How to build a Surf PI 1.2 pulse induction metal detector from a DIY kit.

92 Comments
Posted by Blog Master on July 13, 2012 at 4:12 pm

This post will show you how to build your own metal detector from the Surf Pi 1.2 pulse induction kit.

Ive recently been getting into metal detectors as a hobby for the past few months…Despite being for “old retired men” and nerds, metal detecting is fun to do with a friend, the family, or by yourself. Its pretty entertaining, and I think everyone should give it a try. I think my only qualms with the hobby are the high prices for a capable metal detector. Some such as the Minelab, Whites, and Tesoros go for around $400-600 used (and those are the base models)! Personally, an investment of that cost is nearing the edge of what im willing to spend.

Metal Detecting is COOL!

I remember when I was young, my dad got me a metal detecting kit which piggybacked off an am/fm radio (I found nothing but soda cans and batteries in my backyard)…ever since then though, I was always interested in the hobby. As for gear now, I have a Bounty Hunter Tracker IV which I find is a very good detector for around $100 (I prefer it to the Fisher F2), and a Tesoro Sand Shark which I purchased off ebay for $425. Both detectors work well for their applications (BH tracker IV for land use, and the Tesoro Sand Shark for use at the beach and in salt water).

Anyways, back to the DIY metal detector topic…After purchasing my Sand Shark (for more than I wanted to spend), I noticed how small and relatively simple the circuitboard was. This got me thinking about whether or not there were some DIY methods of building a detector which would cut the costs and lower the barriers to entry for the hobby (while still using high quality gear). What I found were forums packed with very intelligent people working on homebrew detectors, schematics, circuits, and designs with the electrical engineering knowledge to make very interesting and cost effective metal detectors. I was delighted to find several schematics for Pulse Induction, VLF, and CCO detectors on the Geotech forum. What I didnt find however, were simple instructions and details on how to go about building them as the information was scattered and often times incomplete since most people had an understanding of what to do already (most seemed to have a very good understanding of EE).

So I did what I do best, I hit the forums and read as much as I could researching, messaging, and figuring out the best detector kit for the money and ease of build for someone who didnt know how to read a circuit schematic. This blog post is to help those who want to build a DIY metal detector kit for a lot less than a commercial detector, yet still have the advantages of a great quality machine with options for future performance enhancements and tweaks…oh yeah, and save some $$$ as well!

I thank the great minds over at the Geotech Forums such as Silverdog, 6666, Tepco, and others who have answered my questions and posted their findings and explanations to help others in building a detector from the kit to the coil. OK, on to the instructions!

Step 1: Getting the Surf PI 1.2 Pulse Induction Metal Detector Kit and power supply.

  • Go to http://silverdog.co.uk/ and buy the Surf PI 1.2 kit (these are dirt cheap, work very well, and are easy to build!) I got two kits for under $90 shipped to California. Andy runs the shop (and is an avid forum poster) and gives lots of help to those who purchase his kits and run into problems. I highly recommend him!
  • Go to http://www.dealextreme.com and purchase the SKU’s below. These are for the power supply to run the kit (1 charger, 4 batteries (you only need 3 but they are sold in pairs), and battery holder:
    • 1 x 936 - 18650 Charger
    • 2 x 5790 - 18650 Batteries
    • 1 x 100996 - 11.1V 3 x 18650 Battery Holder Case Box with Leads
    • 1 x 126133 (OPTIONAL) – Waterproof Plastic Box w/ Strap for flashlight – Army Green (L-size)

Dealextreme is super cheap and shipping is free, the only downside is waiting the 2+ weeks for the items to arrive since it ships from China.

The Surf PI 1.2 kits come with everything you need to make a fully functioning PI metal detector. However, you will need to get creative and figure out what you can use to make the coil (ill show you how later), metal detector shaft (pvc pipe, wood, cut off crutches, etc), coil and board housing (can be anything such as a waterproof case/see optional SKU, and bucket lid), coil connection to circuit board (some rg6 or usb cable), and power supply (which ive already provided links above).

