Re: Triggered gap

["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>

hi henry,
you're on the right track. just a few things bellow.

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Hhchicken1-at-aol-dot-com>
> 
> Hi list!
> I have decided to make a triggered spark gap to replace my current 'vice and
> a nail'.  I thought I'd better post to the list before I fry myself...
> For the initial tests I will be using a NST labelled 6/35, although it seems
> to be able to jump a gap of more than a centimeter (!). For the gap
> electrodes, I am using the Earth pins from UK mains sockets - I believe they
> are made of copper, and they are much more substantial than the US variant.
> I have set two of them up at a distance where the NST with tank cap attatched
> will not bridge the gap, and have placed a third trigger electrode in the
> middle, offset by quite a large amount, so the gaps between any two
> electrodes are about equal.  With the NST and tank cap (no primary), this
> does not fire.

in my initial testing i used a primary and tank cap without secondary,
this gave me a realistic system that had the same loading as the whole
system.

> For the trigger, I am using a car ignition coil powered by a dimmer switch
> and 3uF cap direct from the 240v 50Hz mains.

sounds good, i use a 2uf 1000v cap.

  This produces (at a guess)
> around 40kV and when fired across a gap produces a tone that sounds quite
> like 50Hz.

sounds great.

  I am all set to connect this to the main gap, but am unsure how
> to safely do it.  As the ignition coil is an autotransformer, if I connect
> the HV out from the coil to the trigger electrode, and the minus terminal on
> the coil (which is also connected to my dimmer) to one of the other
> electrodes, surely I will be almost directly connecting the HV from my NST to
> my dimmer switch? 

connect the hv out from the auto coil to the trigger electrode only,
connect the mains through dimmer and across the + - of the coil, that's
all. a couple things though, always power the trigger circuit first, if
not the safety gaps will light up like a christmas tree. at first use a
plug on the trigger coil for mains power, i'm not sure about the 240v
but for 120v it makes a difference which way the mains is connected
across the + - terminals. one way will give a small kickback into the
mains it seems? switch the leads if you notice a small arc as your
plugging in the nst after the trigger coil is powered and running, the
opposite way will not produce any kickback? i was worried about the
nst's tank currents backing into the mains from the trigger electrodes
at first so i put a couple wraps of the mains for the trigger coil
through a choke, there doesn't seem to be any problem of this though so
i don't worry now.

 Another problem is that my NST is not grounded, I realize
> that this is a must and will do that before I try anything.

i'm actually floating my nst case at present, i ran a new, separate
ground out for this and will be grounding the case from here on. i
didn't touch the nst case at all in the past.

> 
> Thanks for any help you can give me - a schematic would be handy hint hint :)

i have a schematic of sorts that i'll try to get on my site today.
good luck and please report your progress,
marc m.

http://63.229.238.60/temp/trigger_sch.jpg

<This is terry's temp site with the direct url.  Hot-streamer is a little
messed up at the moment so I "hope" this works ;-)) - Terry>

> Henry Hallam