplifier. For many years I looked for construction of HiFi amplifier wit a good parameters, enough power reserve and simple construction. I built a couple of amplifiers with integrated circuits MBA810, TDA2005, LM3886, but I was disappointed by their output quality and noise. I decide to built a classic construction with discrete components and bipolar transistors. Construction from Mr. Dudek was interesting, but I didn't like used components and complexity. All of my requirements satisfied construction of the Leach Amp. Circuit author publicates in a February 1976 in american journal. From these days circuit was not practically changed. Little changes are descripted on authors page.




RGB LED Driver
Posted on Saturday, March 5, 2011   •   Category: LED

RGB LED Driver

The implementation of a RGB LED fader using 555 timer and 4029 digital IC is the objective of this project. During the operation, the RGB LED is continuously cycled through the colors of the rainbow where the speed at which the colors change is adjustable. The switch between the different colors makes the effect very noticeable while a more relaxed effect happens when the colors fade into each other. These two options can be selected on this device. The pulse generator based form a standard 555 timer is formed by IC1, C1, R4, R5, and VR1. The frequency of which, and hence the speed of the effect, as adjusted using the pre-set VR1. The pulses are fed into IC2 which is a 4029 binary counter whose outputs continuously count in a binary progression between 1 to 7. The transistors Q1, Q2, and Q3 are being driven by these outputs which in turn control each of the three colors of the RGB LED. By passing through an RC network, the pulses are shaped before they reach their respective transistors. The fading effect between the colors or abrupt changing is produced by this shaping.




FM Transmitter Bug
Posted on Friday, March 4, 2011   •   Category: FM Transmitters

FM Transmitter Bug

The goal of this project is for me personally to learn a little more about fm transmitters and fm bug making (may the HAM radio gods bless me in this pursuit). The ideal outcome of this project is a very small and full functional FM transmitter that we can stick into a plastic mint box. In order to be able to build this, we'll have to learn a lot about amplifiers, LC oscillators, mixers, antennas and FM. This project assumes you're already comfortable build your own PCB boards. If you're not please take a look at the homemade pcb's tutorial before you continue. It will help you out a lot.




700W Leach Amplifier
Posted on Friday, February 25, 2011   •   Category: Amplifiers

700W Leach Amplifier

Here's a Leach Amplifier based on 2SC5200 and 2SA1943 output power transistors that can provide up to 700W of power. The mechanical design is relatively simple, the transistors are placed on the two cooling profiles with a height of 66 mm, width 44mm, overall length 260mm. They are turned against each other Thus, from the cooling tunnel. Coolers are attaching the nylon backing which allows the assembly of transistors without washers, and thus better transfer of heat. DPS amplifier is at the top of the tunnel and the transistors are soldered from the bottom of PCB.




275W Leach Amplifier
Posted on Friday, February 18, 2011   •   Category: Amplifiers

275W Leach Amplifier

The amplifier design includes not only the final stage of the source (rectifier, filter) and protection against DC voltage output amplifier and speaker connections delayed. As already mentioned, the amplifier is designed as a single-module. This means that on one common board rectifier, filter capacitors, protection And definitely amplifier. Regarding the components of the external solution, the solution based on the original Mr. Marshall Leach. The proposal is adapted for the proposal. in the amplifier are used for temperature sensing diodes are replaced with one sensing transistor mounted on the end of the main condenser and field Tranda. This transistor provides a thermal feedback and thus of a stable quiescent current amplifiers. Privacy speakers are powered directly from the voltage amplifier. As for mechanical design, is probably the most complicated in the whole amplifier. Cooling is done by the Al blocks that are attached to the main cooling profile. ZH6465 profile is used. The terminal transistors to heat is released through Al strips with a thickness of 6 mm in the lateral beams and passing into the cooler. more pictures.




PICKit 2 CLONE
Posted on Friday, February 18, 2011   •   Category: PIC

PICKit 2 CLONE

For a long time I needed a good programmer pussy, even if it is programming, so from time to time the application gets where it is used. So I decided to build the programmer. I chose between a couple of projects from different authors, but eventually won PICkit2. Microchip released the schema directly in the user manual for the programmer. On the Internet there are multiple versions of the programmer, it's usually cropped version of the log analyzer features, UART terminal, etc., 12V inverter is a modified version of it and control the MOSFETs, unlike bipolar transistors used in the original design. And it also showed that becomes due to the switching inductance feta leave. Finally, I chose to use the original scheme, although it is quite complicated and the parts used in our country can not normally buy, but my problems with finding parts easily solved. I bought a transistor, the 16F2550 PIC and a few other things, resistors and fry the rest I bought from "us". The price is pretty high, unfortunately, moving it around and 600CZK, the main prize and two processor makes the EEPROM. Below we describe the involvement and put into operation.




300W 6x LM3886 Bridged Power Amplifier
Posted on Tuesday, February 15, 2011   •   Category: Amplifiers

300W  6x LM3886 Bridged Power Amplifier

After I built several LM3875 and LM3886 gainclone amplifiers, I was totally impressed by their audiophile sound quality. My design goal is to create a audio power amplifier that can deliver 300W into my 4-ohm DIY speaker with low distortion. I want it to produce deep, tight and punchy bass while keeping the excellent mids and highs from my other gainclones. My design uses a PCB to hold 3 paralleled 3886s (i.e. PA150), and then I use the DRV134 to bridge 2 of the PA150 PCB boards. The function of DRV134 is to convert the un-balanced input signal to a balanced signal, so that the non-inverted signal is fed to one PA150, and the inverted signal is fed the another PA150. One of the PA150 is connected to the speaker's positive input, and the other PA150 is connected to the speaker's negative input. Because of this push-pull configuration, the total gain of the amplifier is doubled. Each PA150 has a gain of 20, so the gain of the BPA300 is 40.




Arduino Breadboard Clone
Posted on Saturday, February 12, 2011   •   Category: Arduino

Arduino Breadboard Clone

This Arduino can be used for old school prototyping as well. Just use it as a standard ATmega8 and program it with the ISP connector. And it is one of the cheapest Arduino boards, that you can get. Arduino is a great prototyping platform and most of you probably know already about it. If not, check out the Arduino pages and the Arduino playground and dive into it.




400W Stereo Marshall Leach Amplifier
Posted on Thursday, February 10, 2011   •   Category: Amplifiers

400W Stereo Marshall Leach Amplifier

400W Stereo Audio Amplifier based on the original Marshall Leach involvement, but has made some improvements. Regarding the power supply voltage to the +-75V. VC comparing the performance of the modified Leach 700W/2R on one common board of both channels, as well as protection and control circuits for the fans. Compared to the 700W version a bit different in wiring. Because some things in the 700W version is completely tightened to perfection.




CNC Machine
Posted on Wednesday, February 9, 2011   •   Category: CNC Milling Devices

CNC Machine

The electronics of a CNC machine is a simple but often confusing matter. In the picture (down) is shown the schema of a full system of four axes. Sometimes the breakout board is not present and the parallel port connected directly to the controllers. The main advantage of using single stepper controllers enable the user to connect different motors even in a mixed configuration (unipolar or bipolar steppers) tuning the CNC machine performances to the job to be done. A common and simple solution is the use of a board where the optoisolator (if any) and the controller/drivers are present in the same board, all-in-one. This solution allow a general quicker connection and a simple wiring but force the use of three or four identical (or similar) stepper motors.




10A 1-30V Variable Power Supply with LM317
Posted on Wednesday, February 9, 2011   •   Category: Power Supplies

10A 1-30V Variable Power Supply with LM317

Here is a simple and economical 10A variable power supply with 1.2-30V. LM317 have been used to drive 3 NPN TIP41C transistors (or three 2N3055). Nothing to say about the project, it is really simple. The main supply must be connected to a rectified source (transformer + 20-30A bridge rectifier). For Q1,2 and 3 can be used any power TO220 transistor (TIP132C,TIP41C etc) or three external 2N3055 transistors.




FM Broadcasting Stereo Encoder
Posted on Saturday, February 5, 2011   •   Category: Stereo Encoders

FM Broadcasting Stereo Encoder

This stereo encoder is a halfway between analogue and digital processing. It combines the best from both domains to provide high-quality and easy to build device. The sampling frequency used in this stereo encoder is 97 times higher than the pilot tone frequency. This makes very easy to reject all spectral residues around the sampling frequency without affecting the main signal characteristics. Using of a microcontroller allows to build this stereo encoder with reduced part count and get excellent results in real operation. This stereo encoder advisedly does not contain any preemphasis circuit. Remember the key fact: a compressor/limiter/clipper device must be always present between the preemphasis circuit and the stereo encoder or modulator. Only this configuration ensures loud sound without exceeding the maximum frequency deviation limit (75 kHz). The stereo encoder is designed to provide really good sound. This always needs to use the compressor/limiter/clipper device where the preemphasis is precisely assured.




Crystal Detector Radio Receiver Set Varactor Varicap Capacitor Diode Tuned
Posted on Saturday, February 5, 2011   •   Category: FM Radio / Receivers

Crystal Detector Radio Receiver Set Varactor Varicap Capacitor Diode Tuned

Traditionally, in a crystal detector radio tuned circuits, a mechanical type variable capacitor is used. For those of you who would like to eliminate this mechanical component, here is a modern version of the classic detector set. This radio, as shown on Figure 1, uses a varactor diode instead of the usual mechanical rotary device. The varactor is also known as a variable capacitance or a varicap diode. It provides an electrically controllable capacitance, which can be used in many different circuits. Varactors are small and inexpensive, which makes their use advantageous in many applications. Its disadvantages are a lower Q (quality), nonlinearity, lower voltage rating and a more limited capacitance range. A tuned circuit with a higher Q has a narrow pass-band that makes it better able to pick out a station of many equally strong. A lower Q tuned circuit has a wider pass band. It allows more neighbor stations through and makes listening to either radio stations frustrating. Frequency change with a varactor diode equipped tuned circuit is as simple as a voltage change.




Small AM Transmitter
Posted on Sunday, January 30, 2011   •   Category: FM Transmitters

Small AM Transmitter

So, I needed a small transmitter, which would allow me to transmit good, old music into my AM-only radios. So, one saturday afternoon I got into gear, designed and built a very crude, terribly non-optimized little transmitter. It's almost a joke expressed in electronics, full of poor design, so please don't think that this is the best I can do! You must see it as a quick and dirty 5-hour effort, because that's all the time the transmitter took to design, build, and test. Making this web page about it is taking much longer! I'm putting this thing on the web only because many people have asked me to do so, despite its crude design!




DTMF Phone Decoder
Posted on Sunday, January 30, 2011   •   Category: Phone Circuits

DTMF Phone Decoder

DTMF tone is mainly used in telecommunication technology, such as dialing a phone number, handling various services over the telephone, as a selective choice of radio stations, etc. The individual characters are assigned to different pairs of tones. The described decoder Received characters on the LED display, and stores them in memory, where they can be retrieved later. No matter allows for some sequences of characters on and off properly connected device. In practice, the decoder can be built as in the transmitter and connected to feeder line, the transmitter can then be remotely switched on and off, or you can run such a parameter indicating the traffic reports TA in RDS. The required sequence of tones may be part of the jingle.




Importance of X10 Oscilloscope Probes
Posted on Sunday, January 30, 2011   •   Category: Oscilloscopes

Importance of X10 Oscilloscope Probes

A scope probe is built to minimize ringing by adding resistance. A X1 is better than a piece of co-ax, but a X10 probe is more effective than a X1. A X10 probe has the effect of reducing capacitance by a factor of ten. The trade-off is that is also attenuates the signal by a factor of ten. That is, 1/10 the signal applied to the tip of the probe actually reaches the input of the oscilloscope.




MT8870 DTMF Telephone Dial Tone Decoder
Posted on Sunday, January 30, 2011   •   Category: Phone Circuits

MT8870 DTMF Telephone Dial Tone Decoder

Today, most telephone equipment use a DTMF receiver IC. One common DTMF receiver IC is the Motorola MT8870 that is widely used in electronic communications circuits. The MT8870 isan 18-pin IC. It is used in telephones and a variety of other applications. When a proper output is not obtained in projects using this IC, engineers or technicians need to test this IC separately. A quick testing of this IC could save a lot of time in research labs and manufacturing industries of communication instruments. Here’s a small and handy tester circuit for the DTMF IC. It can be assembled on a multipurpose PCB with an 18-pin IC base. One can also test the IC on a simple breadboard. For optimum working of telephone equipment, the DTMF receiver must be designed to recognize a valid tone pair greater than 40 ms in duration and to accept successive digit tone-pairs that are greater than 40 ms apart.




56W LM3886 / LM3876 Gainclone
Posted on Sunday, January 30, 2011   •   Category: Amplifiers

56W LM3886 / LM3876 Gainclone

It is a 2x56W stereo amp based on National Semiconductor's LM3876T chip (they come in 2 versions T and TF the latter having an insulated case), this type of amp is also known as a gainclone because it is an improved copy of Gaincard amplifier. seriously this amp can outperform most commercial amplifiers/receivers (minus the video upscaling/switching) when built properly ie it has very low THD you will not be disappointed by how good it sounds . When connected to AV equipment such as dvd players this thing gets insanely loud (despite having only 56W per channel), i've have never required more than 25% volume because it hurts my ears NOTE: a even more powerful version using the same circuit with a LM3886 chip can be made giving 68W per channel.




LM386 Amplifiers
Posted on Sunday, January 30, 2011   •   Category: Amplifiers

LM386 Amplifiers

Many electronic projects require the use of a small audio amplifier. Be it a radio transceiver, a digital voice recorder, or an intercom, they all call for an audio amp that is small, cheap, and has enough power to provide adequate loudness to fill a room, without pretending to serve a disco! About one Watt RMS seems to be a convenient size, and this is also about the highest power that a simple amplifier fed from 12V can put into an 8 Ohm speaker. A very low saturation amplifier may go as high up as 2 Watt, but any higher power requires the use of a higher voltage power supply, lower speaker impedance, a bridge circuit, or a combination of those. During my many years building electronic things I have needed small audio amps many times, and have pretty much standardized on a few IC solutions, first and and foremost the LM386, which is small, cheap, and very easy to use. But it does not produce high quality audio... For many applications, the advantages weigh more than the distortion and noise of this chip, so that I used it anyway. In other cases I used different chips, which perform better but need more complex circuits. Often these chips were no longer available the next time I needed a small amplifier.




A Wide Dynamic Range Field Strength Meter
Posted on Saturday, January 29, 2011   •   Category: FM Transmitters

A Wide Dynamic Range Field Strength Meter

This unit is an updated version of the Wide Dynamic Range Field Strength Meter. While the basic function is the same, it has several critical differences: It uses a specialized integrated circuit, the Analog Devices AD8307. This chip is designed specifically as a logarithmic amplifier for use through 500 MHz. Using the AD8307, it has a wider dynamic range (85 dB versus 55 dB) and it has built-in temperature compensation. Because of the different nature of this type of detector - and the fact that it has temperature compensation - means that there is no need for a "zeroing" control. One disadvantage of this approach as compared to the diode approach is that the AD8307 has a lower frequency response than the diode. The frequency limit of the meter is dictated pretty much by the diodes themselves along with their physical layout and related components: There is no reason why the earlier version could not be constructed to work through 10 GHz or so - but the AD8307 is falling flat by the time you get to 1 GHz, making it unsuitable for detecting wireless LANs or PCS-type cell phones.




Oscilloscope Probe Schematic & Anatomy
Posted on Thursday, January 27, 2011   •   Category: Oscilloscopes

Oscilloscope Probe Schematic & Anatomy

Passive Probe are the most general used scope probe. As the name "passive" suggest, it is made from passive components resistor, capacitor & wires. The leading scope probe maker are LeCroy, Tektronix & Agilent. Passive probe usually comes with attenuation factor of 1:1, 10:1 and 100:1. Attenuation factor of 1:1 means whatever signal being probe at the probe tip will be shown exactly as it is at the oscilloscope input. So a signal of 1V at the probe tip will be detected as 1V at the scope input. Attenuation factor of 10:1 means that a signal of 1V at probe tip will be detected as 0.1V at the scope input.




Wideband SWR Meter
Posted on Thursday, January 27, 2011   •   Category: FM Transmitters

Wideband SWR Meter

Everyone involved with radio transmitters needs some instruments to assess basic antenna functionality. Among these instruments, the best-known and most-used one is the Standing Wave Ratio meter. Some radio amateurs develop a cult for these little gadgets, having them in line all the time and watching the needles bounce while they chat. I have seen some guys owning 5 or 6 SWR meters, and no other instrument relating to antenna testing! While it's unfortunate that some people - specially amateurs - assign so much importance to SWR and so little to other parameters, it's also a fact that SWR needs to be known, so if you use transmitters, you need an SWR meter.




70W TDA7294 Amplifier
Posted on Thursday, January 27, 2011   •   Category: Amplifiers

70W TDA7294 Amplifier

The following is a 70W amplifier based on a popular TDA7294 chip. Main technical characteristics of the amplifier are as follows: input resistance - 22 kOhm input voltage - 750 mV nominal output power at 4 ohms and THD 0.5% - 70 Watts Frequency Range - 20 ... 20000 Hz supply voltage - ± 27 V, quiescent current - 60 mA. The amplifier has a built-in thermal protection, and protection against overload and short circuit in the load. For "soft" switching amplifier is SA1. Switch can be powered from a bipolar unregulated power supply. Power AC Transformer - 250-A, the secondary winding should be designed to current than 5A.




Workshop Power Supply
Posted on Thursday, January 27, 2011   •   Category: Power Supplies

Workshop Power Supply

With a maximum capacity of 20 volts and 1 amp, it will supply most of your projects, it's greatest quality is the protection all your projects, it is capable of limiting the maximum current to as low as 1mA, saving your ICs and transistors in case of an accidental short circuit during the experimenting period of your projects. It is also an excellent battery charger.




BA1404 HI-FI Stereo FM Transmitter - Special Edition Kit
Posted on Wednesday, January 26, 2011   •   Category: FM Transmitters

BA1404 HI-FI Stereo FM Transmitter - Special Edition Kit

Be "On Air" with your own radio station! BA1404 HI-FI Stereo FM Transmitter - Special Edition Kit is an exciting transmitter that will broadcast high quality stereo signal in 88MHz - 108MHz FM band. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground. Add 500mW FM / VHF Transmitter Amplifier / Booster for even longer range. Special Edition BA1404 HI-FI Stereo FM Transmitter Kit includes premium components with audio grade gold capacitors, 1% Metal Film Resistors and quality PCB with Red Solder Mask and Plated-Through Holes. The kit is based on the popular BA1404 stereo broadcaster IC which contains all the complex circuitry for generating the stereo FM signal. 38 KHz crystal provides a rock solid stability of sub-carrier for stereo signal.




12V 2A Linear Power Supply
Posted on Wednesday, January 26, 2011   •   Category: Power Supplies

12V 2A Linear Power Supply

As you might expect, I have several power supplies that have more than enough capacity to power my new KN-Q7 transceiver. However, my largest power supply is normally connected to my main 100W PEP SSB transceiver. It is capable of 20A and more, but it’s not easy to connect other equipment to it. I also have a smaller 8A power supply, but I use this to power some other VHF and UHF transceivers. In short, I wanted a simple power supply which I could dedicate to this new transceiver.




10Hz - 60MHz Frequency Meter / Counter
Posted on Friday, January 21, 2011   •   Category: Test and Measurement

10Hz - 60MHz Frequency Meter / Counter

This is 60 MHz frequency meter / counter for measuring frequency from 10 Hz to 60 MHz with 10 Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc. The meter provides very stable readings and has excellent input sensitivity thanks to onboard amplifier and TTL converter, so it can even measure weak signals from crystal oscillators. With the addition of prescaller it is possible to measure the frequency of 1GHz and above. The meter measuring range has been recently upgraded and it can now measure from 10Hz to 60MHz instead of 10Hz to 50MHz.




USB IO Board PIC18F2455 / PIC18F2550
Posted on Thursday, January 20, 2011   •   Category: USB Interface Adapters

USB IO Board PIC18F2455 / PIC18F2550

USB Input / Output Board is a spectacular little development board / parallel port replacement featuring PIC18F2455 / PIC18F2550 microcontroller. USB IO Board is compatible with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB Input / Output Board is self-powered by USB port and can provide up to 500mA for electronic projects. USB IO Board is breadboard compatible. Simply solder included 12-PIN & 8-PIN headers on the bottom side of the PCB and the board can be plugged into a breadboard for quick prototyping.




Solid State Relays
Posted on Thursday, January 20, 2011   •   Category: Miscellaneous

Solid State Relays

Solid State Relays are available almost everywhere these days, however they remain very expensive. Therefore, your efforts to build one yourself pays off. Especially since it only needs a handful components and the circuitry is simple and straightforward. A Solid State Relay is actually not a relay at all. There is no 'relay' present, just the electronics which does the switching. It works the same way as a relay; you can use a low voltage to switch a higher voltage or better. This 'relay' is positioned in between one of the 115/220V AC wires although it is common practice to leave the neutral wire the way it is and switch the phase or hot wire.




AC-AC Solid State Relay or SSR
Posted on Thursday, January 20, 2011   •   Category: Miscellaneous

AC-AC Solid State Relay or SSR

This is a AC Control Input AC Output SSR Solid State Relay. When a Process Controller has an AC output or a system generates an AC signal of above 100V AC to signal the load to turn on, this device can be used. A BTA40-600 and MOC3041 are used in this. A high voltage plastic cap limits current to a bridge which generates a small DC from 230 V AC, this drives MOC3041. The rest is the same. It is better to use a DC control SSR where possible. This AC control SSR is used where only an AC control signal is available. The BTA series has the heatsink tab insulated from the Triac chip inside. The BTB needs electrical insulation to the heatsink.




Switching 110VAC - Relays vs. Solid State
Posted on Thursday, January 20, 2011   •   Category: Miscellaneous

Switching 110VAC - Relays vs. Solid State

Solid state relays do the same thing (switch 110VAC), only electronically. They still have the "control pins" (where the coil would be if it were a relay) and the input and output pins of the switch. However, there isn't a coil inside. Remember we are talking about switching 110VAC here. Because of this, one has to select the solid state switch designed to accomplish this task. One can purchase these devices from many electronic parts stores. Remember to simply check the ratings and make sure you provide yourself with a safety margin. For example, if the part will handle up to 3 amps of current, don't run 3 amps. Instead run something like half that. This way no one will get hurt because of a device failure and the device will work longer than running it at it's maximum rating.




Water Level Indicator with Alarm
Posted on Thursday, January 20, 2011   •   Category: Miscellaneous

Water Level Indicator with Alarm

This circuit not only indicates the amount of water present in the overhead tank but also gives an alarm when the tank is full. The circuit uses the widely available CD4066, bilateral switch CMOS IC to indicate the water level through LEDs.




1Hz to 2MHz Function Generator Kit with XR-2206 IC
Posted on Monday, January 17, 2011   •   Category: Frequency Wave Generators

1Hz to 2MHz Function Generator Kit with XR-2206 IC

This is a 1Hz - 2MHz XR2206 Function Generator kit that produces high quality sine, square and triangle waveforms of high-stability and accuracy. The output waveforms can be both amplitude and frequency modulated. Coarse frequency adjustment is accomplished using 4-DIP switch for the following four frequency ranges; (1) 1Hz-100Hz, (2) 100Hz-20KHz, (3) 20KHz-1MHz, (4) 150KHz-2MHz. Frequency output can be fine tuned using P1 and P2 potentiometers. The kit includes output that can be connected to 60MHz Counter kit to precisely measure output frequency. 1Hz - 2MHz XR2206 Function Generator kit includes premium quality components, including Audio Grade Gold Capacitors, Gold Plated RCA Connector, WIMA Capacitors, 1% Metal Film Resistors and premium quality PCB with red solder mask and plated through holes.




AD8307 USB 0-500MHz RF Power Meter
Posted on Monday, January 17, 2011   •   Category: Test and Measurement

AD8307 USB 0-500MHz RF Power Meter

Measurement of transmitter output RF power has never been easier and more precise. AD8307 USB 0-500MHz RF Power Meter allows to measure the power of transmitters from 1nW to 2W. Output is displayed in dBm, Watts (nW, uW, mW and W range) as well as input voltage. USB RF Power Meter is based on popular AD8307 watt meter IC and PIC18F2550 microcontroller. Instead of using LCD display module the meter connects to a PC via USB port and displays measurements on a computer via USB RF Power Meter software. The software settings can be changed to use 10-50dBm attenuator and thus allowing to measure higher RF power than 2W.




Using HSR312 / HSR412 Solid State Relays
Posted on Sunday, January 16, 2011   •   Category: Miscellaneous

Using HSR312 / HSR412 Solid State Relays

The HSR312 and HSR412 devices consist of a AlGaAs infrared emitting diode optically coupled to a power MOSFET detector which is driven by a photovoltaic generator. The devices are housed in a 6-pin dual-in-line package. The HSR312L and HSR412L employ an active current limit circuitry enabling the device to withstand current surge transients.




Using an Optocoupler
Posted on Saturday, January 15, 2011   •   Category: Miscellaneous

Using an Optocoupler

An opto-coupler is a device that can be used to electrically isolate two circuits, so that a voltage spike or other problem on one side will not destroy the circuit on the other side. A common use for them is when you want to interface a computer to an AC-powered device, such as a light or a motor. Usually, the opto-coupler will not be used to control the device directly, and instead will just transfer a signal from one circuit to another.




