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This circuit, enclosed in a small box, is placed in the fridge near the lamp (if any) or the opening.... [read more]

MP3 players are all the rage these days. The smaller ones in memory-stick format are particularly easy to take with you; your very own ‘personal sound system’ on the move! It’s when you want others to share your taste in music that you find these players to have a lack of power. You can get round this problem with the help of the MP3 booster, a small amplifier that can be used to connect your MP3 player directly to your Hi-Fi. When you next invite your friends to a party you can ask them to bring their ‘personal music’ as well as the usual drinks!... [read more]

This timer was deliberately designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight.... [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]

The EQ-2 it is a circuit of graphic equalizer 6 band of regulation. Each band is regulated from the potesometers RV1-6, that are, for better optical indicate of regulations, Fader. This does not mean that we cannot him replace with simply potesometer. In the center of regulation potesometer, the gain is null (flat), but in terminal has +/- 15 db, boost or cutting off, respectively. For stereo operation, it will be supposed two times.... [read more]

The circuit is a microphone amplifier for use with low impedance (~200 ohm) microphones. It will work with stabilized voltages between 6-30VDC. If you don't build the impedance adapter part with T1, you get a micamp for higher impedance microphones. In this case, you should directly connect the signal to C7.... [read more]