RE: First tesla coil question

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

Hi Ryan:

I think what you should be asking (perhaps you are?) is "How do I adjust
my spark gap for proper operation"?  From the way you phrased your
question, I can't tell how your complete circuit is hooked up.

When running or testing a Tesla Coil, it is very important to have all
circuit components hooked up - NST, gap, capacitor, primary, secondary,
and top load.  It is especially BAD (damages capacitor & NST) to have
only the NST, gap, and capacitor.  Testing the gap with just the NST and
gap (no capacitor) is OK however.

One typically does not diagnose proper gap operation by observation of
the gap sparks.  Either the gap sparks or it doesn't, and instruments
are not at all needed.  The important things to check on your gap are:

1) What is the (total) separation between the electrodes?  The answer is
to a degree academic, as there is no simple "for this NST use that gap
width" answer.  What you must do is set the gap width such that with
ONLY the NST connected to it, the gap will just start to fire.  But I
ask because too narrow hobbles performance, and too wide can kill your
NST or capacitor.
2) The gap electrode geometry is important.  You do not want the spark
to occur at the same, small area on the electrodes, like at the end of a
pointed nail.  This will cause the point to get too hot, which is bad.
Ideally, the electrodes will arc along a long side, as with using
parallel copper pipe segments.  This keeps the heat generated in any
small area low and allows it to be dissipated.
3) The electrode material is important.  While tungsten is best in high
powered applications, copper or brass are fine for low or medium powered
applications.
4) Air flow through the gap almost always helps improve performance.  It
needn't be a huge amount (you don't need a leaf blower or compressor).

If you provide more details about the construction of your gap and other
components, we'd be happy to evaluate and offer constructive criticism
;-)

Regards, Gary Lau
MA, USA

> Original poster: "Ryan Miller" <pballjunkie@xxxxxxx>
>
> Hi All,
>     I've been a subscriber to this email service for a bit of time
> now but this is my first ever contribution to it...or at least use of
> it beyond reading material.  I am attempting to build my first tesla
> coil and want to make certain everything goes as well as possible.  I
> have designed multiple spark gaps each of which appears to work but I
> am stuck on a simple question.  How do I know when it is
> "working"  and not just producing an electrical arc  but instead a
> fully charged shot with my entire capacitor behind it.  I do not have
> any tools beyond a physics textbook, paper, pens, and a 10 dollar
> voltmeter.  The best simple observations I can gather to show that it
> would be working is when it produces the exceptionally loud crack
> with each firing and that it shoots nice clean blue shots across as
> opposed to the fuzzy orange common of electrical arcing.  Is there a
> better way to know or is that all I have to work with without an
> oscilloscope or more tools. I've done all the calculations to find my
> gap spacing on a few models and made a few by trial and
> error.  Thanks for your help.
>
> Ryan Miller
> 19 years old - CA
>
> .-= Miller =-.