DS1802 Stereo Digital Volume Control
Posted on Friday, January 14, 2011   •   Category: Amplifiers

DS1802 Stereo Digital Volume Control

DS1802 is a Stereo Digital Volume Control IC. It consists of two 65-position, 45kΩ digital potentiometers with logarithmic resistance properties incrementing 1dB per step. It can be operated under automatic software control via a serial 3-wire interface where wiper settings are written with 8-bit words, or under push button control with simple contact closure. The part can be used in either 3V or 5V environments and anywhere within the industrial temperature range of -40°C to +85°C. The DS1802 supports daisy-chaining with other devices under single-processor control.




SWR Meter
Posted on Wednesday, January 12, 2011   •   Category: Test and Measurement

SWR Meter

A pair of AD8307 RSSI (Received Signal Strength Indicator) chips are used to produce DC voltages that are proportional to the logarithm of the Forward and Reflected power levels. These DC voltages can then be subtracted in an Op Amp to produce a voltage proportional to SWR which is essentially independent of power level. The Forward DC voltage also drives a separate Power meter. I have modified Paul's design to use a "Stockton" directional coupler, and to provide a peak-reading capability. The meter automatically provides an accurate readout of SWR for any power level between 10mW and 1000W. I arranged for the Power meter to cover the range 100mW to 1000W, but it is easy to change the circuit to set upper and lower power limits to any values in the range 100uW to 1000W.




Low Ohm Meter - Measures 0.001 up to 1.999 Ohm
Posted on Monday, January 10, 2011   •   Category: Test and Measurement

Low Ohm Meter - Measures 0.001 up to 1.999 Ohm

A very simple circuit to measure low resistance values from 0.001 up to 1.999 Ohm. With a "Direct Resistance Readout in Ohms". You must use two separate batteries. One for the DMM and one to supply power to the LM317LZ. I recommend the LM317LZ, which is the 100 mA, T0-92 version of the normal LM317. But you can also use the LM317, in the T0-220 package, if you want. The trimpot must be set precisely to deliver 100.0 mA out to get truly accurate resistance measurements. So you need a very accurate Milli-Amp Meter to adjust this Correctly. (And like Any Test Equipment, This Calibration should be Re-Checked once a year or so.)




ESR METER: Equivalent Series Resistance Capacitor Tester
Posted on Monday, January 10, 2011   •   Category: Test and Measurement

ESR METER: Equivalent Series Resistance Capacitor Tester

The project came from an Italian magazine Nuova Elettronica N212. It's very simple but interesting ESR Meter. I've built it and tested some capacitors and it's very useful. It measures the ESR (Equivalent Series Resistance) of capacitor (electrolytic and not) that s used to tell if a capacitor is good or not. ESR Meter uses a bridge circuit that works at 100KHz.




Capacitor ESR Meter
Posted on Sunday, January 9, 2011   •   Category: Test and Measurement

Capacitor ESR Meter

A typical capacitor checker measures the capacity (usually in micro farads) of the test capacitor. Some advanced units also test for leakage current. Most of these testers require that the capacitor be removed from the circuit. Unless the capacitor has totally failed, they will not detect a high ESR value. In a typical circuit, there may be 10's or 100's of capacitors. Having to remove each one for testing is very tedious and there is a great risk of damaging circuit boards. This tester uses a low voltage ( 250mv ) high frequency (150khz) A/C current to read the ESR of a capacitor in the circuit. The in circuit testing is possible because of the low voltage used for obtaining the measurement. The voltage is low enough that solid state devices in the surrounding circuitry are not activated and do not affect the low resistance reading we are attempting to obtain. A lot of capacitor checkers will be damaged if you happen to test a charged capacitor. This circuit is A/C coupled and will withstand up to 400vdc of charge on a capacitor (but watch your fingers!). The ESR checker will not detect shorted capacitors as they will read with a very low ESR value. If you are trouble shooting a circuit, you will have to use several instruments including your nose, voltmeter and oscilloscope to locate all the possible failure modes. My experience has found that the ESR meter catches about 95% of capacitor problems and potential problems.




Oscilloscope ESR Tester
Posted on Sunday, January 9, 2011   •   Category: Test and Measurement

Oscilloscope ESR Tester

When teamed up with an oscilloscope, this simple circuit provides a means of measuring capacitor ESR. A 555 timer (IC1) configured as a 2.3kHz free-running oscillator acts as the timebase. It provides narrow (7.7µs) pulses to the capacitor under test via a NAND Schmitt trigger (IC2) and transistor Q1. A 100Ω resistor in series with Q1 limits current flow to about 50mA. Therefore, an ESR of 1Ω will produce pulses across the test capacitor of 50mV, which means that an oscilloscope with a vertical sensitivity of 5mV can measure ESR down to 0.1Ω or less.




USB IO Board
Posted on Friday, January 7, 2011   •   Category: PIC

USB IO Board

USB Input / Output Board is a spectacular little development board / parallel port replacement featuring PIC18F2455 / PIC18F2550 microcontroller. USB IO Board is compatibile with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB Input / Output Board is self-powered by USB port and can provide up to 500mA for electronic projects.




30W Digital RF Wattmeter
Posted on Monday, January 3, 2011   •   Category: Test and Measurement

30W Digital RF Wattmeter

This project will explain how I build my new wattmeter. This watt meter will be able to measure power from 300nW to 30W @ (0-500MHz). This wattmeter is based up on a dummy load of 50 ohm which can handle 50W. The measurement will be displayed in Watt on a 2x16 Char display.




ESR Meter
Posted on Monday, January 3, 2011   •   Category: Test and Measurement

ESR Meter

Electrolytic capacitors are by far the electronic parts that suffer aging soonest. If you have any electronic equipment that over the years has degraded its performance, developed quirks, sometimes ending in complete failure, the chances are good that one or more electrolytic capacitors inside it have degraded, causing the problem. Electrolytic capacitors age in several ways: They can become electrically leaky, causing a DC current through them that can make them blow up. They can shift in capacitance value. But the most common way they degrade, by far, is by unduly increasing their equivalent series resistance, which is the undesired internal resistance that appears in series with the wanted capacitance at a given frequency.




USB Mono FM Transmitter
Posted on Wednesday, December 29, 2010   •   Category: FM Transmitters

USB Mono FM Transmitter

This small FM transmitter with a range of about 50 meters designed for connection to the USB port. With lots of mini-transmitters then you have a comprehensive, action-packed radio program. Due to the power supply via the USB port of a high frequency stability is achieved. Alternatively, the receiver, a battery 5 to 12 volts to operate.




5W PLL FM Transmitter
Posted on Wednesday, December 29, 2010   •   Category: FM Transmitters

5W PLL FM Transmitter

Easy to build high-quality PLL FM transmitter with typical output power of 5 W and no-tune design. The transmitter includes RDS/SCA input and Audio/MPX input with optional pre-emphasis. It can be used with or without stereo encoder. Tuning over the FM band is provided by two buttons that control dual-speed PLL. The transmitter can work also without the LCD display. Some experience with building devices of this kind are highly recommended.




iPhone / iPod Touch DIY Microphone
Posted on Wednesday, December 29, 2010   •   Category: iPOD Hacks

iPhone / iPod Touch DIY Microphone

If you have ever wanted to plug in a pro-quality microphone and headphone to an iPhone or iPod touch, pay attention and read on. This guide will show you how to make a cable that will allow you to do just that. It’s not that hard as long as you can solder well, and can locate the right stuff. But in the end, you’ll end up making a little dongle that will allow you to plug in a mic and headphones separately.




Portable Yagi for 144MHz
Posted on Wednesday, December 29, 2010   •   Category: Antennas

Portable Yagi for 144MHz

This simple 7 element Yagi is ideal for portable operation. The elements can be removed and replaced in a few minutes. The 2.42 Metre boom will fit inside my car. All of the elements are made from 6mm solid aluminum rod. The boom is made from 50x25mm (2x1 in) timber. The driven element is a half wavelength dipole. Unlike the more common type of folded dipole, this dipole is folded on one side but not on the other. For want of a better name, lets call it a 'half folded dipole'. The co-ax cable braid is connected to the centre of the dipole. The co-ax centre conductor is connected to the folded dipole section (see diagram above).




GPS Disciplined Frequency Standard
Posted on Monday, December 27, 2010   •   Category: Miscellaneous

GPS Disciplined Frequency Standard

Using the GPS Satellite system offers the advantage of very accurate timing and by extension, frequency control. The long term error is to all intents and purposes zero, with time and frequency accuracy being comparable to the international standard. The traditional route is to use a relatively low cost GPS receiver module which outputs a 1 Pulse per second signal (1 PPS) aligned to UTC. Basic GPS modules such as the Garmin GPS25 and Motorola Oncore have been around for some years and are available at low cost. It is possible to phase lock a divided down crystal oscillator to this 1 PPS signal and transfer its long term stability to , say, a 10MHz reference which is subsequently used for deriving any LO and beacon frequencies. The subsequent PLL system is usually described as a GPS Disciplined Oscillator rather than locked, since it is not, strictly speaking, actually ‘locked’ to the GPS system at all; just controlled by it via the 1 PPS generated by software in the receiver module.




Time Display unit for a GPS module
Posted on Monday, December 27, 2010   •   Category: Miscellaneous

Time Display unit for a GPS module

I decided to build a device to permanently display accurate time received from a cheap GPS module installed in my workshop. Having obtained a PIC18F1320 microcontroller for experimentation, I wanted to learn about the new features of the PIC18F range using only minimal hardware to control the display. I am currently using it with the on-chip 8Mhz oscillator only and driving a six digit led display, multiplexed with further saving of chip pins by a technique pioneered by Charlie Allen of Maxim-Dallas for their MAX6951 LED display drivers called “Charlieplexing” (see their application note AN1880). I would have liked to have used a MAX6951 chip for better display brightness, but they appear to be only available in "Quarter Size Outline Packages" (QSOP) - the leads are very close together,not easy to experiment with. Another alternative would be to use a MAX7219 display driver, this chip has a serial interface and an option to adjust the display brightness - something I may try later.




Animated Christmas Star
Posted on Monday, December 27, 2010   •   Category: Miscellaneous

Animated Christmas Star

The star is about 35cm across and designed to be displayed indoors in a window. I originally created the star three years ago using a 16F872 controller. The original version worked ok - but had no spare memory for adding more features. This new version uses a 18F2620 because I now prefer the 18F series and decided it would be a good general purpose 28 pin chip to use. It has more than enough memory (64K) so I can add as many features as I want now. (It should also work using a PIC18F2525 instead if you find it easier or cheaper to obtain) Since, I made the first version, brighter LEDs are now available and cost is much lower - this project currently uses a total of 60 comprising of 25 Blue, 15 Green and 20 Red.




DS18B20 Bluetooth Thermometer
Posted on Friday, December 17, 2010   •   Category: PIC

DS18B20 Bluetooth Thermometer

One morning I woke up and wanted to know what the temperature outside was, and instead of running over to Home Depot and picking up a $2.00 glass thermometer, I decided to build my own wireless temperature sensor. At the heart of the board is a PIC12F675 microcontroller in an SO8 package. The right-hand side of the board houses the linear power supply (LP2950), bottom-center is the DS18B20 1-Wire temperature sensor, and out in left-field you can see the Sure TTL Bluetooth Module.




MCP9700, MCP9700A, MCP9701 and MCP9701A Temperature Sensors
Posted on Friday, December 17, 2010   •   Category: Sensors

MCP9700, MCP9700A, MCP9701 and MCP9701A Temperature Sensors

The MCP9700, MCP9700A, MCP9701 and MCP9701A Temperature Sensors from Microchip offer exceptional performance for the low price. Each have different temperature ratings and accuracy parameters. MCP9700, MCP9700A, MCP9701 and MCP9701A sensors are available in different packaging and are very simple to interface with. Vdd, GND and Vout are all that are required. You should check the datasheet to get a better idea of the parameters for the device you decide to use, though keep in mind that the user module listed below will automatically calculate the temperature depending on the device in use.




AC Power Meter
Posted on Wednesday, December 15, 2010   •   Category: Miscellaneous

AC Power Meter

If you attempt to save power in the house thoroughly, you can not ignore the standby power consumption of appliances. We made a device to measure the power consumption of appliances. Actually, to say the AC power meters measure the 100V AC current is flowing in the power cord over do it. In general, the voltage is measured casually, is difficult to measure the current. To cut off a part of the circuit current flow from a current meter must be connected to it.




PIC18F2550 Project Board
Posted on Wednesday, December 15, 2010   •   Category: PIC

PIC18F2550 Project Board

The new PIC18F2550 Project Board was designed as the development platform for student projects. The board platform is suitable for developing the microcontroller based instrumentation. Students may build the signal conditioning board, plugs it to PIC project board, develops the code and programs it with loader cable easily.




Video Amplifier
Posted on Wednesday, December 15, 2010   •   Category: Video

Video Amplifier

Circuit Video Amplifier by transistor BC547 & BC557




Table Lamp Circuit with LM555
Posted on Wednesday, December 15, 2010   •   Category: Miscellaneous

Table Lamp Circuit with LM555

If you want a Power Lamp Flasher at normal electric power, try out Table Lamp Circuit like this is. It uses the integrated circuit NE555 as the core component. It controls the blink rate of the lamp. Use the power transistor for about 20W or current 1.6A. The Q3 can be replaced by TIP41 or H1061 or MJ3055 or 2N3055.




Doorbell with 555 IC
Posted on Wednesday, December 15, 2010   •   Category: Miscellaneous

Doorbell with 555 IC

Doorbell with 555 IC




Car 12V to 50V DC Converter
Posted on Wednesday, December 15, 2010   •   Category: AC / DC Innveters

Car 12V to 50V DC Converter

This circuit for Car audio input battery 12V to 50VDC, It use transistor and IC TL072.




PIC18F2455 / PIC18F2550 USB IO Board
Posted on Friday, December 10, 2010   •   Category: USB Interface Adapters

PIC18F2455 / PIC18F2550 USB IO Board

USB Input / Output Board is a spectacular little development board / parallel port replacement featuring PIC18F2455 / PIC18F2550 microcontroller. USB IO Board is compatibile with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB Input / Output Board is self-powered by USB port and can provide up to 500mA for electronic projects.

These are examples of what can be built using USB IO Board:
USB Relay Controller (turn ON/OFF lights or appliances in the house)
Control LEDs, toys, electronic gadgets, wireless control, etc.
USB LCD Controller
USB Volt / Ampere / Wattage Meter
USB CNC Controller
USB Data Logger
USB Temperature Meter / Logger
USB Thermostat
USB Humidity Meter / Logger
USB Stepper Motor Controller
USB RC Servo Controller





USB LCD Controller
Posted on Saturday, December 4, 2010   •   Category: PIC

USB LCD Controller

If you like PC modding this is cool project for you.this is an USB interface for alphanumeric LCD display like 4x20 which can be controlled with LCDSmartie program.USB interface is implemented by using PIC18F2550 microcontroller. Using USB LCD module you can view many types of information taken from PC like temperatures, time/date, MP3 song titles, view emails, RSS feeds all that LCDSmartie or other program supports.




PIC18F4550 Pinguino Development Board
Posted on Friday, December 3, 2010   •   Category: PIC

PIC18F4550 Pinguino Development Board

Pinguino is an Arduino-like board based on a PIC Microcontroller. The goal of this project is to build an integrated IDE easy to use on LINUX, WINDOWS and MAC OS X. This is a simple 40 pin PIC development board as described in RadCom for November 2009. It is designed for a PIC18F4550, but it will work with other 40 pin PICs like the PIC16F877A. It has no bells & whistles attached. No buttons, LED, LCD ICSP etc. All of the PIC pins are easily accessible so that you can add any features you need. This board has been tested with the Vasco PUF and the Pinguino USB bootloaders.




Digital GLCD Oscilloscope
Posted on Friday, December 3, 2010   •   Category: AVR

Digital GLCD Oscilloscope

It was four years ago which I needed an Oscilloscope to be able to see the received codes from PT2272. (This is a Remote Control Decoder chip). Later on I made so many other things with this device which I will explain it later . ( such as the measurement of the low value voltages and even the supplies with high values and so on...). Although on that time I was in hurry so didn't design a PCB and I mount it on a pure, bread board. Its a good portable one, as the Battery is put on it, so you can have it in your pocket.




Charge Monitor for 12V Lead Acid Battery
Posted on Friday, December 3, 2010   •   Category: Battery Chargers

Charge Monitor for 12V Lead Acid Battery

A battery is a vital element of any battery-backed system. In many cases the battery is more expensive than the system it is backing up. Hence we need to adopt all practical measures to conserve battery life. As per manufacturer's data sheets, a 12V rechargeable lead-acid battery should be operated within 10. IV and 13.8V. When the battery charges higher than 13.8V it is said to be overcharged, and when it discharges below 10.IV it can be deeply discharged. A single event of overcharge or deep discharge can bring down the charge-holding capacity of a battery by 15 to 20 per cent. It is therefore necessary for all concerned to monitor the charge level of their batteries continuously. But, in practice, many of the battery users are unable to do so because of non-availability of reasonably-priced monitoring equipment. The circuit idea presented here will fill this void by providing a circuit for monitoring the charge level of lead-acid batteries continuously.




Wiper Speed Control Circuit
Posted on Friday, December 3, 2010   •   Category: Miscellaneous

Wiper Speed Control Circuit

A continuously alive wiper in a car may prove to be a nuisance, abnormally back it is not aqueous heavily. By application the ambit declared actuality one can alter across-the-board amount of the wiper from already a additional to already in ten seconds. The ambit comprises two timer NE555 ICs, one CD4017 decade counter, one TIP32 disciplinarian transistor, a 2N3055 ability transistor (or TIP3055) and a few added detached components.




Anti Theft Car Wireless Alarm
Posted on Friday, December 3, 2010   •   Category: Miscellaneous

Anti Theft Car Wireless Alarm

This is anti theft alarm with wireless connectivity ,called Anti Theft Car wireless alarm The FM radio-controlled anti- theft alarm can be used with any vehicle having 6- to 12-volt DC supply system. The mini VHF, FM transmitter is fitted in the vehicle at night when it is parked in the car porch or car park.




Dome Light Dimmer With Delay For Cars
Posted on Wednesday, November 17, 2010   •   Category: Miscellaneous

Dome Light Dimmer With Delay For Cars

There are two stages: aboriginal one is dabbling and the additional one is fading. Back you accessible the aperture the ablaze turns on. You get central and abutting the door, but the ablaze stays on (delay stage) for an adjustable aeon of time (0-40 sec. for the ethics in the scheme, but you can calmly adapt that i.e. put a bigger capacitor) so you can see area to admit the key or do whatever you do back you get in the car, again fades abroad (fading stage) with an adjustable speed. If you affix the ACC wire (which is absolutely optional) back you about-face the key to ACC position the ablaze turns off (actually fades) alike if the dabbling date is not over (it cancels the adjournment stage).




12V to +-20V Automotive Power Converter (for audio amplifier)
Posted on Wednesday, November 17, 2010   •   Category: AC / DC Innveters

12V to +-20V Automotive Power Converter (for audio amplifier)

The limitation of car supply voltage (12V) forces to convert the voltages to higher in order to power audio amplifiers. In fact the max audio power x speaker (with 4 ohm impedance) using 12V is (Vsupply+ - Vsupply-)^2/(8*impedance) 12^2/32 = 4.5Watts per channel, that is laughable... For powering correctly an amplifier the best is to use a symmetric supply with a high voltage differential. for example +20 - -20 = 40Volts in fact 40^2/32 = 50 Watts per channel that is respectable. This supply is intended for two channels with 50W max each (of course it depends on the amplifier used). Though it can be easily scaled up or the voltages changed to obtain different values.




500W 12 Volt to 220 Volt Inverter
Posted on Wednesday, November 17, 2010   •   Category: AC / DC Innveters

500W 12 Volt to 220 Volt Inverter

This is circuit Inverter 12VDC to 220V 50Hz 500W. It easy to make and low cost.




12V to 220V 100W Transistor Inverter
Posted on Wednesday, November 17, 2010   •   Category: AC / DC Innveters

12V to 220V 100W Transistor Inverter

12V to 220V 100W transistor based power inverter.




100W Power Amp
Posted on Wednesday, November 17, 2010   •   Category: Amplifiers

100W Power Amp

This is a 100W Transistor based Power Amp Circuit. It's an old circuit, but nice circuit amplifier. Uses transistors MJ15003 and MJ15004, power supply +38V,-38V 3A. Output power is 100W for 8 OHM Speaker.




OCL Power Amp
Posted on Wednesday, November 17, 2010   •   Category: Amplifiers

OCL Power Amp

This is old circuit Power amp OCL, But easy circuit and very nice. To use for play music in your home. It low cost too. It use IC 741 or LF351(good) and Transistor x 4 (2N3055+MJ2955+BD139+BD140) and little component. Power supply volt +35V/-35V and 3A for Mono, 5A for Stereo.




Stereo Tone Control Circuit with Adjustable Bass-Treble
Posted on Wednesday, November 17, 2010   •   Category: Amplifiers

Stereo Tone Control Circuit with Adjustable Bass-Treble

PCB Tone control adjustable bass-treble Stereo by IC LM348




Loudspeaker Protection with Soft Start
Posted on Wednesday, November 17, 2010   •   Category: Amplifiers

Loudspeaker Protection with Soft Start

This is a small protection circuit from loudspeakers, from DC voltage that likely to exist after some damage in the power amplifier. If a DC voltage is presented in the exit of amplifier, RL1 it interrupts immediately the line of loudspeakers preventing thus to reach in he. Parallel it provides a delay time of 3 seconds from the moment where the power supply will be applied. This delay protects the loudspeakers from undesirable bangs that are observed when open the supply switch.




TDA2030 Amp OTL 15W
Posted on Wednesday, November 17, 2010   •   Category: Amplifiers

TDA2030 Amp OTL 15W

Circuit of TDA2030 amp OTL 15W




HA1377 Bridge Amplifier BCL cap 17W (Car audio)
Posted on Wednesday, November 17, 2010   •   Category: Amplifiers

HA1377 Bridge Amplifier BCL cap 17W (Car audio)

This is circuit Car audio Amplifier(Bridge Amplifier BCL) , It use IC HA1377, Supply Volt 12V-13V. Speaker 4 OHM. Nice Circuit and Easy to Build.




DC13.8V to DC250V Inverter Circuit
Posted on Wednesday, November 17, 2010   •   Category: AC / DC Innveters

DC13.8V to DC250V Inverter Circuit

I have done a lot of work with valves in recent years. For me valves have many advantages, least of all the price; since they are now "obsolete" it is quite easy to get hold of them for next to nothing at rally's and junk sales. I recently purchased a couple of hundred battery valves for less than SEK1 (US$ 0.15) each. The biggest problem with valves is the PSU needed to provide +250 vDC and 6.3 vAC for the filaments. The transformers are no-longer available at a reasonable price, but a pair of 12v-6v-0v-6v-12v mains transformers will do the job just as well. For portable use only one transformer is required together with a pair of power transistors such as 2N3055 etc.




FT232RL Arduino Programming Board
Posted on Monday, November 15, 2010   •   Category: USB Interface Adapters

FT232RL Arduino Programming Board

This is simple FT232RL programming board for Arduino.




Low Cost USB to TTL for MCUs
Posted on Monday, November 15, 2010   •   Category: USB Interface Adapters

Low Cost USB to TTL for MCUs

One of the most common way to interface a microcontroler to a computer used to be serial port. But right now, serial port have been replaced with USB on most computers. A common way to fix this issue is to use a USB to TTL converter or a USB to RS232 converter + MAX232.




Infra Red Vision System for a Toy Cars
Posted on Monday, November 15, 2010   •   Category: Remote Control

Infra Red Vision System for a Toy Cars

This is the project of infrared vision system for a toy car. It will project 2 modulated IR beams ahead and detect any reflection of these beams on any obstacle ahead of the car. The circuit will then invert the car's motor for a given time thus changing the direction of advance as it goes in reverse. No special control for steering is necessary as the car has the front wheels' shaft in an eccentric support: when going forward it auto aligns itself, when running backwards the shaft turns and the car describes a curve.




LCD Display
Posted on Monday, November 15, 2010   •   Category: Miscellaneous

LCD Display

LCD display consists of an array of tiny segments known as pixels that can be manipulated to present information. As a result of this technology, many types of this displays are used in applications like calculator, watch, messaging boards, clock, equipments, machines and a host of other devices that one can think of. Most of the Display types are reflective, meaning that they use only ambient light to illuminate the display. Even displays that do require an external light source consume much less power than CRT devices.




Fire Alarm
Posted on Monday, November 15, 2010   •   Category: Miscellaneous

Fire Alarm

The thermistor offers a low resistance at high temperature and high resistance at low temperature. This phenomenon is employed here for sensing the fire. The IC1 (NE555) is configured as a free running oscillator at audio frequency. The transistors T1 and T2 drive IC1. The output(pin 3) of IC1 is couples to base of transistor T3(SL100), which drives the speaker to generate alarm sound. The frequency of NE555 depends on the values of resistances R5 and R6 and capacitance C2.When thermistor becomes hot, it gives a low-resistance path for the positive voltage to the base of transistor T1 through diode D1 and resistance R2. Capacitor C1 charges up to the positive supply voltage and increases the the time for which the alarm is ON.




88-108Mhz FM Preamplifier
Posted on Monday, November 15, 2010   •   Category: Antennas

88-108Mhz FM Preamplifier

This VHF amplifier working on Band 2 Radio Spectrum tuning approximately 88 - 108 Mhz The Preamplifier circuit uses two 2N3819 FET's in cascade configuration. The lower FET operates in common source mode, while the upper FET, operates in common gate, realizing full high frequency gain. The bottom FET is tunable allowing a peak for a particular station.




High Current Regulated Supply By LM317
Posted on Monday, November 15, 2010   •   Category: Power Supplies

High Current Regulated Supply By LM317

The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency. For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage. The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1 ohm) equalizing resistors (1volt at 10 amps), so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage.




