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polop

Sat Feb 28 2009, 10:01PM

Registered Member #1537 Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51

voltwad just the ticket thanks, one last nooby question what does ringdown mean? (voltwad said) "Here's the voltage between the terminals. Peak is about 14 or 15 hundred volts and ringdown is about 11 hundred."

And to make a rather tangential question, how would i protect this circuit if i wanted to dump the output of a flash cap (from disposable camera) accros the ionised hv arc, and for that matter protect the capacitor from charging off of the hv output, always fun seeing some air explode lol

edit;
i was looking for capacitors for the villard cascade what would be the ideal value for the sutup with two camera transformers running in opposit polarity, off a 3.7-4.2v supply (can these transformers handle 4.2 volts of lipo power? i may have to lower the voltage before the input.)
i can get a few hundred capacitors from rs for a similar price to one of two from maplin, here is what they have availiable (links dont work though go to

and search high voltage disk ceramic)
the minimum number to buy is 100 lol

my guess is that i will need the highest capacitance i can get at a 3kv rating so a 470pf at 3kv whould that be good, at Â£1.67 for 100 it sounds good to me lol

edit2:
would i need a cascade on the positive and the negitive transformer or should i put one across both outputs? so that the voltage seen by the multiplier is double (slightly more expensive caps are needed, though tis should itcrease efficiance yes?)

ps. many edits is so that i do not multipe post or start another topic on a similar issue

Voltwad

Sun Mar 01 2009, 04:33PM

Registered Member #1829 Joined: Sun Nov 30 2008, 01:06AM
Location: Raleigh N.C.
Posts: 74

what does ringdown mean?

The ringdown is the damped sinusoidal oscillation after the initial spike. If I had a better scope you could see the ground level is just about where the initial peak begins and that oscillation is several hundred volts below ground (negative on the upper trace) rising back to zero before the next peak begins.

how would i protect this circuit if i wanted to dump the output of a flash cap (from disposable camera) accros the ionised hv arc

If the cap is discharging straight to ground a few tens to hundred k resistor on the output of your voltage multiplier should be fine. You should have some resistive load on it anyway if you're drawing arcs. Then a microwave oven diode or a series of smaller diodes chained together would protect the cap from the HV. I'm not sure why you'd want to go to that much trouble to short a 330v photo cap though. If you want a bigger bang an HV cap charged directly from your multiplier and discharged through a set gap would be better. MMCs are a way to go for large energy discharges or a simple rolled foil cap would work too and be able to store at least as much energy as a photoflash without being too bulky.

i was looking for capacitors for the villard cascade what would be the ideal value for the sutup with two camera transformers running in opposit polarity, off a 3.7-4.2v supply (can these transformers handle 4.2 volts of lipo power? i may have to lower the voltage before the input.)

If you look further down on that thread I describe the caps I used for my cascade. I also mentioned higher driving voltages. I didn't drive mine higher than the original flash circuit but some others on that thread in previous posts mentioned that they had. Also you'll want to use a fullwave cascade with that driver circuit. There's a lot of useful stuff in that thread about photo circuits. That's where I started when I built my mini TC.

polop

Tue Mar 10 2009, 08:48PM

Registered Member #1537 Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51

hi there can any one take the effort to make a pin out diagram for the little transfrmers, there are usualy two types the 4 leg ones and the 5 leg ones, i am interested in the 5 leg one, as in am trying to built half of valtwad's circuit, but ive tried a logical aproach using the resistance between pins, and wheni made it with a small transistor it just got hot and with a large transistor i still measured nothing accros every pin i tried (and to ground) never got more than 1.5v suply voltage

Voltwad

Fri Mar 20 2009, 04:54AM

Registered Member #1829 Joined: Sun Nov 30 2008, 01:06AM
Location: Raleigh N.C.
Posts: 74

The best way to figure this out is probably to see how the transformer fit into its original circuit. Barring that, the transformers I used were five pin. The drive coil is tied to the kick coil and the feedback coil is separate. The feedback was the outermost coil and was wound with a larger gauge wire. so I just looked to see which pins had the larger wire soldered to them. This can be difficult if the transformer is wrapped in tape or if the plastic bobbin is molded in such a way that you can't easily see the wires. Then you could just look for two pins with zero resistance between them and open circuit to the other three. Having found the feedback you need to categorize the other three pins. Now, between two of these pins there should be (practically) zero resistance. This is the drive coil. The fifth pin will be your hv out. Now you need to know which drive coil pin is tied to the kick coil and which should be grounded. If you can see the wires coming off the pins then the one with two wires soldered on is the common pin between the drive and kick coil. Otherwise you'll have to try it both ways and see which one works. Hope this helps make some sparks.

polop

Wed Jun 03 2009, 08:32PM

Registered Member #1537 Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51

hello there, sorry for reopening an old thread i have made a circuit work to a certain extent, i get 230v from 1.5 in. but when i put a villard doubler on the end it does not register any voltage at the output.

i have built the circuit as shown and have tried swapping the leads to the voltage multiplier. i have also tried removing the capacitor in the first circuit.
any ideas people.

(ps images from

and

use of these images was due to the lack of program to draw nice schematics)

Arcstarter

Wed Jun 03 2009, 10:09PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

You would have to have an AC input to the multiplier.

polop

Thu Jun 04 2009, 12:10PM

Registered Member #1537 Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51

the out put of the transformer is half wave is that good enough? i can't get voltwads circuit to work ( i was only giving half his ciircuit a go but no output was measured, i do not have a second 5 pin transformer).

Proud Mary

Thu Jun 04 2009, 01:51PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Not perhaps of too much relevance to your own project, but to show what can be done, I saw recently the design of an 80kV X-ray transformer where both primary and secondary 'coils' were printed on PCB board, and a number of such cards stacked in series.

I wonder who will be first to make a printed TC?

Voltwad

Thu Jun 04 2009, 07:28PM

Registered Member #1829 Joined: Sun Nov 30 2008, 01:06AM
Location: Raleigh N.C.
Posts: 74

Hey Polop, first of all, if your circuit is right, it seems you have connected the junction between the two resistors and the 22nF cap to ground. This would short out your LED but i think the transformer would still work. Second, while these transformers do output a non symmetrical waveform, there is still some voltage created on the other side of the ground level as the circuit rings down. A villiard cascade would work better with a sinusoidal voltage but will still work with the direct output from the transformer if you remove the diode from your transformer output. Also remember, the caps need to be rated for the full peak to peak voltage ( and a bit more ) of the transformer.

EDIT: Actually, it doesn't matter if the voltage swings across ground or not, as long as there is a voltage varying back and forth (centered wherever) and current can flow both ways (get rid of the diode) the cascade will still work. You can build a circuit like this at This site. You can edit the properties of the ac waveform and change the dc offset to see what happens. Also you can add a diode between the ac source and the cascade and see what's going on there. This is an awesome little applet and is great for visualizing how voltage and current behave.

polop

Sat Jun 06 2009, 09:01PM

Registered Member #1537 Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51

thanks allot, it was the diode that stoped everything working, it allworks great now, though one more question; will arcing the hv oputput of the villard cascade directly to ground damage any of the components?, with a high value resistor on the output (i used 100kohm) made the output pathetic, though without the resistor the spark was meaty but people always reccoment using the resistor why is this? surely the lack of current on the input (due to pathetic transformer) will limit the current output any way. thanks for he help

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