Posted on Monday, July 11, 2011 • Category: FM Transmitters
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.
Posted on Monday, July 11, 2011 • Category: Sensors
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.
Posted on Saturday, July 9, 2011 • Category: AVR
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.
Posted on Saturday, July 9, 2011 • Category: Phone Circuits
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.
Posted on Saturday, July 9, 2011 • Category: PC Circuits
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.
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