need some help deciding on my first build

[bob808]

Hello everyone. This is my first post here.
I decided to start this hobby as it's an old desire but I don't want to invest much at the beginning and I also have some experience with electronics (not that much, I managed to build a diy tube amp and a chip-amp )
As with all my projects I have a real problem with the case. Are there general cases for these diy projects?
I will use this detector for land mainly not beaches or water (thou it would be fine if I could use it in shallow rivers). I'm not looking for something specific, coins, gold flakes in rivers etc. I like the idea of being able the detect at depth but I'm not sure that I will dig for more than half a meter to find something. I'm looking also for something that has a good discrimination. I'd prefer for this project to have a board ready to buy and be through-hole pcb. I think that I will hunt for a second hand coil as I don't know if I'd like to diy it. Also I know that there are a few technologies used so after reading a bit I incline towards VLF. Seems to fit my purpose. Also I think that it would be great to have 2 sweeping frequencies. I am asking you to point me in the right direction and then I will start to concentrate on a few projects. It is hard for me to read through all the projects on this site so maybe you could point me in the right direction for a few projects at least. I reckon they will not be very costly parts wise, either one.
My main concern is the whole case with the stem. Are there any resources? Or does anyone sell broken metal detectors so I could scavenge the parts?
Thank you

[Qiaozhi]

Hello everyone. This is my first post here.
I decided to start this hobby as it's an old desire but I don't want to invest much at the beginning and I also have some experience with electronics (not that much, I managed to build a diy tube amp and a chip-amp )
As with all my projects I have a real problem with the case. Are there general cases for these diy projects?
I will use this detector for land mainly not beaches or water (thou it would be fine if I could use it in shallow rivers). I'm not looking for something specific, coins, gold flakes in rivers etc. I like the idea of being able the detect at depth but I'm not sure that I will dig for more than half a meter to find something. I'm looking also for something that has a good discrimination. I'd prefer for this project to have a board ready to buy and be through-hole pcb. I think that I will hunt for a second hand coil as I don't know if I'd like to diy it. Also I know that there are a few technologies used so after reading a bit I incline towards VLF. Seems to fit my purpose. Also I think that it would be great to have 2 sweeping frequencies. I am asking you to point me in the right direction and then I will start to concentrate on a few projects. It is hard for me to read through all the projects on this site so maybe you could point me in the right direction for a few projects at least. I reckon they will not be very costly parts wise, either one.
My main concern is the whole case with the stem. Are there any resources? Or does anyone sell broken metal detectors so I could scavenge the parts?
Thank you

Have a look at the kits available on Silverdog's website ->
http://www.silverdog.co.uk/shop/inde...tegory&path=36

[grungymike]

I'm more or less in the same boat, been studying and working on this subject for a while now. A coupla thoughts...

1) gold flakes and coins are two different types of targets that call for different machines.

2) Two general types of detectors seem to be currently popular, VLF (very low freq.) and PI (pulse induction). I used to have a really good VLF type, a White's GMT, good machine, but almost overly sensitive, drove me nuts signalling on hot rocks. PI machines are not bothered by hot rocks or mineralized ground (which is where your gonna find placer gold), but can't discriminate well, in fact I think half of the folks on this site are trying to develop a PI with good discrimination. Personally I'm here to learn how to build my own decent PI machine, based on the Hammerhead or Surfmaster circuit. For treasure and relic hunting I think a VLF type machine is better due to it's discrimination abilities, but a PI machine offers real advantages for nugget shooting, due to it's minimal reaction to mineralization.

Hope this helps...

[mickstv]

I'm more or less in the same boat, been studying and working on this subject for a while now. A coupla thoughts...

1) gold flakes and coins are two different types of targets that call for different machines.

2) Two general types of detectors seem to be currently popular, VLF (very low freq.) and PI (pulse induction). I used to have a really good VLF type, a White's GMT, good machine, but almost overly sensitive, drove me nuts signalling on hot rocks. PI machines are not bothered by hot rocks or mineralized ground (which is where your gonna find placer gold), but can't discriminate well, in fact I think half of the folks on this site are trying to develop a PI with good discrimination. Personally I'm here to learn how to build my own decent PI machine, based on the Hammerhead or Surfmaster circuit. For treasure and relic hunting I think a VLF type machine is better due to it's discrimination abilities, but a PI machine offers real advantages for nugget shooting, due to it's minimal reaction to mineralization.

Hope this helps...

Basic PI detectors which only have two samples, one for target and the other for Earth field cancel will be useless for hunting gold, they wont cancel out any mineralized ground or hot rocks. You need to have multiple samples then use signal weighting to cancel out mineralisation.

[Overtheedge]

... not bothered by hot rocks or mineralized ground (which is where your gonna find placer gold), ...

Placer gold can be found on any kind of ground. Alluvial gold is transported gold. Elluvial is in-situ and is often in heavily mineralized ground, but not always. Think remaining iron content of the matrix.

PI has advantages, but for a lot of Alaska, the high VLF and lower LF detectors do the job (roughly 15KHz-100KHz). Oh and PI is not much good for real small gold. PI needs a target with more mass.
eric

[golfnut]

redo

Hello everyone. This is my first post here.
As with all my projects I have a real problem with the case. Are there general cases for these diy projects?

There are some good extruded ally cases - Hammond do a good one..

http://www.hammondmfg.com/1455.htm


I will use this detector for land mainly not beaches or water (thou it would be fine if I could use it in shallow rivers). I'm not looking for something specific, coins, gold flakes in rivers etc.

For gold you will favour higher frequency machines - say ~ 12 to 20kHz



I like the idea of being able the detect at depth but I'm not sure that I will dig for more than half a meter to find something.

You wont be digging small coins beyond 9" with these kits, so no worries there.



I'm looking also for something that has a good discrimination.

IDX is sharp Disc, easy ground bal, and a usable Sens/Thrsh control - But only 6.5kHz

Although saying that the design is tolerant to change - I made mine at 12kHz to 'see' smaller coins



I think that I will hunt for a second hand coil as I don't know if I'd like to diy it.

Can be tricky but do-able




Also I know that there are a few technologies used so after reading a bit I incline towards VLF.

Good choice for land, wet soil, clay,


Also I think that it would be great to have 2 sweeping frequencies.

No kits do that on here


My main concern is with the stem.

A strong graphite golf shaft (70gram extra stiff) works real well.

Hip-mount the box and the shaft and coil can be only 800grams

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