Hi all,

First post here. I'm experimenting with a project that detects a coin going into a hat. I started by buying a cheap hand-held metal detector on ebay which gave some promising results but the diameter was too small. I removed the copper wound coil and re-wound it to fit the diameter of a hat brim. This little hack is working with big coins but isn't sensitive enough for small ones.

I'm looking for advice on how to increase the sensitivity of something like this. Eg - would it work to use more winds with a longer wire? change wire thickness? Or will I need a more powerful unit to achieve what I need, or possibly a different approach altogether? Any ideas much appreciated. I don't have a great knowledge of the theory behind all this but have decent soldering skills and basic electronic experience with arduino, pressure sensors etc.

Cheers.

 

More information is needed. Can you post a schematic or give a make and model number.

 

Thanks for the reply Dick. Sorry I suspected I would need more info but I don't have a schematic. This link on ebay shows the model number as a TS80. It's a very cheap generic unit from China. I expect it may be less painful to make something from scratch for this application, but it felt very close to working with very little effort so it was tempting to look for an easy solution and maybe learn something along the way.

I just found this video on Youtube which looks helpful too.

 

If you can see anything to adjust on the circuit board (assuming it has a circuit board) you might as well check it out and see whether it is a sensitivity adjustment, since you don't have much to loose by trying.

Without knowing how it works one cannot reliably predict what modifications would result in improved sensitivity.

In the past I've run across several good looking metal detector schemes on the web so I think you are probably on the right track by making one from scratch.

 

You cannot simply rewind the coil with a larger diameter without changing the number of turns.

 

If you can see anything to adjust on the circuit board (assuming it has a circuit board) you might as well check it out and see whether it is a sensitivity adjustment, since you don't have much to loose by trying.

Without knowing how it works one cannot reliably predict what modifications would result in improved sensitivity.

In the past I've run across several good looking metal detector schemes on the web so I think you are probably on the right track by making one from scratch.

Yes it's a circuit board but no obvious adjustment on it unfortunately.

 

You cannot simply rewind the coil with a larger diameter without changing the number of turns.

I probably halved the turns by making a larger coil already. It still works just not sensitive enough. Before giving up on this solution I was going to try doubling or tripling the turns of the larger coil.

 

You have to go back to the original and determine the sensitivity.
You now have only half the number of turns that will be detecting the magnetic absorption and half the sensitivity.
Lay the original coil in the bottom of the hat.