Surf PI 1.2 Kit from Silverdogs – This is what it comes with

Once you have everything in hand, you’ll first want to check out all the parts and sort them out onto a work area, This helps you see your progress and also keep things somewhat organized. Here are a few snapshots of the components which are included in the kit.

Surf PI 1.2 Resistors and other components

Surf PI 1.2 Resistors and other components

Surf PI 1.2 Capacitors and Assorted Components

Surf PI 1.2 Capacitors and Assorted Components

The Surf PI 1.2 Longboard PCB. This is the newest version which has corrected silkscreen indications for R18 & R22

The Surf PI 1.2 Longboard PCB. This is the newest version which has corrected silkscreen indications for R18 & R22

Step 2: Assembly – Its not as complicated as it seems, just work slowly and be careful.

There’s basically two things you have to do to build this board, look at the silk-screened component markings, and reference the PARTSLIST to see which component goes there. For example, in the picture below, you will notice the marking “U5.” In the partslist, you will scroll down till you see U5 and then reference which part is used. In this case its the 78L05. Easy Peasy.

Building the Power Supply for Surf PI 1.2

Building the Power Supply for Surf PI 1.2

Since ive built two of these units, I did have a few suggestions which might be useful for those who are attempting this for the first time.

  • Build the board from Left to Right with the Power Supply on the Left.
  • For the Power Supply Capacitors (see above picture), do a dry run to fit them on the board all at once without soldering them into place. On one kit I built, slightly wider caps were included which took a bit of adjusting to get them to seat nicely with each other.
  • Also pay attention to capacitor polarity. The negative lead is shorter and marked with a grey ‘-’ stripe on the cap itself. On the Surf PI 1.2, two caps are situated in one direction and the third is opposite the other two (look at the picture above).
  • 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 dont easily identify them (at least I couldnt figure it out).
  • When you get to the solder bridges just reuse the cut off leads from the caps or resistors.
Reuse clipped leads from other components for the solder bridges

Reuse clipped leads from other components for the solder bridges

  • When you get to soldering components located near the molex connectors for the coil, power supply, volume, and threshold, do a dry fit to make sure you leave enough space so the components do not interfere with the connectors. I needed to do some adjustment near the R6 and coil connection for the molex connector to fit nicely.
  • If there are several solder holes which interconnect components on the board, fit all the components through first before attempting to solder each individually. Sometimes solder flows too easily and will clog the unused holes. Its best to fit them all at once.
When solder holes are connected, fit the components all at once before soldering

When solder holes are connected, fit the components all at once before soldering

Work slowly and carefully, double check each component to ensure the right part is being used. Remember, resistors are not sensitive to polarity orientation, but capacitors are!

Completed Surf PI 1.2 Pulse Induction Metal Detector Kit Circuit Board

Completed Surf PI 1.2 Pulse Induction Metal Detector Kit Circuit Board – Click for Full Size image

Completed Surf PI 1.2 Pulse Induction Metal Detector Kit Circuit Board solder side

Completed Surf PI 1.2 Pulse Induction Metal Detector Kit Circuit Board solder side – Click for Full Size image

After you have finished soldering all the components onto the board, its time to connect wires from the supplied plugs and terminals to the molex connectors. See pictures below for polarity (otherwise you’ll get potentiometers which work the opposite direction):

Connecting the volume and power supply to Surf PI 1.2

Connecting the volume and power supply to Surf PI 1.2 (click to enlarge)

Connecting the threshold potentiometer to Surf PI 1.2

Connecting the threshold potentiometer to Surf PI 1.2

Step 3: Building the Coil

It seems to me that the most difficult and elusive concepts to grasp of making any detector is building the coil and matching it to the metal detector circuit. While reading the Geotech forums, countless threads are dedicated to just that, however, there are so many variables in doing so I got a little overwhelmed. After trying out several suggestions, I’ve found that the best option is just simply to build an unshielded mono spiral coil using the concepts Tepco has written about on this thread. Its easy to build, gives consistent results, and allows for further modification to the delay sensitivity if desired.

