94 responses

  1. David
    January 17, 2014

    Hey there, great blog!

    Quick question. In the picture with the volume knob and the battery pack, what are those red deals you are using to attach the wires? Fuses sealed in something?


    • Blog Master
      January 23, 2014

      Hey david, those are insulated telco butt connectors. 3m UR2 connectors

  2. Gary
    January 22, 2014

    Great article! I built two of these with your help! thank you!!

  3. John Williams
    January 23, 2014

    Hello – Thanks for the excellent write up on this kit. If you get chance to edit this, your paragraph about all the red Wima caps keeps referring to them as resistors. Just a bit confusing for new to soldering type folks who’ve only done woodwork, Lego and Meccano!

    There are Five (5) 100nF [Polyester film (+/-10%)], and Four (4) 1nF [Stacked Polyester film (+/-5%)] resistors (my kit were red colored Wima 0.1 and 1000 resistors). Before you start, mark them and keep them separate. While building, its easy to lose track of which are which since they look nearly identical and the markings on the resistors don’t easily identify them (at least I couldn’t figure it out).

    I’ve done electronics for 40 years now. There are so many nice kits out there I no longer bother making my own boards etc.
    Off to Normandy in June for the D-Day 70th. Maybe I’ll find a nice big UXB and get on the news with the bomb squad!

  4. Jim
    February 13, 2014

    My first stop in looking for DIY metal detectors. I think I’ll go with this. Thanks for posting.

  5. Geo
    February 14, 2014

    I am looking forward to getting the board kit from silverdog but figured in the mean time, I can build the rest of the unit, coil, handle/shaft and a case for the control board etc.
    On the coil you built, you use 24 awg, is there any reason not to use 18 awg and do less turns/wraps. I was wondering because I have like six 100ft rolls of 18 awg. I figure since it is larger, possibly doing only 24 wraps/turns.

    Any help/advice on this would be great.

    Also, I had seen a utube video where some are making an elyptical coil instead of round, which works best or is one better than the other as far as depth and detection goes.

    Thanks in advance for any answers or advice.

    • Blog Master
      February 16, 2014

      Unfortunately I can’t remember the details about using 24awg vs others except that the differences in awg translate into different turns etc and different uh values for the coil. Try checking out the geotech forums to find info on building a fast coil.

  6. Jose
    February 22, 2014

    What is the frequency range?

  7. Jim
    February 26, 2014

    Sorry if I’m posting in the wrong place, but does ‘Andy’aka ‘Silverdog’ ship to Mexico. I’ve emailed twice and not received a reply.

  8. richard
    March 28, 2014

    Please help, I have built the surf pi 1.2 and although it works it will only detect large metallic objects like a group handle for a coffee machine when less than 10 cm way. This is with the coil made out of speaker wire as in the guide on this page and 11.5 volts of power. I have tried other coils including 24 awg wire also with a damping 200 ohm resistor in parallel which worked even more poorly. I have done the required tuning of the variable resistor trimmer pots and made sure all components are in the right place and are soldered correctly. I have checked the pcb soldering with the wiring schematic. Everything is correct. I am getting close to giving up on the surf pi 1.2. This is very disapointing considering the 16 hours of effort spent up to this point.

    • Blog Master
      March 29, 2014

      hmmm…you may want to write to silverdog. There may be a faulty component in the circuit. I get great sensitivity. Make sure you do not test this near any electrical interference. Go to the beach and test it there.

  9. Erik
    April 2, 2014

    I also built this same kit form silverdog, one of two that I bought. The second one will eventually be a fully submersible MD, one I get this first beach MD working as best as possible. I’m having a small issue with the coil, I’m hoping someone can help me.

    I’ve built several coils, but so far the best depth I’ve gotten yet was by using this same coil outlined in this article. Easily over 12″ in the air using a larger gold ring. Here’s the thing… I took it down to the beach and am getting all kinds of false signals. I really think my coil needs to be shielded, and I’ve tried using foil, and aluminum foil tape. However it never seems to work right and the coils wants to detect the shielding material. Is this a common trait of spiral wound coils? Why can’t I shield this properly? I even tried grounding the foil shielding, and it still didn’t work. i’ve searched the net and have yet to see a single, spiral wound coil such as this showing it properly shielded. Only regular coils, not spiral wound. If anyone has any ideas, links, or anything… i’ll be very happy!!

    • Blog Master
      April 2, 2014

      My friend had this happen as well, turned out the connection to the coil was the problem. Make sure everything is solid, any wiggle in the cable going to and connecting to the coil will cause a false signal when you wave it back and forth scanning the beach. Also lower the sensitivity… If no change its the connection and wiggle from somewhere down the line…

  10. morphy
    May 29, 2014

    Friends, Because of some problems I’m not able to buy this kit from Silvergod but I noticed, there are blueprints of the kit on the website such as partslist and Schematic which I thought they might be enough for me to go ahead and build the thing. I actually wanted to know your idea if the blueprints are completely there to go to or its not all of it which I need to build the kit myself…?
    Thanks in advance

  11. Dave P.
    June 4, 2014

    I just received a kit and looking forward to giving this a try…. I’ll keep you posted.

  12. Paul
    June 12, 2014

    Thanks for the write up. Can we assume the wima caps have no polarity?

  13. pandora
    June 13, 2014

    Thank you for all this detal, schematics and advice.
    I like to know if the coil must to be shielded or no?
    thank you

  14. Paul
    June 14, 2014

    I just finished my surf board. Thanks for the write up and pics. Do the red caps have polarity? I have mine facing down or to the left. I’m using a plastic flower pot for my coil form. It is 28 cm in diameter.

  15. Colin Cornelius
    July 19, 2014

    Hi i am having trouble working out stacked polyester film i have been supplied wima 4x 1000×100-3xwima0.1×63-2×0.1×100 all red.all so a larger watt with no markings like you show in your tutorial pictures i am excited in doing this project as i am a retired vet. your tutorial is excellent and your help to every one is great.I look forward to hearing from you.
    Kindest Regards
    Colin Cornelius

  16. Colin Cornelius
    August 5, 2014

    Hi can any one help i have assembled my surf pi pcb and have 11.0 volts at the coil have i put something in wrong or shorted out something thank you if any one can help would be great.Regards Col

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