FT232RL USB to Serial Adapter for PIC AVR ATMEGA ARDUINO MCUs
Posted on Monday, November 15, 2010   •   Category: USB Interface Adapters

 	 FT232RL USB to Serial Adapter for PIC AVR ATMEGA ARDUINO MCUs

FT232RL USB to Serial UART (TTL) Adapter is a simple and inexpensive way to connect PIC, AVR or ATMEGA MCUs to a PC or Mac via USB connection. FT232RL is an impressive chip because it implements full v2.0 USB protocol, needs no external crystal, has integrated EEPROM for device ID and product description strings and comes with Royalty-Free driver support for Windows, Linux, and Mac OSX. FT232RL chip provides two data lines RXD and TXD that are connected through 1K resistors to a microcontroller such as PIC AVR ATMEGA ARDUINO. Up to 500mA of +5V power can be obtained from USB port and used to power both FT232RL chip and your favourite MCU. When connected to a PC FT232RL is mounted and shows as Virtual COM port in Device Manager making it easy to send and receive data from PIC, AVR or ATMEGA microcontrollers.




USB to Serial Interface
Posted on Friday, November 12, 2010   •   Category: USB Interface Adapters

USB to Serial Interface

USB to serial interface is based on the powerful FT232 chip from FTDI. It enables very easy connection of the user's application to the PC via the USB port, without necessity of any deep knowledge about the complicated USB problems. FT232 chip is capable to transfer data at speeds up to 1M Baud in RS232 mode and up to 3M Baud in the RS485 mode. Schematic contains the on-board serial EEPROM (93LC46) for storing the ID data (VID, PID, serial number and description strings).




13.8V, 40A Switching Power Supply
Posted on Friday, November 12, 2010   •   Category: Power Supplies

13.8V, 40A Switching Power Supply

Amateur radio has been somewhat slow to accept switching power supplies for powering communication equipment. This is a pity, because "switchers", as they are often called, offer very attractive features, like small size, low weight, high efficiency, and low heating. True, they are generally more complicated than linear power supplies, but this is easily compensated by the fact that they can be built for a lower cost. Some early switchers produced an objectionable amount of RF noise, bringing the whole switching technology into bad reputation. But by proper design techniques and careful EMI filtering it is possible to build very quiet switchers.




Off Line-UPS Offers (100 -5000 Watts)
Posted on Friday, November 12, 2010   •   Category: Miscellaneous

Off Line-UPS Offers (100 -5000 Watts)

With increased dependency on electric power for various domestic, commercial purposes and the seemingly declining capacity of power utilities in many countries, the need for additional backup power sources is on the rise. Various modules are already available to address these different needs. However, most modules are too expensive, too bulky, or too rigid in their power capacity, capability, and flexibility. The circuit described here is an off-line uninterruptible power supply. It has an expandable power stage design that can be easily modified for use with power ranges from as low as 100 W to as high as 5000 W with forced cooling.




Automatic Battery Charger
Posted on Friday, November 12, 2010   •   Category: Battery Chargers

Automatic Battery Charger

The following automatic battery-charger design is created with a circuit that could qualify as the simplest window comparator ever built around a single transistor. It starts charging when the battery voltage drops beyond a preset value, and it stops when an upper preset voltage is attained. With the help of a precise variable voltage supply, the upper and lower voltage levels were set. The normally connected (NC) lead of the relay isn't joined to the 15-V dc supply, which blocks this voltage from passing to the battery leads. This will accurately set the upper and lower levels. But the charging supply of 15 V dc was connected to the circuit.




10Hz - 60MHz Frequency Meter / Counter Kit
Posted on Tuesday, November 9, 2010   •   Category: Counters / Frequency Meters

 10Hz - 60MHz Frequency Meter / Counter Kit

This is 60MHz Frequency Meter / Counter for measuring frequency from 10Hz to 60MHz with 10Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc. The meter provides very stable readings and has excellent input sensitivity thanks to onboard amplifier and TTL converter, so it can even measure weak signals from crystal oscillators. With the addition of prescaller it is possible to measure the frequency of 1GHz and above.




Alarm Sounds When Refrigerator Door Remains Open Too Long
Posted on Thursday, October 21, 2010   •   Category: Miscellaneous

Alarm Sounds When Refrigerator Door Remains Open Too Long

Not properly closing a refrigerator door will no doubt invite huge electricity bills. This gadget is an alert device that beeps if you leave the refrigerator door open for more than 20 seconds. When the door opens, the lamp illuminates and the IC (a 4060B counter/oscillator) starts counting down. After a preset delay of 20 seconds, the piezoelectric buzzer beeps intermittently for 20 seconds and then stops for the same amount of time. This cycle repeats until the refrigerator door closes.




Bidirectional H-Bridge DC-Motor Motion Controller
Posted on Thursday, October 21, 2010   •   Category: Motor Controllers

Bidirectional H-Bridge DC-Motor Motion Controller

In applications requiring absolute accuracy in the speed control of dc servo motors, there’s no substitute for the traditional tachometer-based feedback loop. But for somewhat less demanding situations, adequate accuracy often can be achieved without the complication and expense of a tach. This can be done by taking advantage of the built-in electromechanical constants of the motor itself.




LED Torch Using MAX660
Posted on Thursday, October 21, 2010   •   Category: LED

LED Torch Using MAX660

This is a simple LED torch circuit based on IC MAX660 from MAXIM semiconductors. The MAX 660 is a CMOS type monolithic type voltage converter IC. The IC can easily drive three extra bright white LEDs. The LED's are connected in parallel to the output pin 8 of the IC. The circuit has good battery life. The switch S1 can be a push to ON switch.




Lead Acid Battery Charger Circuit
Posted on Thursday, October 21, 2010   •   Category: Battery Chargers

Lead Acid Battery Charger Circuit

Here is a lead acid battery charger circuit using IC LM317.The IC here provides the correct charging voltage for the battery. A battery must be charged with 1/10 its Ah value. This charging circuit is designed based on this fact.The charging current for the battery is controlled by Q1,R1,R4 and R5. Potentiometer R5 can be used to set the charging current. As the battery gets charged the the current through R1 increases.




5V Power Supply With Overvoltage Protection.
Posted on Thursday, October 21, 2010   •   Category: Power Supplies

5V Power Supply With Overvoltage Protection.

For circuits using TTL ICs the supply voltage is a great concern and a slight increase in supply from the rated 5V may damage the IC. Using fuses alone does not solve the problem because a fuse may take several milliseconds to blow off and that’s enough time for the IC to get damaged.




Electronic Mosquito Repeller
Posted on Thursday, October 21, 2010   •   Category: Miscellaneous

Electronic Mosquito Repeller

Here is the circuit diagram of an ultrasonic mosquito repeller.The circuit is based on the theory that insects like mosquito can be repelled by using sound frequencies in the ultrasonic (above 20KHz) range.




Dual USB Charger With Switching Regulator
Posted on Tuesday, October 19, 2010   •   Category: Battery Chargers

Dual USB Charger With Switching Regulator

This is a portable USB Charger. It uses a high efficiency switching regulator that runs at 85 - 94% efficiency depending on input voltage and load. It takes an input voltage from 8 to 16 volts and can run from anything from a 9 volt battery to a car battery. It has 2 USB ports and easily charges 2 power hungry devices at once.




VHF Video Transmitter 60-200 MHz
Posted on Tuesday, October 19, 2010   •   Category: Video

VHF Video Transmitter 60-200 MHz

Here's a simple video transmitter for VHF TV channel will accept baseband video input, hence it can be driven by most CCD cameras and VCR video outputs. It ouputs roughly 80mW and when used with a 40cm telescopic antenna over 100 meters range is possible.




6 Channel Audio Mixer
Posted on Tuesday, October 19, 2010   •   Category: Amplifiers

6 Channel Audio Mixer

The mixer circuit below has 3 line inputs and 3 mic inputs. The mic inputs are suitable for low impedance 200-1000R dynamic microphones. An ECM or condenser mic can also be used, but must have bias applied via a series resistor.




5 - 30 Minute Timer
Posted on Tuesday, October 19, 2010   •   Category: Miscellaneous

5 - 30 Minute Timer

A switched timer for intervals of 5 to 30 minutes incremented in 5 minute steps. Simple to build, simple to make, nothing too complicated here. However you must use the CMOS type 555 timer designated the 7555, a normal 555 timer will not work here due to the resistor values. Also a low leakage type capacitor must be used for C1, and I would strongly suggest a Tantalum Bead type.




Sound Operated Switch
Posted on Tuesday, October 19, 2010   •   Category: Miscellaneous

Sound Operated Switch

This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electric (ECM) microphone.




1W Mono Amplifier with IC TDA7052
Posted on Monday, October 18, 2010   •   Category: Amplifiers

1W Mono Amplifier with IC TDA7052

This circuit is a 1 watt mono amplifier using the TDA 7052 from Philips. It is designed to be used as a building block in other projects where a battery powered audio amplifier is required to drive a small speaker. It will operate best from 6 – 12 V DC and requires no heatsink for normal use.




Temperature Monitor
Posted on Monday, October 18, 2010   •   Category: Test and Measurement

Temperature Monitor

Using a thermistor in the position shown makes a heat activated sensor. A change in temperature will alter the output of the op amp and energize the relay and light the LED. Swapping the position of the thermistor and 47k resistor makes a cold or frost alarm.




3D Sound Audio Delay
Posted on Monday, October 18, 2010   •   Category: Miscellaneous

3D Sound Audio Delay

It is fun to make a variable space in your small room, but it’s hard to make the actuator to move your wall or room partition. Using analog audio line delay, you can adjust your room virtually. Just turn a knob in your audio set and you can adjust your room size. The circuit described here will make your dream come true, giving a feel that your speaker is located 15 meters behind you, even though your room is actually 3 meters wide. Here is the circuit’s schematic diagram.




SG3525 DC Converter 12V to +35V,-35V
Posted on Monday, October 18, 2010   •   Category: Power Supplies

SG3525 DC Converter 12V to +35V,-35V

The selected switching topology is called a "push-pull" converter, because the transformer has a double primary (or a "center-tapped" one, if your prefer). The center tap is permanently connected to the car battery (via an LC filter to avoid creating peaks in the battery lines, which could affect other electronic equipment in the car). The two ends of the primary are connected to a pair of paralleled MOSFETs each that tie them to ground in each conduction cycle (Vgs of the corresponding MOSFET high).




Strobe Light
Posted on Monday, October 18, 2010   •   Category: Miscellaneous

Strobe Light

Strobe lights are widely used by disco lovers to create wonderful visual effects in disco halls and auditoriam. The circuit of a battery operated portable miniature strobe light, which can be constructed using readily available inexpensive components, is described here. For convenience and simplicity, an ordinary neon lamp is used here in place of the conventional Xenon tube.




20 Watts RMS Amplifier Using TDA2004
Posted on Monday, October 18, 2010   •   Category: Amplifiers

20 Watts RMS Amplifier Using TDA2004

The Circuit present here is a 20Watts Car Stereo Amplifier. The main features of this powerful MULTIWATT® package (a trademark of SGS-THOMSON Microelectronics), a power amplifier IC chips designed specifically for car radio application, are the high current capability (3.5A) and the capability to drive a very low impedance (down to 1.6R). Here is the schematic diagram of the standard circuit as shown in its data sheet.




Parrot Sounding AC door Bell
Posted on Monday, October 18, 2010   •   Category: Miscellaneous

Parrot Sounding AC door Bell

Here is a mains-operated doorbell that produces parrot-like sweet voice without requiring any musical IC. The circuit is cheap and easy to construct. The AC mains is fed to the circuit without using any step-down transformer.




Simple DC to AC Inverter
Posted on Monday, October 18, 2010   •   Category: AC / DC Innveters

Simple DC to AC Inverter

This DC to AC inverter circuit work based on unstable multi vibrator does. In this circuit, IC CD4047 is chosen as a heart of unstable multivibrator, because this IC type gives a complementary output that has opposite phase to another ( pin 10 and 11 as seen in Figure 1), and has 50 % duty cycle that satisfy to generate a pulse for inverter.




TPS54232 Constant Current Source
Posted on Saturday, October 16, 2010   •   Category: Power Supplies

TPS54232 Constant Current Source

In this article I continue my project where I needed a constant current source. In the previous article I talked about the first approach the LM317 constant current source which didn’t worked out that well but could of been improved as suggested by some of my readers in the comments. So I decided to use a dc-dc converter and turn it into a constant current source. Since I’m using the TPS54232 in another project and I have it around I decided to use it. This technique can also be applied to other dc-dc converters with a bit of reading on the subject.




Long Range FM Transmitter Circuit
Posted on Saturday, October 16, 2010   •   Category: FM Transmitters

Long Range FM Transmitter Circuit

This circuit is a circuit diagram fm transmitter. This circuit is somewhat different from the previous fm transmitter circuit. Transmitter circuit described here has the additional RF power amplifier stage, after the oscillator stage, to increase the power output of 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element yagi antenna, this transmitter can provide a good enough signal strength to a distance of about 2 kilometers.




LED Lighting For Christmas
Posted on Saturday, October 16, 2010   •   Category: LED

LED Lighting For Christmas

Using light effects for decoration on festive occasions is a normal practice. Designers are coming up with varieties of electronic circuits to fill the imagination of users. Here is an easy-to-assemble circuit for Christmas decoration as shown in Fig.1. It comprises four transistors, eighteen LEDs, a few resistors and two capacitors.




MAINS operate Christmas Star
Posted on Saturday, October 16, 2010   •   Category: LED

MAINS operate Christmas Star

Here is a low-cost circuit of Christmas star that can be easily constructed even by a novice. The main advantage of this circuit is that it doesn’t require any step-down transformer or ICs. Components like resistors R1 and R2.capacitors C1, C2, and C3, diodes D1 and D2, and zener ZD1 are used to develop a fairly steady 5V DC supply voltage that provides the required current to operate the multivibrator circuit and trigger triac BT136 via LED1.




Radio Remote Control using DTMF
Posted on Saturday, October 16, 2010   •   Category: Remote Control

Radio Remote Control using DTMF

Here is a circuit of a remote control unit which makes use of the radio frequency signals to control various electrical appliances. This remote control unit has 4 channels which can be easily extended to 12.




LiPoly charging with MCP73833
Posted on Monday, October 11, 2010   •   Category: Battery Chargers

LiPoly charging with MCP73833

For my latest projects I used a lot of single cell lipo batteries. They are really nice. High power density, low self-discharge, no memory effect and they can deliver quite an amount of current. But lipo battery handling is a bit more complicated as with other rechargeable batteries. You have to take care of under voltage and over charging as that may destroy the battery.




Remote control using telephone
Posted on Monday, October 11, 2010   •   Category: Phone Circuits

Remote control using telephone

Here is a telephone remote circuit which enables switching ‘on’ and ‘off’ of appliances through telephone lines. It can be used to switch appliances from any distance, overcoming the limited range of infrared and radio remote controls.




Telephone Receiver
Posted on Saturday, October 9, 2010   •   Category: Phone Circuits

Telephone Receiver

An interesting circuit for a me- dium performance handy electronic telephone receiver, suited for receiving incoming calls, is described here. This circuit can be connected to almost all types of telephone exchange lines. To simplify the gadget, the dialler section has been omitted. The circuit can be constructed on a medium size veroboard. Wiring and components layout are not very critical. For compactness, enclose the wired circuit in a plastic cabinet as shown in Fig.(a) here. In order to prevent undesired acoustic feedback, it is necessary to adjust the orientation of ear-piece (LS) and mouth-piece (MIC) at the final stage of construction. The circuit consists of four sections: ringer, voltage regulator, transmitter and receiver. The ringer section is built around capacitor C1, resistor R1 and electronic buzzer BZ1.




12V to +/- 30V DC to DC Converter
Posted on Saturday, October 9, 2010   •   Category: AC / DC Innveters

12V to +/- 30V DC to DC Converter

This is a DC to DC converter for car power amplifier. 12V input generates +30V and -30V output for preamp or power amplifiers. Circuit uses SG3525 IC, Mosfets and switching power supply.




Active Antenna AA-7 HF/VHF/UHF, 3-3000MHz
Posted on Saturday, October 9, 2010   •   Category: Antennas

Active Antenna AA-7 HF/VHF/UHF, 3-3000MHz

If you have a shortwave or high-frequency receiver or scanner that is struggling to capture signals with a short, whip antenna, and you'd like the kind of performance that a 60-foot 'longwire' antenna can provide but lack the space to put one up, consider building the AA-7 HF/VHF/UHF Active Antenna described in this article. The AA-7 is a relatively simple antenna that is designed to amplify signals from 3 to 3000 MegaHertz, including three recognized ranges: 3-30Mhz high-frequency (HF) signals; 3-300Mhz very-high frequency (VHF) signals; 300-3000MHz ultra-high (UHF) frequency signals. Those bands are typically occupied by shortwave, ham, government, and commercial radio signals.




Active Antenna
Posted on Saturday, October 9, 2010   •   Category: Antennas

Active Antenna

An antenna with an integrated RF pre - amplifier




10Hz - 60MHz Frequency Meter / Counter
Posted on Friday, October 8, 2010   •   Category: Test and Measurement

10Hz - 60MHz Frequency Meter / Counter

This is 60MHz Frequency Meter / Counter for measuring frequency from 10Hz to 60MHz with 10Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc. The meter provides very stable readings and has excellent input sensitivity thanks to onboard amplifier and TTL converter, so it can even measure weak signals from crystal oscillators. With the addition of prescaller it is possible to measure the frequency of 1GHz and above. The meter measuring range has been extended and it can now measure 60MHz instead of 50MHz.




500W Mos-Fet Power Inverter from 12V to 110V/220V
Posted on Thursday, October 7, 2010   •   Category: AC / DC Innveters

500W Mos-Fet Power Inverter from 12V to 110V/220V

This circuit will provide a very stable "Square Wave" Output Voltage. Frequency of operation is determined by a pot and is normally set to 60 Hz. Various "off the shelf" transformers can be used. Or Custom wind your own FOR BEST RESULTS. Additional MosFets can be paralleled for higher power. It is recommended to Have a "Fuse" in the Power Line and to always have a "Load connected", while power is being applied. The Fuse should be rated at 32 volts and should be approximately 10 Amps per 100 watts of output. The Power leads must be heavy enough wire to handle this High Current Draw!




VHF Audio Video Transmitter
Posted on Thursday, October 7, 2010   •   Category: FM Transmitters

VHF Audio Video Transmitter






VHF/UHF TV Modulator
Posted on Thursday, October 7, 2010   •   Category: FM Transmitters

VHF/UHF TV Modulator

Simple oscillator that generates a frequency in the VHF or UHF region. The oscillator is modulated with the video signal and the modulated carrier wave thus generated is fed into the TV set's aerial input via a cable. Then all that remains to do is tune the TV to the correct frequency.




UHF-TV Preamplifier
Posted on Thursday, October 7, 2010   •   Category: Antennas

UHF-TV Preamplifier






0.1 - 3.5GHz Prescaler
Posted on Thursday, October 7, 2010   •   Category: FM Transmitters

0.1 - 3.5GHz Prescaler

This handy prescaler divides input frequency by 1000. It takes maximum input frequency of 3.5GHz and converts it into 3.5MHz that may be measured using standard frequency meter.




15dB UHF TV Antenna Booster
Posted on Thursday, October 7, 2010   •   Category: Antennas

15dB UHF TV Antenna Booster

This is an UHF band TV antenna preamplifier circuit With 15dB gain to build easily. It is formed based on BF180 UHF Transistor. The first stage is an band pass filter constructed by the C1, CV1, L1, L4, C7 and C3, the second stage is a base-common voltage amplifier with low input impedance to match. Build the L1 ~ L4 as air core coil to obtain high Q-Factor. After assembling, pack it into a proper metallic box and connect the ground of the circuit to the box to reduce noise effect.




25W RF Amplifier
Posted on Wednesday, October 6, 2010   •   Category: FM Transmitters

25W RF Amplifier

RF amplifier with 25W of power for 88-108MHz FM transmitters.




3V FM Transmitter for 88MHz to 108MHz
Posted on Wednesday, October 6, 2010   •   Category: FM Transmitters

3V FM Transmitter for 88MHz to 108MHz

The important part of the circuit is formed of the Colpitts type oscillator. C3,C4,C5,C6,CD1-CD2 and L1 determines the frequency. BF982 and dual gate MOSFET are active parts in oscillator. When the input impedance of the MOSFET gate inputs are high, LC tank is not affected. However transistors force the LC tank and cause phase shift. Two driver stages are added to isolate the antenna from oscillator. First stage (BF199) amplifies the low signal of the oscillator and works as a constant load. The second stage (BFR90) amplifies the signal going through the antenna some more. A short copper wire can be used as an antenna here. Attaching a large antenna to this circuit is unnecessary because the output power is low.




Simple RF Power Meter
Posted on Wednesday, October 6, 2010   •   Category: FM Transmitters

Simple RF Power Meter

Here is a simple set up which will enable them to measure the out put power of their transmitter. All that they require is a good multimeter which has a sensitivity of 20k ohms/4 Watts which is adequate for low power transmitters. Many beginners trying out their skill with QRP TX, for the first time have to overcome many problems before they are able to come on the air. On usual complaint is that, every thing is working fine but the signal is not going out.




Telephone FM Transmitter
Posted on Wednesday, October 6, 2010   •   Category: FM Transmitters

Telephone FM Transmitter

This FM transmitter attaches in series to one of your phone lines. When there is a signal on the line (that is, when you pick up the handset) the circuit will transmit the conversation. In particular it will radiate from the phone line itself. It is a passive device - there is no battery. It uses the signal on the phone line for power. No aerial is needed - it feeds back the RF signal into the phone line which radiates it in the FM band. The frequency of transmission may be adjusted by the trimcap.




ESR Meter
Posted on Wednesday, October 6, 2010   •   Category: Test and Measurement

ESR Meter

The ESR meter is perfect for any electronics repair technicians, engineers or hobbyist. This handy meter measures electrolytic capacitor equivalent series resistance (ESR) in the circuit. ESR is a very important characteristic of capacitors greater than 1 microfarad. This meter makes measurements which are often impossible to check with standard digital capacitance meters.




4W PLL FM Transmitter
Posted on Tuesday, October 5, 2010   •   Category: FM Transmitters

4W PLL FM Transmitter

The PLL transmitter exciter has the functions of providing a stable, low noise, frequency-selectable RF signal and amplify it to a controllable output power sufficient to drive the power amplifier. It uses a PLL frequency synthesizer built with MC145151, which covers the FM band in 100kHz steps. The VCO covers only a few MHz without readjustment.




30Watt VHF Amplifier Circuit for FM Broadcast Band
Posted on Tuesday, October 5, 2010   •   Category: FM Transmitters

30Watt VHF Amplifier Circuit for FM Broadcast Band

The 30 watt amplifier schematic shown below provides an appropriate power boost with an input of 4 watt up to 6 watts. The circuit is designed to cover 88-108MHz FM Broadcast Band. However, the circuit is very stable at my place and provides a clean-output through seven (7) element Butter-worth low-pass filter.




3W FM Transmitter Amplifier
Posted on Tuesday, October 5, 2010   •   Category: FM Transmitters

3W FM Transmitter Amplifier

Presented is a three stage 3W FM Transmitter Amplifier using 2SC9018, 2SC2053 and 2SC1970 transistors. The circuit is supplied by 12-14V DC voltage and requires at least 500mA of current.




TV Transmitter
Posted on Tuesday, October 5, 2010   •   Category: FM Transmitters

TV Transmitter

One of the most useful gadgets a video enthusiast can have is a low-power TV Transmitter. Such a device can transmit a signal from a VCR to any TV in a home or backyard. Imagine the convenience of being able to sit by the pool watching your favorite movie on a portable with a tape or laser disc playing indoors. You could even retransmit cable TV for your own private viewing.




FM Radio Receiver
Posted on Tuesday, October 5, 2010   •   Category: FM Radio / Receivers

FM Radio Receiver

This simple fm radio receiver circuit consists of a regenerative rf stage, TR1, followed by a two of three-stage audio amplifier, TR2 to TR4. In some areas 3 stages of audio amplification may not be necessary, in which case TR3 and its associated components can be omitted and the free end of capacitor C5 connected to the collector of TR2.




PIC Volt Ampere Meter
Posted on Tuesday, September 21, 2010   •   Category: Test and Measurement

 PIC Volt Ampere Meter

PIC Voltmeter Amperemeter can measure voltage 0-70V or 0-500V with 100mV resolution and current consumption 0-10A or more with 10mA resolution. The meter is a perfect addition to any power supply, battery chargers and other electronic projects where voltage and current must be monitored. The meter uses PIC16F876A microcontroller with built-in ADC (Analog to Digital Converter) and 16x2 green backlighted LCD display. With slight modification it is possible to measure higher voltage and current.




30 Watt Linear FM Amp with BLY89
Posted on Wednesday, September 15, 2010   •   Category: FM Transmitters

30 Watt Linear FM Amp with BLY89

A amplifier of medium force RF for the FM, is always essential for the amateur that wants it strengthens some small transmitter, that likely it has already it manufactured! The present circuit can give force 25-30W, with control no bigger than 4-5 W. As it appears in the analytic drawing, the amplifier is manufactured with the transistor TR1 of type LY89 of Phillips. The transistor this is specifically drawn for operation in frequencies up to 175Mhz, with very good results.




250mW FM Transmitter Amplifier
Posted on Tuesday, September 14, 2010   •   Category: FM Transmitters

250mW FM Transmitter Amplifier

This project is a simple 2-transistor VHF power amplifier, with about 16dB gain, and requires no tuning or alignment procedures. Wideband techniques have been used in the design and the circuit is equipped with a "lowpass" filter to ensure good output spectral purity. The project has been designed for assembly on a single-sided printed circuit board. The circuit is specifically designed to amplify the output of 7mW to 10mW WBFM transmitters (wide band) to a final level of 250mW to 300mW.




