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Hobby projects

Computer microphones

Electret microphone

Learn how to interface electret and dynamic microphones to the standard computer sound card.

Metal detectors

Metal detector

Theory of operation and schematics of the most common metal detectors used today: Very Low Frequency (VLF), Pulse Induction (PI) and Beat-Frequency Oscillator (BFO).

Wireless microphone

Wireless microphone

The wireless microphone transmitter can be built in an afternoon with simple, affordable and widely available parts. Take care with transmitter circuits. It is illegal in most countries to operate radio transmitters without a license. But the output power of this circuit is below the legal limits of many countries (e.g., USA and Australia).