DIY Pulse Induction Detector (Impulse III)

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Joined
Apr 19, 2023
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Hello everyone!

I recently wanted to get into gold prospecting and detecting but due to a tight budget we were not able to invest in anything high quality when it came to detectors. I often become obsessed with an idea and when I figured that I couldnt get a detector for a while I started looking around at experiments and DIY projects. Eventually I came across a video of a guy that tests various DIY electronic projects and had a few metal detectors he had made. The most recent being a Pulse Induction metal detector which I could buy the PCB off ebay so I decided to give it a go and see how much I enjoy using it.

Here is a video of me testing it for the first time in the backyard showing my old man. I will add a picture of it when I get home too.
View attachment 10000000_5762773460499796_7004301521683807276_n.mp4


For this build I have used so far:
PCB off ebay
0.4mm Enamel Coated Copper Wire
Some old speaker cable to connect everything together
3D Printed ABS parts
PVC Pipe
Some M3 nuts and bolts for the housing


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It was pretty simple to get going as I just had to solder a battery, speaker and coil. The shaft I used a PVC pipe, the coil housing and unit/battery housing were 3D printed with ABS plastic. The first head I used a curved channel and wrapped the wire. The second head I made I used a flat channel and have made more of an effort to stack the copper wire neatly and I used the amount of coil windings they suggested in the instructions for optimal use (the first head had less copper windings). I am currently looking at optimising the size and sensitivity of the coil to see if I can use it to find some gold nuggets somewhere, maybe out at Warwick or Northern NSW. I am not too knowledgeable with electronics so what I have been able to work out is limited. But recently I came across some videos by DetectorMods on YT and he has a few videos where he has a some coil heads dismantled. The Pulse Induction coil heads all have a conductive shield of sorts, encasing the coil head and a tiny wire connected but I can't seem to work out where this wire goes. Not sure if the PCB needs something on it to attach the wire to ground the shield? Of if it can be grounded in another way. Either way, if you have any knowledge on this, please share!

One thing I had been struggling with is finding a bolt and nut that isnt metallic for the head. I have printed one using ABS but it was difficult to get correct and I have since threaded it so I have gone with just gluing the head together before I make my next iteration.

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I have since taken it out a couple times, once to a small beach with my daughter and we pulled up a bit of rubbish of various sizes. Had a blast doing it. Then we went to Gympie on the way up to Bundaberg for a camping trip and picked up an old button. I was amazed that I was able to pick up something so flat and small. It was a good 6 inches deep (wish I measured).

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Took it to an old gold mine where there were a heap of other people detecting too, found some 'relics' and a chunk of what seemed to be copper ore. No one else was finding anything so I was alright with that, but I would like to test its sensitivity on some gold nuggets and jewellery (surprisingly havent yet).
I am currently re-designing the housing and adding a handle, I want to bring the screen, buttons and speaker up onto the handle for ease of use (especially after designing it upside down to start with...) but I am also looking to add a headphone jack so I don't annoy others too much when needed.

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Thank you for reading, I will keep this updated with future updates, and once I am happy with the design ill share the 3d Print files incase anyone else wants to take on the same project.
 
I think you have done very well - PI coils do not need as precise setup as VLF ones as in mainly the one coil for TX & RX but you have made a working detector and that is huge.

In VLF & IB coils a seperate wire is sometimes used to help balance but the details are beyond me.

Best resource online is www.geotech1.com
and best book is "Ïnside The Metal Detector" by Overton & Moreland which balances practical building tips with electronics has 8 DIY detector designs & some coil building.
 
I think you have done very well - PI coils do not need as precise setup as VLF ones as in mainly the one coil for TX & RX but you have made a working detector and that is huge.

In VLF & IB coils a seperate wire is sometimes used to help balance but the details are beyond me.

Best resource online is www.geotech1.com
and best book is "Ïnside The Metal Detector" by Overton & Moreland which balances practical building tips with electronics has 8 DIY detector designs & some coil building.
Thank you! Pretty stoked with the result so far. I have a goal of finding a gold nugget with it one day so I shall keep learning and tinkering. Thank you for the info I will definitely check it out!
 
Thank you! Pretty stoked with the result so far. I have a goal of finding a gold nugget with it one day so I shall keep learning and tinkering. Thank you for the info I will definitely check it out!
Well done getting it up and running. For nylon bolts have a look at toilet seat bolts.
The shield in the coil is only connected at one point and usually wires back to 0v on the pcb.
 
Appreciate it, Bicter suggested toilet seat bolts, I was going to check those out so please dont go to any trouble!
I don't have any of the actual Minelab nylon bolts left but do have some I'd used on other detectors &/or as spares. They are 1/4" x 2". Unfortunately I don't have any wing nuts left that fit them but do have plenty of normal nylon nuts to suit.
Let me know how you go but they are there if suited. I won't use them all.
 

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