High voltage low current power supply schematic - Page 1
Forum section: electronics / beginners

author: axawire
author_rank: Contributor
timestamp: March 12, 2021, 06:03:16 pm
content: I am looking for a schematic or design idea for a high voltage power supply. I am having difficulty in locating an existing design because certain aspects I may lack the technical search terms for, like if a specific part of the schematic that is required for a certain property is called x say in the search to distinguish it from other power supply types.This is my requirementI need one that has approx. +8kV on the positive terminal and -8kV on the negative terminal. I understand that P.D is relative but I want to replicate this experiment:and I do not believe if I have a power supply that is +1600kV at the positive terminal and 0kV at the negative terminal that I will have the same charge distribution across the wire... I would not end up with the neutral charge in the center but at the negative terminal end? So I need a correlation to the +8kV terminal to actually be having a deficit of electrons and the -8kV terminal having a surplus of electrons and a ground would actually be neutrally charged.Thanks.

author: TimFox
author_rank: Super Contributor
timestamp: March 12, 2021, 06:28:29 pm
content: What is your maximum current requirement?Even with low available current at these high voltages, safety is paramount and the stored charge in any capacitors may still be lethal even if the continuous current capability is less than that required for electrocution.If the current is really, really low, high-voltage rated resistors at each output (with negligible capacitance after the resistors) may improve the safety if the normal-operation voltage drop is acceptable.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 12, 2021, 07:32:19 pm
content: You are looking for an adjustable bipolar high voltage DC power supply. In the 16kV (+ and - 8kV with 0V grounded) range they are rare as hen's teeth.If you have a 16 kV power supply whose output is truly floating, then you can put your earth ground reference wherever you want, I think. Connect the + and 0 (or - and 0) outputs to the resistor chain and ground the center of the resistor chain. But if your PSU's 0 volt level is actually grounded this won't work, of course.ETA re safety: This is almost one of those "if you have to ask, maybe better not do it at all" kind of questions. The current requirement to duplicate the experiment in the video is very low, but that doesn't mean it is safe at those voltage levels. Even physically small capacitors can store lethal energy.

author: Benta
author_rank: Super Contributor
timestamp: March 12, 2021, 09:51:53 pm
content: Scavenge a Van de Graaff generator from an old high school physics lab?

author: TimFox
author_rank: Super Contributor
timestamp: March 12, 2021, 10:18:51 pm
content: They are not bipolar; polarity is fixed and one end is grounded.

author: axawire
author_rank: Contributor
timestamp: March 12, 2021, 11:05:16 pm
content: The power supply in the demonstration is 2mA max.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 13, 2021, 04:40:08 pm
content: Quote from: Benta on March 12, 2021, 09:51:53 pmQuote from: TimFox on March 12, 2021, 10:18:51 pmVDG machine polarity is determined by the material of the belt and the top roller and bottom rollers, mostly. You can make VDG generators of either polarity. Make 2 of identical mechanical design, use Teflon for the top roller on one and Brass (iirc) for the top roller on the other one, connect the bases and earth together with a jumper wire, and the tops will have opposite polarity with earth ground at the bottoms.VDG machines can be really simple and easy to build out of materials easily found around the home. For the experiment in the OPs video you don't need the extreme voltages that a well-designed VDG is capable of. You can get 20 kV easily just using rubber band belts, hobby motors, cardboard tubes and beer cans.For your amusement:

author: TimFox
author_rank: Super Contributor
timestamp: March 13, 2021, 04:50:44 pm
content: I stand corrected on polarity. Van de Graaff’s original patent US 1991236A (1935) gives a straightforward description of the machine.

author: BrokenYugo
author_rank: Super Contributor
timestamp: March 13, 2021, 05:21:56 pm
content: Quote from: alsetalokin4017 on March 12, 2021, 07:32:19 pmThis, it becomes EXTREMELY easy to learn the hard way screwing around at these voltage levels. I'll spare the story but even the leakage current from the face of an old color TV gets hazardous quick if you start charging capacitors.