tesla coil circuit question

Discussion in 'General Electronics Chat' started by lokeycmos, Sep 25, 2011.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    ive been researching tesla coil circuits. i have a question. if you look at the pics on the link one circuit has the cap before the spark gap and the other after the spark gap. do these circuits operate the same way or are there differences. could you please explain the differences as well as the pros and cons of each circuit?TY


    http://kudlemyer.com/tesla/tesla_guide.html
     
  2. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    Hi lokeycmos!

    I've had quite a bit of experience with Tesla coils, and I've tried both methods. They both do essentially the same thing--if the transformer is running off of AC from your outlet, the capacitor will charge up every half cycle (so 120 times per second if you have 60 hz power, 100 if 50 hz) and discharges. Every time your capacitor discharges through the spark gap, it sends a sudden surge of power through the primary coil, which induces current in the secondary. The oscillation takes place between the primary and the capacitor (your standard LC oscillator, only with high voltage). It does not matter which layout you use in this case, because they both do the same thing.
    However, I have read that it is best for a standard transformer if the spark gap is placed across the terminals (parallel to the transformer) and the capacitor in series (i.e. the cap after the spark gap). In this configuration, the spark gap shorts high frequency before it can damage your transformer.
    The other configuration works better if your transformer is made to handle high frequency alternating current, but most transformers (such as an NST or OBIT) should have the spark gap in parallel to the output.
    My personal recommendation: Put the spark gap directly between the two terminals of the transformer. It should work with most non-specialized transformers and there is less chance of you damaging your equipment.
    I hope this helps!
    Regards,
    Der Strom
     
  3. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    that was an excellent explanation! thank you. another Q i have is, how does the the secondary oscilate at such a high frequwncy if the input is only 60Hz (or 120)
     
  4. magnet18

    Senior Member

    Dec 22, 2010
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    The primary capacitor and inductor set up a resonant LC circuit and when the spark gap fires the current goes through the inductor and it resonates, usually at a very high frequency. Because the secondary has the same resonant frequency, it will resonate, and shoot out lightning and stuff
     
  5. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    Thanks magnet, you hit the nail on the head :D

    The tank circuit of the Tesla coil acts as a resonator, as magnet said. This creates a much higher frequency than what comes out of your wall socket.

    Every time the gap fires, it sends a surge of current through the primary coil. As mentioned in my first post, this induces a current in the secondary. This pulse travels up the secondary and then back down, a phenomenon commonly referred to as "ring-up" and "ring-down". To "tune" your tesla coil, you must make it so that the capacitor fires at the exact time that the current in the secondary rings all the way back down to the bottom. The cap fires, sending another surge of current into the secondary, which, if the first "ring" of current is also at the bottom, will add to it. This makes the voltage even higher, as it rings up and down again. If you keep doing this, you can get a massive amount of voltage at the output at the top of the secondary, which is the entire theory behind a Tesla coil.

    Der Strom
     
    magnet18 likes this.
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