Who here has built a metal detctor (even from a kit)?

[Ground Squirrel]

I have built the 'Matchless' Metal Locater from the Thunting.com site. Here in the link to the low-res PDF file...
http://www.thunting.com/cgi-bin/geo...age=metdet&file=/projects/matchless/index.dat

Changes in the internal design of the current stock of 556 timer IC's caused me to have to redesign the "pre-amp" stage and the timing resisters in the output osc. Overall it promised to be an interesting detector, but considering the requirement to build two loops and position them with very high precision, combined with the high amount of builder understanding of the components used in the project, I would rate this one as "poor". Defiantly not a beginner project, and most certainly not a project for someone who does not have analog -and- digital skills at the design level.

The results of the project produced a detector that was able to clearly distinguish the difference between ferrous and non-ferrous metals with pin-point accuracy to an air depth of around 4.5 inches. (I used a 1/4 inch piece of 1/4 inch copper bar and an equal piece of steel bar for testing) It was able to "find" a coin target (US quarter) oriented flat to the coil face at 6 inches. Distances measured with a plastic ruler, no estimates made while testing. Due to the huge amount of time spent re-designing the detector and the fiddly nature of the search coil orientation, I "retired" the project before producing a field-ready model.

The interesting thing about building this project was the very clear "yes" it's there, "no" it's not behavior of the detector. When there was no metal in range, the thing was stable and quiet. When an object entered the working range of the search coil, the detector was clear and unwavering about the material and position of the target.

Building this thing gave me a huge respect for my White's XLT. A LOT of time and skill went into the design and production of this, and all commercial detectors. While this comparison is not fare on any level, just considering the amount of time I spent working on the 'Matchless' Metal Locator... an XLT is a better deal.

GS

 

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[jblank37]

Posted this over in--Best Finds--Anyone hunt in the 1960's or 70's
Thought I would share it here also.

Started back in the late 60's with a home made BFO detector. This consisted of a coil glued to the bottom of a round piece of plywood, mounted to a broom stick with the electronics mounted to it. I worked across the street from a park that was a civil war army depot back in the 1800's. It was common to look for 2 to 3 hours and find at least a 100 coins along with a good number of minnie balls and verious civil war relics. All of these from 1 to 3 inches in depth. I saved up enough to buy my first store bought detector after awhile. It was a Heathkit, That I built myself. I went from this to a White's Coinmaster IV and a White's 66T. This is when I started finding the deeper coins. Alot of these were Indian Head pennies, Liberty Nickels, Buffalo Nickels, Barber Dimes and Quarters, a few Barber Halves, along with 3 Silver Dollars. My oldest coin from this park, a 1865 two cent piece. Never any gold. Also back in these days, I hunted 2 fairgrounds about 3 hours a day for a total of 9 days. Total equaled 1042 coins and 9 rings. No clad! Those were the days. The coins are still out there. Just have to get over them.

Friend's, John

 

[trukker]

Built a BFO detector probably 20 years ago from a circuit in an electronics magazine. All the components were off the shelf at a local radio store like Tandy (Radio Shack to you) and it fired up first time. Circuit board was mounted in a Tupperware box on a broom handle and I found a couple of low value coins and a sackful of ringpulls on a beach.

Got me interested, though, so I did some ferreting about and found a circuit for the PI Magnum, a VLF machine with ground balance, disc and all the bells and whistles. I etched my own circuit boards and started building it but I couldn't get it to work properly. I forget why not, now, but it was finding my wedding ring at 10" on the kitchen table. I've still got all the circuit boards and one fine day I'll start it again.

After that I tried the PW Sandbanks, a PI machine which a friend had and which gave great results for him. Not so for me; the circuit kept going unstable. But, yet again I still have the board and most of the components including an IC which is now obsolete. Not just one, but three of 'em and you can't buy them anywhere for love or money. I've just resurrected this project after all these years cos Mrs trukker needs a detector since I've just bought a commercial detector.


The current state of affairs is that I've discovered the weakness in the circuit and decided how to rectify it; I've had to lose one part of the circuit and use an extra battery instead. I've stripped all the old components off the PCB and cleaned it all up ready for soldering, I've ordered some parts to replace the old ones and I've modified a PC power supply to give a dual-voltage power supply for test purposes. Soon as the parts arrive I'm ready to go.

If it all goes according to plan I'll keep you all updated; if not I'll just slink away into a corner and sulk!!

trukker

 

[Charlie P. (NY)]

I built one in the early 70's that, I believe, Radio Shack marketed under the "Archer" brand.

It could detect a quarter from eight quarter thicknesses deep! Or maybe even a full 1 inch on a good day.

The coil was a bare, exposed printed-circuit-board spiral and the shaft was a telescoping antenna. Not of the highest technology even of that period.

But I did find coins and junk iron.

I figure now it's like a car. I used to be able to do about anything on the slant-six 198 c.i. engine in my '71 Dodge Demon and still am fearless tinkering with my 1956 Ford 640 tractor. Now I don't dare open the hood on my Jetta Turbo as 80% of the mechanical and 95% of the electroincs I lack any understanding of and have no test equipment to calibrate or analyize it with, anywho.

I could possibly build a kit detector if one was offered but how would I calibrate it?

 

[Tykit]

My first detector was a Heathkit, built in it 1971. Great detector. Deepest coin with it was a silver quarter, measured depth 6". Found IH pennies, the whole works with that machine. Then some one talked me into buying a Whites Coinmaster 4, the Heathkit was deeper, had a 10" coil and was very sensitive. Had just one knob, for sensitivity. Now I use Tesoros.

 

[cansadak]

 

[Pinball]

I just took this picture of the one my Dad and I built when I was around ten or so. I believe it is the same one in cansadak's picture I loved playing with the detector when I was younger and believe that is why I bought my BH then my AT Pro this past year. I need to find a schematic for the detector (Archer Kit-Radio Shack) as there are a couple of wires that need soldered back on...but I need to know where. If anyone still has one I would love a picture of both sides of the PCB. Thanks