Re: Tesla Coil Help
Posted by Bert Hickman on 5/31/2007, 6:00 pm, in reply to "Tesla Coil Help"
: We have recently built a high voltage Tesla coil for a graduating project
: for our high school, but we're having some problems. My friends and I were
: hoping that anyone might be able to help us troubleshoot.
: Our coil itself is powered by a 15kV 30mA neon sign transformer. The
: primary coil has 11 turns of 3/8 inch copper tubing, with an inner radius
: of 3.5 inches and an outer radius of 13 inches. The secondary is 26 inches
: tall with 22 gauge copper wire. We have a static spark gap and safety gap
: that are easily adjustable. We built the capacitor ourselves out of
: polyethylene sheets and aluminum. We believe it to work well and have
: found it to be 18nF.
: The problem is that once the coil is wired the transformer fails to fire.
: There is no arcing across the spark gap, and no noise indicating that the
: transformer is working. Our schematic has the spark gap and safety gap in
: parallel with the transformer and in series with the capacitor and primary
: We feel as though we're missing something simple. The components
: themselves seem to be working properly but when wired correctly the coil
: does nothing. We have found it possible to create arcing in the spark gap
: but only when all the components are wired in series. When this happens,
: however, we can tell that the primary coil creates no field because we
: have held a fluorescent bulb near it with no result.
: Any help would be greatly appreciated. Hopefully you have a chance to
: respond soon as we do have some time constraints.
: Ian, Thomas, Chong
Assuming your system is wired correctly, you seem to be having a problem with your NST. It's possible that you may either have an electronic NST or an NST that has a built-in Ground Fault Interruptor (GFI). If the transformer has a "reset" button, then it is a GFI type and may not work properly in a Tesla Coil system without some further work. An electronic NST will not work in a regular spark-gap type Tesla Coil.
If you disconnect the NST from the system, can you [CAREFULLY!] get an arc from each HV terminal to the case of the NST, do the arcs appear to have the the same size and appearance, and do the arcs "buzz" (at 120 Hz) when you stretch out the arc? If they hiss instead of buzzing, or initially jump the gap and then stop until you unplug and re-power up the NST, or if the NST is physically small and light weight, then you may have an electronic NST. An electronic NST will weight perhaps 2-3 pounds while a regular 15/30 NST will weight 15-20 pounds.
If you have a make and model number, or a picture of the NST I may be able to determine if you have the right type. If you'd like to discuss, give me a call at 630-964-2699.