Building a high voltage generator - Page 1
Forum section: electronics / projects

author: maqce
author_rank: Newbie
timestamp: September 10, 2021, 02:04:06 pm
content: Hi everyone,I'm on a school project where I have to produce ozone by discharge. So I need a small high voltage generator and I'd like to make it myself. I already done small experiments with high voltage from a flyback drived with a simple transistor (see the circuit below), maybe could I reuse this type of generator ? Is there a risk of overheat if I run it for like 5 to 10 minutes ? I need a few kV, between 3 to 20kV AC, no need to be precise.Thanks for your help

author: strawberry
author_rank: Super Contributor
timestamp: September 10, 2021, 04:14:30 pm
content: royer,symmetric output voltage, no heat, no feedback winding nor saturable core

author: Benta
author_rank: Super Contributor
timestamp: September 10, 2021, 05:01:14 pm
content: Automotive ignition coil. Cheapest solution overall.

author: Plasmateur
author_rank: Regular Contributor
timestamp: September 11, 2021, 06:36:48 pm
content: https://en.wikipedia.org/wiki/Cockcroft%E2%80%93Walton_generator

author: andy3055
author_rank: Super Contributor
timestamp: September 11, 2021, 08:31:47 pm
content: Quote from: Benta on September 10, 2021, 05:01:14 pmLike Benta said, find an old ignition coil from a car and workout a switching circuit for the primary. But be careful as the output might be much higher than what you want!

author: Benta
author_rank: Super Contributor
timestamp: September 11, 2021, 08:41:33 pm
content: Quote from: Plasmateur on September 11, 2021, 06:36:48 pmBuilt one of those myself back in the '80s. Pretty useless.If you want to produce ozone, you need the air discharge (aka spark).That's why I proposed the the spark coil.It doesn't have to be bulky, modern cars have integrated COP (coil-on-plug) ignition systems, controlled directly by 12 V pulses from the ECU. A visit to a wrecker's yard would be a gold mine for this application. And spark plugs have the right metallurgy to minimise electrode erosion.

author: 2N3055
author_rank: Super Contributor
timestamp: September 11, 2021, 09:15:34 pm
content: You don't use sparks, but a corona discharge electrodes..... Basically a needle....

author: james_s
author_rank: Super Contributor
timestamp: September 11, 2021, 09:23:51 pm
content: Look up the "Mazzilli" ZVS flyback driver, it is easy to build, highly efficient and will do exactly what you want. It's a form of Royer oscillator and is easily scalable from a few watts up to hundreds of watts.

author: Gyro
author_rank: Super Contributor
timestamp: September 11, 2021, 09:30:01 pm
content: Quote from: Plasmateur on September 11, 2021, 06:36:48 pmYes, that's what most commercial ionisers use. I've seen some that don't even have a transformer, just a large number of stages straight off the mains, with a high value resistor on the output (not recommended). It minimises the secondary voltage you need on your transformer.Ionisation works better with DC (which is where the Cockcroft Walton multiplier is helpful). Use sharp points or edges on the negative surrounded by a ring, connected to the positive.P.S. Big Clive has several ioniser and ozone generator teardowns...https://www.youtube.com/user/bigclivedotcom/videos

author: Plasmateur
author_rank: Regular Contributor
timestamp: September 12, 2021, 01:39:03 am
content: Quote from: Benta on September 11, 2021, 08:41:33 pmI've never built one myself, so you're going to be much more knowledgeable than I on this.However, the reason why I suggested this is because I've just seen so many Youtube video on these which indeed produce an air discharge. I was interested in one of these at the time because I was looking for different ways to make a plasma.In this video, the device looks kinda simple -But I've usually seen them submerged in mineral oil.

author: rsjsouza
author_rank: Super Contributor
timestamp: September 12, 2021, 02:44:35 am
content: I have built my own de-ionizer machine to reduce ESD by assembling a Cockroft Walton generator inside a PC power supply housing with an 8cm fan at the air inlet and an 8cm fine metal mesh on the air outlet. It generates around 3.5kV out of the 120VACand it has a reasonable range when I measure its voltage with my electrostatic voltmeter.Another project I saw at the time is at the link below. Sure, it is instructables, but the mechanical arrangement is quite interesting.https://www.instructables.com/How-to-Make-a-Negative-Ion-air-ionizer/

author: james_s
author_rank: Super Contributor
timestamp: September 12, 2021, 03:02:04 am
content: I'm surprised they managed to get that one to work without either submerging it in oil or potting it. When you get up to such high voltages, especially at high frequency electricity starts to behave in strange ways and becomes difficult to keep contained. Electrons will spray off of any sharp points and arc between others.

author: maqce
author_rank: Newbie
timestamp: September 12, 2021, 08:59:50 am
content: Quote from: james_s on September 11, 2021, 09:23:51 pmI planned to do this oscillator, it seems to be the most adapted for me

author: maqce
author_rank: Newbie
timestamp: September 12, 2021, 09:03:33 am
content: Quote from: Plasmateur on September 11, 2021, 06:36:48 pmI don't think it would be great because from what I understood I need to make corona discharge instead of arcs, so this might not be efficient for this

author: 2N3055
author_rank: Super Contributor
timestamp: September 12, 2021, 10:18:58 am
content: Quote from: maqce on September 12, 2021, 09:03:33 amCockcroft–Walton generator provides constant high voltage DC but low current. Ideal for corona discharge..That is most used combination: Cockcroft–Walton generator( voltage multiplier) and corona electrodes.