For the purpose of this tutorial, ill just concentrate on how to make a non-shielded coil, but one can easily adapt this design for use with a shielded application. PI units dont require a shield, but those on the forums have found it helps with ground balancing…if made with the correct materials. I tried to use this coil with an aluminum foil faraday shield but was unsuccessful as the coil detected the aluminum foil. Anyways, on to building the coil!

Materials required:

  • 100ft of 24awg speaker wire (I purchased mine from Do it Best hardware store for $9.99)
  • A dvd spindle cover
  • Super glue
  • A large flat piece of cardboard
  • Double sided tape (I used gorilla double sided tape but I think something less sticky would be better)

Essentially,  you’ll set up a coil winding apparatus like the one in the picture shown below and then wind the speaker wire on its thin edge (towards the cardboard) for 30 turns (my coil tested to 1.4ohms using a multimeter).

Coil winding apparatus using a dvd spindle cover, double sided tape, and some cardboard

Coil winding apparatus using a dvd spindle cover, double sided tape, and some cardboard

The double sided tape keeps the dvd spindle stationary, and allows the wire to be temporarily anchored to the base while you are winding. Put a few dabs of super glue as you wind so the coil will stay tight. For added strength, I ran a bead of super glue down the 4 cardinal points of the coil and cut small strips of plastic from the super glue blister pack to press onto the beads. When the glue dries, you can use a flat butter knife and slide it under the coil near the double sided tape to pop the coil up from below, and remove it from the tape.

Fully wound coil with super glue support

Fully wound coil with super glue support

When you’re done, strip and twist the loose inner coil strands of wire together. Repeat this for the loose strands at the outer end of the coil, so the two speaker wires function as one wire running parallel the length – this is to reduce wire resistance.

Spiral coil leads twisted together

Spiral coil leads twisted together

To connect the coil to the detector, connect the inside leads of the coil to the “+”, and the outside leads of the coil wire to the “-” on the circuit board. Dont worry if one of the wires overlaps the face of the coil.

*Some notes on connecting the coil to the metal detector circuit board:

  • For quick testing, use a 3-4′ length of the same speaker wire to connect the coil to the board.
  • If the coil is too close to the circuit board, you may get a slow steady pulsing or beeping on the buzzer
  • If the coil is sitting on or very close to any metal, you may find you cannot detect anything. Test the coil away from any metal work bench, table, or counter which has any metal in or on it. The best option is to take the whole detector kit outside to test away from any RF or electrical interference, such as electrical wires or wireless routers.
  • To permanently connect the coil to the circuit board, one can use a shielded USB 2 cable or RG6 coax (center contact to inside leads of the coil, outside leads of coil to cable shield).

Step 4: Tuning the Detector (offset and delay)

After you’ve connected the coil to the detector, theres a few adjustments which need to be made so you can get the best performance from the kit. You’ll need a multimeter and a small flat-head screwdriver (like eyeglass repair size) to tune the Offset and Delay trimmers.

1. Turn the unit on (volume knob, or just plug in the battery pack) and see that everything is working as it should (you should get an audible response from adjusting the volume and threshold potentiometers). Set the threshold potentiometer till you have a steady tone which is just above silence.

2. Next lets tune the offset. The offset needs to be set to 0v DC. Connect the multimeter positive lead to pin 6 of the NE5534P and the negative lead to ground. It helps to have someone turn the screwdriver for the next step.

3. Use the flat-head screwdriver to turn the Offset trimmer (circled in red below) till you get 0v reading on the multimeter.

Setting the offset on the Surf PI 1.2

Setting the offset on the Surf PI 1.2

Next you will have to adjust the delay till you can detect some gold/coins/metal.

