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This circuit [Fig.1] is a class AB stereo audio power amplifier designed by Quasar for quality hi-fi applications using a TDA2005 module. It is easy to construct and has a minimum of external components. The module has output current protection and thermal protection. This is circuit, which produces an excellent sound. The supply voltage required 9V-18V DC at 1 to 2 Amps. Maximum output power will only be obtained with a power supply of at least 2A at 15V DC, and using 2 Ohm speakers or 2 by 4 Ohm speakers in parallel. However approximately 4W/ch. can be obtained with only a 15V DC, 1A supply into 4ohm loads.... [read more]

This circuit allows you to set a limit on the maximum output current available from your PSU. It's very useful when you power-up a project for the first time - or carry out a soak-test. By setting an upper limit on the current available from your PSU - you can protect both your power supply - and any device connected to it. It offers a simple and cheap alternative to the Current Limiting Power Supply... [read more]

2 Transistor FM Voice Transmitter... [read more]

This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. LEDs are cheaper than photodiodes and come with a built-in filter, which is useful when the application involves colour discrimination. The photo-voltage of a red LED (its bandgap voltage) is typically about 2V. The source impedance of this voltage is about 800MΩ in daylight, rising to infinity in darkness. A TL071 JFET input op amp is used to amplify and buffer this extremely high impedance signal.... [read more]

Most homes today have at least a few infrared remote controls, whether they be for the television, the video recorder, the stereo, etc. Despite that fact, who among us has not cursed the light that remained lit after we just sat down in a comfortable chair to watch a good film? This project proposes to solve that problem thanks to its original approach. In fact, it is for a common on/off switch for infrared remote controls, but what differentiates it from the commercial products is the fact that it is capable of working with any remote control.... [read more]

This circuit is intended for children fun, and can be installed on bicycles, battery powered cars and motorcycles, but also on models and various games and toys. With SW1 positioned as shown in the circuit diagram, the typical dual-tone sound of Police or Fire-brigade cars is generated, by the oscillation of IC1A and IC1B gates. With SW1 set to the other position, the old siren sound increasing in frequency and then slowly decreasing is reproduced, by pushing on P1 that starts oscillation in IC1C and IC1D.... [read more]