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12V battery to create spark gap?

  1. Jun 2, 2013 #1
    Hey okay, so I have a 12V source which can provide a max of 10 mA, and I also have a switch that can go from open to close in 1 ms, How can I create an inductive circuit that will create a spark gap between electrodes that are 3mm apart? I did the math and found the breakdown voltage to be 2334.24 V, so I guess I need to figure out a way to get my input voltage of 12V to my desired 2334.24V in order to ionize the air and have it actually jump. I just don't know how to build a circuit that would do that?

    I think I would use a capacitor that would initially build up voltage until I reach my breakdown voltage and then release from the switch, and then I'm lost. Any suggestions? Thanks!
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  3. Jun 2, 2013 #2


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    Do you know the usual formulas for a circuit with a coil and a capacitor inside? If not, it would be useful to look them up.

    I think you need a circuit with a period of much more than 1ms (so the switching time is not important). With capacitance and inductance, you can relate the current of 10mA to the peak voltage of the circuit, and find values for both elements which satisfy both constraints.
  4. Jun 2, 2013 #3
    I know that iC=C(dVc/dt) and I know VL= L(diL/dt), so and inductor opposes instantaneous change in current and a capacitor opposes instantaneous change in voltage. I think I somewhat figured it out. I think maybe the 1 ms just is to confirm that the switch closes instantaneously. Thanks for the response!
  5. Jun 2, 2013 #4


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    What do you want to make a spark for?
  6. Jun 3, 2013 #5


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    Why not look at how photographic flash units work? They will produce high energy pulses at several hundred volts. (The limit is only imposed by the fact that the flash tubes use that voltage.)
    But you should really know what you are doing if you are planning to make sparks at high voltages. It could be wandering into the realms of what PF doesn't discuss. If you want 'safer' high voltage sparks, you may be better to try electrostatic methods.
  7. Jun 3, 2013 #6
    I'm not physically building something, I am just designing a circuit schematic that would be capable of doing this with the parameters given haha. Thanks for the advice!
  8. Jun 3, 2013 #7


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    Ah well, as we're just thinking this one. . . . . You just need an oscillator, a transformer and a rectifier to produce a fairly high, intermediate voltage (a couple of hundred) and charge a Capacitor. You then discharge that capacitor through a resonating inductor to produce a seriously big 'ding' in Volts. This requires a fairly hefty solid state switch (SCR, for instance).
    Look at motor car electronic ignition circuits for more techniques.
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