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Is this flyback suitable?

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Dr. Dark Current

Sat Apr 07 2007, 02:31PM

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

uzzors wrote ...

For sure.

I haven't updated anything for a while, and I have many other flyback drivers. I made this one recently, and it gives good sparks and arcs, tested up to 50V.

you can connect the mosfet's gate directly to the pin 3 of the 555, the 555 has enough power to drive even a powerful mosfet's gate up to hundreds khz (tested with osciloscope)

uzzors2k

Sat Apr 07 2007, 03:18PM

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

True, but the transistors can save the NE555 in the inevitable event of failure.

Electroholic

Sat Apr 07 2007, 04:13PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

the totem pole was used to increase pk-pk voltage on the gate drive signal, mainly to lower the "low" voltage to turn the fet off completely. It will increase efficiency, so less heating on the fets.

btw sparky, windings look a little bit thin?

...

Sat Apr 07 2007, 08:54PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Those windings are a little thin, but if you aren't running very much power it should be ok...

Also, you should attach a wire from the pin you were drawing arks from to the ground of the driver circuit, otherwise the secondary is floating and can stress the insulation on the flyback. Not to mention that it is less dangerous...

hydrogen

Sat Apr 07 2007, 09:08PM

Registered Member #631 Joined: Sat Apr 07 2007, 09:38AM
Location:
Posts: 1

hi, i'm new in HV stuff also, and not wanting to open nearly identical tread, i'll post my questions and problems here.
So i have similar (sort of) flyback from crt monitor, pic:
Image122wv0

and a 555 circuit from:
HERE

I assume the other 3 leads protruding from (2 from the top and 1 from the bottom) are not necessary and can be ignored.

QUESTION 1:
where the arcing should occur? Don't I need the second lead of the secondary winding? The page says that arcing should happen between big fat wire witch had a suction cup on it and +12 terminal of my power supply (computer's PSU).

So I hook up the output form 555 circuit to the one of primary winding of the flyback (tried all and all polarities) and I hear the wine but no sparks.

I probably should try winding the primary winding myself right?
Image127jo5

Some clip is blocking most of the space I hope spacing of the windings aren't very important.

Thanks in advance.
mod edit- oversized images

Steve Conner

Sat Apr 07 2007, 10:12PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Oi! Your pictures are way too big! I resized them.

uzzors2k

Sun Apr 08 2007, 09:54AM

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

You should be able to fit a small primary on there, try 8 turns for 12V, and drop some turns until the 2N3055 starts heating. If you run out of space just take the core off and grind off the excess plastic. The other wires are lower high voltage lines, and can be ignored. (don't touch them though!) Bring the HV wire (the fattest one) to the pins on the bottom of them flyback and one of them will arc to the HV wire. That is your ground wire. You can try the internal primaries first if you like, they will produce some sparks too.

Sparkie

Sun Apr 08 2007, 12:53PM

Registered Member #627 Joined: Thu Apr 05 2007, 04:05PM
Location: London
Posts: 32

Hey

I was using a 5-7amp 13.8v psu to run my flyback, but last night while messing with it, the arc halfed in size, then 2 seconds later, a capacitor exploded in the psu. It was a small 47uf 16v electrolytic. I have replaced with a 47uf 35v. My question is, how can I stop these high voltage spikes going back into the psu? Maybe wrap the + and - 12v wires in two ferrite rings like you would use for RF, or would that not work. I have also been using a 12v 7AH Gel cell, any fear of that exploding?!

Also, if I build the zvs driver or the 555 driver, will they still send HV spikes out the 12 end?

Also added some pics of it all boxed up.

Thanks for all your help!

FlybackBoxed1

Oh and yes, i have now made the primary from thicker wire, made a slight improvement, and don't run as hot.

Dr. Dark Current

Sun Apr 08 2007, 01:58PM

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

Sparkie wrote ...

Hey

I was using a 5-7amp 13.8v psu to run my flyback, but last night while messing with it, the arc halfed in size, then 2 seconds later, a capacitor exploded in the psu.

Put a filter capacitor of reasonable size (at least 2200uf) across the output of your power supply.

Sparkie

Sun Apr 08 2007, 02:23PM

Registered Member #627 Joined: Thu Apr 05 2007, 04:05PM
Location: London
Posts: 32

Thanks jmartis. What kind of voltage? I have a 10,000uf 35v High-ripple, will that do? Will the HV spikes not damage that, I wouldnt want that to explode! Safe to build it into my box? Also, is it correct that I should ground one half of the secondary? Won't that put HV into my 12v negative?

Thank you!

Edit: Heres a vid of it running off 14v. Im quite impressed!!

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