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Re: Colorado Notes and laser caps
TESLA COIL, PULSED, QUESTION
Hi,
Could you describe how often the coil fired and
the nature and appearance of the resulting
streamers?
Barry
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From: "tesla"-at-poodle.pupman-dot-com-at-PMDF-at-PAXMB1
To: Benson Barry; "Tesla-list-subscribers"-at-poodle.pupman-dot-com-at-PMDF-at-PAXMB1
Subject: Re: Colorado Notes and laser caps
Date: Saturday, February 08, 1997 9:43AM
<<File Attachment: 00000000.TXT>>
> Subject: laser caps
> Subject: laser caps
Subscriber: tom_mcgahee-at-sigmais-dot-com Fri Feb 7 23:09:09 1997
Date: Fri, 7 Feb 1997 17:36:52 -0500
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re: Colorado Notes and laser caps
Gary,
The 14 spark gaps may indicate that the caps are wired in what is sometimes
called a Marx configuration. Are there any coils connecting the caps? If
there are, then what you have is a form of high voltage Multiplier circuit.
Many people are familiar with the Marx multiplier circuits that use
capacitors and rectifiers. Well, there is a form of the Marx multiplier
that uses coils and capacitors. The way it works is this: The capacitors
are initially connected in parallel with one another via the
inter-connecting coils. (the coils can be just a couple of turns of wire...
it doesn't take much!). When the capacitors reach a certain critical
voltage at least one of the spark gaps conducts. What happens then is very
interesting. ALL the spark gaps will fire simultaneously and the currents
will cause the coils to build up a very high opposition to this current
spike. The result is that for a fraction of a second the capacitors that
had been in parallel now ACT like they are in series. Since the voltage
drop of the spark gaps is LOW when they are conducting, this results in a
VERY HIGH output voltage pulse.
Now, before everybody starts thinking "Off the Topic, what has this got to
do with Tesla Coils?" let me say that in 1964 I saw a very large Tesla coil
that was part of a traveling science show. The coil threw about six foot
sparks, which was quite good for a Tesla coil in those days. After the show
I pestered the people responsible for the show until they reluctantly let
me look at the thing up close. Inside a big metal box was a bunch of coils
and capacitors. When I asked the guy what all that was about, he explained
to me that it was a coil-capacitor Marx multiplier used to step up their
couple of KV main transformer voltage up to 30KV. I should mention that
another thing that made this Tesla coil somewhat unconventional was the
fact that the resonating capacitor was connected directly in parallel with
the primary of the Tesla coil. The Marx multiplier would dump a nice big
bunch of energy into the L/C primary circuit, and then the primary would
happily ring away until it was hit again by the next dump of energy. Note
that this strange Tesla coil was a pulse-driven design with no topload
other than a flat copper plate on the top. And *that* was there so that the
performer could stand on top of the coil and throw sparks off of metal
electrodes on his hands. If these guys had bothered to put a toroid on this
baby, it probably could have done much better. Also, this was the *only*
Tesla coil that I had ever encountered that had a capacitor connected
directly in parallel with the primary. When I got home I pulled out my most
prized possession, a book published in 1956 on the occassion of the 100th
aniversay of Tesla's birth by the Nikola Tesla Museum in Beograd,
Yugoslavia. This book is a huge compendium of Tesla's lectures, patents and
articles, entitled "Nikola Tesla * Lectures * Patents * Articles" that
comprises about 600 pages of material written by Nikola Tesla. It is not a
book about Tesla, but rather ALL of it is material written BY Tesla.
Excellent stuff! Anyway, at the absolute end of this huge book is a
photograph of a page from Tesla's Colorado Springs notebook. And there is a
hand drawing by Tesla of a Tesla coil circuit in which one capacitor is
used to produce the disruptive discharge, and the other is placed directly
in parallel with the Tesla primary.
I was reminded of this L/C arrangement by a recent remark made by Richard
Hull in one of his postings here on the Tesla list. And then today this
Laser power supply with its multiple spark gap thing reminded me of the
first time I ever saw such a circuit, and how I had thought the designer
must have made some sort of mistake, because their Tesla coil was so
different from all the ones I had information on, only to discover that
Tesla had done the same thing many years earlier.
There is still room for fruitful modern research based on such little
things from the past. We may be tempted to just pass by, look at it with a
shake of our head and say "boy, those guys weren't as smart as us." Some of
them, like Tesla, were even smarter than we think. And that includes those
of us that think he was a genius.