Miniature Headphone Amplifier
Posted on Saturday, September 11, 2010   •   Category: Headphone Amplifiers

Miniature Headphone Amplifier

The small AF amplifier Suitable for laptops and MP3 players. IT may be powered from the PC (Game or USB) or AC adapter.The basis of the amplifier is an integrated circuit TDA2822M. With this circuit you can build an amplifier with output up to 2x 1 W. This high power circuit is only able to supply at peak times, when excited, would be permanently unable to work. Involvement of the amplifier is to figure 1. The input signal passes through frequency-dependent volume control on the divider. Frequency-dependent divider produces frequencies around 100 Hz, with a positive influence on the subjective sound quality when using small speakers. IO is the involvement of manufacturers' recommendations. The amplifier output can connect speakers with an impedance of 8 ohms (or greater), or headphones. IO supply voltage can be in the range of 1,8 to 15 V. The low supply voltage power amplifier is very small, at high supply voltage and load speakers with low impedance circuit may be a little overheated. With 8 ohm speakers are suitable voltage in the range of 6-9 V. I used to supply voltage 5 V, which are derived from the game port. Voltage of 5 V can be obtained even from the keyboard connector, PS / 2 port and USB. A better option is a network adapter, there are no problems with earth loops.




Aircraft / Airplane Radio Receiver
Posted on Saturday, September 11, 2010   •   Category: FM Radio / Receivers

Aircraft / Airplane Radio Receiver

The communications between commercial aircraft and the ground can be interesting, amusing and sometimes even disturbing. However radios that receive the approximately 220MHz to 400MHz band commonly used for aircraft (both military and commercial) are not easily found. And scanners can be complicated, large and expensive. With an easy to build circuit such as this one, everyone can enjoy listening in on these conversations.




5W PLL Stereo FM Transmitter
Posted on Friday, September 3, 2010   •   Category: FM Transmitters

5W PLL Stereo FM Transmitter

5W PLL Stereo FM Transmitter features PLL synthesized drift free operation with high quality BH1415 chip. 5W RF output power is achieved with 2SC1971 6W transistor in the output stage. Front panel digital control comes with LED display and case is made high quality aluminum. The board features EMI filtering on audio and power inputs and comes with Microphone and Audio inputs. Once transmitter is turned on it starts broadcasting with previously selected frequency. Overall this 5W PLL Stereo FM Transmitter provides professional broadcast audio quality and rivals commercial broadcasts.




FM Transmitter with Mic & Line Input
Posted on Friday, September 3, 2010   •   Category: FM Transmitters

FM Transmitter with Mic & Line Input

This is a unique FM transmitter that provides both a built-in sensitive microphone and an RCA jack for line input. It has two modes of operations, "Microphone" and "Line", which are selectable using a jumper. In the "Microphone" mode, it can be used as a wireless microphone transmitter. In the "Line" mode, it can be easily connected to any audio source to broadcast the audio signal to any FM receiver within its range. 500mW FM / VHF Transmitter Amplifier / Booster can be added for longer transmission range.




50mW FM PLL Transmitter SD USB MP3 Player
Posted on Friday, September 3, 2010   •   Category: FM Transmitters

50mW FM PLL Transmitter SD USB MP3 Player

Features PLL tuned transmitter / exciter for rock solid frequency stability over the entire FM band. Displays Transmitted Frequency on backlighted LCD. PCB includes antenna output to which a piece of wire, or VHF amplifier can be connected for greater transmission range. Includes 3.5mm audio jack cable. Plays MP3 from SD and USB memory (SD and USB connectors on board). IR Remote can be used to control the transmitter.




BH1417 Stereo PLL FM Transmitter
Posted on Friday, September 3, 2010   •   Category: FM Transmitters

BH1417 Stereo PLL FM Transmitter

This is a high quality stereo PLL FM transmitter incorporating a Phase-Locked-Loop (PLL) synthesizer. It is based on the Rohm BA1417 PLL FM Transmitter Integrated Circuit and offers a choice of up to 14 preset transmission frequencies spaced every 200 KHz between: 88.7 – 88.9 MHz (Low Band Mode) and 106.7 – 107.9 MHz (High Band Mode). It has outstanding frequency stability thanks to the PLL crystal controlled design and offers excellent high-fidelity audio performance. It is ideal for use in your home or office to transmit MP3 songs or internet radio stations from your computer to any standard FM radio. It can also be connected to any other audio source, such as an iPod, a MP3 Player, Walkman, Discman or XM Satelite Radio receiver. The circuit incorporates a stereo audio input jack as well as a DC adapter jack which makes it quick and easy to setup. Transmission frequency selection is done through a DIP switch.




50mW BH1417 Stereo PLL FM Transmitter
Posted on Thursday, August 5, 2010   •   Category: FM Transmitters

50mW BH1417 Stereo PLL FM Transmitter

This is an excellent 50mW Hi-Fi PLL FM Stereo Transmitter that features BH1417 chip. ROHM's new Japan has BH1417 is one of the most simple and practical integrated circuits, which combines phase-locked loop circuit, stereo encoder circuit, transmitter circuit, as well as other additions. Pre-emphasis circuit, limiter circuit and low pass filter can significantly improve the sound quality. The total harmonic distortion up 0.3%, stereo separation to 40dB, RF output level is 100dB. BH1417F is an excellent new IC chip, this circuit improves signal to noise ratio (S / N) of pre-emphasis circuit to prevent signal over emphasized limiting circuit, the control input signal frequency low-pass filter circuit (LPF), generate stereo stereo composite signal modulation circuit, FM transmitter phase-locked loop circuit (PLL) component. BH1417F excellent frequency characteristics, it can achieve 40dB of isolation, transmitted sound quality is similar to local FM radio stations.




5W PLL Stereo FM Transmitter
Posted on Thursday, August 5, 2010   •   Category: FM Transmitters

5W PLL Stereo FM Transmitter

5W PLL Stereo FM Transmitter features PLL synthesized drift free operation with high quality BH1415 chip. 5W RF output power is achieved with 2SC1971 6W transistor in the output stage. Front panel digital control comes with LED display and case is made high quality aluminum. The board features EMI filtering on audio and power inputs and comes with Microphone and Audio inputs. Once transmitter is turned on it starts broadcasting with previously selected frequency. Overall this 5W PLL Stereo FM Transmitter provides professional broadcast audio quality and rivals commercial broadcasts.




HiFI Headphone Amplifier
Posted on Wednesday, July 28, 2010   •   Category: Headphone Amplifiers

HiFI Headphone Amplifier

This is an article about my new PCB design for HiFI headphone amplifier using audiophile OPA2132 OP-AMP chip. Main feature is that the new PCB fits exactly to the classic Altoids tin-can. This new headphone amplifier incorporates moreover bass-boost circuit and constant current charger for 9V battery.




Make a Sound Card with PCM2704
Posted on Wednesday, July 28, 2010   •   Category: Audio DAC

Make a Sound Card with PCM2704

This device is fully functional sound card for PC. The main advantage of using PCM2704 against PCM2702 is much easier construction. As you can see on the block diagram it has built-in 5V and 3.3 voltage regulator, HID interface (MUTE, VOL+, VOL-), S/PDIF output. The circuit can be powered directly from USB port. Next advantage is that the output DAC is able to drive directly 32ohms headphones, but the output power is only 12mW. For all details please refer to the PCM2704 datasheet.




Phone FM Transmitter
Posted on Thursday, July 15, 2010   •   Category: FM Transmitters

Phone FM Transmitter

This Phone FM transmitter connects in series to your telephone line and transmits the telephone conversation over the FM band when you pick up the telephone handset. Transmitted signal can be tuned by any FM receiver. The circuit includes an "On Air" LED indicator and also provides a switch which can be used to turn off the transmitter. A unique feature of the circuit is that no battery is needed to operate the circuit since power is taken from the telephone line. The transmitter uses only a short piece of wire aerial about 4" / 10 cm long to transmit the signal and some of the RF signal is also radiated through the telephone line itself. The circuit might be used to share or record conversations, but is not intended for illegal use.




500mW FM / VHF Transmitter Amplifier / Booster
Posted on Thursday, July 8, 2010   •   Category: FM Transmitters

500mW FM / VHF Transmitter Amplifier / Booster

This is a high performance low noise 500mW amplifier / booster for all low power FM transmitters such as BA1404, BH1417, BH1415, 433MHz transmitter modules, etc. The amplifier chip is an integrated circuit containing multiple transistor stages and all other parts conveniently within a single small package. Boosting your FM transmitter has never been easier and the output signal can also directly drive 2n4427 or 2n3886 transistors for 1W or 5W of RF output power.




1W portable PLL transmitter
Posted on Saturday, June 12, 2010   •   Category: FM Transmitters

1W portable PLL transmitter

This small FM transmitter includes a limiter, a microphone amplifier and a PLL digital tuning. All the parts are placed on one circuit board. The RF power is switchable between 1W and 0,2W. The schematic diagram is divided into three parts: RF part (numbered from 1), PLL (numbered from 30) and audio part (numbered from 50).




TX-500 - 500mW FM Transmitter
Posted on Saturday, June 12, 2010   •   Category: FM Transmitters

TX-500 - 500mW FM Transmitter

The TX500 is a simple to build 500mW FM Transmitter. It consists of three blocks; modulator / oscillator, two stage 500mW VHF amplifier and LED based power meter. The TX500 allows to transmit audio signals to FM band at frequencies from 88 MHz to 108 MHz. Due to the very low power consumption of less than 100mA the circuit may be perfectly powered by using 9-12V battery or power supply if you prefer. The circuit has been divided into separate stages so that it is be better for everyone to understand how every part works independently.




BH1417 Stereo PLL FM Transmitter
Posted on Saturday, June 12, 2010   •   Category: FM Transmitters

BH1417 Stereo PLL FM Transmitter

BH1417 is a latest FM Transmitter IC from RHOM that includes a lot of features in one small package. It comes with pre-emphasis, limiter so that the music can be transmitted at the same audio level, stereo encoder for stereo transmission, low pass filter that blocks any audio signals above 15KHz to prevent any RF interference, PLL circuit that provides rock solid frequency transmission (no more frequency drift), FM oscillator and RF output buffer.




Yagi Antenna
Posted on Saturday, June 5, 2010   •   Category: Antennas

Yagi Antenna

To improve signal transmission or reception in specific directions, basic elements, either vertical or horizontal, can be combined to form arrays. The most common form is the Yagi-Uda parasitic array commonly referred to as a Yagi array or beam. It consists of a driven element which is either a simple or folded dipole and a series of parasitic elements arranged in a plane. The elements are called parasitic because they are not directly driven by the transmitter but rather absorb energy from the radiated element and re-radiate it.




Simple Dipole Antenna
Posted on Saturday, June 5, 2010   •   Category: Antennas

Simple Dipole Antenna

It is very easy to create a simple 1/2 wave dipole, all you need is some lengths of wire such as the core of some mains flex or even a straightened out metal coat hanger, some co-ax cable and a connector for your scanners antenna input (usually BNC or SMA). Dipole Antenna The formula to calculate the length of the antenna is 147/frequency in MHz, this give the total length of the dipole in centimeters. For example, to make a 150MHz dipole: 147/150 = 98cm so each element of the dipole should be 49cm






J-Pole Antenna
Posted on Saturday, June 5, 2010   •   Category: Antennas

J-Pole Antenna

Tuned for 89MHz in the FM broadcast band.




Fast PIC NiMH / NiCd Battery Charger
Posted on Thursday, May 27, 2010   •   Category: Battery Chargers

Fast PIC NiMH / NiCd Battery Charger

This battery charger charges a NIMH 5-pack battery used in the BiPed robot in less than 1 hour, and charges the 10-pack NiCd used in the Snuf robot in about 30 minutes. To prevent overheating of the battery, the charging current is turned off when the slope of the battery-voltage turns from positive into negative. A second termination-criterion of the charging process is provided for safety: the charge time is limited to about 1 hour.




Cell Phone Detector
Posted on Wednesday, May 26, 2010   •   Category: FM Radio / Receivers

Cell Phone Detector

This handy cell phone detector, pocket-size mobile transmission detector or sniffer can sense the presence of an activated mobile cellphone from a distance of one and-a-half meters. So it can be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorized video transmission.




Small FM Radio
Posted on Wednesday, May 26, 2010   •   Category: FM Radio / Receivers

Small FM Radio

Perhaps this is one of the simplest and smallest FM Receiver that can receive the FM stations available locally. Its simple design makes it ideal for a pocket sized FM receiver. The output of the receiver drives a head phone.The circuit works off a small 4.5 volt battery or two 3.6 volt Lithium button cells.




1 Watt Four Stage FM Transmitter
Posted on Saturday, May 22, 2010   •   Category: FM Transmitters

1 Watt Four Stage FM Transmitter

This FM transmitter circuit uses four radio frequency stages: a VHF oscillator built around transistor BF494 (T1), a preamplifier built around transistor BF200 (T2), a driver built around transistor 2N2219 (T3) and a power amplifier built around transistor 2N3866 (T4). A condenser microphone is connected at the input of the oscillator.




Plane Motor Controller with High-Rate ESC, BEC and Brake
Posted on Thursday, May 20, 2010   •   Category: Miscellaneous

Plane Motor Controller with High-Rate ESC, BEC and Brake

This electronic speed control (ESC) for brushed motors combines the features of two of my earlier designs. One was a high-rate 30A ESC with a brake, and the other a high-rate 12A ESC with a BEC (receiver battery eliminator circuit).




Folded Dipole Antenna
Posted on Thursday, May 20, 2010   •   Category: Antennas

Folded Dipole Antenna

A modified version of the simple dipole is the folded dipole. It has two half-wave conductors joined at the ends and one conductor is split at the half-way point where the feeder is attached. If the conductor diameters are the same, the feedpoint impedance of the folded dipole will be four times that of a standard dipole, i.e. 300 ohm. The height above the ground The height of an antenna above the ground, and the nature of the ground itself, has a considerable effect on the performance of an antenna.and its angle of radiation. See PROPAGATION A dipole antenna can be arranged to operate on several bands using other methods. One way is to install "traps" in each leg.




1.2 - 12V / 1A Low Voltage LED Indicator Power Supply with LM317
Posted on Thursday, May 20, 2010   •   Category: Power Supplies

1.2 - 12V / 1A Low Voltage LED Indicator Power Supply with LM317

This is a 1.2 - 12 V, max 1A power supply with a low voltage indicator LED. The indicator part incluedes three diodes and one LED. For example you are charging a battery, you can observe the charge status at that moment. Another advantage of this circuit, when the drawn current exceeds 1A (practically 0.85A), the current protector in LM317 intervens and LED indicator warns you about the very low output voltage. Be careful while choosing the transformer. Most of the products are specified as 10VA but their outputs are not as said. Another good property of this circuit is the mains noise does not pass to the DC part.




Digital VGA Switch
Posted on Thursday, May 20, 2010   •   Category: Video

Digital VGA Switch

Digital VGA switch for switching between two PC monitors with MAX465 IC.




Ground Pole Antenna
Posted on Thursday, May 20, 2010   •   Category: Antennas

Ground Pole Antenna

This Antenna is most widely used all over the world. For example, when you see a police car it has a transmitter with Ground Pole Antenna The body of car serves as ground). It accepts load from 50 ohm source and has larger power output than Half-Wave Dipole Antenna.




TV Transmitter with Audio
Posted on Sunday, May 16, 2010   •   Category: Video

TV Transmitter with Audio

TV transmitter consists of of the two sections: video transmitter and audio amplifying. Both of them actually is transmitters. The main one generates video carrier while the smaller one generates the exact 4.5 (5.5 in some countries) MHz FM audio carrier. When it is supplied to the main section, the combination generates the audio carrier that is the total of the video frequency plus 4.5 MHz (this is the same in the US but different in other countries: 3.5 in the UK, 5.0 in Italy, 5.5 in Australia and so on: see the channel plans).




2W RF Amplifier For 24/23 CM
Posted on Thursday, May 6, 2010   •   Category: FM Transmitters

2W RF Amplifier For 24/23 CM

This page describes TX ATV Transmitter for 23 cm with output adjustable from 100 to 250mW.




RS232 Serial to USB Converter
Posted on Thursday, May 6, 2010   •   Category: USB Circuts

RS232 Serial to USB Converter

This is simple RS232 Serial to USB Converter that doesn’t need any further explanations. You can use it for any projects that might need it. Diagrams for USB and DB-9 female connectors are provided.




Wireless Temperature and Humidity Sensor with USB
Posted on Thursday, May 6, 2010   •   Category: AVR

Wireless Temperature and Humidity Sensor with USB

This project is based on obdev's RemoteSensor example and their firmware-only USB implementation; the main change is the replacement of the analog sensors with a Sensirion SHT11 digital temperature and humidity sensor.




Half-Wave Dipole Antenna (Open Dipole)
Posted on Thursday, May 6, 2010   •   Category: Antennas

Half-Wave Dipole Antenna (Open Dipole)

It accepts load from 75 ohm source and has much smaller power output than Ground Pole Antenna. Use this antenna only when you don't have GP Antenna. Construction: Two aluminum rods ,each of length "L" in meters are joined together through an insulator as shown in fig. From center, 75 ohm cable is feeded just like ordinary TV antenna.




NiCd Charger with Thermal Peak Detection
Posted on Sunday, May 2, 2010   •   Category: Battery Chargers

NiCd Charger with Thermal Peak Detection

The electric model aircraft and car industries have produced a bewildering array of field chargers for NiCd motor battery packs. These range from simple 6 or 7 cell chargers consisting of a resistor and mechanical timer, to more complex chargers with peak detection, cycling, and the ability to handle 36 cell packs.




Ultrasonic Parking Assistant
Posted on Sunday, May 2, 2010   •   Category: Sensors

Ultrasonic Parking Assistant

The basic theory behind the Parking Assistant is the Sound Navigation and Ranging (SONAR) technique that is used for finding the distance and direction of a remote object underwater by transmitting sound waves and detecting reflections from it. First, a series of short ultrasonic pulses are transmitted using a transducer that changes voltage into sound waves. The transmitted pulse is reflected off an object, and the reflected wave is then received by another transducer that converts sound waves into voltage. The transmitted signal is also known as the ‘ping’ and the received signal is known as the ‘pong’. By counting the elapsed time between the ping and the pong, the distance between the device and an object can be easily calculated by multiplying the elapsed time with the speed of sound.




Dipole Antenna
Posted on Sunday, May 2, 2010   •   Category: Antennas

Dipole Antenna

A simple dipole antenna can be used for improved FM broadcast signals. A dipole is basically a length of conductor (wire) split into two portions and signal is taken off at the split. It has a nominal 3 dB gain over an isotropic source and is directional, tending to favor signals broadside to the wire. The dipole is customarily an electrical half wavelength of wire at the frequency of interest, since the impedance under this condition is theoretically 72 ohms resistive and is a good match to a 50-75 ohm source or load generally presented by interfacing equipment such as receivers and transmitters designed to work into this range of impedances.




PIC Programmable Security System
Posted on Sunday, May 2, 2010   •   Category: PIC

PIC Programmable Security System

This project uses the 12F675, it was chosen because of its low cost, A/D convertor and flash memory. This security system was designed to be used in a simple installation with just a hidden switch and not a keyboard. There are several features such as a battery monitor built into the code that also make it good for remote locations just run off a battery. Also all the delays and and other parameters are put into flash memory just by using a visual basic program and the serial port of a PC.




PLL FM Transmitter
Posted on Friday, April 30, 2010   •   Category: FM Transmitters

PLL FM Transmitter

This new FM transmitter is very simple and doesn't need any RF tuning. First of all ,we have used an integrated VCO: The POS150 from Mini-circuits. This excellent RF circuit covers all the FM Band in a voltage range of 4V to 8V. The Kvco factor is very stable all over the FM band, consequently, we have applied the BF signal directly on the control voltage line coming from the PLL.




SAA1057 PLL Synthesized FM Transmitter
Posted on Friday, April 30, 2010   •   Category: FM Transmitters

SAA1057 PLL Synthesized FM Transmitter

The functioning of all is provided by a microcontroller from MICROCHIP "PIC16F84" which provides support for buttons, LCD 2 lines of 16 characters and the circuit pll "SAA1057. The VCO is entrusted to the transistor Q8 associate of his two diodes varicaps "BB109, a floor buffer Q7 separates the VHF signal obtained in two ways, on the one hand to Q9 to enslave loop phase and on the other hand to the Q5 and Q6 together which takes care to amplify the signal before attacking Q11, a "BFR96" which plays the role of HF switch via a timer "NE555" which receives information from the push and "SAA1057" ensuring HF cutoff in the event of failure of a locking or unlocking of the pll.




40MHz Frequency Counter Module
Posted on Friday, April 30, 2010   •   Category: Test and Measurement

40MHz Frequency Counter Module

This circuit is ideal for adding a low cost frequency display to a function generator or other design. I doubt if it is possible to get a cheaper design using off the shelf components!. In fact, I challenge anyone to make a cheaper design using garden variety components!. The upper frequency limit is dependent upon the upper limit of the 74HC390 chips which is roughly 40MHz.




USB RDS Coder Board using ATmega32
Posted on Friday, April 30, 2010   •   Category: AVR

USB RDS Coder Board using ATmega32

This board is a RDS coder using an ATMEL AVR ATmega32. This board can be controled by a RS232 link, USB interface or SPI. TA data is displayed wiyth a LED and can be controled by : - Hardware input - RS232 - USB - SPI (not yet implemented)




Low Pass Filter For FM 88-108 MHz
Posted on Friday, April 30, 2010   •   Category: FM Transmitters

Low Pass Filter For FM 88-108 MHz

Filter used for eliminate unwanted harmonic frequency at second and third. Notch filter, Band Pass Filter (BPF), and High Pass Filter (HPF) sometime combined in constructing LPF design. Schematic below for FM Broadcast Lowpass Filter 88-108 MHz. It has been tested with a good result. Note : Make the coils at 74 nH and trim them to adjust exact value.




FT232 USB Interface Adapter
Posted on Thursday, April 29, 2010   •   Category: USB Interface Adapters

FT232 USB Interface Adapter

Control up to three devices from a PC with FT232 IC (USB to Serial UART) from Future Technology Devices International FTDI. Circuit is simple and does not require external microcontroller or any type of firmware programming. PC control software written in VB6 is included.




USB DS1820 PC Thermometer
Posted on Thursday, April 29, 2010   •   Category: PIC

USB DS1820 PC Thermometer

This is a digital thermometer based on USB PIC16C745 microcontroller from Microchip and DS1820 sensor from Dallas Semiconductor. Temperature readings are sent over USB port in HIDCOMM USB mode to VB6 program on a PC. Hex program and sample Visual Basic 6 application is included.




MC145170 PLL FM Transmitter
Posted on Thursday, April 29, 2010   •   Category: FM Transmitters

MC145170 PLL FM Transmitter

In order to simplify the transmitter design, we've used the new pll circuit from Motorola :the MC145170. This PLL includes the prescaler and a serial standard bus called SPI.




Temperature / Light Brightness Meter with LCD
Posted on Thursday, April 29, 2010   •   Category: PIC

Temperature / Light Brightness Meter with LCD

Circuit measures the temperature and ambient brightness of the surrounding environment at the location it is placed. The data from the ADC is the calculated and displayed on the LCD. The main CPU unit on board the device is the PIC16F873.




Infrared Remote Volume Control
Posted on Thursday, April 29, 2010   •   Category: Remote Control

Infrared Remote Volume Control

This is a true 'minimalist' remote, having but three functions: Volume Up, Volume Down and Mute Volume is controlled by a motorized (motorized for US readers) pot rather than any of the 'digital' pots that now abound, and this was done for a number of very good reasons.




19 KHz MPX Low Pass Filter
Posted on Wednesday, April 28, 2010   •   Category: FM Transmitters

19 KHz MPX Low Pass Filter

This map, armored also enables automatic MONO / MPX through a low-pass filter, even with a multiplex on its entry by using an ON / ON, panning, the whole spectrum MPX more RDS is sent to the synthesizer, on the other hand when it is in a position MONO, the low-pass filter is activated and share its cutoff frequency at 15 KHz, only modulation G + D is sent to the synthesizer, as 19 KHz. 19 KHz carrier, the signal multiplex and subcarrier 57 KHz is thereby eliminated, which provides ease of use for example in a string of issue relay tuner, if the link between the issuer Departure and receiver re-issue was not of good quality stereo, you sufficient to switch to mono to improve sound quality, you can then connect the RDS encoder at the re-issuer.




PIC18F2445 USB Experimental IO Board
Posted on Wednesday, April 28, 2010   •   Category: PIC

PIC18F2445 USB Experimental IO Board

Manji broj proizvođača proizvodi IC kola za USB podršku. Najpoznatiji su: Cypress Semiconductor, FTDI, Philips i drugi. Microchip je 2000 godine proizveo mikrokontrolere PIC16C745 i PIC16C675 koji su imali podršku za USB komunikaciju i tako se pridružio ostalim proizvođačima. Ovi mikrokontroleri podržavaju USB 1.1 standarad, odnosno USB sa brzinama rada do 1.5 MBs. Nova serija Microchip-ovih mikrokontrolera urađenja u flash tehnologiji PIC18F2445/2550/4455/4550 je podržala USB 2.0 standrad. Ovo su moćni mikrokontroleri sa brzinama takta i preko 40Mhz i veličinom programske memorije od 32K reči. O stanadardima za USB možete na sajtu http://www.usb.org. Upravo na ovim mikrokontrolerima urađen je interfejs sa USB komunikacijom.




