Commercially available BFO metal detectors are not common. More common are VLF (very low frequency) and PI (pulse induction) types.In short: a metal detector consists of two oscillators,one the search coil[part of an oscillator] and a referance oscillator ,the two frequences are non linearly mixed.Oscillators are adjusted for O beat . When a metalic object comes near the search coil ,its inductance is changed causing a change in frequency,the beat note is herd as a tone.
We'll look forward to seeing your design and a report on its performance.lol... I actually in the middle - well, the end- of a project where me and my group have to make a metal detector , using one coil.
I can see it is an old thread, but hey..would love to share what I have ( have to hand in on may 26th09).
yeah? am thinking of posting the whole thing in the project forum.We'll look forward to seeing your design and a report on its performance.