Electrical – What kind of power supply do you run through a metal detector coil?

acdcpower supply

I am planning on building a decent metal detector out of a variety of existing components but although I understand the basic concept of most metal detectors involves the induction of current in a metal object by a coil on the detector, I am slightly confused on what type of power supply a metal detector needs. From what I have read, it sounds like it runs AC through the coils, but I haven't actually seen any sources say anywhere that it is explicitly alternating current, but describes something that sounds like alternating current but is called something else (Pulsed or something like that). Is it alternating current or is it something else that I'm not familiar with? I am not asking what AC or DC is, just what is used in a metal detector. Or does a metal detector typically use a combination of DC and AC, converting DC to AC and back again?

Best Answer

This is the simplest metel detector circuit I could find.

Note how it runs on a battery (B1 on the right). Batteries only deliver DC so the circuit is powered by DC.

But in order to detect metals, a coil is used (L1).

That coil together with C1 and IC1a forms an oscillator.

That oscillator applies AC to the coil.

Any metal objects near the coil will influence its value and that will change the frequency at which the oscillator runs. That oscillation signal can then be fed to a radio or some detection circuit which is not shown here.

So: the circuit is powered by DC

But it generates AC from that DC to make the metal detection work.

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