Posted on Saturday, October 31, 2009 • Category: Battery Chargers
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.
Posted on Saturday, October 31, 2009 • Category: FM Transmitters
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.
Posted on Saturday, October 31, 2009 • Category: PIC
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.
Posted on Thursday, October 29, 2009 • Category: FM Transmitters
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.
Posted on Tuesday, October 27, 2009 • Category: FM Transmitters
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.
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