Developing HV DC Pulses

Of course, it's pretty unlikely that the tube model was fitted to points that far out of the normal operating range. But then, there's no harm done.

Cheers

Phil Hobbs

The oil drops don't expect anything. They move - fairly slowly - under the influence of an electric field, and what has been written about the approach suggests that sustaining the field for 10 msec works best,

A voltage that alternates between two well specified voltages.

DC and AC are short for direct and alternating current, so it's not pedantically correct to use them when you are more interested in voltage.

No; the insulation between the line windings and the case is probably NOT going to tolerate kilovolts on the case. And, in case of a wiring fault, the case is a big chunk of metal that you'd just as soon wasn't hot

That transformer insulation was my concern, I'd like to know the construction, I'll bet there is a lot of spacing between primary and secondary. While I understand the hot transformer case danger, the transformer is isolated within a locked plastic case. I could use a 1 amp fuse and if there was a transformer winding short, it would easily pop the fuse. (I have more transformers) I'm just looking for a way around these large a exposed aluminum tubes running at HV. Any Ideas how to do that? Last resort, I'll build a plexiglas or lexan box around them. Thanks, Mikek

You definitely will never need to put zeners across the neon. The neon will always fire eventually and then hold at a slightly lower voltage.

Size your neon series dropper resistor so not too much current is drawn at the highest voltage, I think 8kV in your case. The neon will still be lit at 100V but just a lot dimmer.

piglet

Ok the first spec I saw said current is 0.5ma to 5ma. I found the GE Glow lamp Manual,

4 shows well over an amp flowing through a neon tube. Can't verify if this causes damage but does shorten lifetime.

Wouldn't I size the resistor for higher current at 8kV so that it has at least 0.5ma at 100volts? Thanks, Mikek

Put a cap across the neon and it will blink, always the same brightness.

I have ordered a function generator, this will have a read out for frequency and I can set duty cycle with some specificity. I think this will simplify setting the input. Does that mod look OK, There is a suggestion to add a zener circuit on the function generator to prevent any voltage over 6V driven into the function generator. Will this work, or do I need an interface circuit between the cathode and the function generator.

That's helpful. Mikek

Most any fungen can drive the gate of a mosfet directly. The mosfet is the interface circuit.

You could add a zener at the fungen output, but it's not necessary. You don't need the 50 ohm resistor either.

The fungen manual said the edges are fast, so it should be terminated or it will ring.

Probably minor, but, "Out of an Abundance of Caution". If I need more output, I can change or remove it.

Mikek

If the gen is a 50 ohm source, that's wrong. Loading will cost half the available voltage swing.

That's true, how much voltage swing do I need to drive a 2N7000" The manual says, Continuously adjustable from 4 V p-p to 14.5 v p-p, open circuit. So, a little over 7vpp into 50Ω. A pair of diagonal cutters will solve it, if it's a problem.

I'm gathering parts for the 24V PS. I have 24V regulators, I can make it adjustable from 20V to about 35V. Good plan? Or would lower up to 24V be better?

Mikek

If 7v p-p means +-3.5, it's not enough.

But don't believe me about this stuff.

It has a DC Pulse called a CMOS output. Schematic of output section.

Mikek

The CMOS output circuit is insane.

Not the point John. Will it put out a 7 volt pulse into 50Ω? Is that enough to saturate the 2N7000. Here's the specifications of the fungen.

I have no idea what your Push pull circuit was, I don't have LTspice. I sent it on to Dmitry, he has modified it, I don't know what he did. Yours to peruse. Thanks, John.

The concern I have, though, is between the primary and the case. That might NOT have been designed or tested for output-voltage levels.

Yeah, that's about what I'd do. Maybe two layers, even, with ceramic standoffs. But, the transformer was designed and potted so the case could be safely grounded, I'd use that too.

Referring back to the wiring as it is now, the secondary is floating with no reference to ground.

Also the transformer is in a locked plastic case, with no way to physically come in contact wit it. I don't understand how it is safer to have the center tap grounded vs having the secondary floating. The way I understand it at this point, the reason you can feel (get a shock) is because your body capacitively couples to complete the circuit. Eurika? Does grounding the center tap halve the potential you can feel (get shocked). I don't know, I thought it was safer with the secondary floating, just unsure now. I'm trying to protect my son, he's sharp and more leery of electricity than I am, but running dozens of 5 minute experiments in a short time, power on / power off repeatedly, it is easy to get complacent! Add to that, the next set, may be at 1 minute intervals. Thanks, Mikek