USB Li-ion Battery Charger
Posted on Wednesday, April 28, 2010   •   Category: Battery Chargers

USB Li-ion Battery Charger

This is a charger for lithium ion batteries which takes its power from the USB port of a computer. It uses the MCP73861 or MCP73863 Li-ion battery charger chip manufactured by Microchip. Microchip MCP73861 or MCP73863 are advanced, fully-integrated, single-cell Li-Ion/Li-Polymer charge-management devices allow these peripherals to utilize the full power of the USB port.




Solar Battery Charging
Posted on Wednesday, April 28, 2010   •   Category: Battery Chargers

Solar Battery Charging

This instructable will show you how to make your own solar battery charger from very simple components. It is taken from my documentation provided with a kit I supply - you should easily be able to source the same components yourself of course.




15V / 28V 4A Transmitter Power Supply
Posted on Wednesday, April 28, 2010   •   Category: Power Supplies

15V / 28V 4A Transmitter Power Supply

Power supply used for professional FM broadcasting transmitter.




LM3876 GainClone Amplifier
Posted on Tuesday, April 27, 2010   •   Category: Amplifiers

LM3876 GainClone Amplifier

The amp is based on the Project 19 PCB, so uses a pair of LM3876 (or LM3886) power opamps, run from a ±35V supply. I used a cut-down P88 preamp PCB because I only wanted one preamplifier stage, but the entire board can also be used. Alternatively, the P19 amp can be run at higher gain than normal, alleviating the need for a preamp at all. The down side of this is that the noise level will be higher, and background noise may be audible with efficient speakers and/ or very quiet surroundings.




Atmel Solar Panel Battery Charger
Posted on Tuesday, April 27, 2010   •   Category: Battery Chargers

Atmel Solar Panel Battery Charger

Batwatch is a simple monitor for a solar panel battery charger, using an Atmel ATtiny13V. It periodically measures the charge current and battery voltage, and shows them by blinking two LEDs. I built this circuit into the plug of a VW solar charger panel that is used to prevent a discharge of the battery when a car is not used for some time. A modern car contains a large amount of electronics, and a quiescent current of 40-50mA (about 1Ah per day!) is considered "normal".




Basic PIC18F4550 USB Communication Interface
Posted on Tuesday, April 27, 2010   •   Category: PIC

Basic PIC18F4550 USB Communication Interface

When the device is connected to the computer, a Virtual COM Port (VCP) will be created. This is shown at the Device Manager Window under Ports(COM & LPT). In this case, COM5 was created when the PIC18F4550 was attached to the USB Port. It may be interesting to note that if you plug in your PIC in different USB ports, the VCP created will be different.




AVR ATMega8 PLL Module with MC145170
Posted on Tuesday, April 27, 2010   •   Category: AVR

AVR ATMega8 PLL Module with MC145170

This is the transmitter PLL module with ATMega8, MC145170 and 16x4 LCD Display.




Basic USB-RS232 Communication with PIC Microcontrollers
Posted on Tuesday, April 27, 2010   •   Category: PIC

Basic USB-RS232 Communication with PIC Microcontrollers

The quickest way to display something is probably sending the data to the computer to be displayed on the monitor. One of the ways to do this is to use the USART module on board the PIC Microcontroller by making use of the pins RC6 and RC7 which is also the TX and RX pins respectively when the SPEN bit on the RCSTA register is set.




MC145151 PLL FM Transmitter
Posted on Friday, April 23, 2010   •   Category: FM Transmitters

MC145151 PLL FM Transmitter

This PLL has been designed with an old Motorola circuit :the MC145151. The VCO is based on a "Colpitz" oscillator equiped with a Fet Transistor.(J310) Two varicap Diodes are used in order to reduce the global noise of the VCO. In addition,these two diodes allow the PLL to keep the lock status through a large range of climatic conditions. An another J310 is used in order to match the impedance between the oscillator and the fist amplifier stage. A MSA1105 from Minicircuits increases the RF power level coming from the VCO to +14dBm. A simple low pass filter rejects the second harmonic to -20 dB.(Worst case) Finally, a 7 dB attenuator and a second amplifier stage (BFR96S) achieve this radio design.




Infra/radio remote control transmitter/receiver with PIC
Posted on Friday, April 23, 2010   •   Category: Remote Control

Infra/radio remote control transmitter/receiver with PIC

The encoder/decoder parts are to be connected to a transmitter/receiver module which takes care of the transmission of digital signals by radio or infra waves. The communication signal format is designed to be used for radio transmission (it has a constant 50% signal/silence ratio), but it can work with infrared devices as well.




Variable Laboratory DC Power Supply
Posted on Friday, April 23, 2010   •   Category: Power Supplies

Variable Laboratory DC Power Supply

Voltage range: 0.7 - 24V Current limiting range: 50mA - 2A A Variable DC Power Supply is one of the most useful tools on the electronics hobbyist's workbench. This circuit is not an absolute novelty, but it is simple, reliable, "rugged" and short-proof, featuring variable voltage up to 24V and variable current limiting up to 2A. Well suited to supply the circuits shown in this website. You can adapt it to your own requirements as explained in the notes below.




Simple 4-CH Remote Control
Posted on Friday, April 23, 2010   •   Category: Remote Control

Simple 4-CH Remote Control

You can construct your own long range infrared (IR) wireless remote using Motorola's MC145026 emitter and MC145027 detector chips. With your remote you can control devices up to 20 feet (7 meters) away. It operates similiarly to a TV remote. You just point the emitter at the detector, push a transmit button. The detector then interprets your data signal. You can use this circuit to remotely turn on/off devices (like a motors, relays, home appliances).




TTL <> RS232 Converter
Posted on Friday, April 23, 2010   •   Category: Miscellaneous

TTL <> RS232 Converter

This small realization, based on one of the most common IC (MAX232) is designed to create a small and convenient TTL to RS232 and vice versa converter. All you need is 4 caps, one IC and 2 connectors. If you want to add a small regulator on the board (already foreseen on the PCB) you just need to add a 78L05 regulator and a cap.




1 Watt Universal RF Amplifier
Posted on Friday, April 23, 2010   •   Category: FM Transmitters

1 Watt Universal RF Amplifier

This is a universal 1 Watt RF class C amplifier that is ideally suited for low power FM transmitters. Input should be at least 100mW to achieve 1W output. It is recommended to enclose the amplifier in a metal case.




LED Bargraph Optical Tachometer
Posted on Thursday, April 22, 2010   •   Category: LED

LED Bargraph Optical Tachometer

For the electric R/C enthusiast, a tachometer can be a very useful piece of equipment. When I first built this tach back in 1995, it was essential, as there were very few off-the-shelf electric R/C power systems that just worked. At that time, you had to experiment with batteries, speed controls or switches, connectors, and wiring, and a tachometer was a tool to help you measure the results.




Intelligent NiCd/NiMH Battery Charger
Posted on Thursday, April 22, 2010   •   Category: Battery Chargers

Intelligent NiCd/NiMH Battery Charger

This cheap and easy to build NiCd/NiMH Battery Charger is suitable for automatically charging a wide range of batteries for many applications. Proper chargers are usually expensive and cheap chargers supplied with the original equipment often incorrectly charge the cells and dramatically shorten their life.




2W RF Amplifier For 24/23 CM
Posted on Thursday, April 22, 2010   •   Category: FM Transmitters

2W RF Amplifier For 24/23 CM

This page describes TX ATV Transmitter for 23 cm with output adjustable from 100 to 250mW.




Lithium Ion / Lithium Polymer USB Battery Charger
Posted on Thursday, April 22, 2010   •   Category: Battery Chargers

Lithium Ion / Lithium Polymer USB Battery Charger

This is a MAX1811 based USB charger that can handle both Lithium Ion and Lithium Polymer 3.7V battery. It requires very few external components and provides ability to select between 4.1v and 4.2v battery regulation for different types of LiPo batteries. You can select between either 100mA and 500mA current charging mode and LED provides the status of the charging.




PCM2902 Soundcard with Microphone Input
Posted on Thursday, April 22, 2010   •   Category: Audio DAC

PCM2902 Soundcard with Microphone Input

Many of us have a pair of headphones connected to the output of the computer sound card us either to enjoy songs, or a game. Very likely your headphones and microphone, which also connect to the appropriate slot your sound card. But at some point broke down the female plug my sound card, and because quite a lot to change the plug when I put the headphones and when the speakers. A small structure is a sound card, USB, with stereo inputs / outputs, button to increase / volume button for volume and mute! When connected Windows will recognize as a sound card! With all the materials to be SMD, the cornered enough and fit into a small plastic box, which by one measure has a cable with USB plug, sound to go acoustic (Left / Right) and condenser microphones. The supply of (as imagined) is done by the USB port. The heart of the integrated circuit is PCM2902 of Burr-Brown by Texas Instruments. It is stereo 16-bit DAC and ADC, fully compatible with USB 1.1. DAC sampling frequencies are 32, 44.1 and 48 kHz, ADC has 8, 11.025, 16, 22.05, 32, 44.1 and 48 kHz. If you want more sound intensity, you will need to connect TDA 7050 amplifier to audio output.




Solar Panel Controller
Posted on Wednesday, April 21, 2010   •   Category: Battery Chargers

Solar Panel Controller

The purpose of this project is to realize a Solar panel controller. Initially developed for a sailing boat, the target to reach was to control the level of charge and discharge and to protect a 12 volts lead battery connected to a 32 watts solar panel.




PIC PIN / PORT Extender
Posted on Wednesday, April 21, 2010   •   Category: PIC

PIC PIN / PORT Extender

This circuit based around 74LS154 will extend PIC / AVR microcontroller output PINs from 4 to up to 16. It can also be used for extending parallel port output pins.




LCD Terminal
Posted on Wednesday, April 21, 2010   •   Category: PIC

LCD Terminal

The LCD Terminal just like a normal terminal, it can connect to any host via RS-232 serial cable. A PC keyboard must connect to it as the input device and what ever you type will send to host via RS-232 and display on a 40x4 LCD. Data receive from host can also display on the LCD unit. You can use this device as any Unix/Linux machine's console.




PIC16F877 APRS Weather Station
Posted on Wednesday, April 21, 2010   •   Category: PIC

PIC16F877 APRS Weather Station

Weather Station is PIC16F877A based and has a 4x20 LCD, a data logger output and accepts 1Wire wind instrument. It has a built-in APRS TNC. Connect it to your portable rig thru a DIN5 connector and you have a true portable weather station.




Digital Video Selector 1.0
Posted on Wednesday, April 21, 2010   •   Category: Video

Digital Video Selector 1.0






PIC12F675 - Flashing LED
Posted on Wednesday, April 21, 2010   •   Category: PIC

PIC12F675 - Flashing LED

Simple little circuit for testing PIC12F675 microcontroller. When you start learning a programming language like C++, Visual Basic or any other language your first step is to write a program that displays "Hello World" on a computer's monitor. When you start learning how to program PIC microcontrollers an equivalent to that is blinking a LED.




USB-PC 8-CH Power Switch
Posted on Wednesday, April 21, 2010   •   Category: USB Circuts

USB-PC  8-CH Power Switch

PowerSwitch provides 8 bits of parallel output intended to switch e.g. the power supply to electronic devices. The PowerSwitch firmware is accompanied by a command line tool for Unix to control the device. (The command line tool can also be compiled on Windows using minGW and libusb-win32.)




USB LED Load
Posted on Tuesday, April 20, 2010   •   Category: USB Circuts

USB LED Load

The board supports driving two separate tri-color LEDs. More can be setup inline if desired. Currently the software only uses the second LED and its color represents the CPU load of the system in real-time. Blue for idle and gradients light blue, green, yellow, orange, and finally red indicating heavy CPU utilization. If the system fails to respond, the LED begins flashing RED to indicate a lack of communication from the software. This lets you easily identify a crashed machine in a rack for example.




LCD 2 USB
Posted on Tuesday, April 20, 2010   •   Category: AVR

LCD 2 USB

LCD2USB is a open source/open hardware project. The goal of LCD2USB is to connect HD44780 based text LCD displays to various PCs via USB. LCD2USB was meant to be cheap and to be made of easily available parts. It is therefore based on the Atmel AVR Mega8 CPU and does not require any difficult to obtain parts like separate USB controllers and the like.




AVR-USB Remote Sensor
Posted on Tuesday, April 20, 2010   •   Category: AVR

AVR-USB  Remote Sensor

RemoteSensor is a wireless thermo- and hygrometer with an USB port on the receiver. You can draw fancy diagrams of temperature and humidity for up to 16 wireless sensors.




Intelligent NiCd/NiMH Charger/Cycler with 128x64 Graphical LCD
Posted on Tuesday, April 20, 2010   •   Category: Battery Chargers

Intelligent NiCd/NiMH Charger/Cycler with 128x64 Graphical LCD

The accu cycler project presented here is an excellent solution for charging and discharging NiCd and NiMH accumulators for R/C modelers and others who make use of these accumulator types. With its performance it is very close to the many of the commercial products available on the market.




0-500MHz PIC16F876 RF Power Meter
Posted on Tuesday, April 20, 2010   •   Category: Test and Measurement

0-500MHz PIC16F876 RF Power Meter

RF Measurement has been an expensive work so far the cost of measuring RF Power Meter instruments are concerned. RF Power Meter is based on PIC16F876 microcontroller, AD8307 and 2x20 LCD display. Full documentation is included.




Serial LCD Controller
Posted on Monday, April 19, 2010   •   Category: PIC

Serial LCD Controller

Serial LCD/VFD Controller is a HD44870 based LCD/VFD controller via RS-232. The control command is compatible with Matrix-Orbital's LCD module. So, you can use any MO friendly software to control this baby such as LCDC.




PIC NIC Ethernet Controller
Posted on Monday, April 19, 2010   •   Category: PIC

PIC NIC Ethernet Controller

PICNIC is a project to add 10BaseT Ethernet controller to PIC17F877, and it can run as an network-enable device. This project is based on tristate's PICNIC product. And I just change the temperature sensor's circuits to improve the precision on A/D convert and add another Temp-Sensor channel.




USB - LCD with PIC Microcontroller & FT232
Posted on Monday, April 19, 2010   •   Category: USB Circuts

USB - LCD with PIC Microcontroller & FT232

USB LCD/VFD Controller is a HD44870 based LCD/VFD controller via USB interface. The control command is compatible with Matrix-Orbital's LCD module. So, you can use any MO friendly software to control this baby. Such as LCDC... The firmware are based on David Potter's Serial LCD/VFD Display, but I almost rewrite the entire code.




DTMF Decoder with LCD Display
Posted on Monday, April 19, 2010   •   Category: AVR

DTMF Decoder with LCD Display

The DTMF decoder 2 is a useful tool used for decoding DTMF (Dual Tone Multi frequency) generated by telephones. The decoded digits are viewed on a 16x2 LCD screen.




USB to RS232 Converter
Posted on Monday, April 19, 2010   •   Category: USB Circuts

USB to RS232 Converter

Why build my own USB to RS232 converter when there are adapters already available from many suppler? The Answer is simple: Neither the strand "USB to RS232 converter" actually worked *properly* with all the devices I tried. But, They did not seem to support ALL the RS232 lines. The USB to RS232 converter using the FT8U232AM and a Maxim-IC MAX235




Ethernet Weather Station
Posted on Friday, April 16, 2010   •   Category: PC Circuits

Ethernet Weather Station

Using an add-on card to the already existing avr ethernet board we build a weather station. That is: A weather station with a build-in webserver. My original plan was to have sensors for temperature, air pressure and wind. I started a prototype and it worked very well except for the wind measurement part. I plan to improve the wind measurement hardware and add it at a later point in time.




1.5V to 5V Converter
Posted on Friday, April 16, 2010   •   Category: LED

1.5V to 5V Converter

In many cases can be very handy to be able to convert 1.5V to 5V. Then you can power microcontroller or LED from a single AA or AAA battery. It is simple to do this as there are special IC’s as MAXIM MAX1674 or MAX7176. This is step-up DC-DC converter that can convert voltages from 0.7V to any in range from 2V to 5.5V. MAX1676 have already preset pins for 3.3V and 5V, that makes easer integration in 3.3 and 5V circuits. IC can dissipate up to 444mW. Bellow is a circuit that converts 1.5V to 5V.




USB to RS232 Dongle
Posted on Friday, April 16, 2010   •   Category: USB Circuts

USB to RS232 Dongle

With serial and parallel ports being phased out on new computers, hardware designers and hobbyists have no choice but to convert the USB port back to RS232 serial. FTDI have a very nice chip that does just that, the FT232AM. This chip converts USB to a standard high-speed serial port. The bonus with FTDI is the drivers are already written for you. All you have to do is design the hardware and download the serial USB drivers from FTDI's web site.




Ni-Cd Charger
Posted on Friday, April 16, 2010   •   Category: Battery Chargers

Ni-Cd Charger

This is a NiCd/Ni-MH charger that can charge with constant current and automatic charge termination when the total voltage for all cells reach the setting voltage.




PIC12F675 PIN PONG
Posted on Friday, April 16, 2010   •   Category: PIC

PIC12F675 PIN PONG

This project is based on ideas from Rickard's electronic projects page and David B. Thomas VCR Pong. However, I have developed the simplicity even further, eliminating most of the external components. Using microcontrollers with internal 4MHz clock generator there is no need for the xtal. The 12f675 part also operates on wide voltage range, and the regulator can be removed. For game controller, I plan on using the old Commodore 64 style paddless. They include firing buttons, which I plan on using as power switch and game reset. 16F675 has a low power sleep mode with 1nA current consumption, so I plan on using that to switch off.




2 Channel RF AVR Remote Control
Posted on Thursday, April 15, 2010   •   Category: Remote Control

2 Channel RF AVR Remote Control

How many times you needed some remote control to handle some electric device ? many times. There are lot of remote controls like infrared, RF, SMS (like my other circuit) and more. The basic small-range remote controls are 2, Infrared and RF (Radio Frequency). One of the weaks of Infrared is that the signal can not pass the walls. So, if you want to control your garage door, the only way is to use some RF remote control. The circuit (transmitter and receiver) use few components and ordinary (I love few component circuits) . Its easy to build it because you don't have to tune-up any coil or variable capacitor. The RF modules are fix to work in 418MHz area.




Li-Po Charger and Balancer
Posted on Thursday, April 15, 2010   •   Category: Battery Chargers

Li-Po Charger and Balancer

This is a Li-Po charger and balancer project for R/C hobby.The charger circuit is based on the circuit of Electron head and all folks in the DIY electronics topic on the rcgroups.com.




IR Proximity Sensor
Posted on Thursday, April 15, 2010   •   Category: Sensors

IR Proximity Sensor

It is the same principle in ALL Infra-Red proximity sensors. The basic idea is to send infra red light through IR-LEDs, which is then reflected by any object in front of the sensor. Then all you have to do is to pick-up the reflected IR light. For detecting the reflected IR light, we are going to use a very original technique: we are going to use another IR-LED, to detect the IR light that was emitted from another led of the exact same type! This is an electrical property of Light Emitting Diodes (LEDs) which is the fact that a led Produce a voltage difference across its leads when it is subjected to light. As if it was a photo-cell, but with much lower output current.




Li-ion Battery Charger
Posted on Thursday, April 15, 2010   •   Category: Battery Chargers

Li-ion Battery Charger

This is a simple to build charger for single 3.7V lipo battery. The heart of the charger is TL431 shunt regulator that controls the incoming current. Charger comes with a convenient charging LED indicator. As charging current goes down so does the intensity of the LED.




MP3 Player with SD Memory Card
Posted on Thursday, April 15, 2010   •   Category: AVR

MP3 Player with SD Memory Card

The MP3stick is a simple and small portable MP3 player. A microcontroller Atmel AVR ATmega128 is the heart of the circuit. MP3 decoding is done by an VLSI VS1011b decoder IC. A MMC/SD card works as memory medium for MP3 files, playlist files and skin files. The player is designed to draw his power from a LiIo/LiPo battery with 3.6V. a charger circuit, based on MAX1811, is included. All information will be shown on a Nokia color LCD with 128x128 pixel and 256 colors.




RC5 Infrared Remote Control Receiver for Media Centers
Posted on Tuesday, April 13, 2010   •   Category: Remote Control

RC5 Infrared Remote Control Receiver for Media Centers

RC5 Infrared Remote Control Receiver for Media Centers A few time ago I decided to create a media center box to replace my DVD player, satellite receiver, VCR and my kid's Play Station 2 , to one device. So, I made a core 2 duo processor system that actually replaced with succeed, all my electronic devices. The only thing that was missing was a remote control to switch On/Off my Media Center. After I searched on the net to buy a complete remote control system, I saw that the price was a little bit high (about 90 euros). I checked my stuff to find my old 7-in-one remote control that I had bought 2 years ago and I started to build my own remote control receiver circuit.




Universal RC5/RC6 Transceiver with PIC16F628
Posted on Tuesday, April 13, 2010   •   Category: Remote Control

Universal RC5/RC6 Transceiver with PIC16F628

This project is an expansion from another project from this website. On the one side you can read the RC5, RC5X and RC6 codes from remote controls on a LCD and on the other hand you can send all thinkable RC5, RC5X and RC6 codes to a device. Besides is for this project a PCB layout drew to make it still more easier for you.




LM386 Audio Amplifier
Posted on Tuesday, April 13, 2010   •   Category: Amplifiers

LM386 Audio Amplifier

This simple amplifier shows the LM386 in a high-gain configuration (A = 200). For a maximum gain of only 20, leave out the 10 uF connected from pin 1 to pin 8. Maximum gains between 20 and 200 may be realized by adding a selected resistor in series with the same 10 uF capacitor. The 10k potentiometer will give the amplifier a variable gain from zero up to the maximum.




USB to RS232 Adapter with FT232
Posted on Tuesday, April 13, 2010   •   Category: USB Circuts

USB to RS232 Adapter with FT232

We employ two UART boards in the course, one which can be connected to the serial connector of the PC (UART-RS232), and a second that can be connected to a USB port (UART-USB). The former is used in the lab and is part of the standard take-home equipment. The latter is part of the (limited!) number of take-home targets for students who are working on a Laptop without serial connector. In both cases, communication is done with the UART module of the microcontroller. In the case of the normal UART board, the MAX232 simply transforms the voltage levels to RS-232 standards (± 3-15V; in our case 12V, with LOW=+12V and HIGH=-12V). In case of the UART-USB, the FT232BM transforms the UART protocol to the USB protocol. This is transparent to the controller, which communicates over the normal TX and RX pins.




Voice Message Recorder / Player
Posted on Tuesday, April 13, 2010   •   Category: Audio DAC

Voice Message Recorder / Player

The voice messages are recorded into the on-board microphone, then each message can be individually triggered by an external signal. The inputs can respond to simple electrical contacts, logic levels or voltages, and all inputs are debounced to prevent false triggering by electrical noise. Each message can be arranged to play once on a selected change of input state (high-to-low or low-to-high), or to repeat continuously until the trigger condition is removed. These options are selected by DIP switches.




PAL/NTSC Video Text Generator
Posted on Monday, April 12, 2010   •   Category: PIC

PAL/NTSC Video Text Generator

Perfect low cost solution for: * New video security installations * SSTV transmitters * Amateur video * Existing installed security installations * Scientific experimentation monitoring * and any other application that needs the time and date recorded on an image!




40MHz 32 Channel Logic Analyser
Posted on Monday, April 12, 2010   •   Category: Test and Measurement

40MHz 32 Channel Logic Analyser

This project was published in Electronics Australia in Oct/Nov 96. It is a 32 Channel, 40Mhz, fully PC controlled TTL/CMOS logic analyzer with internal/external triggering and trigger delay. Internal triggering is fully maskable (High/Low/Don't Care) on all 32 channels. The whole things fits on one single sided PCB with virtually no wiring!




20MHz High Speed Function Generator
Posted on Monday, April 12, 2010   •   Category: Frequency Wave Generators

20MHz High Speed Function Generator

The High Speed Function Generator was published in the professional electronics section of the Aug 1996 issue of Electronics Australia, and has proven to be extremely popular. The kit is no longer available from any of the kit suppliers. The project is capable of generating 20MHz or greater Sine, Square, Triangle, and TTL waveforms.




UV LED Controller using a PIC 16F628A Microcontroller
Posted on Saturday, April 10, 2010   •   Category: PIC

UV LED Controller using a PIC 16F628A Microcontroller

If you need an UV LED timer, or a timer for any other purpose you may be interested in the UV LED Controller that was constructed using a PIC 16F628A Microcontroller. There is a schematic and code available however the original project was not documented in English. Have a look at the Google translation that did a decent job of translating this one.




PIC18F2550 Project Board
Posted on Saturday, April 10, 2010   •   Category: PIC

PIC18F2550 Project Board

The new PIC18F2550 Project Board was designed as the development platform for student projects. The board features MCU: PIC18F2550 with external xtal, ADC: one channel 0-2.5V sigma-delta converter, Linear Technology LTC2400/LTC2420, 6-channal 10-bit ADC 0-5V, Display: Two connectors for text LCD or GLCD, USB: onchip USB port with type B connector, Power supply: onboard low dropout regulator, rechargeable battery, Code programming: 10-pin header for In Circuit Loader. The board platform is suitable for developing the microcontroller based instrumentation. Students may build the signal conditioning board, plugs it to PIC project board, develops the code and programs it with loader cable easily.




