![\"Metal](\"https:\/\/i0.wp.com\/www.adrianandgenese.com\/blogger\/wp-content\/uploads\/2012\/07\/tesorotigerfull.gif\" "\\"Metal")
<\/a><\/p>\nI 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<\/a> 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).<\/p>\n 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\u00c2\u00a0the 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\u00c2\u00a0with the electrical engineering knowledge to make very\u00c2\u00a0interesting 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\u00c2\u00a0building 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).<\/p>\n 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\u00c2\u00a0ease 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\u00c2\u00a0performance enhancements and tweaks…oh yeah, and save some $$$ as well!<\/p>\n I thank the great minds over at the Geotech Forums<\/a> 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!<\/p>\n 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\u00c2\u00a0make 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),\u00c2\u00a0and power supply (which ive already provided links above).<\/p>\n Surf PI 1.2 Kit from Silverdogs – This is what it comes with<\/p><\/div>\n 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.<\/p>\n Surf PI 1.2 Resistors and other components<\/p><\/div>\n Surf PI 1.2 Capacitors and Assorted Components<\/p><\/div>\n The Surf PI 1.2 Longboard PCB. This is the newest version which has corrected silkscreen indications for R18 & R22<\/p><\/div>\n Its not as complicated as it seems, just work slowly and be careful.<\/p>\n There’s basically two things you have to do to build this board, look at the silk-screened component markings, and reference the\u00c2\u00a0PARTSLIST<\/a> 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.<\/p>\n Building the Power Supply for Surf PI 1.2<\/p><\/div>\n 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.<\/p>\n Reuse clipped leads from other components for the solder bridges<\/p><\/div>\n When solder holes are connected, fit the components all at once before soldering<\/p><\/div>\n Work slowly and carefully, double check each\u00c2\u00a0component to ensure the right part is being used. Remember, resistors are not sensitive to polarity orientation, but capacitors are!<\/p>\n Completed Surf PI 1.2 Pulse Induction Metal Detector Kit Circuit Board – Click for Full Size image<\/p><\/div>\n Completed Surf PI 1.2 Pulse Induction Metal Detector Kit Circuit Board solder side – Click for Full Size image<\/p><\/div>\n After you have finished soldering all the components onto the board, its time to connect wires from the supplied plugs and\u00c2\u00a0terminals to the molex connectors. See pictures below for polarity (otherwise you’ll get potentiometers which work the opposite direction):<\/p>\n Connecting the volume and power supply to Surf PI 1.2 (click to enlarge)<\/p><\/div>\n Connecting the threshold potentiometer to Surf PI 1.2<\/p><\/div>\n 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\u00c2\u00a0to build an\u00c2\u00a0unshielded mono spiral coil using the concepts Tepco has written about on this thread<\/a>. Its easy to build, gives consistent results, and allows for further modification to the delay sensitivity if desired.<\/p>\n 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!<\/p>\n Materials required:<\/p>\n Essentially,\u00c2\u00a0 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).<\/p>\n Coil winding apparatus using a dvd spindle cover, double sided tape, and some cardboard<\/p><\/div>\n 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\u00c2\u00a0small 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.<\/p>\n Fully wound coil with super glue support<\/p><\/div>\n When you’re done, strip and twist the loose\u00c2\u00a0inner 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.<\/p>\n Spiral coil leads twisted together<\/p><\/div>\n To connect the coil to the detector, connect the inside\u00c2\u00a0leads 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.<\/p>\n *Some notes on connecting the coil to the metal detector circuit board:<\/p>\n 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.<\/p>\n 1. Turn the\u00c2\u00a0unit on (volume knob, or just plug in the\u00c2\u00a0battery pack) and see that everything is working as it should\u00c2\u00a0(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.<\/p>\n 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\u00c2\u00a0for the next step.<\/p>\n 3. Use the flat-head screwdriver to turn the Offset trimmer (circled in red below) till you get 0v reading on the multimeter.<\/p>\n Setting the offset on the Surf PI 1.2<\/p><\/div>\n Next you will have to adjust the delay till you can detect some gold\/coins\/metal.<\/p>\n Setting the delay on the Surf PI 1.2<\/p><\/div>\n 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!).<\/p>\n 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<\/a>, #33<\/a>, and #35<\/a> by Tepco on this thread<\/a>.<\/p>\n 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.<\/p>\n For more information and ideas on how to do so, check out the Surf PI thread on Geotech<\/a>. For instructions on how to build a straight shaft to use with this (or any) metal detector, see my post here<\/a>.<\/p>\n<\/a><\/p>\nStep 1: Getting the Surf PI 1.2 Pulse Induction Metal Detector Kit and parts.<\/strong><\/h3>\n
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<\/a><\/a><\/a><\/a>Step 2: Assembly <\/strong><\/h3>\n
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<\/a><\/a><\/a><\/a><\/a>Step 3: Building the Coil<\/strong><\/h3>\n
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Step 4: Tuning the Detector (offset and delay)
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<\/a>Surf PI Detection Depth:<\/strong><\/h3>\n
Additional Information:<\/strong><\/h3>\n
\nSince this detector is essentially a White’s Surfmaster Pi unit, check out the manual<\/a> on how to adjust the delay and other useful bits of information on detector usage.<\/p>\nNeed to build a metal detector shaft?<\/strong><\/h3>\n