Is this flyback OK for my Plasma ball ?

[warmania]

Hello, I'm new here and I'm starting a new project to build a plasma ball.

I'm actually trying to chose the good flyback (it will be controlled by a NE555

I found this one who should deliver about 10-20 kV. Is it okay ? It's a flyback to supply laser and so I'm not sure it could delivers AC current (which I need here). If you have other ideas for the transformer I'll be very glad to let me know.

https://fr.aliexpress.com/item/32709548311.html?spm=a2g0o.productlist.0.0.211e579bvQrA7B&algo_pvid=0c91115f-eecd-47b3-8729-d4b2fce13437&algo_expid=0c91115f-eecd-47b3-8729-d4b2fce13437-0&btsid=0ab50a5715821071730128485e377b&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

Have a good day

[John123]

Difficult to say since they don't provide any information on the internal primary coil voltage requirements, you might have to remove the glue from the space between the core and casing and wind your own windings.

[ElectroXa]

Hello 

I bought a similar flyback, it won't work for plasma ball as  it outputs DC voltage, and plasma balls requires (high frequency) AC to work.
Edit : I found on eBay an AC flyback : https://www.ebay.fr/itm/283635925903

[John123]

I bought a similar flyback, it won't work for plasma ball as  it outputs DC voltage, and plasma balls requires (high frequency) AC to work.

Give it a few minutes on my resonant half bridge and it'll soon turn into an AC flyback!

[davekni]

Interesting project!  I'm also finishing up a DIY plasma ball, documented on this forum:
https://highvoltageforum.net/index.php?topic=924.msg6187#msg6187

Ended up using some small transformers from EBay because they fit in my box better.  But initially I fried the diodes in an old DC flyback transformer.  Frying them completely required more than just full-out over-voltage.

Wanted to avoid much total power into the diodes to avoid frying neighboring windings, so used short pulses.  Frying took two steps.  First drove the flyback with sine-wave bursts on the primary (from a ZVS circuit) with a HV capacitor on the secondary.  Increased voltage of the bursts until avalanche-breakdown of the diodes.  This was a single event once the voltage got high enough.  (Output capacitance is needed to maintain the positive output voltage so that the diodes experience max voltage during the negative half cycles.)

Unfortunately, this only partially fried the diodes, down to ~2-3kV.  To finish frying, shorted the primary winding and discharged a 11nF capacitor to the secondary through a spark gap.  Discharges repeated ~10 times per second, every time the capacitor charged enough to trigger the spark gap.  Required several minutes of this to get well-shorted diodes.

I've heard that the Sanyo F0239 and F0241 flybacks are AC.  The latter is on EBay for $29.  Don't have any personal experience with these.

[warmania]

Interesting project!  I'm also finishing up a DIY plasma ball, documented on this forum:
https://highvoltageforum.net/index.php?topic=924.msg6187#msg6187

Ended up using some small transformers from EBay because they fit in my box better.  But initially I fried the diodes in an old DC flyback transformer.  Frying them completely required more than just full-out over-voltage.

Wanted to avoid much total power into the diodes to avoid frying neighboring windings, so used short pulses.  Frying took two steps.  First drove the flyback with sine-wave bursts on the primary (from a ZVS circuit) with a HV capacitor on the secondary.  Increased voltage of the bursts until avalanche-breakdown of the diodes.  This was a single event once the voltage got high enough.  (Output capacitance is needed to maintain the positive output voltage so that the diodes experience max voltage during the negative half cycles.)

Unfortunately, this only partially fried the diodes, down to ~2-3kV.  To finish frying, shorted the primary winding and discharged a 11nF capacitor to the secondary through a spark gap.  Discharges repeated ~10 times per second, every time the capacitor charged enough to trigger the spark gap.  Required several minutes of this to get well-shorted diodes.

I've heard that the Sanyo F0239 and F0241 flybacks are AC.  The latter is on EBay for $29.  Don't have any personal experience with these.

Hi, thank you for your reply, well done for your project it's really nice ! I'd like to inspire a bit from this project for mine as I'm new in high voltage projects (still a student)

So you used the "20KV high frequency high voltage transformer ignition coil inverter driver bNWUS" for your project because I don't see them in your pictures ?

Ideally, I'd like to make about 10cm arcs (I know it's a lot) using differents sorts of gas.
It feels a bit strange but is it possible to connect two transformers in series circuit to increase the voltage ?
(the two of them would be controlled by the same NE555)

EDIT: I can't take the bNWUS because they don't deliver here in Switzerland.

[warmania]

Hello 

I bought a similar flyback, it won't work for plasma ball as  it outputs DC voltage, and plasma balls requires (high frequency) AC to work.
Edit : I found on eBay an AC flyback : https://www.ebay.fr/itm/283635925903

Thank you for the link

[davekni]

Unfortunate that you can't buy the tiny "20kV" transformers in Switzerland.  (The final image before the scope traces shows two of those transformers side-by-side with ferrite pieces joining the ends.)  These little transformers aren't really good for 20kV.  Two in series helps, although the one at the higher-voltage end still has it's primary winding close to ground potential, so sees the full voltage from primary to the HV end of the secondary.  I'm running the series pair at only ~5kV RMS (~7kV peak).

The larger 15kV AC flyback transformer that John shared should work well.  10cm "arcs" shouldn't be difficult at 15kV peak.  It does depend on the gas and especially on the pressure.  From what I read, commercial plasma balls (like the 20cm diameter one I have) use ~8kV peak (~5.6kV RMS) with ~60-70kPa absolute pressure of a neon/xenon mix.  Those gasses are expensive for playing, so I experimented with helium and argon.  If the absolute pressure is low enough, you'll get 10cm with only a few kV.  Even air works if pressure is low enough.  Low-pressure discharges are dimmer, however.  I haven't matched the brightness of my commercial plasma ball, even though the power level (voltage and current) is similar.