vega electronics metal detector circuit using bc547

[jaseela123d]

The metal detector circuit shown here should represent the limits of simplicity for a metal detector, but the design works surprisingly well. It uses only a Schmitt inverter hexadecimal 40106 IC, a capacitor and a search coil - and of course the batteries. An IC1b pin 4 cable needs to be connected to a medium wave radio antenna, or it must be wrapped around the radio. It can be used even as hand held metal detectors.


As shown, the metal detector gives a respectable range for blow frequency operation (bfo) up to 90 mm for a bottle cap. In fact, for the ultimate in simplicity, the capacitor C1 can be omitted. In this way the author reached an incredible range of 150mm for the bottle cap. However, with the frequency being raised to more than 4MHz, instability becomes a significant problem.