Casting about for metal detector circuits, I came across this plan at circuitdigest.com. I have only the dimmest understanding of the circuitry, and I don't understand the Arduino sketch code at all.
I fabricated a coil and breadboarded the circuit. It does work after a fashion, but it strikes me as a peculiar, flaky device. Here's a view of what I have so far.
Never mind the presence of metal, the least disturbance of the coil is apt to set the buzzer sounding off and the LED flashing.
Placing the coil on a metal object yields a hearty buzzing and flashing for a few seconds.
If the coil is left undisturbed on the metal, the buzzing and flashing cease.
If the coil is then removed from the metal object, the result is intense buzzing and flashing for a few seconds.
Eventually, the buzzing and flashing settle down and the thing goes quiet, except for the occasional, random buzz and flash for no perceptible reason.
The device doesn't so much respond to the presence of metal as it responds to disturbance by metal either entering or leaving its field.
I'm thinking to do up a halfway proper prototype with a long shank and a handle and all, that I can take out in the backyard and probe around with, to give the circuit a fair trial. We'll see.
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A Prototype -- FRIDAY, APRIL 20, 2018
Here's what I came up with for a quick-and-dirty prototype.
I took it outside for a trial, and my verdict is that the thing is useless. The device is always randomly sounding off -- a random noise generation circuit would yield about the same effect. The device is just too flaky to be of use.
Anyway, I now have a basic framework on which I can try out other approaches. There are surely better ways to go about constructing a metal detector.
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