Newest circuit diagrams
A single chip metal detecor with a range of a few inches. This is useful for decting nails or screws in walls and floors, or for locating buried mains cable.
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A microphone amplifier that may be used with either Electret Condenser Microphone (ECM) inserts or dynamic inserts, made with discrete components.
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A variable power supply with adjustable voltage and current outputs made with the L200 regulator.
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This is a similar power supply that I used to power my FM Transmitter. After suffering long problems with mains hum, this design using a pi filtered C-L-C approach. This circuit offers excellent ripple rejection.
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A simple device to indicate various levels of hot water in a tank.
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Beeper or flashing LED alert 1.5V battery powered portable unit
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Simple photo-sensitive circuit. 3V battery supply
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This circuit can be used to "sweep" an area or room and will indicate if a surveillance device is operative. The problem in making a suitable detector is to get its sensitivity just right; too much and it will respond to radio broadcasts, too little sensitivity and nothing will be heard.
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Beeps if you leave open the door over 20 seconds
3V battery operation, simple circuitry
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I've had a few requests for a quiz circuit, so here is a 4 input design which can easily be modified.
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