Experiments with spiral coils

[Esteban]

http://www.tesla-coil-builder.com/rmfd_experiment.htm

[mikebg]

What happens with timeconstants of conductive ground?

According J.Corbin, the timeconstant of conductive ground depends on diameter of TX loop.
According (R)EMI group, the conductive ground has a series of timeconstants inverse proportional to squares of natural odd numbers: 1, 9, 25, 49, 81 etc. They all depend on diameter of TX loop.
J. Corbin measured the second timeconstant (9 times smaller than fundamental), but misnamed it as magnetic viscosity.
However what happens with timeconstants of conductive ground when the TX coil is not as loop (frame), but as flat spiral?

[Esteban]

According J.Corbin, the timeconstant of conductive ground depends on diameter of TX loop.
According (R)EMI group, the conductive ground has a series of timeconstants inverse proportional to squares of natural odd numbers: 1, 9, 25, 49, 81 etc. They all depend on diameter of TX loop.
J. Corbin measured the second timeconstant (9 times smaller than fundamental), but misnamed it as magnetic viscosity.
However what happens with timeconstants of conductive ground when the TX coil is not as loop (frame), but as flat spiral?

I make small printed spiral coil and a PI detector can't detect it (the tracks). In general, some PI detectors tend to reject thin material as metalic paper. Seem the thiny tracks produces the same effect.

[WM6]

I make small printed spiral coil and a PI detector can't detect it (the tracks). In general, some PI detectors tend to reject thin material as metalic paper. Seem the thiny tracks produces the same effect.

Hi Esteban

how do you draw your spiral coil?

I am searching for good drawing tools for spiral coil, but I did not find something usable.

[homefire]

I too would like a program to do spirals.

[WM6]

I too would like a program to do spirals.

Once I found on web PCB drawing tools (dont remember name) that declare to be capable to draw spirals. But demo didnt work.

[Qiaozhi]

Easy-PC can create spiral tracks.
http://www.ohioautomation.com/datash...0datasheet.pdf

[Qiaozhi]

Here's a simple example ->

[mikebg]

Don't use PCB material for TX coil!
According to (R)EMI group, the foil of flat spiral must be oriented in the direction of magnetic lines as steel lameles in a transformer core. The group opposes the use of material for PCB because the tracks shoud be very wide to get a little resistance of TX coil. Broad tracks cause strong eddy current signal.
Is the drawing showed a TX coil, which is studied in 8W dissipation. I have such a coil produced in Germany. It was set in a medical device for RF heating of the patients.
As lack of copper foil and aluminum foil is difficult for soldering, they made a TX coil of Ribbon Litz wire. The wire is formed by 30 reels ( 28 reels of wire and 2 reels of cotton thread). Coil is wound like transformer bobbin. But that is not truly flat spiral, because Ribbon Litz is wound with several turns per sheet. The cotton thread is to minimize stray capacitance.

[homefire]

I think Tesoro uses them?

The SandBanks Detector has reference to them and they knock down the Cap of the coil most well.

[Esteban]

I think Tesoro uses them?

The SandBanks Detector has reference to them and they knock down the Cap of the coil most well.

Appie make spiral coil with coaxial cable (inside part, no the shielded). According him, works good. But is not a flat coil.

[Esteban]

Hi Esteban

how do you draw your spiral coil?

I am searching for good drawing tools for spiral coil, but I did not find something usable.

Was a copy from magazine. I make a negative film of it and translate to the PCB. But I remember that somebody show me in a program and make with it fantastic perfect spirals with all the dimensions you want, beautiful. I remember that I post spirals made by this program, some years ago. Maybe is in Archive section today...

[nakky]

You can make it, whit Sprint Layout 5.0.

Grt Nakky

[Esteban]

Flat spiral coil calculator:

http://www.circuits.dk/calculator_fl...l_inductor.htm

[Esteban]

You can make homemade. Those are the tips I save for to make spiral with wire. Mantain your hands wet when you winding this, because you can't made with gloves in your hands cause the glue. This is some hardzarous job. You need patience. In this case, 71 turns wire 0.7 mm. Here not separation between turns. Winding is clockwise, but can be also anti-clockwise. Coil is 210 uH, 0.7 ohm. Form is 12.5 cm diam., coil is 11.5 cm.