Simple Spark Gap Circuit

Discussion in 'The Projects Forum' started by kevin1337, Apr 25, 2015.

  1. kevin1337

    Thread Starter New Member

    Apr 25, 2015
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    Hi,

    I'm working on a simple project and have run across a problem. Been a long time since I've done circuits and cant seem to get this problem solved.

    I need a simple circuit that when a switch is flipped it will produce a spark over a 3mm gap. Does anyone have an idea on how to do this? I've tried creating a simple/modified marx generator to create the spark but still no luck.

    Been using:
    1 Mohm resistors
    4kV 102 pF Capacitors
    9V Battery

    Thank you,
    kevin
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    Given the voltage and the capacitance, the energy stored in the capacitor is 40 nano-Joules. I'm sure it is not enough to jump the gap. The dielectric strength of Air is 3 MV/m or about 9000 Volts for the 3 mm gap. I think you are a ways away from that level.
     
  3. kevin1337

    Thread Starter New Member

    Apr 25, 2015
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    Thank you for the advice. How might I go about changing the circuit? I've tried putting multiple capacitors in series... up to four (4) of the 4K capacitors but still no spark. Is my charging voltage too low?
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    How is a capacitor supposed to create any spark? It will never make more voltage than the 9V you are putting in. You need a transformer or inductor to create any sparks.
     
  5. kevin1337

    Thread Starter New Member

    Apr 25, 2015
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    Thank you kubeek.... I think that is what I am missing.
     
  6. BR-549

    Well-Known Member

    Sep 22, 2013
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    Try this.
     
  7. kevin1337

    Thread Starter New Member

    Apr 25, 2015
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  8. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    I had to google the Marx generator as I had never heard of a passive DC voltage multiplier; It relies on the input voltage being high enough to reliably produce an arc so a 9V input is a non-starter.

    If the TS just needs big sparks;

    http://www.ebay.co.uk/itm/Boost-Hig...225?pt=LH_DefaultDomain_3&hash=item5d578158e9
     
  9. kevin1337

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    Apr 25, 2015
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  10. DerStrom8

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    Feb 20, 2011
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    Marx generators work by charging capacitors in parallel and discharging them in series. This is how you get a higher voltage out than what you put in.

    In order to use a 9v battery to charge the capacitors, you'll need a driver circuit along with the transformer. You cannot run a transformer on DC.
     
  11. kubeek

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    Sep 20, 2005
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  12. kevin1337

    Thread Starter New Member

    Apr 25, 2015
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    Blocco's idea of the Boost Step-up Pulse Power Module High-voltage Generator is exactly what I need. I was over complicating a simple solution. Didn't know this device existed.
     
  13. #12

    Expert

    Nov 30, 2010
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    I didn't know it existed, either, but it looks scary to me! 40KV on some tiny little hook-up wires? The diameter of the winding wires must be microscopic. Treat it gently. I don't think it will survive much abuse.
     
  14. kevin1337

    Thread Starter New Member

    Apr 25, 2015
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    So #12 gives me another noob question....

    If I want a spark to last something like 0.1 seconds (or just a small amount of time really) then stop for like 1.0 second then make another 0.1 sec spark... then repeat over and over until a switch is hit. Is there an easy way of doing that?
     
  15. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    I have a couple of these modules and I can confirm that they are terrifying, but I haven't manage to destroy one yet.

    Lower voltage modules are also available:

    http://www.ebay.co.uk/itm/New-DC-3V-to-7KV-Boost-Step-up-Power-Module-High-voltage-Generator-1PCS/251541077786?_trksid=p2045573.c100033.m2042&_trkparms=aid=111001&algo=REC.SEED&ao=1&asc=29479&meid=9c8ffe9335154039a5f41c08e0cf390f&pid=100033&rk=4&rkt=4&sd=251875437450
     
    Last edited: Apr 25, 2015
  16. #12

    Expert

    Nov 30, 2010
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    It's called an astable oscillator. Easily done with an LM555 timer chip. You will need to add a current carrying transistor to provide the 2 amps your module needs and you have to let it cool off enough. It is rated to run for 5 seconds before overheating but no mention of cooling time required. I don't think a 10% duty cycle would work. Too much heat.
     
  17. kevin1337

    Thread Starter New Member

    Apr 25, 2015
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    Thank you, reading up on it now. Looks like this might work.
     
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