Popular Circuits

Due to the huge interest in this project, I have just recently finished the NEW schematics. The older schematics were scanned and pretty poor quality. These new ones should make it considerably easier to recognize the parts used for the project. The Ming RF transmitter and receiver boards used for this project are relatively inexpensive and perform admirably considering the meager price. Using the quarter wave antennas, I have had some excellent results with operating distance as well as overall operation.

Don't be fooled by the relative simplicity of this transmitter. With 4W of power, it's not a toy! Since it operates in the FM band (88-108MHz), a licence is required for broadcasting. With a good and properly mounted antenna this baby has a range of up to 50km. In mountainous terrain or in built-up areas, this figure is smaller, of course. The circuit is fairly small. The last two transistors dissipate quite a lot of heat. Make sure to protect them with sufficiently large heatsinks or else you'll have a nasty meltdown. The coils are not all that critical, but should still be winded carefully to ensure efficient operation. Use enamel-coated wire at least 1mm thick. As with all RF circuits, work slowly and pay attention to details.

This project is offered totally Free for those who are interested in it. I have tried to make this article as complete as possible, but I will Not assume any lilability for any "Errors or Omissions" in this article. If Needed, I will attempt to help you as much as possible with any problems. However I have no control of your abilities or skills, so build it totally at your own risk!

A VHF band TV transmitter using negative sound modulation and PAL video modulation. This is suitable for countries using TV systems B and G. The frequency of the transmitter lies within VHF and VLF range on the TV channel, however this circuit has not been tested at UHF frequencies. The modulated sound signal contains 5.5 -6MHz by tuning C5. Sound modulation is FM and is compatible with UK System I sound. The transmitter however is working at VHF frequencies between 54 and 216MHz and therefore compatible only with countries using Pal System B and Pal System G.

In the early '80s, I read some articles on LED arrays. They described using arrays of 64 or more LEDs as crude oscilloscopes and other interesting things. I decided I'd make one myself - a really big array, 256 LEDs arranged as 16 columns by 16 rows. In 1983, while I was in my final semester of electronics classes at Monterey Peninsula College, I designed my array. I wanted a high-density array, in part to make the PC board smaller, but mainly to give a better appearance. So, I used the smallest LEDs I could find, 2mm x 2.5mm. I was lucky and found that All Electronics was selling them in 200-packs for something like $20. I bought two packs - a fair sum for me at the time.

This is a high quality power supply with a continuously variable stabilised output adjustable at any value between 0 and 30VDC. The circuit also incorporates an electronic output current limiter that effectively controls the output current from a few milliamperes (2 mA) to the maximum output of three amperes that the circuit can deliver. This feature 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.

I spent much of 1997 designing and building my ultimate dream amplifier, which I named "The Emperor's New Amplifier"TM (TENA) for a quality it shares with the fabled emperor's wardrobe-- transparency. It was also an oblique reference to the marketing hype that pollutes high-end audio. I thought about commercializing it, especially when the lab where I worked announced it was shutting down, but I soon realized that marketing high-end tube amplifiers is not a reliable way to make a living. (I'm paycheck-addicted.) Counterpoint Electronics, a high-end audio manufacturer located in a 45,000 square foot building five miles from where I lived at the time, vanished overnight. Then I thought I might write a magazine article, but the move to Colorado distracted me.

This is a simple low-cost 50W off-line switching power supply. It operates over a universal AC line input range 90-264 VAC and provides a 12VDC output at more then 4A load. Line and load regulation is better then 0.5%. The unit can operate at power line frequencies from 50 Hz to 1 kHz. It has overcurrent, overtemperature and overvoltage protections as well as passive inrush current limiting.

This preamplifier is requirement result of many friends to give a high quality preamplifier, capable to drive high quality power amplifiers with good sound, it's not however difficult to making, it combines simplicity and handiness. It does not allocate a lot of facilities and various filters, but is drawn so the acoustic signal follows the smaller course without it's influenced by stages they do not need, with result the coloration of reproduced sound. It follows the modular philosophy that gives the possibility of changing each module and adapted in yours acoustic taste. Thus it will constitute the base for long-standing listening and experimentations. Use relay in the input selection ensures the smaller way and the better possible quality, because the relay contacts are not influenced easily by temperature changes and environment, offer smaller ohmage and parasitic resistance in the signal course. This of course depends also from the relay quality that you will select; I propose choice of relay small size and very high quality.

The original application of the circuit in Figure 1 was to locate coins, but it applies wherever you need to locate metal objects. The circuit uses a beat-frequency technique: Whenever a metal object comes close to the search coil, the metal causes the coil's inductance to decrease. Though the inductance change is small in itself (a coin, for example, causes a small frequency shift), beating the frequency against that of another fixed oscillator at almost the same frequency produces a noticeable audio-frequency shift.