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This experimental project shows how to build a simple PI (Pulse Induction) metal detector based on ATtiny13 / AVR microcontroller.My goals were to make a circuit as simple as possible and to use only popular / cheap electronic parts. The device has been tested with very small coil (55mm diameter, about 30 turns of 0.5 DNE) andonly 3V power supply. It’s my first design of PI metal detector and I’m really happy with the results! The prototype was able to detect little coins (6cm distance) and wires in the wall.The code is on Github, here.

How It Works?

Presented metal detector uses PI method togenerate a voltage spike in a search coil connected in parallel with capacitor.Next, ATtiny13 uses an Analog Comparator to measure a decay time to zero of resonant circuit.When a metal object nears the loop it will decreasetime it takes for the pulse to decay to zero. The change in the width of resonance time is measured to signal the presence of a metal target.

Note that the typical PI detector designs avoid resonant circuit and the measured factor is slightly different!”

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