Re: Super Small TC

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


It appears your flyback isn't providing enough current to properly charge
the cap in the LC tank circuit.

You might try rectifying the output with "fast" diodes and then using a .05
MFD 30 kV cap as a large "flywheel" to provide more constant charging
current for the LC tank circuit.

Use a height/dia. ratio of around 6:1 for the sec. coil.

Also, as you suspected, a coil with this small of a radius would require a
helical primary to obtain the proper coeff. of coupling.  You might use
Terry F.'s archives data to measure the coeff. of coupling.  You need around
0.12 to 0.22 range for best power transfer.

Dr. Resonance

 >
 > I'm not sure whether this project was a waste of time or not. I had set
 > aside work on my big coil because I can't afford a good pulse cap right
 > now, but I thought I'd try something else in the meantime. I had purchased
 > a large spool of #38 AWG magnet wire, for reasons which I can't even
 > remember, and I wondered if I could use this to produce a super-small
tesla
 > coil. So I set to work to wind the smallest TC secondary possible, and in
 > less than on hour this is what I had produced: approx. 450 windings on a
 > 1/2" wide, 2" long paper tube - with no breaks or overlap! According to
 > various TC calculating tools, the resonant frequency was quite high -
 > somewhere in the 4 MHz range. So I built a small flat-spiral primary (#16
 > AWG) and a proper-sized tank cap - which only required three small PPS
 > (poly-phenylene substrate, I think) caps. For a power supply, I used an
old
 > TV flyback transformer and set the spark gap to about 3kV. With! tuning,
 > the best spark I could get from the secondary was about 1/16" (with no
 > topload). Obviously there are some problems somewhere! As a newbie I'd
love
 > to know where I went wrong, though I'm sure there are plenty of errors in
 > this unusual design. The first thing I'm thinking is that a flat-spiral
 > primary isn't right for a coil this small, and maybe a helical one would
 > work better.
 > Any advice would be appreciated.
 >
 >
 >