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.

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.

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.

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.

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 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.

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.

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 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!

Several people have requested that I set up a web page with construction details for the second of two power amplifiers that I published in Audio magazine. This amplifier is the monophonic 270 watt Double barreled Amplifier. For the original article, I specified plus and minus 85 V dc power supply voltages. The voltage can be increased to about 93 V to obtain a power rating of 300 W.

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.

This is a very simple RF transmitter circuit that consists of the Holtek HT-12E encoder chip and AM 418MHZ-transmitter module (WZ-X01). Using the hybrid RF xmit/receive modules make building the RF remote control a lot easy. The transmitter can be powered with any voltage from +3 to +12V. The recommended oscillator is Foscd (decoder) = 50 Fosce (encoder). See data sheet for more details. The circuit diagram for the receiver (WZ-R01)is shown in figure 2. The decoder U1(HT-12D) receives serial addresses and data from the encoder that are transmitted by the RF transmitter module.

This project has not been called a GOLD! detector as this name has been left for the more complex detectors that actually discriminate been gold and other metals. There is an enormous difference between detecting gold and ordinary metals (called base metals). Apart from the fact that gold is over 1000 times more expensive, its magnetic differences are such that we can produce a metal detector that will discriminate between metals, both ferrous and non ferrous, and GOLD!

I think everybody saw Laser Effects that shows up stages, discos or festivals. There are two categories on the laser effect. One is Beam Effect, it shows the laser beams that flying in the air to the audience. The other is Screen Effect, it shows the laser graphics that drawn on the screen by a moving laser spot. The first one is preferred better than second. The beam effect is very exciting, so that many Laser Light Shows are also being given. The laser equipments working in the laser light show are called Laser Projector.

A 'TV modulator' is really no more than a transmitter. It is a very small transmitter, admittedly, but none the less that is what it is. What does a modulator actually do? In general -and this design is no exception to the rule - it is a simple oscillator that generates a frequency somewhere 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.

The simplified circuit [Fig.2] shows that each sub-amplifier consists of two voltage gain stages. The first stage consists of a complementary two stage common emitter [Q1-7] whose gain is about x2.3. The second stage is a current mirror stage [Q13-14] which drives the voltage across a load resistor tied to 0V.

Figure 1 shows a technique for generating a high-quality sine wave from a square-wave source. Using textbook methodology, you can easily convert a square wave into a sine wave: Feed a square wave at the desired frequency into an appropriate four- to six-pole lowpass filter. The filter's output is a sine wave; the higher the order of the filter, the purer the sine wave. In practice, this conversion technique is difficult to implement, because such filters require several components and are difficult to adjust.

A regenerative radio receiver is unsurpassed in comparable simplicity, weak signal reception, inherent noise-limiting and agc action and, freedom from overloading and spurious responses. The regenerative radio receiver or, even super-regenerative radio receiver or, "regen" if you prefer, are basically oscillating detector receivers. They are simple detectors which may be used for cw or ssb when adjusted for oscillation or a-m phone when set just below point of oscillation. In contrast direct conversion receivers use a separate hetrodyne oscillator to produce a signal.

This is an image Schematic. No Description available.

A few years ago I built one of those projects that never worked, but it did do something unusual. The PSU side of a portable receiver was very unusual in that it GENERATED RF in the HF spectrum. The fault was traced to a couple of errors on the PCB. After a little investigation I used the error to build myself an HF CW QRP transmitter, based upon an LM317T voltage regulator chip!!! The circuit is given above and needs very little explanation. It operates from a 10 volt supply and regulates to about 4.5 volts. This is used to excite the tuned circuit VC1/L1. The tapping is about 3% of the total number of turns of L1. A 6% L1 tap is coupled to the control input if the LM317T regulator chip and BINGO - It "hoots". You can draw WATTS of power from a 12% tapping of L1.