Suggestions for a 'pinpointer' design

[Mark]

First off thanks to Carl for a first class resource for those of us who might be inclined to build our own stuff from scratch!!


I'm interested in building my own pinpointer. But I'd like to do this entirely from scratch (ie components & up). I already have a TinyTec - so modifying a stud finder is not that interesting.


What would be interesting would be a pinpointer that has far better depth that the currently available products - specifically the ability to pick up a dime at about 3 inches, with a zero motion, all metal operation. None of the universal pinpointers are capable of doing this.


My secondary objective is low cost and ease of use...


I think that some type of BFO would be the best bet, and PI would be silly.


Any Ideas or suggestions?


Thanks - Mark

[Don]

Re: Suggestions for a 'pinpointer' design

Why would PI be silly?


I was thinking earlier today that having a small wand-coil to plug into my friend's Maxi-something would be a handy tool. The 2 by 4 foot coil leaves entirely too much space to wonder about, and the 4 by 4 foot only helps a little bit.

[Carl]

Re: Suggestions for a 'pinpointer' design

>What would be interesting would be a pinpointer that has far better depth that the currently available products - specifically the ability to pick up a dime at about 3 inches, with a zero motion, all metal operation. None of the universal pinpointers are capable of doing this.


Thought about this, too...


>I think that some type of BFO would be the best bet, and PI would be silly.


I think one of the commercial pinpointers is PI. Does anyone know for sure what the different makes are? An easy design might be a VCO-type detector.


- Carl

[Mark]

Re: Suggestions for a 'pinpointer' design

There is a PI design on the market now - The VibraProbe. The selling points for it are:


- It vibrates when near metal, which makes it good for use with headphones (for the main detector), or near surf - so that you need not strain to hear a beep.


- It's waterproof - so again, it's good near the water.


However, the detection range is less than 1 inch.


I think if low cost / simplicity are needed, PI seems like overkill. A design factor I failed to mention the first time around is the need for a small coil. I picture the whole 'coil' fitting into a 1" (or so) diameter PVC pipe, with the coil at one end and the circuitry at the other end (maybe inside the pipe, maybe in a box)...


Carl - You mentioned a VCO design - is there a reference to this type you could point me towards (no pun intended!)?


thanks - Mark

[Carl]

Re: Suggestions for a 'pinpointer' design

>There is a PI design on the market now - The VibraProbe. The selling points for it are:


>- It vibrates when near metal, which makes it good for use with headphones (for the main detector), or near surf - so that you need not strain to hear a beep.


I've seen the little vibrator motors for about $2 from Circuit Specialists. I plan to get a couple next time they are available


>Carl - You mentioned a VCO design - is there a reference to this type you could point me towards (no pun intended!)?


The VCO design uses only one oscillator instead of the traditional two. If a target attempts to change the oscillator frequency, a detector feeds back a voltage, usually to a varactor, to re-stabilize the frequency. Thus the output is a voltage that indicates whether a target is present. I will try to get more info and maybe post a circuit.


- Carl

[Unregistered]

ryobi pin pointer

Take the coil out of a ryobi stud and PIPE finder, $36.00 hardware store, 4 wires, use heat gun, make a cable, 4ft, put most sensitive end of coil at the end of a plastic 5/8 pipe that is in plumbing, has writing down entire length, hot glue coil in pipe, very close to end. I have made 5 of these, the metal pot inside is for metal mode sensitivity, the other pot is for wood. Use "deep metal" setting. I use this in New Mexico, detects little gold nuggets, but not tiny flakes, 300khz or so. [email protected].

[Ray-NM]

Pin Pointer

I opened up my Whites pinpointer and adjusted the pot in it for greater sensitivty. I think it will detect a coin at about 2 inches now. the only problem with changing the setting is the ground mineralization seems to affect it more. But I solved that by turning it off and on when near the ground sort of like a manual ground balance. It will also pick up very small pieces of gold. That was the orginal Idea in the first place was to get the really small pieces.
RayNM

[kt315]

I have tested Hammerhead with ferrite corn coil and it was working good. to trigger on pinpointer coil or search coil is not new decision.

[Mr. Bill]

The Detector Pro Uni-Probe, and the Pocket Probe are of PI design.

Tuned properly, depth between 5"/6" on nickel.

Mr. Bill