Re: Micro Tesla Coil design

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jolyon Vater Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>

just a quick word to say that the ignition coil is NOT the tesla coil per se
in my circuit but the high voltage transformer which supplies it.

Due to high output impedance/ low output current of the transformer it gets
progressively more difficult to charge larger values (eg more than a few
hundred pF) of tank capacitor to the breakdown voltage of the gap without
either (i)narrowing  the gap and keeping the BPS the same or (ii) keeping
the gap width the same and changing the BPS e.g. by adding a rectifier so
that energy is stored in the cap over one or more cycles of the input
voltage and is not  allowed to discharge except via the gap; I myself use
the latter approach and save energy in the gap over several charging cycles.

By this means I can charge caps up to 22nF or more to the voltage of the gap
but with bigger caps it takes more time to store up the required energy. The
energy stored in the cap IS the energy that is supplied to the primary of
the TC when the gap fires.

By the way, does anyone know how to calculate the resonant or LTR cap values
for an ignition coil HV transformer driven by a squarewave - I suspect they
are not large.

Jolyon.

Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, December 22, 2002 8:11 PM
Subject: Re: Micro Tesla Coil design


 > Original poster: "robert & june heidlebaugh by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <rheidlebaugh-at-desertgate-dot-com>
 >
 > Joyon: Just as a suggestion an ignition coil like a TC requires a
capacitor
 > to tune and produce maxinun power transpher. Usualy a 0.22uf is used. With
 > out this capacitor the spark is poor. Yes some high voltage brute force
 > circuits can force a coil to preform without a capacitor, but not
 > efficently. Yes I have been accosted by people who profess other uses of
the
 > capacitor, but real testing proves them wrong. I recomend the capacitor
use
 > to use less power to give a better spark.
 >    Robert  H
 > --
 >
 >
 >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  > Date: Fri, 20 Dec 2002 14:50:44 -0700
 >  > To: tesla-at-pupman-dot-com
 >  > Subject: Re: Micro Tesla Coil design
 >  > Resent-From: tesla-at-pupman-dot-com
 >  > Resent-Date: Fri, 20 Dec 2002 14:53:34 -0700
 >  >
 >  > Original poster: "Jolyon Vater Cox by way of Terry Fritz
 > <twftesla-at-qwest-dot-net>"
 >  > <jolyon-at-vatercox.freeserve.co.uk>
 >  >
 >  > I know this sounds pessimistic but but with input powers as low as this
 >  > isn't there a real risk that micro coils (nice) can turn out to be a
 >  > micro-perfomance coils (not so nice!) unless they are designed well,
which
 >  > can be tricky to do.
 >  >
 >  > Throughout most of my (limited) experience I have found that it is easy
to
 >  > build a TC that works but less easy to build one that works well. I
have
 >  > been lucky to get more than 1 inch of spark from anything powered by my
 >  > ignition coil driver and when I did (and got 6" of spark) I also had to
use
 >  > a DC rectifier, 22nF of bottle capacitors AND a 25" dia topload -hardly
a
 >  > "micro"-coil is it! Am I doing something wrong here?
 >  >
 >  > Jolyon
 >  >
 >  > ----- Original Message -----
 >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  > To: <tesla-at-pupman-dot-com>
 >  > Sent: Friday, December 20, 2002 1:13 AM
 >  > Subject: Re: Micro Tesla Coil design
 >  >
 >  >
 >  >> Original poster: "Ed Phillips by way of Terry Fritz
<twftesla-at-qwest-dot-net>"
 >  > <evp-at-pacbell-dot-net>
 >  >>
 >  >> Tesla list wrote:
 >  >>>
 >  >>> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
 >  >> <dhmccauley-at-spacecatlighting-dot-com>
 >  >>>
 >  >>> Might still be a bit big to be considered a "microcoil".  I'm looking
 >  > for a
 >  >>> transformer thats no bigger than a C-battery maybe.
 >  >>> Something like 2kV, 1mA max output or similar.
 >  >>> Secondary coil might only be 3/8"-1/2" in diameter.
 >  >>> Be very high frequency - that could pose problems in itself.
 >  >>>
 >  >>> Dan
 >  >>
 >  >> Try a model airplane engine ignition coil, which fits that description
 >  >> pretty well.  Drive with a transistorized interruptor circuit.  I have
 >  >> one running in a hand-held transmitter to play with coherer receivers;
 >  >> runs off a four cell NiCad pack.
 >  >>
 >  >> Ed
 >  >>
 >  >>
 >  >>
 >  >
 >  >
 >
 >
 >