P.I. coil

[Tom]

I need help in making a coil for a P.I. detector that has an IRF9640 chip driving the coil. How do I figure the impedance to get the maximum transfer of energy to the coil? I have read that a P.I. coil is not hard to make , so any help will be appreciated. Thanks Tom

[G.Gueorguiev]

Re: P.I. coil

>I need help in making a coil for a P.I. detector that has an IRF9640 chip driving the coil. How do I figure the impedance to get the maximum transfer of energy to the coil? I have read that a P.I. coil is not hard to make , so any help will be appreciated. Thanks Tom

Hello Tom,
I don't know what is your PI-scheme but I have done many PI which have had one coil.You must wound 26 turns of 8x27s.w.g (8x0.30mm)enamelled copper wire. Diameter must be 30cm.I'd like to see this project.If you can give me your sshme i *.pdf or *.gif.
GG

[Carl]

Re: P.I. coil

Maximum transmitted energy would occur for a coil with zero ohms, but this is not really desirable. Some detectors even throw in a series resistor to limit the coil current.

Without knowing more about the detector or the coil that comes with it, it's hard to answer. But you probably won't damage anything by experimenting. Try 30-40 turns of wire to start with, you can use magnet (enameled) wire, 26-30 gauge maybe, or wire-wrap wire which has a thicker insulation. Both are carried by Radio Shack.

[Rick S]

Re: P.I. coil

I would try to target the mircoheneries 300 to 400 range. Ohms would be on the coil around 1.5 to 4.0. The size of coil I would start with would be a 10" to 11". Eric Foster's coils are about 300uh, 2.0 ohms and a 11" diameter coil. To make the coil use a piece of wood with a 11" circle drawn on it. Then place finishing nails about every 10mm or so around the paraimeter angling the nails slightly outward to avoid wire from slipping off form. After you have wrapped 22-26 turns measure the inductance and ohms. Add or subtract turns to desired requirements. Hope this helps alittle. Rick S

[Tom]

Re: P.I. coil

Thanks For all the information I will try your designs and get back to you with the results. Tom