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Finished up ZVS need advice.

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Proud Mary

Tue Jun 23 2009, 07:45AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Nice to see someone experimenting with valves/tubes, on your flickr site, Myke! I've always liked the Clapp oscillator myself.

Dr. Dark Current

Tue Jun 23 2009, 08:50AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

brtaman wrote ...

Good news, I rewound a new toroid (took it out of a PC PSU ;)) with 21 turns and much thicker enamel wire, my eyeball says 16 gauge at least. Result? 10.2 amps at 12v and at least 20kV (arc forms at 24-26mm) I can draw the arc out for at least 15-20cm (eyeball ruller don't like to get to close to the action). I don't think I can get much more out of the driver @ 12v...but I am very happy getting up to 120ish W, thanks to everyone who helped!

15-20cm with 12 volts? That's truly insane.

I have played A LOT with these little transformers but have never seen something like this. Got video?

brtaman

Tue Jun 23 2009, 09:34AM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Hey,

It's an eyeball estimate (over-estimate to boost my tiny HV ego) :), now that I think about it might be gross over-estimate due to the joy of pulling 120W out of the flyback, I will post a video and take pictures tonight and this time I will find a plastic ruler to get a definitive length. Hopefully it will be around my original estimate, as I would feel like an ass if it came up short.

I just realized another thing though. My crap multimeter only goes up to 10amp. -.- Meaning that I could be pulling more from the PSU and not even know it.

Which brings the question, does anyone have a decent "junk" multimeter (20amp current measurements), that is gathering dust, and would like to trade for something?

I can trade/build:

200-250mw 650nm laser (red) (Have a Laser power meter so it is up to you)
2x 200v 1000uF caps
2x 200v 330uF caps
2x 200v 220uF caps
1x 400v 1XXuF cap
+a lot of assorted mosfets, some of which might be usefull to you guys.

If no, could you recommend me one that is good for hobby use but not necessarily professional grade?

Thanks
brtaman

uzzors2k

Tue Jun 23 2009, 10:14AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

This would look nice in a MOT PSU.

KLH

Tue Jun 23 2009, 04:26PM

Registered Member #1819 Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137

brtaman wrote ...

I just realized another thing though. My crap multimeter only goes up to 10amp. -.- Meaning that I could be pulling more from the PSU and not even know it.

Why not just use a low value current sense resistor on the primary side? There are 0.001 Ohm to 0.1 Ohm resistors readily available (and cheap) from Mouser Electronics. Judging from the standard ZVS schematic, it would be best to place the current sense resistor between the DC link inductor and the positive supply. Then all you would have to do is measure the voltage drop across the resistor with almost any standard multimeter and then use Ohm's law to solve for the current through the resistor. You must make sure, however, that the resistor value that you choose will provide a measureable output voltage for your multimeter without dissipating too much power.

brtaman

Tue Jun 23 2009, 05:12PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Dr. Kilovolt wrote ...

15-20cm with 12 volts? That's truly insane.

I have played A LOT with these little transformers but have never seen something like this. Got video?

I guess my initial estimate was pretty bad, sorry about misleading. The thing is, before when I was testing, the arc would slowly turn from white to purple which would allow me to extend it longer.

Well no sense talking about it here it is:

Some arcs are around 8+ cm, that is as far as it wants to go with the white arc?!?!? -.- For some reason today the arc wants to stay white hot and not turn into purple...any ideas on this one? The arc seems much thicker in every way compared to yesterday? It is much more humid today...but wouldn't that allow a further arc?

All in all it seems more powerful today just without the added purple extension?

thanks for the tip uzzors that looks perfect for the TC build I am preparing for.

Thanks
brtaman

Dr. Dark Current

Tue Jun 23 2009, 05:55PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

brtaman wrote ...

All in all it seems more powerful today just without the added purple extension?

Possibly you were closer to resonance previously. I have noticed that too with this driver, smaller cap made thinner but longer arcs than bigger cap.

uzzors2k

Tue Jun 23 2009, 05:58PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Good results for just 12V.

Running at higher frequencies will make the arcs more spindly and purple, so try decreasing the number of turns or tank capacitor size and see what happens.

brtaman

Tue Jun 23 2009, 06:12PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Hey,

Dr. Kilovolt, what is your opinion for SGTC use. Should I go for good resonance (like before) or just for brute power like now?

Thanks, uzzors, I am on 3+3 turns though, you think it would be better even lower? I am pretty happy with the way it is now because before the white arc would turn into purple much sooner and would then expand. With this version it just keeps on going in white + the arc seems much thicker?

EDIT: One thing I noticed during tests, even though the PSU is rated at 15amp@12v, when I draw the arc out and the ciruit starts drawing 10amp there is a noticeable decline in fan speed insinuating a voltage drop on the 12v rail?

Thanks
brtaman

Dr. Dark Current

Tue Jun 23 2009, 06:28PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

brtaman wrote ...

Dr. Kilovolt, what is your opinion for SGTC use. Should I go for good resonance (like before) or just for brute power like now?

For a SGTC you need more power/current.

brtaman wrote ...

EDIT: One thing I noticed during tests, even though the PSU is rated at 15amp@12v, when I draw the arc out and the ciruit starts drawing 10amp there is a noticeable decline in fan speed insinuating a voltage drop on the 12v rail?

Is that a computer PSU? Some of the cheap ones can not even supply their rated current without huge voltage drop. Others overheat/explode...

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