ML PI coil patent app.

[Altra]

This looks interesting. Flat wound coil variation. I think, I'll give it a try.

https://patents.google.com/patent/US...=US20210273335

[Orbit]

Hi Altra !
A flat cable for a computer could be used here ?

[Altra]

Hi Altra !
A flat cable for a computer could be used here ?

That could work, but that wire is usually very fine gauge with high resistance. I have some 18awg (1mm) twin speaker wire to try. Not sure how to form it yet.

[ionut_mtb]

Better just use double sided tape on a cylinder, use the wire that you have best result for pi coils (litz, tinned copper, normal copper wire) put another tape on the outside and after try to bend the wires like in the picture.

[dbanner]

To achieve precise geometry, perhaps a 3D print for the shape to provide the rigid form.

Then wind a flat spiral coil on adhesive backing (maybe double sided Scotch tape) and stick on to 3D printed form.

Then seal and harden the coil with some kind of brush on sealant.

[dbanner]

Maybe this cannot work.

If you were to flatten out the 3D shape, perhaps it is not a concentric circle. It may have some wobbly shape.

[green]

Some gold nuggets and possible test targets. Didn't test gold chain today, it was borrowed and measured awhile back for time constant. I purchased the 1 gram of nuggets (a thru g) awhile back. #9 lead shot harder to detect than any of the nuggets. Nugget e a little less signal than #8 lead shot.
Nuggets vary a lot. Think, need to pick one of the lead shots for a desired target before defining coil and amplifier specs?

Need about a 3 times signal increase to increase detection 1 inch from chart for 133mm coil.

[Altra]

That's a nice collection of targets Green. That #8 shot is tiny.

I think you could wind a flat coil to spec, bond the wire with flexible glue. Then make a wooden form to hold the front and rear parts of the coil at 90 degrees. Finish by brushing on a few coats of epoxy resin to lock the windings into that shape. A basket coil could be wound on a preformed plastic jig with slots. Another idea, wind the coil flat glued to a piece of that plastic sheet that can be formed with warm water. Don't remember the name of this plastic, but it's used for making removable arm cast etc.