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### Topic: HV supply ideas (Read 3204 times)previous topic - next topic

#### winner10920

##### Jul 08, 2012, 11:10 pm
What do you think would be the simplest way to make a HV supply? Preferably dc, and id rather make it than buy one so I can incorporate it to be controlled by my arduino(voltage/current regulation)
im looking for like 0-50kv adjustability and maybe 0 - 5ma current, also what would be the best way to measure the HV and current safely? Does the regular resistor voltage divider still make sense to use as well as a resistor current shunt?

#### RuggedCircuits

#1
##### Jul 08, 2012, 11:19 pm
Hmm...even if you have 169VDC (120VAC rectified) you will need a voltage boost of about 300, so I think a transformer is going to be a good way to start. 50kV x 5mA --> 250W so this is a fair amount of power you are delivering. It's going to be tough to get right, easy to get wrong, and easy to hurt yourself or start some fires.

Maybe start by checking out the 4HV site (http://wiki.4hv.org/index.php/Main_Page) for some ideas.

A voltage divider isn't going to do it unless you can find resistors that can withstand 50kV. Typical resistors are good to a few hundred volts, beyond that and the voltage just jumps from one terminal to the other, bypassing the resistance altogether.

--
The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected

#### Grumpy_Mike

#2
##### Jul 08, 2012, 11:38 pm
50KV what are you going to use that for?

A CRT colour TV set generates 25KV at no where close to that current and that is a dangerous thing to make, especially if you have to ask here about it.

#### jackrae

#3
##### Jul 08, 2012, 11:46 pm
Goole TESLA COIL and you'll find what you are looking for - but controlling from 0 to 50kV is pushing the frontiers of science.

#### winner10920

#4
##### Jul 09, 2012, 06:36 am
Just a project idea, more of a challege to push myself towards
as for the transformer I guess that sort of thing is best bought? I figure I could make a smaller hv transformer at higher frequencies but then rectifying it may pose expensive and or dangerous
and dc multiplying with capacitors I guess is another expensive road,
I've seen HV supplys but alll quite expensive, I just need something preferably cheap since if more for educational expirementation

#### PeterH

#5
##### Jul 09, 2012, 01:20 pm

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.
I only provide help via the forum - please do not contact me for private consultancy.

#### Curmudgeon

#6
##### Jul 09, 2012, 03:23 pm
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.

#### winner10920

#7
##### Jul 09, 2012, 03:32 pm
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?

#### Grumpy_Mike

#8
##### Jul 09, 2012, 03:37 pm
Quote
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.

#### PeterH

#9
##### Jul 09, 2012, 05:42 pm
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?
I only provide help via the forum - please do not contact me for private consultancy.

#### jackrae

#10
##### Jul 09, 2012, 06:58 pm
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.

#### AWOL

#11
##### Jul 09, 2012, 07:09 pmLast Edit: Jul 09, 2012, 07:25 pm by AWOL Reason: 1
Quote
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.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

#### JimboZA

#12
##### Jul 09, 2012, 07:09 pmLast Edit: Jul 09, 2012, 07:12 pm by JimboZA Reason: 1

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?  )

Will the real Dr Frankenstein please stand up?
Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)

#### Grumpy_Mike

#13
##### Jul 09, 2012, 07:24 pm
If you want to play with high voltages play with one of these:-
http://en.wikipedia.org/wiki/Van_de_Graaff_generator

#### dc42

#14
##### Jul 09, 2012, 07:34 pm
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.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

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