

Weekend Projects reader Robert writes in with his version of the Treasure Finder, a homemade metal detector, including custom board mods and alternative wire coil material. I don’t know where Robert lives, but I hope it’s near lots of treasures, and he cuts us in on any hoards he finds!

I completed this project in about 4 days. I made things harder for myself by not bothering with an etched circuitboard, just wired up on perfboard. Worked first time though!

My capacitors on the coils are very temperature sensitive. If I touch them with my finger, the tone goes crazy. Not sure if this is because I fried them when soldering though. I was going to use a friends oscilloscope but when I wired things up, it just worked and I could fine tune with the brass locknut.

Great guide!

For the coils I used 30SWG ‘kynar wire’ instead of magnet wire as that’s all I could find.

I rushed things near the end as I wanted to be able to take it out and try it. Couldn’t resist adding a power LED though.

Well done, Robert! Have you completed one of our Weekend Projects? Send us an email with your story and get a shoutout on Makezine!


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  1. Eric Gigante says:

    Has anyone else made the “treasure finder”?  I would like to try and make it but was wondering how it works in the end.  Is it a ok metal detector?  I’m looking for something that my wife and I can go to the beach and play around with.

    1. Robert Davies says:

      Like anything it depends on the quality of the ingredients.  I used the cheapest components I could find and its still very functional (enough to find loose change if you listen carefully)  
      However the capacitors are very temperature sensitive so taking it from a warm environment to a cold one can send it haywire.  I solved this problem by covering the capacitors in a thick layer of heat glue (better to use some kind of chemical resin) to insulate them.  Also a sturdy box would help.
      One advantage of building the detector yourself is making your own detector coil.  You should be able to make the coil any size depending on how deep underground you want to search.  I made mine the size of a compact disc and it searches about 5-10cm deep.

      1. Troy Watson says:

        Are you the builder of the meter featured in this article? Have you a blog?

        1. Robert Davies says:

          Yes I built the detector via Steve Hobleys guide (
          Treasure Finder ) on Makezine, and he credits for the PCB design.

  2. Eric Gigante says:

    Is there a way to add a discriminator to this metal detector?  I am interested in buying an in-expensive one but still would like to make one to compare and have fun with.

    1. Robert Davies says:

      I believe a discriminating metal detector works on a different principle so this would not be possible with this design. 

      I bought a cheap discriminating metal detector from Maplin Electronics(uk) and it’s a very sensitive device if you know how to use it.  Like all metal detectors it has trouble discriminating between metals with similar electrical characteristics.  For example aluminium foil and gold/silver are effectively indistinguishable.  Most trash where I was detecting was old iron nails though so it is still useful to filter them out.  

      The detector that I built gives a variable tone whereas the bought one only beeps or does not beep, so I think my homemade one is more fun to use.The Maplin detector needs to be constantly ‘swept’ around in discriminator mode also.

  3. ben says:

    I just finished building the detector and all I can get is a constant tone. I’ve hooked up a volume control and it just lowers the tone. Adjusting the brass nut has no effect either. any suggestions?

  4. roland says:

    hello , plz i need a circuit for a good metal detector for 1 meter underground and more is so good . thnks

  5. i’ve had zero luck building this – and am extremely frustrated. – and i definitely recommend sourcing it from mouser/online rather than going to radioshack, significant difference in cost – like 10X.

    i etched a board soldered it and nothing worked (no tone, or anything). used a dmm to check connections, no obvious issues. de-soldered the board, etched another one, same deal.

    breadboarded it on two tiny breadboards, same results. breadboarded it on a large breadboard, same result. put it on a perfboard, and now the speaker will emit white noise. (very quietly). unwinding the coil hasn’t seemed to help, and using the frequency setting on the dmm on the coil yields 0hz…. which makes me suspect that region of the circuit.