Re: Triggered spark gaps for coils

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

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

gary

Tesla list wrote:
> 
> 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.

i thought that moisture might cause a premature triggering of the gap
before the pulse?
good to know that once it is set it should be stable, any ideas on gap
spacing as per voltages, like 1/3 rd more then self triggering?

> 
> 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.
oh, i must have totally misunderstood the air quench gap idea? i
automatically see compressors blowing the arc out.
i have a nice high velocity turbine type blower that i may be able to
play with. would it be better to draw through the cylinder containing
the gap or blow through? in jim's post he mentions air passing over the
annular trigger electrode as well as through the cathode, maybe it would
be very easy to set it up along the lines of a flow bench, drawing
through a ventury with paths along various parts for cooling.

> 
> 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!). 

yes i was going to bid that, respect prevented me, but i have several
pulse transformers now that i can use including a massive radar pulse
trans. 

 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. 

hmm, i think i know someone on the list that has a beautiful zero
crossing circuit devised already.

 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.

basically our sync. gaps are firing at various points of the waveform
now, i would think that as long as your firing at a point where the tank
is charged to peak then that would be optimum? i may be missing things
here. i've had little luck finding much as way of search's for triggered
gaps other then eg&g. i wonder if the modified strobe circuit that terry
rigged for phasing sync's could be a simple starter trigger? how much
current does it look like would actually be needed to get ignition?
would this be a factor of the arc channel diameter of the tube
containing the gap? 
i have a BUNCH of gas tube surge suppressers rated for 250v each, maybe
for starters i can gang some up for 3kv each side and trigger the center
to try to get a little of the trigger circuit expierience(out load
thinking)
thanks for the input
marc

> 
> 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)