  • Get a gold ring and wave it over the coil.
  • Use a flat-head screwdriver to turn the Delay trimmer till you are able to detect a gold ring at its greatest distance. I had the greatest sensitivity to gold and coins when I turned the dial all the way clockwise (I heard clicking from the trimmer signifying its maximum).
Setting the delay on the Surf PI 1.2

Setting the delay on the Surf PI 1.2

Surf PI Detection Depth:

For reference, I am getting about 11-12″ detection on a US Nickel, faint signal at 10″ on a US quarter, and the same distance for a medium sized white gold ring. For a very thin white gold eternity ring (with miniature diamonds all around it), I get about 5-7″ detection (interestingly enough, when compared side by side with my Tesoro Sand Shark, the Sand Shark only gets about 6″ of depth maximum for any of the above items…so relatively speaking, this kit is wonderful!).

This seems to correlate with the others on the Geotech forum who have built this machine using the stock components. However, this detector has the capability to be tuned to be more sensitive by swapping some components. To learn more about how to do so, check out post #31, #33, and #35 by Tepco on this thread.

Additional Information:

You should now have a fully working pulse induction metal detector capable of finding tons of stuff at the beach. One just needs to figure out how to house the coil, board, and appropriate controls.

For more information and ideas on how to do so, check out the Surf PI thread on Geotech.
Since this detector is essentially a White’s Surfmaster Pi unit, check out the manual on how to adjust the delay and other useful bits of information on detector usage.

For instructions on how to build a straight shaft to use with this (or any) metal detector, see my post here.

DIY straight shaft for metal detectors

DIY straight shaft for metal detectors

Disclosure of Material Connection: Some of the links in the post above are "affiliate links." This means if you click on the link and purchase the item, I will receive an affiliate commission. Regardless, I only recommend products or services I use personally and believe will add value to my readers. I am disclosing this in accordance with the Federal Trade Commission's 16 CFR, Part 255: "Guides Concerning the Use of Endorsements and Testimonials in Advertising."

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92 Comments

  • On March 15, 2013 at 11:40 pm Omar said

    Hello friends, buy the kit and I put it together neatly and carefully, then check the welds.
    I turned it on and had a high pitch, I followed the calibration steps: Connect the positive lead of the multimeter to pin 6 of NE5534P and the negative lead to ground and went to 0Volt.
    Before following currencies tried moving but nothing happened, I returned to calibrate and climbed to 1.37 Volt and there if metal detecting ..
    The second problem is that in 0Volt or 1.37 Volt not calibrate the trimmer as Delay, I said it with an oscilloscope, but would help to know what to do.
    I also want to know which are the points TP1 and TP2.
    I built 4 coils of different sizes and all they detected up to 2 inches is a roll of copper wire of 400 grams, and an inch is the most that I could detect my gold ring …
    6 days ago I keep testing and do not know how to follow.
    Request help and suggestions to finish assembly.
    Is there a technical manual?
    Thank you very much!
    Omar

  • On March 16, 2013 at 10:37 am multieagle said

    I would like to give this a try. However, I am not an electrician nor do I have any skills with use of electronic meters, diodes, transistors, soldering, etc. etc. So my question: Can I expect any measure of success learning as I go? Or should I just walk away from the idea?

    What equipment, other than the kit and other parts, would I need: voltage meter, hobby soldering kit, tools?

    I already metal detect on land and have really wanted to do some water detecting with a pulse machine. However, could never rationalize the cost as I live far from the ocean, and am seldom near a fresh water lake.

    Thanks much.

    Gord

  • On March 16, 2013 at 9:29 pm Blog Master said

    Yep, provided the kit is put together perfectly and none of the components are bad, your kit should just start working if everything was followed in the guide. You can learn as you go, but to fully understand the circuit, you’ll have to read everything you can about the types of components and circuits that are utilized in the schematic. The good news is that all you need is a multimeter, household tools, and soldering iron/solder!

  • On March 19, 2013 at 6:22 am Mick said

    Hi,
    Thanks for your excellent write up. I had very little trouble putting this excellent kit together with your help. I do have some background in electronics but that was 20 odd years ago.
    Do you know of any tips for tuning with an oscilloscope, test points or any pictures etc. of signals
    Thanks again for taking the trouble to put this together.