PLL FM Exciter / Transmitter
Posted on Saturday, April 10, 2010   •   Category: FM Transmitters

PLL FM Exciter / Transmitter

This is a PLL controller that works with the VCO/Modulator that I designed. Use these two modules together for a complete baseband-capable exciter unit. This PLL controller features a rock-stable crystal controlled reference, in conjunction with a programmable dividing network which allows the transmitter to be tuned in 100Khz steps from 79.9Mhz to 109.7Mhz by means of digital thumbwheel switches. Oscillator, buffer and driver stages use 2N3866 power RF transistor and output stage used 2N3553 4W RF transistor,




USB Bit Whacker
Posted on Saturday, April 10, 2010   •   Category: USB Interface Adapters

USB Bit Whacker

The UBW board is a small board that contains a Microchip PIC USB-capable microcontroller such as PIC18F2455, PIC18F2550, PIC18F4455 or PIC18F4550 and headers to bring out all of the PICs signal lines and board is powered from the USB connection. I designed this board to be a simple parallel port replacement tool for Bruce Shapiro for use in his bits-to-bytes-to-bots class. Apologies to all other 'Whacker' projects like EDTP's Packet Whacker for stealing a great name . All tools used to design this project are free, and the design is open to anyone to use for whatever they wish.




Hi-Fi PCM2702 USB Audio DAC
Posted on Saturday, April 10, 2010   •   Category: Audio DAC

Hi-Fi PCM2702 USB Audio DAC

Regulator: This board supplies DAC board with +/- 15V for analog section. MUR860 in rectifier bridge, LM317 and Lm337 as regulator IC's and BG-STD at the output. LM317, LM337 power supply PCM2702: A little modified version of producent application. BlackGate-STD used in OPA2602 power supply, BG-N in analog and Sanyo OS-Cono in digital PCM section. At the output Panasonic FC.




Special Edition Accurate LC Meter with Green Backlight LCD
Posted on Friday, April 9, 2010   •   Category: Test and Measurement

Special Edition Accurate LC Meter with Green Backlight LCD

Build your own LC Meter and start making custom made coils and inductors. This LC Meter allows to measure incredibly small inductance making it perfect tool for making all types of RF coils and inductors. LC Meter can measure inductance starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitance from 0.1pF up to 900nF. The circuit includes an auto ranging and reset switch to make sure the readings are as accurate as possible. This is a Special Edition LC Meter with upgrade to top notch components. It includes upgraded high precision capacitors, inductor, 1% Metal Film resistors and Gold Plated Machined IC Sockets, header pins and LCD header connectors. This edition is designed for professionals that require unprecedented measurement accuracy.




PCM1794A Audio DAC
Posted on Friday, April 9, 2010   •   Category: Audio DAC

PCM1794A Audio DAC

This is DAC with integrated circuit PCM1794A. It is one of excellent audio DACs from Burr Brown (Texas Instruments). It has 24-bit resolution, 192kHz sample frequency, 8x oversampling digital filter, differential current output and SNR 127dB.




DIR9001 SPDIF Decoder
Posted on Friday, April 9, 2010   •   Category: Audio DAC

DIR9001 SPDIF Decoder

For transfer of digital audio between devices is standardized S/PDIF interface (electrical) and TOSLINK (optical) for commercial use, or AES3 for professional use. S/PDIF decoder module is used for converting of this interface to I2S interface, which is usually used on audio DACs. For conversion we can use for example integrated circuit CS8416 or DIR9001. In building of DAC in past I had troubles with resetting circuit CS8416 in hardware mode. Now I select DIR9001 which works perfectly and he has lower jitter than CS8416.




USB Audio DAC with PCM2704
Posted on Friday, April 9, 2010   •   Category: Audio DAC

USB Audio DAC with PCM2704

I needed high quality DAC convertor from USB to S/PDIF. Circuit has analog output for headphones and digital S/PDIF output with electrical and optical(TOSLINK) interface. We can use too 3 HID buttons for setting volume and mute. For USB input is used standard miniUSB connector. Headphone output uses standard 3.5" stereo jack socket. For signal conversion from TTL level to differential signal is used RS-485 bus transceiver. For optical output is used optical transmitter TOTX173 from Toshiba.




USB - Relay Board
Posted on Friday, April 9, 2010   •   Category: USB Circuts

USB - Relay Board

Here is the new 6 channel relay USB board to switch different devices, lighting or motors by a computer program via the USB interface.




MAX3420 – Maxim USB Peripheral Controller
Posted on Thursday, April 8, 2010   •   Category: USB Circuts

MAX3420 – Maxim USB Peripheral Controller

The MAX3420 is a USB peripheral controller chip with an SPI bus. This page hopefully contains enough information to help you easily make use of the device in your projects. The MAX3420 provides a very simple approach to adding a USB interface to a circuit. It uses a SPI bus to connect to your system. It does require a reasonable amount of configuration and control, so you’ll need to connect it to some form of microprocessor/microcontroller.




USB audio DAC
Posted on Thursday, April 8, 2010   •   Category: Audio DAC

USB audio DAC

This is a simple USB Audio DAC based on PCM2902 chip from Texas Instruments. The power is drawn directly from USB port. Circuit includes DAC and ADC, SPDIF outputs, input and HID part with 3 buttons for MUTE, VOL+ and VOL-.




USB Device Charger
Posted on Thursday, April 8, 2010   •   Category: USB Circuts

USB Device Charger

With this tiny thing you can charge almost all devices that are charged via USB, like iPods or mobile phones, with only two AA-Cells.




2-Channel IR Relay Controller
Posted on Thursday, April 8, 2010   •   Category: Remote Control

2-Channel IR Relay Controller

This project is a 2 channel infrared (IR) remote controlled relay driver with power saving. It works with 12-bit SIRC IR signals as used by Sony remote controls. The board uses Microchip's low cost PIC10F200 microcontroller along with a handful of easy to find components making this possibly the lowest cost remote controlled relay driver around. The controller also features a power save feature which reduces the relay holding voltage to 50% of the relays nominal operating voltage once the relay has switched on.




PICkit 2 PIC Programmer
Posted on Tuesday, March 30, 2010   •   Category: PIC

PICkit 2 PIC Programmer

PICKit 2 Starter Kit is the low cost ICSP programmer for Flash PICs with USB interface introduced recently by Microchip. Only subset of PIC microcontrollers is supported, but the list is including all the recent devices from PIC16 and PIC18 families. The software upgrades are free and Microchip updates them in timely fashion. Even more, the source code and schematic are freely available.




JDM2 PIC 18F Programmer
Posted on Tuesday, March 30, 2010   •   Category: PIC

JDM2 PIC 18F Programmer

JDM2 PIC 18F Programmer is programmer based on JDM design which takes all necessary signals and power supply from RS232 serial port. It supports 8, 18, 28 and 40 pin PIC microcontrollers which allow serial programming and I2C EEPROM memories. Programmer comes with ICSP cable for direct connection to prototype boards. The supported devices depend on the current version of ICPROG software. JDM2 programmer is supported by ICProg, PICPgm and WinPic PIC programming software .




AVR ISP Programmer
Posted on Tuesday, March 30, 2010   •   Category: AVR

AVR ISP Programmer

This board can program an AVR microcontroler ATMEL (ATmega8, ATMega32, ...) from a parallel printer LPT1 using ISP functionality In System Programming. This programming type can program and/or configure microcontroler directly on the target board without rmoving device and put it on a separate programmer. This board is compatible with programming software "PonyProg".




USB Programmer for Atmel AVR Microcontrollers
Posted on Tuesday, March 30, 2010   •   Category: AVR

USB Programmer for Atmel AVR Microcontrollers

USBasp is a USB in-circuit programmer for Atmel AVR controllers. It simply consists of an ATMega48 or an ATMega8 and a couple of passive components. The programmer uses a firmware-only USB driver, no special USB controller is needed. Works under multiple platforms. Linux, Mac OS X and Windows are tested. * No special controllers or smd components are needed. * Programming speed is up to 5kBytes/sec. * SCK option to support targets with low clock speed (< 1,5MHz). * Planned: serial interface to target (e.g. for debugging).




Serial Port PIC Programmer
Posted on Tuesday, March 30, 2010   •   Category: PIC

Serial Port PIC Programmer

The PIC programmer project presented here is intended to be used by more experienced developers who already have access to a simple PIC programmer, because the programmer hardware is built around one 16F627(A) or 16F628(A) microcontroller that has to be preprogrammed with firmware. The presented solution uses PC's serial port for reliable communication between the programming software and 'intelligent' PIC programmer hardware.




RCD Programmer
Posted on Tuesday, March 30, 2010   •   Category: PIC

RCD Programmer

I believe that the "JDM Programmer" is cheap and very useful PIC Programmer. However, since "JDM Programmer" cannot control VDD, the algorithm "VPP before VDD" is inapplicable. Programming to the latest device from this reason may go wrong when using CONFIG settings as "Internal oscillator" "MCLR OFF". These devices are given power from the "JDM programmer",and execute program code. An error may come out by verification, or it may become impossible erasure and become impossible re-programming . In order to solve this problem, I designed a programmer based on the "JDM programmer." Since this programmer was made of resistors, capacitors, and diodes, I named this the "RCD Programmer." "Hardware settings" of IC-Prog are the same as the "JDM programmer."




RS232 Serial Port PIC Programmer
Posted on Tuesday, March 30, 2010   •   Category: PIC

RS232 Serial Port PIC Programmer

PIC Programmer is an essential tool if you wish to learn or build projects with Microchip PIC Micro Processors. This serial programmer is for those who do not have a Parallel Port on their PC. Programmer may be used with PIC PROGRAMMER Professional Serial programming software from Oshosoft or other serial programming software.




PICkit2 Compatibile MPLAB Programmer
Posted on Friday, March 19, 2010   •   Category: PIC

PICkit2 Compatibile MPLAB Programmer

This is a PICkit 2 MPLAB compatibile Programmer. It is a low-cost development tool with an easy to use interface for programming and debugging Microchip’s Flash families of microcontrollers. The full featured Windows programming interface supports baseline (PIC10F, PIC12F5xx, PIC16F5xx), midrange (PIC12F6xx, PIC16F), PIC18F, PIC24, dsPIC30, dsPIC33, and PIC32 families of 8-bit, 16-bit, and 32-bit microcontrollers, and many Microchip Serial EEPROM products. With Microchip’s powerful MPLAB Integrated Development Environment (IDE) the PICkit 2 enables in-circuit debugging on most PIC microcontrollers. In-Circuit-Debugging runs, halts and single steps the program while the PIC microcontroller is embedded in the application . When halted at a breakpoint, the file registers can be examined and modified.




70V PIC Voltmeter Amperemeter
Posted on Friday, March 12, 2010   •   Category: Test and Measurement

70V PIC Voltmeter Amperemeter

This PIC Voltmeter Amperemeter was designed to measure output voltage of 0-70V with 100mV resolution and 0-10A current with 10mA resolution. It is a perfect addition to any DIY laboratory power supply, battery chargers and other electronic projects where voltage and current consumption must be monitored. The heart of the meter is PIC16F876A microcontroller with built-in analog to digital converters and 2x16 green backlighted LCD display. Circuit design uses very few external components making it possible to fit this handy meter on a small PCB.




USB FM Transmitter MAX2606
Posted on Friday, February 19, 2010   •   Category: FM Transmitters

USB FM Transmitter MAX2606

This MP3 Player FM transmitter can be used to listen to your own music throughout your home. The transmitter circuit use no coils that have to be wound. When this FM transmitter used in the car, there is no need for a separate input to the car stereo to play back the music files from your MP3 player. This FM transmitter use a chip made by Maxim Integrated Products, the MAX2606. The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit. The variable-capacitance (varicap) diode and feedback capacitors for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency. The supply voltage to the IC should be between 2.7 and 5.5 V, the current consumption is between 2 and 4 mA.




1.3W VHF RF Amplifier 2SC1970 88-108 MHz
Posted on Friday, February 19, 2010   •   Category: FM Transmitters

1.3W VHF RF Amplifier 2SC1970 88-108 MHz

This RF power amplifier is based on the transistor 2SC1970 and 2N4427. The output power is about 1.3W and the input driving power is 30-50mW. It will still get your RF signal quit far and I advice you to use a good 50 ohm resistor as dummy load. To tune this amplifier you can either use a power meter/wattmeter, SWR unit or you can do using a RF field meter.




5 Watt FM Amplifier
Posted on Friday, February 19, 2010   •   Category: FM Transmitters

5 Watt FM Amplifier

This design is a 2 stage amplifier that has about 17db of gain, suitable for an input of 50 to 100 MW. Its basically a Veronica 5 watt vco transmitter, without the vco. The transistors are a 2N4427 and a MRF237. Output power is 2.5 to 5 watts, depending on input drive and dc voltage. At 13.7 vdc with 50 MW of drive, the output was 2.5 watts. The maximum dc voltage recommended is about 15-16 volts.




Audio DAC
Posted on Saturday, October 31, 2009   •   Category: Audio DAC

Audio DAC

The described device is used to convert the digital signal format S / PDIF (AES3) to analog signal. It can be used for any device with an output of uncompressed digital audio (CD or DVD players DVD, minidisc, PC sound card, CD-ROM). The device does not signal processor, and therefore not able to play compressed or encoded multichannel signal (AC3, MP3, respectively. Mpeg). Separate transmitter can improve the signal to noise ratio and to reduce interference, which is especially true for PC sound card.




Intelligent NiCd/NiMH Battery Charger
Posted on Saturday, October 31, 2009   •   Category: Battery Chargers

Intelligent NiCd/NiMH Battery Charger

This cheap and easy to build NiCd/NiMH Battery Charger is suitable for automatically charging a wide range of batteries for many applications. Proper chargers are usually expensive and cheap chargers supplied with the original equipment often incorrectly charge the cells and dramatically shorten their life. This 'intelligent' charger was designed for high current and rapid charge applications such as cordless power tools and model racing cars. These battery packs are expensive and sometimes difficult to purchase. This charger uses the cell manufacturer's recommended charge method, to safely and quickly charge batteries.




ALTOIDS Tin Part 15 Version FM Transmitter
Posted on Saturday, October 31, 2009   •   Category: FM Transmitters

ALTOIDS Tin Part 15 Version FM Transmitter

The transmitter uses 2 MPSH10 (equiv BF494 or NTE229) transistors in a double-ended free-running voltage controlled oscillator (VCO) operating at half the output frequency on each side and combined at L2, which is tuned to the 2nd harmonic of the VCO and covers the 88-108 MHz range. A standard 9 volt battery is used for power and fits inside the tin. The mono audio input circuit is totally passive with 70us pre-emphasis provided and the audio quality is great.




Generator of exact pulses
Posted on Saturday, October 31, 2009   •   Category: PIC

Generator of exact pulses

Circuit is very simple. The generator uses a PIC12F629 microcontroller with clock frequency set by an external RC. Output frequency can be set trimmer P1 in the range of about 2 to 170 Hz. Oscillator frequency can be adjusted if you change C1 capacitance. Pulses are generated with a period of 200 Tcy. All pulses are of equal length. Output frequency is 800 times lower than the frequency of the oscillator.




1 Watt FM Amplifier
Posted on Thursday, October 29, 2009   •   Category: FM Transmitters

1 Watt FM Amplifier

This is a 1 watt amplifier. This design is a 2 stage amplifier that has about 16db of gain, suitable for an input of 5 to 20 MW. The transistors are a 2N4401 and a 2N4427. At 13.7 vdc the most I could get out of the unit was 1/2 watt, you could probably raise the dc voltage to 16 volts and get more output but then a much better heatsink would be required. But for the sake of this project, we'll call it a 1/2 watt amplifier.




30W VHF FM Amplifier for 88 - 108 MHz with BLF245 MOSFET
Posted on Tuesday, October 27, 2009   •   Category: FM Transmitters

30W VHF FM Amplifier for 88 - 108 MHz with BLF245 MOSFET

The achievement of this 30-watt amplifier has been designed to take place on a heatsink microprocessor PC equipped with its fans, the advantage of this method of cooling has been selected for the fact that it is not very common and expensive. The size of the printed circuit will adapt quite easily to the type of heatsink as you have available, if possible, because in many cases, those of recovery, the fans have already lived and the price of a model remains very affordable.




100W FM AMPLIFIER
Posted on Tuesday, October 27, 2009   •   Category: FM Transmitters

100W FM AMPLIFIER

This Power amplifier is equipped with a bipolar transistor,the famous MRF317 As lots of FM amplifier application ,the power transistor is in a C class bias. All the impedance networks (Input & Output) have been determined by using the software: Mimp.EXE. A 9 elements low pass filter ensures that we meet at least a 60 dB rejection from the carrier.(RF Simulation with RFSIM99) The FM amplifier has a 10 dB gain with a 60 to 65% efficiency. The Input VSWR is around 1.4 and there's no problem to reach the max power in all the FM band.




BA1404 HI-FI Stereo FM Transmitter
Posted on Tuesday, October 27, 2009   •   Category: FM Transmitters

BA1404 HI-FI Stereo FM Transmitter

Be "On Air" with your own radio station! BA1404 based transmitter is an exciting product that will broadcast high quality stereo signal in 88MHz - 108MHz FM band. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground.




1W Linear FM Amplifier
Posted on Tuesday, October 27, 2009   •   Category: FM Transmitters

1W Linear FM Amplifier

That RF Amplifier is for boosting small fm transmitters and bugs. It use two Philips 2N4427 and its power is about 1Watt. At the output you can drive any linear with BGY133 or BLY87 and so on. Its power supply has to give 500mA current at 12 Volts. More voltage can boost the distance but the transistors will be burned much earlier than usual.! In any case do not exceed the 15Volts. The Amp offers 15 dB in the area of 80Mhz to 110 Mhz. L4, L5, and L6 are 5mm diameter air coils, 8 turns, with wire 1mm wire diameter.An easy project, with great results.




ASUS Eee Car Charger
Posted on Tuesday, October 27, 2009   •   Category: Battery Chargers

ASUS Eee Car Charger

« Atheros Drivers ASUS Eee Car Charger Building a 12v car charger for the ASUS Eee The ASUS Eee is a fantastic ultra-portable notebook with almost everything required for geeks (and nothing that isn’t). Plus it features fantastic build quality and is very well priced. If you live in New Zealand you can get them from DSE; at the time of writing they are the exclusive supplier. I worked out it’s the same cost as importing one once you include all the duties and tax, plus you get the advantage of a proper NZ-style mains charger. Anyway, being so small I thought it would be nice to be able to carry this around in the car. Unfortunately I couldn’t find a car charger available anywhere at the time so I decided to tackle the problem myself. As a bonus this provides an opportunity for an external high-capacity battery. Commercial Equivalent I thought at this stage it would be worth noting that a commercial car charger is now available for less than it cost me to build this from Expansys and is available in most countries (select your location on their site). It outputs 9.5v from 10-18v in at up to 2.5A I’d actually recommend it over the design here is it seems to perform better at lower voltages (that one works down to 10V). However I have kept this page up as a reference for those who enjoy tinkering. Design The charger included with the Eee is rated at 9.5v, 2.315A. There isn’t a fixed voltage regulator available for this exact voltage, so the circuit needed to be designed around an adjustable regulator. I decided to design the charger around the LM2576 “Simple Switcher” IC from National Semiconductor. There are tons of ICs like this available, many of which are a bit more efficient, however I selected this one because it is readily available and relatively cheap. It also has a lower drop-out voltage (~2V) than many other chips I looked at which is important when powering the device from a car or 12v SLA battery.




USB to Serial Adapter RS-232
Posted on Wednesday, August 26, 2009   •   Category: USB Interface Adapters

USB to Serial Adapter RS-232

The USB to Serial adapter (converter) lets you use a serial PDA, GPS, cell, etc. with a standard USB port. This adapter is the easiest way to add a serial port to your computer. Many PDAs, digital cameras, GPS units, barcode scanners, and other equipment require a serial connection, and many newer computers don't come equipped with serial ports anymore.




30W Digital Wattmeter for RF (0-500MHz)
Posted on Saturday, August 22, 2009   •   Category: FM Transmitters

30W Digital Wattmeter for RF (0-500MHz)

This watt meter project is very similar to my last wattmeter project. The main reason I made a new project is becasue I needed a unit which could handle higher power than 1W. I found a 50 ohm dummy load which could take 50W of power. Of course I could use attenuates for my 1W meter, but I prefered to build a new unit. The new thing with this project is that it will only display the power in Watt on the LCD display.




R/C Battery Voltage Monitor
Posted on Saturday, August 22, 2009   •   Category: Battery Chargers

R/C Battery Voltage Monitor

The Simple-Volt automatically detects the number of LiPo cells connected (assume charged pack) and continually monitors the battery voltage and compares it to the preset cutoff/warning voltage corresponding to the number of detected LiPo cells (9v for 3s, 12v for 4s and 15v for 5s... basically, 3 volts minimum per cell). When the battery voltage is greater than the cutoff voltage +1v, the Green LED will be on solid. If the battery voltage is > cutoff voltage+.5 but < cutoff voltage+1v, the Green LED will slowly flash. If the battery voltage is > cutoff but < cutoff+.5v, then the Red LED will begin flashing. If the battery voltage < cutoff voltage, both Green and Red LEDs will flash very fast while also emitting an intermittent beeping sound from the peizo alarm buzzer.




CLASS A MOSFET AMPLIFIER
Posted on Saturday, August 22, 2009   •   Category: Amplifiers

CLASS A  MOSFET AMPLIFIER

I was in my final 6 month work term with an electronics company as a trainee. Within this company there are a few audiophiles who are tube lovers and spend astronomical amounts of money on their audio equipment. My training supervisor had found Mark's Class A MOSFET Amplifier Project and suggested that I design a PCB and build this project as part of my training. I followed the Class A MOSFET Amplifier Schematic with the following exceptions. Instead of the 2SK1058, I used the 2SK2221 mosfet which I had on hand. I compared the datasheets of the 2SK1058 and the 2SK2221 and the differences between the two were very small. The other change was to use a 6800 uF capacitor on the output instead of a 4700 uF capacitor.




+/- 15V Power Supply
Posted on Saturday, August 22, 2009   •   Category: Power Supplies

+/- 15V Power Supply

The main balanced power supply is constructed with the usual suspects, 7815 (pos 15 volt regulator) and 7915 (neg 15 volt regulator). These are fed from rectified AC via a PCB mount 6VA power transformer. I have use four diodes in a bridge rectifier configuration rather than a dedicated bridge rectifier as people have had trouble finding P04 and W04 rectifiers and it allows you to get esoteric with low noise switching diodes. I used the simple and easy to get IN4004 but some at Tech Talk have suggested more exotic devices.




Bench Power Supply
Posted on Saturday, August 22, 2009   •   Category: Power Supplies

Bench Power Supply

I frequently have a need for a variable supply when testing homebrew circuits, and the triple power supply is just what I need on the bench. With an amp out at 13.5 V, it will easily handle that QRP full-gallon. It even has 6 and 12 V AC available, for those rare filament-power circuits.




13.8V 10A Power Supply
Posted on Saturday, August 22, 2009   •   Category: Power Supplies

13.8V 10A Power Supply

As is commonly the case, this supply was born of necessity. There is absolutely nothing special about the circuit, except that as shown, it is quite capable of up to 20 Amps intermittently or 10A continuous. Simply use a bigger transformer, bridge rectifier and more capacitors and output transistors to get more current. The basic circuit should be good for up to 100A or so, using a 5A TO3 regulator IC, but it can obviously be increased further (if you really do need a 500A supply!).




A Low-Cost 50MHz Frequency Meter
Posted on Saturday, August 22, 2009   •   Category: Test and Measurement

A Low-Cost 50MHz Frequency Meter

This new 50MHz Frequency Meter is autoranging and displays the frequency in either Hz, kHz or MHz. This makes the unit easy to read, as it automatically selects the correct range for any frequency between 0.1Hz and 50MHz and inserts the decimal point in the correct place for each reading. The design is easy to build too, since it uses a programmed PIC microcontroller to do all the clever stuff. Apart from that, there's an LCD readout, a couple of low-cost ICs, two transistors, a 3-terminal regulator and a few sundry bits and pieces to complete the design. Note that although we have specified this Frequency Meter at 50MHz maximum, most units will be capable of measuring frequencies somewhat higher than this. In fact, our proto-type meter was capable of making frequency measurements to above 64MHz.




AVR Frequency Counter
Posted on Saturday, August 22, 2009   •   Category: Test and Measurement

AVR Frequency Counter

This is a simple, inexpensive and versatile frequency counter with LCD display and some special extra features.The counter contains only three inexpensive ICs (well, add a regulator and three transistors), and operates from 6 - 15V DC at about 25mA. The most expensive single item is the LCD display, which is an industry standard 16 x 2 dot matrix module, which can often be found used or at bargain prices.




Lithium Ion / Lithium Polymer USB Battery Charger
Posted on Thursday, August 20, 2009   •   Category: Battery Chargers

Lithium Ion / Lithium Polymer USB Battery Charger

This is a MAX1811 based USB charger that can handle both Lithium Ion and Lithium Polymer 3.7V battery. It requires very few external components and provides ability to select between 4.1v and 4.2v battery regulation for different types of LiPo batteries. You can select between either 100mA and 500mA current charging mode and LED provides the status of the charging.




USB Lipo Battery Charger
Posted on Thursday, August 20, 2009   •   Category: Battery Chargers

USB Lipo Battery Charger

The MAX1551 and MAX1555 charge a single-cell 3.7V lithium-ion LiPo battery from both USB and AC adapter sources. They operate with no external FETs or diodes, and accept operating input voltages up to 7V. On-chip thermal limiting simplifies PC board layout and allows optimum charging rate without the thermal limits imposed by worst-case battery and input voltage. When the MAX1551 and MAX1555 thermal limits are reached, the chargers do not shut down, but progressively reduce charging current. The MAX1551 includes an active-low POK output to indicate when input power is present. If either charging source is active, active-low POK goes low. The MAX1555 instead features a active-low CHG output to indicate charging status. With USB connected, but without DC power, charge current is set to 100mA (max). This allows charging from both powered and unpowered USB hubs with no port communication required. When DC power is connected, charging current is set at 280mA (typ). No input-blocking diodes are required to prevent battery drain. The MAX1551 and MAX1555 are available in 5-pin thin SOT23 packages and operate over a -40°C to +85°C range.




