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From: davec@mhuxu.UUCP
Newsgroups: sci.electronics
Subject: Re: Tesla Coil
Message-ID: <6204@mhuxu.UUCP>
Date: Thu, 11-Dec-86 17:32:15 EST
Article-I.D.: mhuxu.6204
Posted: Thu Dec 11 17:32:15 1986
Date-Received: Mon, 15-Dec-86 03:15:32 EST
References: <4815@reed.UUCP> <823@A60.UUCP> <824@A60.UUCP> <904@sfsup.UUCP>
Organization: Bell Laboratories, Reading, PA
Lines: 57

> In article <824@A60.UUCP> ron@A60.UUCP (Ron Burns) writes:
> >In article <823@A60.UUCP> lee@A60.UUCP (G. Lee) writes:
> >>In article <4815@reed.UUCP> shadow@reed.UUCP (Matthew Giger) writes:
> >>>
> >>>	Does anyone out there know much about tesla coils?  They are a
> >>
> >>  A friend of mine and I build a tesla coil last spring with great results.
> >
> >       Um.... that would be me.
> >
> >Gene did forget one very important item.  As a series resonant LC circuit,
> >you need a capacitor.  this is placed in series with the neon sign xfmr
> >secondary, the spark gap, and the Tesle coil primary.
> >
> >[ description of capacitor ]
> 
> Not necessarily.  In fact, I would hazzard a guess that Gene could have
> omitted the spark gap as well and it would have still worked.
> 
> Spark gaps and capacitors are there to accumulate a charge, then release
> it through the primary in one large burst; much like the capacitor and
> point in a car.  The difference is that the circuit that Ron is
> referring to is strictly for DC power, Genes is for AC.  Yes, those
> neon sign transformers put out AC, so you really don't even need the
> sparkgap.

> David C. Miller, consultant

Not all AC is the same though.  There's the matter of frequency, the
ac produced by the breaking of the arc through the LC circuit is in
the hundreds of kilohertz.  The current produced by the neon sigh
transformer is 60 Hz.   Many of the more interesting effects of the
Tesla coil are produced by the high frequency, not just the voltage,
so you can't leave out the capacitor or the gap.
	The last time I built a Tesla coil I used Coke(TM) bottles
filled with salt water and coated in aluminum foil for the
Capacitors.  This seemed to work better than any I've built using
glass plates or plexiglass.  (It also looks Bizarre.)
	I also experimented with different topology's for the
circuit.  Series connections, parralell's and combinations.  I think
the one that worked best was to have everything in paralell.  I also
tried two capacitors, one accross the gap, and the other accross the
sign transformer. That also worked well.

The tesla coil effects are quite fun.  We once lined up about 10 of
the neighborhood kids up (I was pretty young when I built my first
Tesla coil.) and had one end of the line hold the coil, and the
other end held a flourescent tube, which glowed quite brightly.
	It's good to remember that while you might not get shocked
by the pretty spark's, they are still hot and will burn skin at the
point of contact.  So make contact via a metal object, like a
keyring.

Have fun, (and don't electrocute yourself...)

	Dave Caswell
		allegra!mhuxu!davec