Metal detector for small objects (fine chains)

[Harp]

I hope I'm in the right place with this question

As I have no experience with comparing metal detectors, I use the welfare of this forum to find a answer.

Some time ago, I saw a woman scans the beach with a commercial metal detector.
I do not know which is that model, but, in conversation I found that it can not detect very fine feminine chain.



I'd like to make a metal detector that is capable to find chains at a reasonable depth (assuming it can find all of larger objects) of the sea beach in dry/wet sand, out of the water.

I'd like to emphasize that I am interested just for a devices with a reliable scheme, available for DIY hobist, which, according to your experience, good for mentioned conditions.

Any recommendations?
Thanks!

[Waikiki_Sweep]

I see Minelab Excalibur II-1000 on the pic. It is not detecting small gold chains even with its $1500 price.

Any metal detector is practically useless to find small gold chains.
You can find chain if it has a medallion or ring on it. Or lock on it is big enough.
As with my experience chains approx. 4mm. wide or more are detectable somehow with very good expensive detector but detecting range is low anyway.
Interesting that fake gold chains (cooper, brass, iron) are much easier to detect.

Best detector for small gold chains are here:

If seriously, try to build a machine with small coil designed to find small gold nuggets. Than you can find a size of smaller chain that can be detected. But anyway you will detect mostly locks on chains not chains itself.

[kt315]

minelab exalibur, not for gold chains, it is true. look at side of HAMMERHEAD-PI of Carl Moreland (this site he is a moderator and creator) and will get
a bear on gold chains. begin from now.

[Harp]

Hello all!

I found HH version 1 pdf, but does not have a pin numbers to the ICs. Other versions that I found use a microcontroller, which is not in my DIY abilities. Can some help for the right link?
I also looking Surf Pi Pro from Carl-NC.
http://www.geotech1.com/forums/attac...7&d=1327255499
which I may assemble him easier, if it is better (or same) characteristics than HH?
The idea of a small coil designed is good, but I would like for the beginning a good electronic technology, which would later added the appropriate coil.

Thank you!

[Silver Dollar]

Did you look at this, it has all the pin numbers;

http://www.geotech1.com/pages/metdet...ead/HHv1p5.pdf

You can buy a board from SilverDog too. I got one it's a nice PCB!

http://www.silverdog.co.uk/shop/inde...&product_id=74

(He has the full kit too)

[Waikiki_Sweep]

Try that kits from Silverdog: http://www.silverdog.co.uk/shop/inde...tegory&path=36
Assembling a kit is much faster and easier.
Also you can buy a SurfPI kit and modify its resistors and capacitors to PI PRO values. It gives you boost in sensitivity. Schematics SurfPI and PI PRO are practically the same.

But you can forget about that "small gold chains" especially if you are going to assemble PI detector: SurfPI, HH, PI PRO ....

Instead if PI machines VLF detectors usually can sense smallest bits of foil and aluminum that is more close to small gold chains.

But VLF's fail in salt water or wet send or high mineralization ground. Check conditions where you will use your detector before to decide what to build.

For example, I have checked that my VLF machine Garrett ACE250 can sense 4x4 mm piece of kitchen aluminum foil. PI detector requires several times bigger piece of such foil to be detected.

Another example. I have found small hollow platinum ring (that looks like a mesh with stones) using my ACE250 easily and another guy tried to find it with original Whites Surf PI PRO. He can't hear anything when he even rob that ring against coil.

Another example. One nasty guy dumping cooper BB's on the beach to upset competitors. He using Whites Dualfield and can't hear it from some distance.
Other guys with Minelab Excaliburs (just like that one on your photo) hearing that small pieces of cooper clearly and loudly and start digind it.

So PI machine at least in its usual configuration good for rings and coins and bad for small gold chains.
To dig small gold with PI machine you need a very advanced design like QED. Serious prospecting machines $3500-4500 are using PI technology with edvanced ground balance, ...
Also some expectations for a "Chance PI" are circulating but not much confirmations of gold flakes digging success I can find yet.

[kt315]

I found HH version 1 pdf, but does not have a pin numbers to the ICs.
---
a banner GEOTECH at top of page is clickable. then you go and open METAL DETECTOR section. click. then you open PROJECTS section and have to see
in PULSE INDUCTION DETECTORS section a link on Carl Moreland HAMMERHEAD. click again - you have to find all PDFs.

[Harp]

Thank you all for pdf and information. Much has been helpful!
I now have a complete and detailed instructions so that it remains the only decision that I will build. I think it will be a surf pi pro ... for simplicity, and I already have almost all the components for it.
PCBs from SilverDog is really nicely done, but I look to make a completely different design, so I could take advantage some other features.
Thank you once again!