Another PI coil shield method.

[mickstv]

Hi all, just thought I would post up my method of coil shielding for my PI. It seems to work well, the shield doesn't increase the minimum time to first sample compared to an unshielded coil.


Below is a link to a PDF I put together, showing how to make the shielding material.


http://www.mediafire.com/view/0nneyl...hield_idea.pdf

[Thomas]

I'm just curious, was the braid tinned copper or stainless?

[mickstv]

Hi Thomas, well all I can say is it isn't tinned copper, I checked the suppliers website but it doesn't mention the braid type. I suspect its aluminum braid.

All I know is I can't detect it with my PI, but metering it, it has zero ohms resistance for the length I used.

Also I tested the coil before and after, adding the shield didn't increase the decay time, but it did stop hand capacitance.

[Davor]

Winding a thin wire around a coil would produce the same effect, only it is a tedious thing to do. Mesh braid seem a reasonably easy method. I like your way of keeping it tidy by adhesive tape.

[mickstv]

Hi Davor, I actually tried the thin wire idea first, it took ages to finish and it didn't work that well, it still had issues with hand capacitance. But I'm very happy with the new shield method.

[6666]

Thanks Mick

[Mechanic]

Nice Job Mick! Thanks for sharing!

Cheers Mick

[greylourie]

Good guide ! Bit like an improvised version of the shielding Stefan has described in a post. Definitely going to sticky this method for future reference. Thanks Mick.

[mickstv]

I'm going to order some more litz wire in the next couple of weeks. Once i get it I'm going to try a modified version of the method from my first post, if it works I'll make another PDF so others can try it.

[mohandes]

I'm going to order some more litz wire in the next couple of weeks. Once i get it I'm going to try a modified version of the method from my first post, if it works I'll make another PDF so others can try it.

hi
my English not well . i see your PDF and read your post, you say do not increase depth or sens but remove ground cap ???
and i dont understand how shielding the coil use , have 3wires in PDf , black , and two yellow, where them connection ?
i want use use braid tinned copper , and now i see your new idea , so if you say us more explain more better.
regards

[mickstv]

hi
my English not well . i see your PDF and read your post, you say do not increase depth or sens but remove ground cap ???
and i dont understand how shielding the coil use , have 3wires in PDf , black , and two yellow, where them connection ?
i want use use braid tinned copper , and now i see your new idea , so if you say us more explain more better.
regards

Coil shield purpose is to remove ground capacitance. Some shielding methods reduce sensitivity, but this one doesn't reduce sensitivity.

The black wire is shield ground, the other two wires are coil wires. You connect the black to one of the coil wires, this connection point then becomes the coil common wire i.e. it connects to your battery the other single coil wire goes to the mosfet.



You need to select a braid material that isn't detected by your detector when waved over the coil.

[kt315]

Coil shield purpose is to remove ground capacitance.

NOT NOT AND AGAIN NOT!!!!!
coil shield purpose is TO DECREASE of THE INFLUENCE of ELECTROSTATIC FIELD OF FARADEY BETWEEN THE COIL WINDINGS AND GROUND, to protect FROM ELECTROSTATIC CHARGE

[mickstv]

NOT NOT AND AGAIN NOT!!!!!
coil shield purpose is TO DECREASE of THE INFLUENCE of ELECTROSTATIC FIELD OF FARADEY BETWEEN THE COIL WINDINGS AND GROUND, to protect FROM ELECTROSTATIC CHARGE

My post was correct.

Please do not post in this thread again, if you plan to continue shouting i.e. "using bold uppercase and stupid emotions" that is just bl00dy rude and stupid.

[kt315]

ok. correct. where you see the capacitance of ground? WHAT it is?

[mickstv]

ok. correct. where you see the capacitance of ground? WHAT it is?

If an unshielded coil is moved around, the capacitance between it and the ground or other objects changes, this causes a response. The shielding isolates the coil from the ground.