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Making a high voltage arc

  1. Aug 19, 2007 #1
    so I need to construct a device that creates a high voltage arc for an experiment, unfortunatly I don't know how to amplify the voltage without a series of transformers.

    I believe there is a way of doing this with a few capacitors, and right now I have about a dozen 12 MFD capacitors, and a couple of transformers. is there anyway that I can make a high voltage arc with these?

    the experiment would benefit from both a large current and a longer duration arc, as the purpose of the arc is to create as much plasma as possible.
     
    Last edited: Aug 19, 2007
  2. jcsd
  3. Aug 20, 2007 #2

    AlephZero

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    You are probably thinking about diode voltage multilpliers. See http://www.techlib.com/files/voltmult.pdf

    Warning: I take no resposibilty for your death, if you experment with high voltages without understanding what you are doing!
     
  4. Aug 20, 2007 #3

    berkeman

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    Yeah, I second that. Luke, do you have an advisor for this project? What have they told you so far with respect to safety issues and precautions? I doubt you would have been given this assignment by an instructor without the proper training and skills necessary to know how to keep yourself safe.

    That having been said, and assuming you have either the skills or supervision to keep yourself and others safe in this project, then you can generate the high voltage using the diode ladder that Aleph mentioned, or with a flyback transformer arrangement, as is used in CRT picture tube high voltage generation. You can google or wikipedia search on the term flyback transformer for more info.

    Please stay safe in your work on this project!
     
  5. Aug 20, 2007 #4

    dlgoff

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    For an AC source, you could use a neon sign transformer. With my 9kV transformer, I can get an arc of about 2 inches. How short of duration do you need the arc to be?
     
  6. Aug 20, 2007 #5

    Danger

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    Luke, I agree with Aleph and Berkeman's concerns about your project. This is some very hazardous stuff that you're getting into. Keep in mind that it's not only your own safety at issue; others could be injured if something goes amiss. It's particularly nasty if you're using caps rather than something like a straight transformer system. Those things can hold a lethal charge for a very long time after you think that the system is safely shut off. At the very least, please have an electrical expert check your work at every stage (in person, not just on line). You might even be voiding some insurance policy or another, and would definitely be considered legally liable in the event of an accident.
     
  7. Aug 20, 2007 #6

    berkeman

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    Good point by Danger (and you wonder where he got is name!). If you use the diode-cap ladder, please keep in mind that shutting off the source AC voltage will not discharge the rectified DC high voltage output.

    Luke, I really need to hear your response to my question about your advisor on this project, okay?
     
    Last edited: Aug 20, 2007
  8. Aug 20, 2007 #7
    i've been zapped by a neon sign transformer before, no big deal.
     
  9. Aug 20, 2007 #8

    Danger

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    I suspect that there's more good luck than good management involved in that. It's not something that you should make a habit of.
     
  10. Aug 21, 2007 #9

    AlephZero

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    The guy that used to live next door to me was a professional carpet-fitter (employed full time by a reputable large company.) One day I was drilling some fixing holes in something outside my house using a hand drill, and he offered to lend me his electric drill. I took one look at the battered state it was in and politely declined the offer.

    A week later, he was drilling a hole in somebody's wooden floor and hit a live electrical cable - which shouldn't have been there, but he didn't bother to check first.

    The defective earthing on his drill killed him.

    Sometimes you get lucky, sometimes you dont... :yuck:
     
  11. Aug 21, 2007 #10

    Danger

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    That's a very good illustration of something that most people don't think of. Although it's a tad off-topic, it's certainly worth publicizing. The grounding is not just to protect against internal malfunctions in a machine; it can save you from contact with an external source as well.
     
  12. Aug 21, 2007 #11
    currently there is no advisor on the project, however this is not my first go with high voltage, and have worked with sources in excess of 10 kv, and with a microwaves volatge doubler circuit which at the peak run 5 kv at 8 amps (very short duration pulses)

    essentially the goal of the experiment is to create a stable ball of plasma in a microwave.

    the device consists of a magnetron liberated from a microwave oven which is connected to a resonating chamber which if all goes well will be able to maintain a plasma.

    the electrical arc will function with provide a consistent source of ionized gas which will then absorb energy from the microwaves and grow until it reaches equilibrium.

    that covers the initialization of the plasma however the containmet is a bit more complicated and the min focus of the experiment
     
  13. Aug 21, 2007 #12

    berkeman

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    Wow, that sounds like a fun project! A kilowatt microwave generator and several kV of high voltage. It doesn't get much better than that :biggrin: (assuming that you know what you need to know about RF shielding, high voltage safety, and the like).

    Do you know yet which of the three methods that we've listed would work best for you?
     
  14. Aug 21, 2007 #13
    I'm leaning towards the diode ladder as I believe that will provide the most instantaneous power, which in turn should create the most ionized particles.

    I also have a number of the necessary caps lying around to make the construction easier.

    as for shielding,Faraday Cages and microwave detectors galor.
     
  15. Aug 21, 2007 #14

    Danger

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    Okay, Luke... you've convinced me that you know enough about this to play safe. Just remember to incorporate some way to discharge those caps in a guaranteed manner if you have to shut down. (I'm thinking of something based upon a goldfish bowl... :uhh:)
     
  16. Aug 22, 2007 #15

    berkeman

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    Anybody else reminded of the classic movie, "Real Genius"? It's like lasing a stick of dynamite.....
     
  17. Aug 22, 2007 #16

    Danger

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    I think that I saw that several years ago, but I can't remember for sure. Maybe I should rent it sometime.
     
  18. Aug 22, 2007 #17

    berkeman

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    Yeah, you would really enjoy the movie "Real Genius" -- great fun, and it's pretty amazing how many of the things in the movie actually happened way back in my college years. LOL.

    http://alumnus.caltech.edu/~erich/real_genius_refs.html

    "I was thinking of the immortal words of Socrates, who said..... I drank what??
     
  19. Oct 2, 2007 #18
    Shocking. Just shocking.
     
  20. Oct 4, 2007 #19
    "I am reminded of the immortal words of Socrates when he said 'I drank what?'" Val Kilmer ~ Real Genius

    I love that movie!
     
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