Is the output of my ignition coil AC?

1. Jun 20, 2017

eigenmax

Hello,
I am working on a project that requires both high voltage AC and DC.
I was going to use an ignition coil for the AC because I thought it's output would be AC, but when I saw this illustration, https://www.google.ie/url?sa=i&rct=...cH4F28DNcL3AnRFD_vluFa7A&ust=1498033191615843 , I got confused. It shows the output to be DC.
If powered as is shown in the illustration, is it AC or DC?
Thanks ,
Max

2. Jun 20, 2017

davenn

I would expect it to be pulsed DC .... the pulses being produced by the points / CDI or what ever other system is utilised

Dave

3. Jun 20, 2017

eigenmax

Ok, thanks. Finally, so if it is pulsed DC, I expect it won't be able to power a Cockcroft-Walton multiplier?
Thanks,
Max

4. Jun 20, 2017

jim hardy

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/ignition.html shows that yes, you should get unipolar pulses out of your coil . But it might 'ring' ie decaying sinusoidal oscillation , unlike the clean pulse in the hyperphysics images.

Is that a Model-T Ford spark coil ? Looks like it'd buzz and make continuous stream of pulses.

If your multiplier capacitively coupled(as in this wikipedia link) it won't mind the DC content at its input.
https://en.wikipedia.org/wiki/Cockcroft–Walton_generator

old jim

5. Jun 20, 2017

eigenmax

I got the schematic to power my coil from . Yes, the image in the link is what I was looking at. Is the video correct in sating that it gives AC output?
Thanks again,
Max

6. Jun 20, 2017

jim hardy

We always want simple answers. But Mother Nature makes us work harder than that before she gives us understanding.

Interrupting current through the coil initiates a spark. That's always one polarity.

The capacitor allows "ring down" which is AC.

Not trying to be obscure here, just precise.
It's a repeating transient waveform.
That transient waveform has two components - damped AC and decaying DC.

So your video is i would say oversimplified.

I think the truest answer is "Unipolar pulses with substantial AC components ".

old jim

7. Jun 20, 2017

eigenmax

I understand now,
thank you.

8. Jun 20, 2017

eigenmax

Sorry, but as a final question, how would I choose Cockcroft-Walton multiplier parts based on the output of this setup? What capacitances, recovery times , etc ?
Thanks,
Max

9. Jun 20, 2017

jim hardy

What voltage are you looking for ? High, if you're starting with an ignition coil.
What current ?

I'll defer to somebody who has more high voltage experience than i.

Last edited: Jun 20, 2017
10. Jun 20, 2017

jim hardy

Furthermore,

PF will want some assurance that you have the skill to build this thing safely.
With Ignition coils and high voltage capacitors you could easily build something that will blow a child's fingers off or electrocute an adult.

11. Jun 20, 2017

eigenmax

Yes, I can handle these systems safely, I assure you.

12. Jun 20, 2017

eigenmax

Well, the current is unimportant to me, but I'm putting in about 10kV from the ignition coil, through a six-stage multiplier this should create 120 kV ( please correct me if I'm wrong). Also, the third stage of the six-stage multiplier should output 60 kV, right?
Thanks,
Max

Mod note: Thread temporarily closed pending moderator action.

Last edited by a moderator: Jun 20, 2017
13. Jun 22, 2017

Staff: Mentor

Thread will remain closed due to the dangerous nature of this project (given the OP's level of experience).

14. Jun 22, 2017

Staff: Mentor

Thread is closed due to the dangerous nature of the discussion (and the level of experience of the OP).