    Rgds
    Mick

  • On March 23, 2013 at 6:52 am emi said

    finally got my surf 1.2, assembled already, doing the final touch on my coil, lets see if work good.

    what i want to ask is: how I add an headphone, togheter with the small speaker? what i would like to achieve is to have the speaker working, but when i insert the headphone the speaker stop working and the sound come out from the headphone.
    anywhere where I can recycle piezo to make the headphone?
    thanks

  • On March 27, 2013 at 1:49 pm Blog Master said

    Have you tried wiring up the headphone and speaker in parallel?

  • On March 29, 2013 at 9:30 am MichelHollander said

    have you foto’s from how you get the wire from the coil to the machine ??

    best regard Michel

  • On April 10, 2013 at 6:31 pm MichelHollander said

    Hello i came here true a site where soebody tries to sell his home made puls detector. is the working from the surf 1.2 just as deep as on the movie from this kid and have you foto’s from the finished metal detector??

    http://goldfinders.com.au/# http://www.youtube.com/watch?v=kQZasbwb9yM
    Hope to here from you soon, i already ask this question in dutch, sorry for that!!

  • On April 11, 2013 at 8:38 am C Buss said

    I got the kit and excited about putting it together. When checking the components I noticed that two of the electrolytic volt values were different? The 1000uf was 16v instead of 25v and the 220uf was 25v instead of 10v. Not really worried about the 220uf but not sure 1000uf is good since the voltage rating is lower than that called for. Can anyone comment on that?

  • On April 11, 2013 at 7:53 pm Blog Master said

    Best person to ask is to email silver dog, he will know the answer

  • On May 9, 2013 at 4:33 am Harry said

    You should consider compiling this into a PDF and selling it for a few dollars, it might make it a bit easier for us to read through rather than of your blog. Just a suggestion.

    Looking forward to giving this a go.

  • On May 15, 2013 at 11:20 pm zweiundzwanzig said

    First: Thx for your decription.
    I have two Questions on the schematic: Is TS1 and TS2 the connection to speakers/earphones? Why doesnt it connect to ground? What is TP1 and TP2?
    Thx for your help…

  • On May 16, 2013 at 6:56 am Blog Master said

    Tp1 and tp2 is for tweaking the unit with a scope, but you won’t need that unless you’re troubleshooting or customizing the board or building a super sensitive coil. I don’t see ts1 or ts2 markings, but I do see a speaker marking silk screened on the board. Ground connects to battery ground

  • On July 7, 2013 at 4:27 am Maxwell said

    Great! thank you, I know nada about electronics/…well a tad but not enough to save myself.
    You have made it sound like Childs Play!.
    I have been looking at this site for awhile and have built my detector shaft and outer coil all out of electronic conduit pvc.I used 25mm for this, except the coil where I used 20mm and is made up of a T junction and flexi conduit.
    For the continuouse coil, I used Cat5E Multistrand wire.The wire from coil to contreol box is all inside the pvc tubing. so my next step is to purchase a board from Silverdog to get this little project on the beaches.
    Thanks again.

  • On July 25, 2013 at 10:20 am J Pattison and Scott Pattison said

    We purchased a kit, Surf pi 1.2 about three weeks ago and spent several days following your excellent instructions. After following the set up procedure we are pleased to say it worked first go!!

    Spent the evening on the beach finding two one pound coins, four fishing hooks and various nails and screws. The coins were app 150mm deep.

    If i may a handy hint, take a photo of the board so when assembled you can read what markings are under the components, (useful when checking the assembly).

    We used a plastic overflow pipe for the handle but found it bent to much, we then used a metal shaft but could not get the detector to work correctly (even after running through the setup procedure again and again)We now have to find a better shaft.

    The batteries caused a few problems we could not get a holder?
    The way we held the three off batteries was to use the plastic water pipe, slide the batteries
    inside the tube drill a small hole through the tube 5mm from the end and slide a copper ridge wire through the holes bend ends over to secure, this is the + end.