Li-ion Battery Charger with TL431
Posted on Thursday, August 20, 2009   •   Category: Battery Chargers

Li-ion Battery Charger with TL431

This is a simple to build charger for single 3.7V lipo battery. The heart of the charger is TL431 shunt regulator that controls the incoming current. Charger comes with a convenient charging LED indicator. As charging current goes down so does the intensity of the LED.




Ultrasonic PSoC Range Finder
Posted on Wednesday, July 8, 2009   •   Category: Robots

Ultrasonic PSoC Range Finder

The PSoC Range Finder is a simple, inexpensive ultrasonic distance meter that requires only the PSoC device, two 40-kHz ultrasonic transducers, two resistors, and two capacitors. Typical applications include positioning for robotics, generic distance measurement, and liquid-level measurement without contact.




2.5 GHz Frequency Counter
Posted on Wednesday, July 8, 2009   •   Category: Counters / Frequency Meters

2.5 GHz Frequency Counter

An AVR controller can be used as a counter, although it is a bit more involved than with a PIC. The reason is that a PIC (at least the 16F84) has an asynchronous counter input. This input will handle frequencies up to app. 40 MHz. AVR's have a synchronous counter input which is sampled with the clock frequency, so it cannot measure frequencies over half the clock frequency. So, when using a 4 MHz clock, input frequencies must be lower than 2 MHz. Use 40% of the clock frequency to be on the safe side. The input frequency can be measured by starting an AVR counter. Wait some predetermined time and then stop the counter. Read the counter register, account for the measurement time, and you know the frequency. This sounds simple enough. Things get a little more complicated if you use an external (to the AVR) prescaler to measure higher frequencies. A prescaler can be seen as a counter itself, that produces an output pulse for every n counts of input pulses. Even if this external prescaler has not counted up to its limit, you will want to know this count value, because it adds to the AVR count value to get a resulting counter with more bits. An example: the AVR internal counter is 16 bits. It can count up to 65536 before overflowing to 0. If you use an external 14-bit counter (a 4020) as prescaler, it will increment the internal AVR counter at every 16384th input pulse. If you know the value of the 14-bit counter after the measurement time, you have effectively a 30-bit counter:




Posted on Wednesday, July 8, 2009   •   Category: Remote Control


The UIR is a device that enables you to control your PC with ANY remote controller you have (TV, VCR, CD or Stereo). Original hardware & software was designed by Martinus & Ties Bos. You should check their site first. There it was, now it has either moved or is unavailable. In this article you can find improved and simplified hardware scheme, software & hints for building the device. The device is very simple: minimal version uses only 3 components! So if you are not planning a big serial production you will build it on experimental (universal) circuit board. This is the most correct schema:




IR Remote Controlled Car (PWM motor control using ATmega8)
Posted on Wednesday, July 8, 2009   •   Category: Robots

IR Remote Controlled Car (PWM motor control using ATmega8)

The circuit uses two PWM channels of ATmega8 for controlling the speed and direction (reverse, forward) of the car, based on the command received from the IR remote. Here, a Sony TV remote was used. The IR codes were received by using TSOP1738 IR detector from Vishay.




SD Card Interfacing with ATmega8 (FAT32 implementation)
Posted on Wednesday, July 8, 2009   •   Category: AVR

SD Card Interfacing with ATmega8 (FAT32 implementation)

Here is my project on interfacing of SD Card (microSD). MicroSD cards are available very cheap nowadays, a great option for having a huge memory in any embedded system project. It is compatible with SPI bus, so interfacing is easy. SD card adapters are also easily available in market, so one can easily make an bread-board adapter by soldering few pins on it. In this project, I've used 1GB microSD card from sandisk (later on tested with transcend card also) The microcontroller is AVR ATmega8 running at 8Mhz internal clock. MAX232 is used to interface the circuit with PC for monitoring the data. A 3.3v supply is used for powering the mega8, microSD and max232.




Audio Volume Relay Attenuator with IR Control
Posted on Tuesday, March 24, 2009   •   Category: Audio Attenuators

Audio Volume Relay Attenuator with IR Control

The circuit provides both audio volume and input channel selection. A stepwise volume control is implemented with a set of tiny relays and RN60D / RN55D Dale resistors. In a high-end audio system, a noticeable sound improvement over potentiometers is obtained, also compared to 'audio grade' potentiometers. Its IR remote control provides convenience over solutions with stepped attenuator rotary switches. The sealed relays will maintain contact quality over a practically endless lifetime. The design represents a audio 'preamplifier' of top-class sonic quality, in a compact and affordable implementation. Compact and simple circuit with just 6 tiny relays implement a 64-step logarithmic stereo attenuator. The 64 steps of 1.0dB together span a 63dB audio attenuation range. By avoiding any active electronics, a very clean and open sound is maintained. An IR receiver allows remote control. The IR 'eye' and a numeric display are on a small front-mount printed circuit board, separate from the relay board. The device can learn and store your favorite key codes. The controller understands the popular Philips 'RC5' protocol, Philips' newer 'RC6' protocol, and Sony's SIRC protocol. This also ensures interoperability with all 'generic' IR-controllers.




24-Bit 192KHz PCM1793 DAC with DIR9001 Receiver and OPA2134 OPAMP
Posted on Friday, January 30, 2009   •   Category: Audio DAC

24-Bit 192KHz PCM1793 DAC with DIR9001 Receiver and OPA2134 OPAMP

24-Bit 192KHz PCM1793 DAC is is perfect solution for upgrading audio components such as CD Player, DVD Player, Blue Ray Player, Computer, and Satellite receiver. It can be easily connected via Coaxial S/PDIF or Optical Cable and provides convenient analog output connectors. PCM1793 Audio DAC board features advanced Burr-Brown PCM1793 DAC chip, high quality OPA2134 op-amp, and latest DIR9001 digital line receiver. PCB board is built with high quality components such as Nichicon Audio capacitors, WIMA capacitors, gold plated connectors, gold plated PCB tracks and metal film resistors. PCM1793 DAC provides detailed heights and exceptionally good sound stage. PCM1793 DAC Specifications - Burr-Brown PCM1793 - 24-Bit 192kHz Sampling Advanced Segment Audio Stereo DAC - Dynamic Range: 113 dB THD+N: 0.001% - 8× Oversampling Digital Filter - Digital input receiver DIR9001 - Burr-Brown OPA2134 OPAMP - Coaxial / Optical Inputs, Analog Output - Nichicon KZ Audio capacitors, WIMA capacitors - The receiver provides better quality than the popular CS8412 / CS8414 / CS8416 - Power Supply: 12V / 1A




Accurate LC Meter
Posted on Tuesday, December 2, 2008   •   Category: PIC

Accurate LC Meter

Build your own LC Meter and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging and "Zero Out" function to make sure the readings are as accurate as possible ...




Stereo FM Transmitter BH1415F
Posted on Monday, November 10, 2008   •   Category: FM Transmitters

Stereo FM Transmitter BH1415F

Here is a stereo FM Transmitter based on BH1415F wireless audio link IC. Phase Locked Loop controller use Microchip PIC16F628 and the the PLL frequency programming can be displayed with 8×2 and 16×2 LCD display. The frequency range can adjustable from 88-108 MHz.




BH1415F FM Stereo PLL Transmitter
Posted on Monday, November 10, 2008   •   Category: FM Transmitters

BH1415F FM Stereo PLL Transmitter

This is FM PLL Stereo based BH1415F IC from Rohm, it's has built in PLL and Stereo Encoder. You can download the schematic, pcb layout and Hex code. The transmitter menu display with LCD, and this have step 100Khz, 200Khz,.....1000Khz and have Mode menu (stereo/mono). In Action, LCD Display can solder directly on the bottom.




Accurate LC Meter with Green Backlight LCD
Posted on Monday, November 10, 2008   •   Category: LC Meter

Accurate LC Meter with Green Backlight LCD

This is one of the most accurate and simplest LC inductance / capacitance Meters that one can find, yet one that you can easily build yourself. This LC Meter allows to measure incredibly small inductances starting from 10nH to 1000nH, 1uH to 1000uH, 1mH to 100mH and capacitance from 0.1pF up to 900nF. LC Meter's circuit uses an auto ranging system so that way you do not need to spend time selecting ranges manually. Another neat function is the "Zero Out" switch that will reset the initial inductance / capacitance, making sure that the final readings of the LC Meter are as accurate as possible.




USB 8bit Interface Board
Posted on Monday, November 10, 2008   •   Category: USB Circuts

USB 8bit Interface Board

This is a USB (universal serial bus ) interface board which can be used to connect 8 (parallel) data lines to the USB. The interface comes with a small internal FIFO (384 byte Tx, 128 bytes Rx) and 4 handshake lines which make it suitable for interfacing microcontroller designs to the USB. It can, also be used as simple 8bit IO when the so-called “bitbang mode” is enabled. Note. however, that in this mode, the bits will not come out in a constant bitrate but in chunks of 64 bytes with specified baud rate followed by a delay.




PWM Motor Driver with H-Bridge
Posted on Monday, November 10, 2008   •   Category: Motor Controllers

PWM Motor Driver with H-Bridge

This pulse wide modulated driver is designed for DC Motors with a maximal power consumption of 200 watts. It works with a so called H -Bridge. It has three input pins, two for the direction and one for the pwm-signal. The inputs are designed for logic level signals ecpecially for microcontroller outputs.




USB Audio DAC
Posted on Sunday, November 9, 2008   •   Category: USB Soundcards / USB Headphones

USB Audio DAC

I want to build high quality preamplifier with built-in DAC from SPDIF or USB for my power amplifier Leachamp. I had available circuit PCM2902. I tried to design DAC from USB with this circuit on one-sided PCB and I was successful.




Compact Fluorescent Lamp (CFL) Schematics
Posted on Sunday, November 9, 2008   •   Category: Fluorescent Lamps

Compact Fluorescent Lamp (CFL) Schematics

Compact fluorescent lamps have some benefits in comparison with classic light bulbs. It is lower power consumption (to 80%) and much longer lifetime (5 to 15 times). Disadvantages are longer starts mainly at more expensive types, impossibility to use darker and price.




The Leach 200W Amplifier
Posted on Sunday, November 9, 2008   •   Category: Amplifiers

The Leach 200W Amplifier

This article descripts, how I built amplifier from Mr. Marshall Leach known like "The Leach Amp". I built amplifier from the original instructions on these pages: http://users.ece.gatech.edu/~mleach/lowtim/. Article about bulding of this amplifier I found later in journal A_Radio Praktická elektronika 11/2002. For many years I looked for construction of HiFi amplifier wit a good parameters, enough power reserve and simple construction. I built a couple of amplifiers with integrated circuits MBA810, TDA2005, LM3886, but I was disappointed by their output quality and noise. I decide to built a classic construction with discrete components and bipolar transistors. Construction from Mr. Dudek was interesting, but I didn't like used components and complexity. All of my requirements satisfied construction of the Leach Amp. Circuit author publicates in a February 1976 in american journal. From these days circuit was not practically changed. Little changes are descripted on authors page.




DIY flexible printed circuits
Posted on Sunday, November 9, 2008   •   Category: PCB

DIY flexible printed circuits

Produce your own single-sided flexible printed circuits using a solid ink printer, copper-coated polyimide film, and common circuit board etching chemicals. You will find flex PCBs inside most cellphones or similar miniaturized gadgets. Flex PCBs are useful for making tiny cables and extremely lightweight circuits. However, few shops yet make custom flex PCBs for reasonable prices in small volumes.




10MHz DDS Sine/Square Function Generator with AD9835
Posted on Sunday, August 3, 2008   •   Category: Frequency Wave Generators

10MHz DDS Sine/Square Function Generator with AD9835

Here is an extremely simple and low cost Sine/Square wave generator based on the Analog Devices AD9835 Direct Digital Synthesis (DDS) Generator chip. The frequency can be set for any frequency from 1Hz to 10MHz in 1Hz resolution steps! All this with three push buttons and a novel “sliding window” LED display. The controller chip is a Microchip PIC16F628.




NOS-DAC
Posted on Wednesday, May 7, 2008   •   Category: Audio DAC

NOS-DAC

This project is a set of two DAC's made for my friend. The first one is NOS-DAC designed by Peter Daniel based on TDA1543 and CS8412 SPDIF receiver. The other one is a little modified version of USB PCM2702 DAC from TI application note. The heart of this part is low-cost 16-bit Philips DAC. As a SPDIF decoder was chosen Cirrus Logic CS8412 IC with SN75179 as an input driver. Each IC have it's own AN800x regulator and there are separate wiring for alalog and digital section.




TDA1543 Nonoz III DAC
Posted on Wednesday, May 7, 2008   •   Category: Audio DAC

TDA1543 Nonoz III DAC

The Nonoz III sounds the most accurate of all. It has better dynamics, more detail and maybe is even a bit smoother than version I and II. For the past months, I have been busy with experiments to improve the Nonoz II DAC. This has resulted in the Nonoz III DAC. I have the feeling that some parts of the Nonoz III can be improved and tuned. Still, I think that the current version is worthy of a release. In the next months, I'll see what improvements can be made... ICs used: TDA1543 DAC, CD8412 S/P-DIF Receiver




BH1417 PLL Stereo FM Transmitter
Posted on Tuesday, May 6, 2008   •   Category: FM Transmitters

BH1417 PLL Stereo FM Transmitter

This is a high quality PLL Stereo FM Transmitter with build-in VHF amplifier for longer transmission range. It is based on BH1417 chip that offers high quality crystal clear stereo transmission. Eight available frequencies are controlled by grounding S1, S2 and S3 pins on header connector. Includes, high quality ROHM BH1417 transmitter chip, on-board amplifier increases transmission range, uses 7.6MHz crystal for rock-solid PLL FM transmission, crystal based Stereo Encoder and 3.5 standard audio input jack.




LM3886 GainClone Amplifier
Posted on Monday, May 5, 2008   •   Category: Amplifiers

LM3886 GainClone Amplifier

This a LM3886 amplifier that features both balanced (XLR) and unbalanced (RCA) audio inputs. I've changed the internal circuits of this ChipAmp or so called "GainClone" to use premade circuit boards. The reason for this is that the bass/ low frequency response of the prior version was not as powerful as I would have liked. It is said that simply adding more capacitance to the power supply improves this, but worsens the high frequency characteristics. Boards use a noninverting amplification scheme, versus the inverting circuit I had used previously, I have heard some people mention that noninverting is better in some respects so wanted to try it. At the bottom of the page you will see the different schematics for the inverting and noninverting designs. In addition, Images will now load in a new window.




XLR Balanced to RCA Unbalanced Adapter
Posted on Sunday, May 4, 2008   •   Category: Audio DAC

XLR Balanced to RCA Unbalanced Adapter

This circuit will convert differential sources single ended unbalanced RCA signal. It is useful to connecting DAC with balanced outputs such as PCM1794, PCM1798, PCM1730 to an amplifier that only have RCA audio inputs. INA134 is used as a XLR differential digital receiver or buffer for RCA inputs.




Audio DAC with PCM1730
Posted on Sunday, May 4, 2008   •   Category: Audio DAC

Audio DAC with PCM1730

There are 3 circuit boards, one for the receiver DIR1701, one for the DAC and one for a second filter for balanced outputs. I made separate boards for easier upgrade in the future.. The result is fantastic, I'm hearing details I couldn't hear before. Well done Burr Brown - TI. IC used: PCM1730, DIR1701, OPA627




S/PDIF DAC Digital to Analogue Converter
Posted on Sunday, May 4, 2008   •   Category: Audio DAC

S/PDIF DAC Digital to Analogue Converter

This is quite possibly the simplest S/PDIF receiver and DAC available. It uses the absolute minimum of parts, and also minimizes the connections and control functionality usually provided. It is still a serious project, and is not recommended for beginners. As shown, the connection is COAX (but will almost certainly handle TTL just as well). If you want a dedicated TTL to COAX converter, there is an adapter shown at the end of this article. The spare gates in the 74HC04 package may be used for the adapter if desired.




LM3875 Gainclone
Posted on Saturday, May 3, 2008   •   Category: Amplifiers

LM3875 Gainclone

Gainclone in the inverted mode with the pot at its input is great amplifier, so it will work fine without any preamp or input buffer. However, here is a suggestion for the further improvement of some parameters of the sound of the inverted gainclone. During experiments, I paid special attention not to loose the good sides of the original, unbuffered inverted gainclone.




DS1802 Digital Stereo Volume Control
Posted on Saturday, May 3, 2008   •   Category: Volume Control

DS1802 Digital Stereo Volume Control

The DS1802 is the dual audio 45kOhm (typically) pot with 65 steps (64x1dB and mute), known around for its possibility to be controlled by its own pushbuttons instead of, usually needed, certain logic circuitry. It is available in DIP package and hence seems very appealing for DIY. Most of the digital potentiometers (there are exceptions like WM8816 and X9312) can not accept signals much beyond their supply voltages. For DS1802, 0.5V below the potential at its Gnd pin is the bottom, and 0.5V above the Vcc (whose safe maximum is 5.5V above the Gnd pin) is the upper limit. There are a few ways to center the signal inside these boundaries and Dallas recommends Wheatstone Bridge circuit (see App Note 161). I decided to shift the supply rather than signal, thus with one more regulator I could keep the signal path clean. So, DS1802’s Gnd pin went down to -2.5V and all the other pins of DS that normally should go to ground went to this pin: Agnd, Zero-Crossing (enabled) and Mode (stereo), as well as the Up/Down buttons. Resistive networks themselves are connected straightforward. The DS1802’s pin layout appeared almost ideal for such application.




PCM2702 USB audio DAC
Posted on Sunday, April 27, 2008   •   Category: Audio DAC

PCM2702 USB audio DAC

High quality USB Audio DAC with PCM2702. The PCM2702 is a single chip digital-to-analog converter offering two D/A output channels and an integrated USB 1.0 compliant interface controller. The newly developed SpAct™ (Sampling Period Adaptive Controlled Tracking) system recovers a stable, low-jitter clock for internal PLL and DAC operation from the USB interface audio data. The PCM2702 is based upon Texas Instruments Enhanced Multi-level Delta-Sigma Modulator, an 8x oversampling digital interpolation filter, and an analog output low-pass filter. The PCM2702 can accept a 48kHz, 44.1kHz and 32kHz sampling rates, using either 16-bit stereo or monaural audio data. Digital attenuation and soft-mute features are included, and are controlled via USB audio class request.




1W iPOD FM Transmitter
Posted on Thursday, April 24, 2008   •   Category: FM Transmitters

1W iPOD FM Transmitter

Many people prefer to listen to their own music (or voice) on radio. This project explain how you can build and connect a powerful 1W amplifier to your FM transmitters. A perfect solution for those wishing to listen to their favorite tunes in the car, house, garden, school, campus, party, you name it.... Why not share your music with every one else in your city!




BH1415F FM Stereo PLL Transmitter with LCD
Posted on Thursday, April 24, 2008   •   Category: FM Transmitters

 BH1415F FM Stereo PLL Transmitter with LCD

BH1415F FM Stereo PLL Transmitter Transmitter power amplifier, the output signal from BH1415F by 2 SC9018, 2SC3355, 2SC2053 amplified signal can reach more than 500 mW, adjusting well to achieve greater power. Measured by the pull rod antenna used to be launched in the open 800 meters above. Uses external antenna will be launched even further. attention in 2053 need to be installed and tested at the load connected to leave, or else very easily burn 2053, 50 European amateur production of 2 W can be used instead of resistance. installed and tested at three levels circuit can be installed and tested.




Headphone Amplifier CMoy
Posted on Thursday, April 24, 2008   •   Category: Headphone Amplifiers

Headphone Amplifier CMoy

Here is very simple portable hi-fi headphone amplifier built around OPA2132 amplifier chip. Instead of R5 and R25 is used only wires. These resistors are assembled only in case of oscillation. The value should be few ohms. Now I have to find some good box, and put my CMoy inside. It will be maybe most difficult part of building CMoy amplifier :-). The sound is very good for so easy and small device. It can improve the sound of MP3 players, mobile phones and other portable devices. I would like to make some measurement of frequency characteristics, THD and also try to use different OpAmps, but unfortunately I don't have enough time to make it now.




ATmega48/88/168 Development Board
Posted on Thursday, April 24, 2008   •   Category: AVR

ATmega48/88/168 Development Board

This is versatile development board for AVR microcontrollers ATmega48/88/168. It is good for testing and debugging embedded programs. It has many built-in peripheries connected to microcontroller so you can use them without soldering. ATmega microcontrollers are produced by ATMEL and they include a lot of features: I/O, Timers, PWM generators, ADC, RS232, TWI, SPI, Analog Comparator, Oscillator, EEPROM… These microcontrollers are very versatile, easy to program and easy to use. This is the reason why I like these microcontrollers and why I decided to make development board for them.




USB Sound Card with PCM2702
Posted on Thursday, April 24, 2008   •   Category: USB Soundcards / USB Headphones

USB Sound Card with PCM2702

Make a sound card is no more a complex issue. If you use great IC PCM2702 from BURR BROWN / Texas Instruments you can create a fully functional USB sound card. This sound card can be powered from USB port and has one stereo output. You don’t need to install any driver for Windows XP and Vista, because they are already inside. This is really plug and play.




25 W Class A Amplifier
Posted on Wednesday, April 23, 2008   •   Category: Amplifiers

 25 W Class A Amplifier

Musical Fidelity would let you believe that this is a Class A design. However, in common with most commercial amplifiers, it is a class AB amplifier - it simply has a rather high standing current in the output stage, which results in the first 8 watts or so being class A.




Single Chip FM Transmitter
Posted on Wednesday, April 23, 2008   •   Category: FM Transmitters

Single Chip FM Transmitter

A simple FM transmitter links your home-entertainment system to a portable radio that can be carried around the house and into the back yard. For example, you can play music on the CD changer in your living room, and listen to it on a portable radio by the back-yard barbeque. IC1 is a voltage-controlled oscillator with integrated varactor. Its nominal frequency of oscillation is set by inductor L1, and a 390nH value places that frequency at 100MHz. Potentiometer R1 then lets you select a channel by tuning over the FM band of 88MHz to 108MHz. Output power is about -21dBm into 50 (most countries accept emissions below 10dBm in the FM band). The home system's left and right audio signals are summed by R3 and R4, and attenuated by the (optional) potentiometer R2. R2's wiper signal serves as a volume control by modulating the RF frequency. Signals above 60mV introduce distortion, so the pot attenuates down from that level. In the absence of a standard FM radio antenna, 75cm (30 inches) of wire will suffice as a transmitting antenna. For best reception, it should be mounted parallel with the receiving antenna. The IC operates on a single supply voltage in the range 3V to 5V, but you should regulate the applied voltage to minimize frequency drift and noise.




The Joystick Controlled Ultrasonic Explorer
Posted on Tuesday, April 22, 2008   •   Category: Robots

The Joystick Controlled Ultrasonic Explorer

The robot is controlled by a NXT-G program that listens to Bluetooth messages that tell it what to do. Normally, the commands are movement commands. These commands control the speed of the robot, whether it will go straight or turn left or right, or whether it will stop. It can also receive a command to do a radar-style scan with the ultrasonic sendor. When it gets such a command, it stops moving, and performs a sequence of ultrasonic measurements while rotating the sensor. It sends these measurements, along with data about what angle the sensor was looking at, back to the PC. When the scan ends, the robot starts responding to movement commands again.




An Infra-Red Link Using an AVR
Posted on Tuesday, April 22, 2008   •   Category: AVR

An Infra-Red Link Using an AVR

In this project I created an infrared (IR) link that provides bi-directional communication between the NXT and the new Power-Functions system, which consists of a battery box, motors, a remote control (an IR transmitter) and an IR receiver that controls the motors. I previously built an IR transmitter for the NXT which used an MSP430 microcontroller and which was able to send Sony IR commands (the specifications of this protocol are widely available).




8 Channel RF Remote Control
Posted on Tuesday, April 22, 2008   •   Category: Remote Control

8 Channel RF Remote Control

This is an 8 Channel RF Remote Transmitter and Receiver that will allow to remotely control various electronic projects. RF Remote Control provides 2 latched and 6 momentary outputs that could be used to control your favorite devices such as amplifier, robotic devices, RC cars, computer, home appliances, lamps and many other cool gadgets.




4 Channel Wireless RF Remote Control
Posted on Sunday, April 20, 2008   •   Category: Remote Control

4 Channel Wireless RF Remote Control

This is an assembled 4 Channel RF Remote Transmitter and Receiver with an impressive 200m range. Is simple to connect and it will allow you to remotely control various electronic projects. RF Remote Control provides 4 momentary outputs that could be used to control your favorite devices such as amplifier's volume control, selection of audio sources, wireless light control, light dimmers, robotic devices, motors, RC cars, computer, home appliances, and many other cool gadgets. If required momentary outputs can be easily converted to toggle with 4013 digital low cost IC.




