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This is the very basic circuit, showing only the
neccesary components. The high voltage transformer is shown as
"NST", meaning Neon Sign Transformer, since that is
what most coiler use to power their systems. The case of the
transformer is grounded, which also forms the ground for the
center tap of the secondary. (center tap is connected to the core
internally) The spark gap is shown connected parallel to the
transformer output, but its location is interchangeable with the
tank capacitor. The cap is shown simply connected between on leg
of the gap and one side of the primary coil. The primary is
shown as having an adjustable connection on the side opposite the
capacitor, obviously, which side the adjustable tap is on
doesn't matter. The distance between the primary and secondary
should be variable in your setup, so as to be able to change
coupling. Just know that you need to fiddle with it to get
optimal performance, it isn't neccesary to understand coupling.
The secondary is shown with only a very small terminal, as no
discharge terminal is neccesary to have a functional system. You
may not want the arcs coming directly from the top turn of the
secondary, and the streamer length will greatly improve with a
large terminal, so It should really be used with any system.
Also, be sure that the ground for the secondary coil is the one
used to connect to the transformer case, and not the electrical
ground. The special ground for the secondary coil is referred to
as the "RF ground", and should be a separate connection
to a ground rod driven into the ground somewhere. In a pinch, a
house's cold water pipe can be used.
Ah, a more
complete system. In order to prevent damage to various
components, and reach a maximum performance with a coil, I'd
recommend something at least as complex as shown. Now there is
fuse protection on the 120V side, a center-grounded saftey gap,
RF chokes, and a large discharge terminal. The saftey gap serves
the purpose of shunting any really high voltage out of the
primary system, hopefully before it can damage the transformer or
capacitors. Each side is set so it will -just- not arc to ground
when only the transformer is connected to them. This way,
anything significanlt higher than the voltage the transfomer is
rated at will arc harmlessly to ground, which should, BTW, be the
RF ground, not the electrical ground. The RF chokes should be
somewheres about 1mH in inductance. I built two using 26 AWG,
wound on 2" id PVC, each about 5" long, and one
measures 2.18mH, the other, 2.17mH. Everything else is the same
with this system as the first shown, accept for the discharge terminal, which should be
electrically connected to the top turn of your secondary coil.
One thing to watch out for is making any kind of connection that
forms a shorted turn on the primary or secondary, or even just
near them, as it will suck massive amounts of power out of the
system.
I would definately approve of this
configuration, which has all items for optimal, and safe,
performance.The changes include the addition of a variac
(variable autotransformer) to control line voltage, replacing the
RF chokes with power resistors and RF bypass caps, and adding a
strike ring to guard against arcs from the secondary to the
primary. Now I am getting beyond myself, here. I have niether a
strike ring, RF bypass caps, or power resistors in my system,
though I surely wish I did. The RF bypass caps should be rated at
the same voltage as the tank cap, and have a value of a few
hundred pF. The power resistors should be about 25-50W, 500-1K
ohms. Be very sure that any strike ring has a gap in it of at
least 2", since completing it as a whole loop will drain
energy away,as well as heat up the ring.
email: electrophile@juno.com