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Coiling again
Hi ...
Finally I moved enough junk out of the garage - stored there during
some renovations - to set up my coil again. Instead of the two 15/60
neons, I used the pig so kindly sent by Dr. R., and I increased the
capacitance to .05 uF but everything else is the same - DC H bridge
rotary driving an 8 inch coil of 1100 turns, 27 inch by 7 inch toroid.
To no great surprise the pig makes a much stiffer supply; with the neons
I had to increase the variac as the BPS went up, with the pig the
effect is very much less. Alas my garage is much too small, the
sparks reach out to connect to every wall, the furthest being only
52 inches away, but even at 52 inches it connects solidly and often
lingers for several seconds.
I can't help but think the H-bridge must be hard on the capacitors.
Each presentation represents a voltage reversal of the full DC, and
the RF oscillations are impressed on top of that. The only reason
the caps have survived is I have enough in series to withstand 100kV.
MicroSim indicates the cap bank is seeing 80 kV peak, and pulse
caps don't particularly like voltage reversals.
I have decided to build a Marx gap, two capacitors of 0.1 uF each
charged in parallel at one gap presentation, then discharged in series
at the next. The disadvantage is I'll need two presentations for each
bang. The advantages are numerous. The charge and discharge
cycles are completely separated, eliminating RF back into the
charging circuit. The caps only see RF oscillating around zero,
I can use a charging choke to increase efficiency, and I still have
complete control over break rate. A MicroSim circuit indicated I can
nearly double the output over an H-bridge. I'll be glad to mail a .sch
circuit to anyone interested.
I've had a lovely 3/4 inch thick g-10 rotor machined with 24 holes
for electrodes on a 20 inch center, which should give me plenty of
flexability on electrode configuration. I should be able to get a
drive and housing for it built in the next month or so.
Good to smell ozone again!
Cheers LR