Wireless PLL Stereo FM TX with LCD
Posted on Sunday, April 20, 2008   •   Category: FM Transmitters

Wireless PLL Stereo FM TX with LCD

Now you can use your MP3 Player to listen your favorite tunes through any FM stereo receiver. Wireless FM transmitter wirelessly connects portable music players to your car or home stereo quickly and easily. Just plug the FM Transmitter into the headphone jack of your MP3 or any audio source including iPOD, PDA, CD Player, Cassette player or connect it to your PC or laptop computer. Tune your card stereo or receiver to the clearest FM frequency, and enjoy your digital music with full sound and convenience. Features: - PLL tuned transmitter / exciter for rock solid frequency stability over the entire FM band - Displays Transmitted Frequency on blue backlighted LCD - 100KHz frequency increments - Includes three frequency memory buttons - PCB includes antenna output to which a piece of wire, or standard VHF amplifier can be connected for greater transmission range - Uses PLL synthesizer chip up to 1.4GHz - Includes 3.5mm audio jack cable - Small size




433MHz RF Modules
Posted on Saturday, April 19, 2008   •   Category: Remote Control

433MHz RF Modules

These tiny RF modules are great for building your own wireless remote control or wireless link. Remote control that allows to control different devices can be easily implemented with wide range of encoder/decoder chips (such as HOLTEK HT12E + HT12D or MC145026 + MC145027) or PIC / AVR microcontrollers. RF Module can also be used for sending data at up to 4.8KB/s.




Single Chip Radio FM Receiver
Posted on Saturday, April 19, 2008   •   Category: FM Radio / Receivers

Single Chip Radio FM Receiver

This a is complete FM radio receiver in a single chip. The board features a reset and scan button that tunes to the next radio station in a fraction of a second. Receiver offers excellent sensitivity and impressive loudness from such a small speaker. Just connect red (+) and black (-) leads to 2-5V voltage supply (or two to three AA battery cells), extend green antenna wire and you are ready to listen to your favorite FM radio stations.




8 Channel IR Remote Control
Posted on Tuesday, April 15, 2008   •   Category: Remote Control

8 Channel IR Remote Control

This is an 8 Channel IR Remote Transmitter and Receiver based on SM5021 encoder and SM5032 decoder ICs. It is simple to build and will allow you to remotely control various electronic projects. IR Remote Control provides 2 latched and 6 momentary outputs that could be used to control your favorite devices such as amplifier's volume control and selection of audio sources, wireless light control, light dimmers, robotic devices, RC cars, computer, home appliances, and many other cool gadgets.




Single chip USB MP3 Player with IR Remote
Posted on Tuesday, April 15, 2008   •   Category: MP3 Players

Single chip USB MP3 Player with IR Remote

This MP3 player is similar to iPOD shuffle that is based on the latest innovative BU9432 chip from RHOM. It features USB 1.1 / 2.0 Controller, MP3 decoder, system controller for loading MP3 files from a USB flash drive, USB hard drive, USB CD-ROM or USB DVD-ROM drive all in one chip. Once USB flash drive is connected, BU9432 automatically searches for MP3 files for playback. Audio is controlled by tactile buttons; Play, Stop, Previous Song and Next Song. BU9432 can decode VBR MP3, MP2, MP1, Layer 1, 2, 3 files with Sampling rate: 8K - 48KHz and Bit rate: 8Kbps - 448Kbps. It can also recognize FAT16 and FAT32 USB flash drive / hard drive with capacity from 32MB to 2TBytes. Audio playback is exceptionally good with 93dB signal to noise ratio and 88dB dynamic range.




BH1417 PLL Stereo FM Transmitter Module
Posted on Tuesday, April 15, 2008   •   Category: FM Transmitters

BH1417 PLL Stereo FM Transmitter Module

This is a high quality PLL Stereo FM Transmitter with build-in VHF amplifier for long transmission range. It is based on BH1417 chip that offers high quality crystal clear stereo transmission. Eight available frequencies are controlled by grounding 3 pins on header connector. This transmitter comes assembled and is ready to use. Features: - Two on-board transistors increase transmission range - Uses 7.6MHz crystal for rock-solid PLL FM transmission - Crystal based stereo encoder - Very small size




PLL Synthesizer Module
Posted on Monday, April 14, 2008   •   Category: PLL Circuits

PLL Synthesizer Module

PLL Synthesizer module is an add-on based on SA1057 and PIC16F84 that converts any existing FM Transmitter into stable rock-solid PLL transmitter. Frequency is selected through 8-DIP switch. PLL Synthesizer board will also require a 100K resistor and varicap diode such as MV2105 or MV2109 to control the frequency of the transmitter's oscillator.




200mW FM Transmitter
Posted on Monday, April 14, 2008   •   Category: FM Transmitters

200mW FM Transmitter

Here is the latest and greatly improved TX200 VFO/VCO FM transmitter. The most versatile transmitter to date that can be turned into high fidelity stereo PLL based 200mW FM transmitter. It is a perfect circuit for transmitting your music around the house and yard. TX200 uses only two coils; one in the oscillator and the other one in the 200mW VHF amplifier so it should be fairly easy for anyone to build. It also includes built-in pre-emphasis and C5 for enhanced sound quality. While assembling the transmitter care must be taken to make sure that C1 is directly connected to L1 and C9 to L2. These caps eliminate the distortions form the DC supply and improve the sound quality greatly. 9V voltage supply is also very important because it provides the exact amount of current to Q1 to produce loud and clear sound quality.




Lithium Ion Battery Charger
Posted on Friday, April 11, 2008   •   Category: Battery Chargers

Lithium Ion Battery Charger

Lithium Ion batteries pack a lot of power by weight compared to other types. There are 2 things that need to be handled differently than nicad on NiMH: 1. They cannot be used as a direct substitute (even if they look like other AA's) since they run at about 3.6 (or so) volts. 2. They cannot be charged in the same way as nicad or NiMH. After a bit of research, I came up with this design. Normally, you put in a specified current (about 0.2C) until 4.2 volts is reached. Then, you keep the voltage tightly regulated at 4.2 volts until the charge rate drops to 10 percent (about 0.02C). This design uses a regulated supply for both parts of the charging. Only the charging current is monitored since the supply voltage is maintained at 4.2 volts. The charging current is controlled using variable pulse width of the voltage feed.




LM338 13.8V 5A Power Supply
Posted on Friday, April 11, 2008   •   Category: Power Supplies

LM338 13.8V 5A Power Supply

Many times we needed one relatively powerful supply in order to we supply various appliances with + 13.8V, as transceivers CB, charge lead-acid batteries, etc. The circuit it uses known completed that is capable gives in the his exit, current in continuous operation 5A and 12A peak current. It does not only need few external component. Exist a point which it will be supposed you are careful in the drawing and in board. Board has been drawn so as to exist the possibility of using also two case types completing. In the first case the IC1 in case TO-220 is placed above in pcb, in second with case TO-3, it can it�s placed above in heatsink and terminal his they are connected in the connector G3, in this case, certain we leave empty the place of IC1 above in pcb.




MAX038 Signal Generator
Posted on Friday, April 11, 2008   •   Category: Frequency Wave Generators

MAX038 Signal Generator

The Max-80 function generator IC is specified to work to 20 MHz. So far, this unit works nicely to 50KHz. Since I seldom need signals higher than that, it has taken up a happy home on my workbench and further development is iffy at best. There are two basic approaches to controlling the frequency in this type of device. One way is to adjust the voltage to the IC manually and then read out the frequency with a counter. The problem here is you need to fiddle around with the control knob and while waiting for the one-per-second updates on the display. The other way is to set the display with the control knob and then have the circuit diddle the control voltage to the IC until it settles on that frequency. This is done by calculating the period for the target frequency and then using the PIC to read the pulse width. It then sends short correction pulses to an integrator which controls the IC.




AVR ISP Programmer (In-Sytem programmer) for ATMEL
Posted on Friday, April 11, 2008   •   Category: AVR

AVR ISP Programmer (In-Sytem programmer) for ATMEL

This AVR ISP original by ATMEL you can found on "AVR software and technical Library - April 2003" CD-rom.It small component count I design new PCB and change some component that easy to build small PCB .The new firmware was writen by John Samperi for AT90S2313. This code can program more devices.




FANCY LEDS
Posted on Friday, April 11, 2008   •   Category: LED

FANCY LEDS

The idea of this project came from my youngest son. He was dreaming of a small tool able to write symbols or pictures on a screen. As a graphic LCD (even bought at Crownhill :) ) was too expensive (or too easy??), the solution adopted was to pilot a matrix of Leds. This way, with only some cheap transistors, common red Leds, and a 16F628 , the dream could become reality.




Fading LEDs
Posted on Friday, April 11, 2008   •   Category: LED

Fading LEDs

Two strips of LEDs fading in a complementary manner 9V Battery-operated portable unit. This circuit operates two LED strips in pulsing mode, i.e. one LED strip goes from off state, lights up gradually, then dims gradually, etc. while the other LED strip does the contrary. Each strip can be made up from 2 to 5 LEDs at 9V supply.




Class-A Headphone Amplifier
Posted on Friday, April 11, 2008   •   Category: Headphone Amplifiers

Class-A Headphone Amplifier

Even if simple the circuit, plirej' all condition, regarding the distortion and the response of frequency. The resistance of entry is 250K and the load that can drive is between 100R and 2K. The circuit use negative coupling. His exit functions in Class A, having as active charge the BC308 and resistance 39R. The bias current is roughly 14 mA and total 15mA. The gain of unit is 25. The power supply, can be from 6V up to 24V DC. The frequency response with load 200R, it is 37ΗΖ - 470KΗZ (-1dΒ), the output voltage is 1.5V (11mW), the distortion 0.5%.




1 GHz Frequency Counter
Posted on Friday, April 11, 2008   •   Category: Counters / Frequency Meters

1 GHz Frequency Counter

This simple counter is useful for frequency measurements of various wireless equipments, especially transmitters, receivers and signal generators in VHF/UHF band. Features * Display range: 0,0 to 999,9 MHz, resolution 0,1 MHz * Correct rounding, reduced blinking of last digit * Over-range indication * Fast measurement - short measuring period * High input sensitivity in VHF/UHF band * Switchable intermediate frequency offset for use with receiver.




1 min - 2 hours Timer with Buzzer and Optocoupler
Posted on Friday, April 11, 2008   •   Category: Timer Circuits

1 min - 2 hours Timer with Buzzer and Optocoupler

A small circuit that can find a lot applications of measurement time. She has the possibility us inform with sound signal from the BZ1. At the same time, exist the possibility drive a external circuit via the optocoupler IC2, after we connect the applicable circuit in contacts [ A ] and [ B ]. The circuit is based on IC1 (4060), which include in his inside, oscillator and a binary divider of 14 stage. The frequency operation of oscillator is determined by a circuit R-C that connected in pins 9,10,11 of IC1. We give supply in the circuit, with switch S1, is presented a pulse in 12 [ RESET ] via C1 and R3, null him counter, require the measurement of pulses to begin from the zero. Than the count get at in 14th digit then exit Q14 in the pin 3, acquire high logic level. This voltage drive the base the Q1-2, the transistors turn on, thus buzzer BZ1 sound, also the IC2 is ready to drive, via contacts [ A][B ], any suitable external circuit. The time delay is regulated with the potentiometer RV1, in time delay that begin from 1 minute up to 2 hours, proportionally with the combination of prices that they will have the RV1 and C2.




LM3875 Gainclone Amplifier
Posted on Friday, April 11, 2008   •   Category: Amplifiers

LM3875 Gainclone Amplifier

GainClones have VERY few components and this one is based on the National Semiconductor LM3875 IC. The PCBs and components are very simple and quick to make, only took about 20 mins to assemble both amps and rectifier board. DC offset was about 80mV on one channel and about 40mV on the other. I used the optional Ci capacitor in the national datasheet for the IC which reduced it to between 0-4mV: This is the capacitor I chose, its an Elna Starget (expensive). The case was MUCH more time consuming and difficult to make though. I bought all the aluminum from a scrap metal yard including the heatsink. I got my aluminum panels cut at a sheet metal shop as I cant make straight cuts with a hack saw.




1Hz to 1MHz Function Generator with XR-2206 IC
Posted on Thursday, April 10, 2008   •   Category: Frequency Wave Generators

 1Hz to 1MHz Function Generator with XR-2206 IC

Frequency Generator is an essential laboratory equipment for every electronic. It allows a variety of measurements and experiments. The module described here is based on high quality XR2206 IC and is extremely compact and inexpensive. Output frequency is from 1Hz to 1MHz. It provides sine, square and triangle waves around 1Hz to 1MHz, depending on the timing capacitors used. Over two Potentiometers the amplitude and frequency can be set. About trimmers can also have the purity of the sine signal and the offset of the output voltage can be changed.




Phone Line Controller
Posted on Thursday, April 10, 2008   •   Category: Phone Circuits

Phone Line Controller

It might be "yet another" «device» controller that operates over phone-line, but this one works for sure :) The task was to build a device that connects to the phone line and has a relay as an output switch. It should also sense if the connected «consumer» is turned-on or off and report to the administrator at the other end of the phone line. The administrator would then call-in the device, log in with the password, and check the state of «consumer», turn it on or off, change password or some other settings. Current version has only one relay.




Dual Fan Controller
Posted on Thursday, April 10, 2008   •   Category: PC Circuits

Dual Fan Controller

Each fan turns off when the temperature drops 5 degrees below its turn-on temperature. For example, if the dial is set to 80 degrees, the fan turns on at 80 degrees and turns off at 75 degrees. This prevents the fan from cycling on and off rapidly, which would occur if the fan turned on at 80, started to cool the cabinet, and then immediately turned off at 79.




Controlling Devices Through a Computer's Parallel Port
Posted on Thursday, April 10, 2008   •   Category: PC Circuits

Controlling Devices Through a Computer

This is a very easy and fun to build project that will allow you to control up to eight external devices through your computer's parallel port. You may for instance control different appliances such as lamps, computers, printers, tv sets, radios, music systems, air conditioners, air fans, garden sprinklers and anything else you can think of, all through your computer. You can do a simple test by connecting a LED directly to a ground and any PINs 2 through 9 of your parallel port. The voltage on the parallel connectors is around 4.5V but it drops to around 2V once you connect the LED. You may use a 100 Ohm resistor if you want to, but it is not necessary since the current is very low.




1.5W VHF Amplifier
Posted on Thursday, April 10, 2008   •   Category: FM Transmitters

 1.5W VHF Amplifier

This project will explain the basic function of a class-C transmitter. I will explain how to dimension a transmitter and the purpose of the different components. I will also explain how you can build a 1.5W PA transmitter. The project will include PCB, components and instructions how to make coils, assembly and testing.




BH1417 Stereo PLL FM Transmitter
Posted on Thursday, April 10, 2008   •   Category: FM Transmitters

BH1417 Stereo PLL FM Transmitter

This is the latest BH1417 FM Transmitter design from RHOM that includes a lot of features in one small package. It comes with pre-emphasis, limiter so that the music can be transmitted at the same audio level, stereo encoder for stereo transmission, low pass filter that blocks any audio signals above 15KHz to prevent any RF interference, PLL circuit that provides rock solid frequency transmission (no more frequency drift), FM oscillator and RF output buffer. There are 14 possible transmission frequencies with 200KHz increments that users can select with a 4-DIP switch. Lower band frequencies start from 88.7 up to 89.9 MHz, and upper band frequencies start from 107.7 up to 108.9 MHz.




Alarm Phone Dialer with MT8880 and PIC 16F84A
Posted on Wednesday, April 9, 2008   •   Category: Phone Circuits

 Alarm Phone Dialer with MT8880 and PIC 16F84A

Just hook this Alarm Phone Dialer up to something you would like to monitor, for example, a high water alarm, low temperature alarm, back window, garage door, etc. When the system is activated it will call a number of programmed numbers to let you know the alarm has been activated. This would be great to get alerts of alarm conditions from your home when you are at work. The microcontroller code is provided on the site.




Active Antenna AA-7 HF/VHF/UHF, 3-3000MHz
Posted on Wednesday, April 9, 2008   •   Category: Antennas

Active Antenna AA-7 HF/VHF/UHF, 3-3000MHz

If you have a shortwave or high-frequency receiver or scanner that is struggling to capture signals with a short, whip antenna, and you'd like the kind of performance that a 60-foot 'longwire' antenna can provide but lack the space to put one up, consider building the AA-7 HF/VHF/UHF Active Antenna described in this article. The AA-7 is a relatively simple antenna that is designed to amplify signals from 3 to 3000 MegaHertz, including three recognized ranges: 3-30Mhz high-frequency (HF) signals; 3-300Mhz very-high frequency (VHF) signals; 300-3000MHz ultra-high (UHF) frequency signals. Those bands are typically occupied by shortwave, ham, government, and commercial radio signals.




2-CH RF Remote Control
Posted on Wednesday, April 9, 2008   •   Category: Remote Control

2-CH RF Remote Control

On these pages, I will introduce Remote Controller with Radio Frequency. The electric wave sending-out is controlled with the code by PIC for transmission and the code is deciphered by PIC for receiving.




18F4550 USB Interface
Posted on Wednesday, April 9, 2008   •   Category: USB Interface Adapters

18F4550 USB Interface

This article contains information about getting a USB interface working between an 18F4550 PIC and a PC using C# .NET 2.0, using the Microchip-supplied driver mpusbapi.dll. In this article, the PIC is configured using some (slightly modified) demo code originally for the PICDEM FS USB demo board, in which it is configured as a generic class device, with one IN + OUT interrupt endpoint. The device is set up with a bootloader, allowing the PIC to be programmed through software after the initial programming.




12V DC to 220V 100W Inverter
Posted on Wednesday, April 9, 2008   •   Category: AC / DC Innveters

12V DC to 220V 100W Inverter

This is 100W inverter circuit. It uses 4047 IC and IRF540 Mosfet instead of 2N3055 transistor. Power output is 100W from 2-3A transformer.




0.3-1.5V LED Flashlight
Posted on Wednesday, April 9, 2008   •   Category: LED

0.3-1.5V LED Flashlight

It's a little wisp of a circuit that allows you to drive a blue or white LED from a low voltage. Normally, if you want to light up a blue or white LED you need to provide it with 3 - 3.5 V, like from a 3 V lithium coin cell. But a 1.5 V battery like a AA cell simply will not work. But using the Joule Thief, it works like a charm. Not only does it work with a brand new battery, but it works until the battery is nearly dead-- down to 0.3 V. That's well below the point where your other toys will tell you the battery is dead, so it can steal every last joule of energy from the battery (hence the name). To learn how to make one, watch the video, which is available in a variety of formats.




Build a charger for your iPod or MP3 player
Posted on Wednesday, April 9, 2008   •   Category: iPOD Hacks

Build a charger for your iPod or MP3 player

Using the USB port on your computer to charge your player’s batteries is not always practical. What if you do not have a computer available at the time or if you do not want to power up a computer just for charging? Or what if you are travelling? Chargers for iPODs and MP3 players are available but they are expensive and you need separate models for charging at home and in the car. SILICON CHIP’s new charger can be used virtually anywhere. While we call the unit a charger, it really is nothing more than a 5V supply that has a USB outlet. The actual charging circuit is incorporated within the iPOD or MP3 player itself, which only requires a 5V supply. As well as charging, this supply can run USB-powered accessories such as reading lights, fans and chargers, particularly for mobile phones.




Controlling Stepper Motor with a Parallel Port
Posted on Tuesday, April 8, 2008   •   Category: Stepper Motors

Controlling Stepper Motor with a Parallel Port

This is an easy to build stepper motor driver that will allow you to precisely control a unipolar stepper motor through your computer's parallel port. With a stepper motor you can build a lot of interesting gadgets such as robots, elevator, PCB drilling mill, camera panning system, automatic fish feeder, etc. If you have never worked with stepper motors before you will surely have a lot of fun with this project.




TDA7000 FM Receiver / TV Tuner / Aircraft Receiver
Posted on Tuesday, April 8, 2008   •   Category: FM Radio / Receivers

TDA7000 FM Receiver / TV Tuner / Aircraft Receiver

This simple one chip FM receiver / TV tuner will allow you to receive frequencies from 70 up to 120MHz. With this small receiver it is possible to pickup TV stations, entire 88 - 108MHz FM band, aircraft conversation and many other private transmissions. It is a perfect companion to any FM Transmitter especially if FM band in your area is very crowded. TDA7000 receiver offers very good sensitivity therefore it will even allow you to pickup weaker signals that cannot be heard on conventional FM receivers.




DIY Bench Power Supply
Posted on Tuesday, April 8, 2008   •   Category: Power Supplies

DIY Bench Power Supply

This is a bench power supply with regulated DC outputs -12V, -15V, +5V, +12V, +15V, and variable and one +35VDC unregulated output. I based this bench supply almost exclusively upon Andrew Kilpatrick's design. I did add a few things, but it's essentially the same and I am not writing here to claim any shred of originality. I spent somewhere around 80$ US on the project (including the GIANT transformer), which isn't bad compared with commercial supplies boasting similar features. Please note that I DID find a few minor errors in Kilpatrick's schematic, which have been fixed here. For details, read Kilpatrick's original page.




8W PLL Stereo FM Transmitter with LCD
Posted on Tuesday, April 8, 2008   •   Category: FM Transmitters

8W PLL Stereo FM Transmitter with LCD

Very stable FM transmitter based on TSA5511 synthesizer. Frequency is performed with three buttons through PIC16F84 microcontroller. Frequency is displayed on 16×1 LCD.




Designing PCB with Eagle CAD
Posted on Tuesday, April 8, 2008   •   Category: PCB

Designing PCB with Eagle CAD

To design my circuit boards, I use the freeware version of the Eagle Layout Editor by CadSoft Computer GmbH. The software is located in the download area of their site. I give an introduction to Eagle under the category Eagle CAD. For convenience, here is a list of the posts: * Eagle 1: Description * Eagle 2: Libraries * Eagle 3: Setup * Eagle 4: Schematics * Eagle 5: Components * Ground Pour * Setting All Drill Sizes * Setting All Pad Sizes




Interfacing an AVR Controller to a GPS Mobile Phone
Posted on Tuesday, April 8, 2008   •   Category: AVR

Interfacing an AVR Controller to a GPS Mobile Phone

My goal is to build a kind of a mobile tracker. There are many different use cases you can think of but one of the obvious is a device, that is able to report where it is. This device can be put in your car and it could trigger an alarm, if the car got stolen. Actually it could tell you where it is. There are already mobile tracking devices out there, but they seemed to be too expensive and too closed for my needs. Another option is one of these new Nokia N95 which have built-in GPS. They are really nice, but about 600€, which is not a bargain. So I decided to do my own.




50MHz Frequency Counter
Posted on Tuesday, April 8, 2008   •   Category: Test and Measurement

50MHz Frequency Counter

This is 50MHz Frequency counter based on AVR.It is designed by Ulrich Radig from German.He writes:The construction of a small Frequenzzähers thanks to the current Atmel AVR controllers or even the microchip PIC controller (to name but two) relatively quickly and easily. These are mostly internal timer / counter of the controller is used. The counter is supported by the adjacent signal at high input clock counted. The timer will be the counter to a specified time ever out and reset. Let’s take a look at a 20Hz TTL signal taktet to counter it is now in the counter register for a second of value 20 This is exclusively on the display or serial interface. After a successful auction at a relevant Internet auction house, I bought some 7Segment ads, I had to think of something. The result was therefore a little cheaper said 50MHz frequency counter, which I will not be denied.




PCM2706 High Fidelity USB Soundcard / USB Headphones
Posted on Monday, April 7, 2008   •   Category: USB Soundcards / USB Headphones

PCM2706 High Fidelity USB Soundcard / USB Headphones

This is a high fidelity external USB Soundcard / USB Headphones project that can be built for your PC or Mac. It is based on the latest PCM2706 IC which functions as a high quality, crystal clear 16-BIT Stereo DAC. It is a single chip digital-to-analog converter that offers two D/A output stereo channels, digital S/PDIF output and requires very few external components. PCM2706 includes integrated USB 1.0 & USB 2.0 compliant interface controller and it is conveniently powered directly from USB connection. PCM2706 is a USB plug-and-play device and does not require any driver installation under Windows XP and Mac OSX. PCM2706 chip also provides seven functions that are controlled with tactile switches. It provides volume (up / down), Play, Stop, Previous Track & Next Track controls. These functions do not need any software or driver installation and work instantly after connecting PCM2706 to a computer's USB connector.




PIC Dual Temperature Meter
Posted on Sunday, April 6, 2008   •   Category: Test and Measurement

PIC Dual Temperature Meter

This is a simple to build PIC Temperature meter that allows to measure temperature in two different locations at the same time. Meter can display both Celsius and Fahrenheit values (together or individually) and is capable of measuring temperatures from -55 to 125 degrees Celsius (-67 to 257 degrees Fahrenheit). Never before such a useful and powerful circuit could be built with so little components and yet provide endless possibilities. This is all possible thanks to the use of PIC16F628 microcontroller and 2x16 character LCD display that act like a small computer which can be customizable thanks to upgradeable hex firmware. Presented PIC temperature meter uses two very exciting DS18S20 1-Wire digital temperature sensors. Unlike regular sensors where temperature readings are passed as varying voltage, DS18S20 passes temperature information in a digital format as data. This brings many new possibilities and enables to pass temperature information over much longer distances just over a two wire cable.




Dual Channel 70V PIC Voltmeter
Posted on Sunday, April 6, 2008   •   Category: Test and Measurement

Dual Channel 70V PIC Voltmeter

PIC voltmeter can measure 0-70 Volts which should be more than enough for most of electronic projects providing excellent reading accuracy and resolution. It has two input channels for measuring two voltage sources at the same time. This PIC voltmeter project uses PIC16F876 microcontroller with built-in ADC (Analog to Digital Converter) and 2x16 backlighted LCD display.




PIC Programmer for PIC18F2550
Posted on Saturday, April 5, 2008   •   Category: PIC

PIC Programmer for PIC18F2550

Developed specifically for programming of PIC 18F2550 micro controllers, this parallel port, no-power, programmer is the smallest of all programmers ever built. A DB25 Male Connector, one capacitor and a resistor makes this Port Powered programmer. Programmer takes its power from Parallel Port pins 2-9. VPP for this programmer is 5V and hence "LVP" must be selected in programming software.




AVR Programmer<