    The other end, purchase a plastic Stopend, drill a hole through end for the – wire (fit a small spring on inside and solder to the – wire. Make sure the main tube is the correct length so when the end is fitted all the batteries will push up together, this works fine. ( any one require a diagram let me know).

    We are very pleased with the kit and to you for the assembly instructions.

  • On July 25, 2013 at 10:33 am jon said

    Please, a need help. I buil the Surf 1.2 kit, everything right, but dont´s works. Dont´s do de Beep, only if I take the board with the hand,do the beep. But dont´s detect metal. I build 4 diferent coils, and nothing.

  • On July 29, 2013 at 8:07 am Blog Master said

    Make sure you do not have the kit on or near any metal within 4 feet all around, if you do it will cause the unit not to beep as it will interfere with the operation

  • On September 18, 2013 at 6:42 am Mario said

    I am finishing to build the surf PI.
    What is the ideal value of Coil (uH) for the surf PI circuit?
    And about resistence Coil?

    Thanks for help me.

  • On September 23, 2013 at 5:09 pm Mark said

    Well I built mine and it appeared to work however while I was trying to set the 0v on pin 6 I slipped with the ground probe which shorted the Fet to the ne5534 I then could not set the voltage at all. so popped to Maplin’s and got their last ne5534ap fitted it and all is well again so be carful with your probes when measuring on pin6
    Dont be cack handed like me haha.

    I built a 12v battery pack which is just a bit longer than the board, and plan to fit it all into plastic tubing and seal it all up so it is waterproof!

    https://dl.dropboxusercontent.com/u/22562965/mysurf.jpg

    Tried to add the image but not sure if it will attach
    Cheers Mark

  • On October 26, 2013 at 7:03 am Gary said

    the wire for the coil is it 2 core or single core? studying the picture it looks like 2 core joined together is this correct?

  • On October 28, 2013 at 1:32 pm Blog Master said

    its just regular speaker wire so it has two separate wires bonded together. But you will tie those two ends together in effect making one wire although two cores.

  • On November 4, 2013 at 2:40 pm John said

    Hi, thanks for the write up on the detector. I have finished building mine due to your instructions. I have a question about the coil though. I have wound 30 turns of 24awg speaker wire and connected the two wires together at each end. I checked the resistance with a digital multimeter and I have 39.6. Ohms. Yours tested at 1.4. What do you think went wrong with my resistance being off so far from yours? I do get a change in signal and have not made the adjustments yet but they are very weak at only about 4 inches away. Thanks for any assistance you can offer.

  • On November 17, 2013 at 9:30 pm Todd TX said

    Hi,
    Great instructions! I’m wondering if you would put something out on building coils and especially casting or other methods for housing the coil.
    thanks

  • On January 17, 2014 at 6:55 am David said

    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?

    Thanks!

  • On January 22, 2014 at 12:38 pm Gary said

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

  • On January 23, 2014 at 8:34 am John Williams said

    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!

  • On January 23, 2014 at 8:16 pm Blog Master said

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

  • On February 13, 2014 at 8:18 pm Jim said

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

  • On February 14, 2014 at 12:55 pm Geo said

    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.
    Geo

  • On February 16, 2014 at 9:53 pm Blog Master said

    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.

  • On February 22, 2014 at 10:56 pm Jose said

    What is the frequency range?

  • On February 26, 2014 at 11:13 pm Jim said

    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.

  • On March 28, 2014 at 8:03 pm richard said

    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.

  • On March 29, 2014 at 8:05 pm Blog Master said

    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.

  • On April 2, 2014 at 12:35 pm Erik said

    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!!

  • On April 2, 2014 at 6:14 pm Blog Master said

    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…

  • On May 29, 2014 at 12:04 pm morphy said

    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

  • On June 4, 2014 at 4:09 am Dave P. said

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

  • On June 12, 2014 at 7:27 pm Paul said

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

  • On June 13, 2014 at 9:21 am pandora said

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

  • On June 14, 2014 at 10:12 am Paul said

    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.

  • On July 19, 2014 at 6:09 pm Colin Cornelius said

    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

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