HV supply ideas

Grumpy_Mike:
dangerous thing to make

The prospect of killing yourself, or some other poor schmuck who happens to touch the wrong thing a few days after you've been playing with it, seems very high. Do you have any experience of working with high voltages? If not, I suggest you file this idea away and look for something less lethal. You probably could do it with enough effort, but if you succeed you're very likely to kill somebody by accident.

If you want out of the gene pool, I won't make you stay. This might be your best bet:http://en.wikipedia.org/wiki/Cockcroft%E2%80%93Walton_generator. You can even find youtube videos of these at even higher voltages, presumably posted by the bereaved.

Isn't 5ma below that threshold that would cause problems? I think I heard 7ma thru the heart could kill, the only thing I would be worried about is arc burn/pinholeing
I like the looks of that walton generator, what do you think would be the easiest way to adjust it? I guess id have to vary how many stages or is there an easier way?

Isn't 5ma below that threshold that would cause problems?

No, because of the high voltage we are talking about a lot of power, that has to be considered as well. Anyway if 7mA is fatal what makes you think 5mA is safe? You might survive but you might not.

Insulation against 50KV is a bit of an art, you can't get away with a bit of insulating tape you know.

Do you sincerely believe that you're capable of controlling the voltage and current consistently and reliably enough to avoid the possibility of a lethal current? Frankly, given that your first inquiry about it is on a forum that has nothing to do with high voltage electrics and that you seem to be starting from no knowledge at all about the issues, I'm not inclined to think that you are.

If you're wrong, you or somebody near to you could easily be killed. Just how brave do you want to be on their behalf?

Change the word "brave" to what you really mean ie STUPID

No offence intended but take it if you must

You obviously don't know what you're doing or dealing with so please accept the advice already given.

I think I heard 7ma

A couple of tens microamps at the heart is sufficient to cause fibrillation.(ever seen the size of the battery in a pacemaker?)
The best you can hope is that a high frequency will keep current away from the heart by reason of the skin effect.
Don't think - find out for sure.

winner10920:
I just need something preferably cheap since if more for educational expirementation

Ok I'm a simple civil engineer and not versed in this arcane electrical stuff, but to me the words "50kV" and "cheap" should not be used together in the context of "educational experimentation"...

(My son's a firefighter / emt.... shall I get him suited up just in case? :slight_smile: )

Will the real Dr Frankenstein please stand up?

If you want to play with high voltages play with one of these:-

50kV @ 5mA is 250W so you're talking about quite a lot of power, which won't be easy. I suggest you reduce your ambitions, say start with 10kV @ 1mA. Also, 5mA may not be a lethal current under normal conditions, however you are going to need smoothing capacitors, which will deliver a much larger current for short periods - with the potential to deliver a lethal shock. BE VERY CAREFUL!

I built something similar to drive a laser a long time ago. The conventional approach would be a flyback converter feeding a transformer and voltage multiplier circuit (HV diodes + capacitors). However, I found it easier to use a separate oscillator (555) driving a flip-flop, which fed a push-pull output stage using a centre-tapped transformer (bifilar wound). I adjusted the supply voltage to the centre tap to vary the output voltage. The transformer was made from ferrite E-cores and a 2-section bobbin, which are obtainable from the usual component distributors. I potted the transformer in wax or epoxy (can't remember which) to reduce the chance of flashover. I also potted the voltage multiplier stack in epoxy.

You can use a voltage divider to monitor the output voltage, however you need to take the voltage rating of the resistors into account. In practice, this means that the upper resistor needs to be a chain of lots of resistors in series.

Here is a "big boy's power supply" 200-300kV.

I think the bloke is insane, he seems to know what he is doing but I would not be surprised if his vlog stopped abruptly one day.

Everybody's resistance is different and changes quite a lot e.g. if your fingers are a bit sweaty.
So what you might be lucky and get away with one day might kill you the next.

The spasm caused by an HV shock might make you bite your tongue, tear muscles, or cause you to break bones as you hit things and fall over.

I got a belt of a TV crt tube once. It was unplugged, but still holding a charge and was something I am happy to avoid repeating.

OP - pick a field in which you have expertise. Think of the most foolish and irresponsible thing a novice could do in that area. Imagine the advice you would give such a person. Follow it.

Perhaps I will start a bit smaller maybe 10kv, hv seems to get expensive quick and im not that rich
Other than a flyback transformer and a hv transformer would an electronic fluorescent ballast provide good starting point to feed to a multipler?
and I understand the safety concerns, I play around in a locked shed that only I have access to, and im an electrician which doesn't qualify me in HV at all but im pretty good with being safe, 240v isn't fun to get shocked with so I imagine 24kv would suck

So I guess for the arduino control tho, it would be easier to measure the input voltage/current and calculate the output voltage? I don't even know of a common multimeter that goes above 500v for me to test if the arduino was properly measuring HV

Ok so for starters I used a 555 timer driving a 2 stage multiplier off 12 v and I got 38, so not bad so far but that's at 2.2Mhz, how hard do you think it would be to have a higher voltage version using some 600v mosfets for switching directly rectified 240v mains?

Before you go much further, you probably want to double-check the insulation rating of any wire you're using.
You may be surprised, but I hope not shocked.
EHT can take very odd paths - beware.

On the lower voltage side 240vac I know im good with that, but I doubt on the other end its fine so im gonna keep those wires short and away from everything else, and the circuit ill probably leave in mineral oil so it doesn't flash over and destroy itself

Make sure all your joints are nice and smooth too, no point radii.

If you switch directly from rectified 240v mains then the output won't be isolated, making it even more dangerous - unless your design includes an isolating transformer. Also, how will you adjust the output voltage?

I was thinking if I could measure the output somehow directly or indirectly, I could change the duty cycle to change the voltage, basically changing the vrms input to the multiplier