…Treasure Finder for MAKE:Projects

by Stephen Hobley on November 19, 2011

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This was my favo[u]rite of all the MAKE projects I’ve been working on.

This project uses 2 oscillators in a configuration very much like a Theremin to create a beat frequency (BFO) metal detector.

Range is a few inches for the smaller detection coil, but the detection range can be increased by adding a larger coil.

What I really liked about this project was how the oscillator coil is tuned – using a brass nut on a PVC sleeve.

Full build instructions can be found here…


{ 6 comments… read them below or add one }

Wayne Hilburn February 20, 2012 at 5:17 pm

Why such a large circuit board? I realize there are signal generation areas of the circuits, but for such few componants, it seems very large for its purpose.

Wayne Hilburn February 20, 2012 at 5:22 pm

By the way, ive enjoyed the projects on your site and I do a lot of the same kinds of things, so I wanted you to know I wasnt being facetious with my previous question, my thoughts are that, as with the salt in your etchant soultion and the “out of the box” concepts the problem solving process added to your skills, that there may be a purpose for such a large circuit board.

Stephen Hobley February 20, 2012 at 5:24 pm

I goofed up when I printed the etch mask – I printed it at 300dpi, and that was the last piece of transfer paper I had!

Wayne Hilburn February 21, 2012 at 5:43 pm

You made me smile…..
Glad im not the only one…… 🙂

alex April 7, 2013 at 9:31 am

how deep in the ground can you pick up a coin?

gert strooizout November 8, 2013 at 5:13 pm

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