This PSU has been especially designed for current-hungry ham radio transceivers. It delivers safely around 20Amps at 13.8V. For lower currents, a separate current limiting output, capable of 15ma up to a total of 20A has been added...

This page features basic, visible light photo-detector circuits that can be used to detect trains. These methods would normally be used with the photo sensor mounted between the rails...

This is a slightly revised version of the 6-transistor H-bridge designed by Mark Tilden and found on the BEAM Tek website (now only available via archive). I encourage anyone interested in H-bridges to read Mark's article, as it gives an excellent....

The supply of circuit becomes from a AC line in the J1. This voltage can be from a separate transformer 2X12V (the prices of materials that I give it is for 2X12V AC), from existing coil 12V in their M/T of power amplifier or if it cannot become somebody....

Based on Valvo FD-1A module, TBA120, and MC1310. Operation of the receiver is based on the phase locked loop principle. The FD-1A contains an RF amplifier, oscillator and mixer (made with BF324, BF451 and BF324 transistors, respectively). Tuning is performed....

Using the circuit of 40-metre band direct-conversion receiver descr- ibed here, one can listen to amateur radio QSO signals in CW as well as in SSB mode in the 40-metre band. The circuit makes use of three n-channel FETs (BFW10). The first FET (T1) performs....

Once again my collection of projects creation has been interrupted by another necessity. Patrick and other people have asked me for a circuit of a VHF power amplifier. These circuits are my "standard" building blocks that can be used to amplify RF power....

This simple circuit generates narrow pulses at about 700-800Hz frequency. The pulses, containing harmonics up to the MHz region, can be injected into audio or radio-frequency stages of amplifiers, receivers and the like for testing purposes. A high-pitched....

The circuit comprises simply the PWM source, capacitor C, and resistors RD and RW. For CMOS circuits, you calculate the open-circuit output voltage as VCONT=D½§VDD, where VCONT is the control circuit`s output voltage, D is the PWM duty cycle, and VDD is....

Tired of always spending money on flashlight batteries only to have them fail just when you need them? Try this simple circuit out. It would make an excellent science fair project. The white LEDs are quite bright, they provide enough light to illuminate a....

You'll find that this is a very easy project to build. It will transmit good quality sound in the FM band ( 88 - 108 mhz ). One inportant item is that the IC chip operates on 3 volts DC. The chip will get destroyed if it is operated on any voltage higher....

A complete AM radio set based on the MK484 IC (formerly ZN414). It uses a PNP transistor and can drive a 150R loudspeaker. Chad has built a complete radio receiver using 1 IC and a single transistor. The IC requires around 1.2 to 1.6V and this is supplied....

This is a circuit thich I originally included in my book, 22 Tested Transistor Projects, published by Babani Press in 1976 (ISBN 0 900162 63 S). It is one I had great fun with. It uses the PUT Complimentary Feedback Pair as a sensitive detector of changing....

Here`s a simple lie detector that can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as the ones the professionals use, but it works. It works by measuring....

The circuit in Figure 1 eliminates the need for adjustments. The circuit uses dc-coupled feedback to control the current in the output resistor. Hence, the output voltage is predictable and constant...

A simple but useful circuit for all they have problem with parking car, in spaces without good visibility. The electric circuit appears in picture 1. It is constituted by the IC1 and components round he. When the car bumper touch soft and push lightly the....

The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. Try Conrad Electronic for what appears....

Electromechanical door chimes can enhance your home, but they are vulnerable to costly repair problems. A defective pushbutton switch or a careless visitor can maintain the chime in an energized state for a prolonged period, thereby damaging the chime. The....

Take care with transmitter circuits. It is illegal in most countries to operate radio transmitters without a license. Although only low power this circuit may be tuned to operate over the range 87-108MHz with a range of 20 or 30 metres...

This is a simple circuit which I built to one of my audio amplifier projects to control the speaker output relay. The purpose of this circuit is to control the relay which turns on the speaker output relay in the audio amplifier. The idea of the circuit is....

It is quite easy to get a watt or more with very simple equipment, but to get more than 5 watts becomes a little more difficult. This article describes a 10 watt linear amplifier that is capable of delivering over 15 watts into 50 ohms and uses cheap plastic....

If you want to build one yourself, you have to get two audio transformers which have 1:1 transformation ratio and greater than 1 kohm impedance. There are high quality audio transformers in the markes that meet those specs, but those can be quite expensive.....

This circuit provides 16 watts of amplification. it is built using two LM383 power audio amplifiers. use suitable heat sinks with the ic`s...

The circuit is very simple and incorporates darlington output transistors that will provide more than enough output current than is needed to drive a 3-ohm speaker. The gain may be pre-set for a variety of input levels, making it suitable for amplifying....

Forget to turn off the ceiling fan in your bathroom? Install the simple timer in Figure 1. It`s located out-of-sight in the fan unit, and you turn it on via the wall switch. The circuit costs virtually nothing, using "junk" parts. When ac power appears, a....

For designers of radar or sonar echo-ranging systems, an echo imitator can ease development and adjustment chores by generating a controllable pulse that's similar to an incoming echo signal. A decade ago, you'd probably use several 555 timers and their....

Simplified circuit diagram of the two-stage Colpitts oscillator. In comparison with the classical single-transistor Colpitts oscillator [1,2,5] the two-stage modification includes an extra transistor Q2 and an extra capacitor C3. We note that both....

This circuit will allow you to turn on any piece of equipment that operates on 115 volts ac. The receiver circuit is based on the Radio Shack infrared receiver module (MOD), part number 276-137. It is also available from some of the other sources listed on....

The versatile 5 pin L200C regulator offers both voltage and current regulation in a single package. The IC also features thermal shutdown and input over voltage protection up to 60 Vdc. The package is also available as L200CV which has straight pins for....

The circuit in Figure 1 is an FPGA-based, synchronous FIFO that uses the same clock for read and write operations. The circuit can generate FIFO-occupancy flags with a minimum of logic. The boxed area in Figure 1 shows a more conventional occupancy meter.....

This ZIP file contains information about building a small radio transmitter, which has a PCB 1.75" x 2.5" (45mm x 68 mm) and has a range of about 30 yards or so. The documentation with the circuit says the freq range is 100-108 MHz, but I have found it to be....

In recent years, following CD`s introduction, vinyl recordings are almost disappeared. Nevertheless, a phone preamplifier is still useful for listening old vinyl discs from a well preserved collection. This simple but efficient circuit devised for cheap....