are you using the large, can-type ignition coil, or one of the smaller ones? What Frequency do you estimate your spark works at?
Posted: Mon Jun 07, 2010 4:49 pm
by Hotwired
It's a small coil, the kind you might get on small bikes, maybe some lawnmowers. With a large coil I might get longer sparks but at the expense of size and weight.
A full size car coil is much bigger than the entire build including battery pack so... nothing to gain.
Guess is about 20 sparks/second with 3V input from fresh batteries but as I say it depends on voltage, you can hear the difference when you've had it running for a while.
Mind you, for cannon ignition, the difference between 0.05 and 0.1 of a second is irrelevant. It charges a capacitor to the same degree for each spark and just one spark has been able to light gas mixes reliably.
Posted: Mon Jun 07, 2010 8:38 pm
by ramses
Thanks, that's the answer I was hoping for. Are you using a SIDAC to dump the capacitor?
Posted: Tue Jun 08, 2010 10:31 am
by Hotwired
Nope, it's a spark gap type switch.
I'm musing over solid state alternatives but I expect I'd either have to lower the frequency, restrict runtime to short bursts or increase the size of the package.
Those 30kv ignitors sold by USG and others who do cheap spark ignitors for gas use a solid state component.
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I can't say for sure which component it is because the versions I have use a switching component which looks like a diode, has worthless markings and could be any one of a number of things which conduct at X voltage and a sidac is one of those.