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Is the output of my ignition coil AC?

  1. Jun 20, 2017 #1
    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. jcsd
  3. Jun 20, 2017 #2

    davenn

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


    Dave
     
  4. Jun 20, 2017 #3
    Ok, thanks. Finally, so if it is pulsed DC, I expect it won't be able to power a Cockcroft-Walton multiplier?
    Thanks,
    Max
     
  5. Jun 20, 2017 #4

    jim hardy

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    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.


    Your link redirects me to here - is that correct ?
    http://www.sciencemadness.org/talk/files.php?pid=91557&aid=2775.

    upload_2017-6-20_9-23-46.png

    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
     
  6. Jun 20, 2017 #5
    Thanks for replying,
    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
     
  7. Jun 20, 2017 #6

    jim hardy

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    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.


    SparkWaveform1.jpg

    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
     
  8. Jun 20, 2017 #7
    I understand now,
    thank you.
     
  9. Jun 20, 2017 #8
    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
     
  10. Jun 20, 2017 #9

    jim hardy

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    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
  11. Jun 20, 2017 #10

    jim hardy

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    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.
     
  12. Jun 20, 2017 #11
    Yes, I can handle these systems safely, I assure you.
     
  13. Jun 20, 2017 #12
    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
  14. Jun 22, 2017 #13

    berkeman

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