Circuit-Zone.com - Electronic Projects
Posted on Friday, March 25, 2011 • Category: Test and Measurement
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.
Posted on Friday, March 25, 2011 • Category: 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.
Posted on Friday, March 25, 2011 • Category: USB Circuts
 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.
Posted on Friday, March 25, 2011 • Category: LED
 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.
Posted on Thursday, March 24, 2011 • Category: Test and Measurement
 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.
Posted on Thursday, March 24, 2011 • Category: FM Transmitters
 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.
Posted on Wednesday, March 23, 2011 • Category: Audio Attenuators
 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.
Posted on Wednesday, March 23, 2011 • Category: Miscellaneous
 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.
Posted on Wednesday, March 23, 2011 • Category: USB Circuts
 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.
Posted on Tuesday, March 22, 2011 • Category: USB Circuts
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.
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