In this article I discuss making a metal detector. A metal detector is very simple to make. In fact, it’s nothing but a voltage divider. In my article on negative resistance, I talk about a voltage divider circuit that instead of stepping down voltage, actual increases it.

It will be this very circuit that serves as a metal detector.
That circuit being a voltage divider is made of voltage source and two resistors. These resistances are not normal dc resistances but instead AC resistances: namely a capacitive reactance and an inductive reactance.

You can make a voltage divider circuit with these special resistors.

Now, by changing the inductance of the inductor, you will drastically change the amplitude of the output voltage.
It just so happens that by simply bringing a metal into the vicinity of the magnetic field of the inductor, will change the inductor’s inductance –

after all an inductor works by using magnetic fields to store current! In this case I place a US quarter on folded paper so that there is space between the inductor and the coin.

Making a functional working metal detector using a simple voltage divider circuit. You do not need much electrical experience to follow this article.
And the result: The voltage drastically changes -
From 12V..... 16V!

And that is a metal detector. Simple as that!

Inductor Capacitor Oscillator Caculator Applet

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