Re: 200kHz good, 100kHz better.
I've just managed to get a 9" arc out of my solid state design, by moving
from a 210kHz coil (best 6") to a 104kHz coil. And I think I can do better
still by building an output transformer with a higher ratio. The other
bonus of halving the frequency is less switching loss in the circuit. The
snag is a bigger output transformer. (my first results were very poor
because the transformers that were good at 200kHz didn't have enough
primary inductance for 100kHz.) Pike suggested going as low as 50kHz
- would such a monster coil have better results or is there a law of
that comes into play.
The 100kHz coil is wound on a 25 litre bucket, white (polythene?),
sold in Boots the chemist here for brewing beer, wound with 0.4mm wire
from top to bottom. (Given that American wire gauge is different from
British wire guage and that the whole scientific world has gone metric -
shouldn't we drop wire guage sizes all
together - or is this heresy;)
Without a discharge electrode sparks break out not on the toroid
but on the wire between the coil and the toriod - how do I stop this?
I'm really into silicon rubber (that sounds bad) but I've taken up Rob's hint of
a layer of clear sealant between layers in the output transformer. Of course,
because layers take 24hrs to cure, it now takes a week to wind an output
transformer. I put on a layer of insulation tape as well. The first transformer
runs quite happily.
Thanks for all the comment on modulating coils - and for the interesting
suitable music to play over an electrical arc - Bach's Toccata and Fugue in D,
Black Sabbath, but upon reflection I really want to get hold of an old
episode of Captain Scarlet: "This is the voice of the Mysterons"!
Alan Sharp (UK)