RE: Triggered spark gaps for coils

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Commercial triggered gaps are typically used for laser applications where
the delay from the trigger pulse to gap conduction matters and is measured
in nanoseconds.  We can tolerate tens of microseconds of jitter and there
will be no observable impact to performance.  I doubt that any realistic
environmental variation short of flooding is going to make any difference to
us.  And it can have no more impact than in conventional RSG's.

We also will be using our gaps at a higher PPS rate and for longer run times
than laser applications will.  Keeping the electrodes cool will be difficult
without forced air cooling.  Laser applications want the gap to conduct
until all the cap's power has dissipated completely.  We want the gap to
quench sooner, and this will be impossible unless airflow is present to move
away metal ions.  We need airflow.  I'm not suggesting air compressors or
tanks.  A vacuum cleaner motor or fan will do nicely.

For the trigger transformer, an auto spark coil will probably suffice,
although I had the good fortune to win an ebay auction for an EG&G trigger
transformer (sorry Bert!).  Unfortunately I'll not be able to do any
experiments with it anytime soon as we're moving to a new house and things
are in a state of packing, to be followed by a state of extensive
renovations...

The trigger circuit will need a 60 Hz zero-crossing detector with a 120 Hz
output, followed by a variable delay circuit to vary the phase.  I don't
think you want to trigger at variable voltage levels along the mains
waveform, as mains-voltage is subject to significant dips (not to mention
spikes) as your coil draws more or less power.  I'll not be able to
speculate on exact circuit configurations until I'm able to build and test
them, several months away at best.

Regards, Gary Lau
Waltham, MA USA

Original poster: "Metlicka Marc by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<mystuffs-at-orwell-dot-net>

 all,
while i agree that the building of a triggered gap shouldn't have to
involve exotic materials and such, i'm not sure i agree that not sealing
and air blown are ok either.
i would think that we would want a somewhat reliably repeatable gap and
wouldn't atmospheric conditions also change the characteristics of the
gap? i myself really wouldn't want another thing that needs tuned every
time the environment changed. a somewhat sealed unit should keep this to
a minimum. also depending on how permanent ones coil system is locked
into one location, a compressor is just another thing to tote around.
maybe a compressed gas cylinder could be an option with many gasses
available?
now that several ideas and comments on the actual gap have been
presented, i would like to ask if anyone has any suggestions as to what
might be some good triggering circuit configurations?
an idea i had was to us a diac or sidac that could be adjusted to
trigger at various levels of the wave from, say just past zero crossing
to 99% of peak. pulsing it into a trigger or pulse transformer
now don't hit me with the "just past zero won't work" because i
understand, this is just a reference. what i'm looking for is solid
circuit considerations, opinions and ideas.
with terry's work on ssgaps and all i think we still could find some
interesting things out with these?
so far there has been much discussion about how the actual gap should be
built,what will work and what won't, that's ok. but i think once a good
triggering circuit is devised then many different styles of gap or
triggering electrodes can be tried. as terry always tries to do, off the
shelf common components maybe, so most all can have a go at it? not real
sure how many on the list are actually planing on building or
experimenting with this, but if a simple little circuit can be adopted
for triggering, then i think many more would try.
i am going to work at it for sure,
marc m.
(my apologies for any spelling mistakes to those that hold a direct link
with spelling and intelligence)