[wjyates]

I have car coil driven by 555 ic that part seems to work fine
From car coil I have 3 20Kv 500pF caps then my spark gap
Conneted to my pri. Pri is 3/16 copper wire 8'' dia approx 6'' tall
At 7 windings
Sec is 28ga wire 3 1/2 dia 14 1/2 '' tall 1080 windings
Can't get any spark at the spark gap
Seems like caps are not charging

Can anyone help
THANKS

[statictable]

WJ, I can't help you but did want to say, Great Work... Fun... hope it fires for you. ST

[BinaryBedlam]

wjyates,

Judging by the date of your original question, I'm guessing you already have an answer, but I'd like to respond anyway in case others stumble across your post with the same question.

For some reason, on all the articles written about Tesla Coils out there, this is never brought up.

You are correct, your capacitor is not even charging. This is because you are using a flyback/ignition coil for your HV source instead of a neon sign transformer (NST). You are operating it at well over 60 Hz with your 555 timer, right? Probably something like 1kHz or more, right? So think about the output of the ignition coil, sure it's high voltage, but its also high frequency AC. What is AC? Back and forth. You are charging and draining the capacitor like a thousand times before it ever has a chance to fire across your spark gap.

Solution? You need to rectify your ignition coil's output with diodes thus making a DC Tesla coil, OR you could use a HV supply with a much lower frequency, like an NST. An NST will still output AC, BUT the frequency is low enough that the caps will at least have a chance to charge up and fire across the spark gap before the voltage swings the other way.

Hope this helps,
BinaryBedlam