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help requested on getting flybacks to work

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LAN_403

JamesH

Sun May 06 2007, 02:47PM

Registered Member #579 Joined: Mon Mar 12 2007, 09:45AM
Location: Burntwood, Staffs, England
Posts: 46

I KNOW THERE ARE LOTS OF POSTS ON THIS AND I HAVE LOOKED AT THEM

I have been working on trying to get some LOPT working

I can get a spark but only half a mm
I have a N555 timer circuit oscilattor that drive Ignition coils great
I have prototype**** of the two 2n3055 transistor circuit of Jochen Kronjaeger

Ihave tried these drivers with single coil primary and the two plus two for thentwin transistor job

Power is from 5V ( 3A), 12V and 12+V -12 V PSU ... all ranges tried

I do get it singing, but no sparks
My BABY TESLA is waiting new capacitors , my NST is waiting parts for a Terry Filter SO I AM SPARKLESS AND SUFFERING WITHDRAWL

HELP needed PLease

( ****you will understand when you seethe pictures - only 1/4 watt resistors so I had to use 20 in parallel)

Dr. Dark Current

Sun May 06 2007, 04:53PM

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

with the 2n3055 driver, did you use 5 turn primary, 2 turn feedback and a LARGE HEATSINK FOR THE TRANSISTOR?
If it doesn't work, swap the feedback leads. If it again doesn't work, swap primary leads. If now again doesn't work, swap again the feedback leads. (this means that only 1 out of 4 combinations is right!)
If you can get the flyback to "whistle" but have nearly no output, swap both feedback leads AND primary leads.
hope this helps

lamazoid

Sun May 06 2007, 06:00PM

Registered Member #573 Joined: Fri Mar 09 2007, 11:26AM
Location: Russia
Posts: 14

Why to use so many resistors?

...

Sun May 06 2007, 07:09PM

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

you need a lot of resistors because the small 1/4w ones can't dissipate nearly enough power for an inefficient driver like the 2n3055 one.

One think to check, what value resistors did you use, and how did you group them (it looks like you did 2 series banks of 20, which would make the overall value 1/10 that of individual resistors).

You might also try a single 2n3055 driver, as there are less coils to get the phasing wrong on...

lamazoid

Sun May 06 2007, 07:43PM

Registered Member #573 Joined: Fri Mar 09 2007, 11:26AM
Location: Russia
Posts: 14

... wrote ...

One think to check, what value resistors did you use, and how did you group them (it looks like you did 2 series banks of 20, which would make the overall value 1/10 that of individual resistors).

That's exactly what i wanted to say :)

YoshiEggz

Mon May 07 2007, 05:40PM

Registered Member #521 Joined: Wed Feb 14 2007, 06:03PM
Location: Ontario - Canada
Posts: 9

Make sure your POLARITY is correct on the flyback coils, The flyback has internal diode on output and will produce a almost useless output if the input pulse is reverse polarity.

The most simple design is to build a 555 timer circuit, then connect a 4.7K resistor from the output of the 555 to drive input of IGBT.

Connect one side of the flybacks filament coil to +7-8 VDC and the - lead to the IGBT and then from IGBT to ground.

switching the ground instead of the + line allows you to use a smaller power supply for the 555 and a different source of + for the coil, while both the 555 timer and coil share the same ground plane.

For IGBT I use the STGW30NC60W N-CHAN 600V 60A TO-220 package.

Dr. Dark Current

Mon May 07 2007, 05:56PM

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

YoshiEggz wrote ...

The most simple design is to build a 555 timer circuit, then connect a 4.7K resistor from the output of the 555 to drive input of IGBT.

Connecting 4.7k resistor to IGBT/FET gate will probably result in no output, since its gate is like a capacitor and needs high peak currents to switch it rapidy. You'd be better with a 10 ohm resistor, even connecting the 555's output directly to the IGBT/FET gate is ok.

JamesH

Tue May 08 2007, 09:27AM

Registered Member #579 Joined: Mon Mar 12 2007, 09:45AM
Location: Burntwood, Staffs, England
Posts: 46

Thanks for all the replys

I have got a very small BW Tv LOPT sparking very well
One 2n3055 transistor mounted on a CPU chip heat sink and driven by a 12 8A battery

special thanks to jmartis . two turns only on the feed back was the break through

I am working my way through the other suggestions ... I hope to make about 4 Flybnacks work with different drivers ............. I need to buy extra parts also for some of the schemes

LAST MINUTE >>>> second , med size flyback working on the same driver... but 2n3055 getting VERY HOT

1178616328 579 FT24909 Little Flyback Sparking

lamazoid

Tue May 08 2007, 02:38PM

Registered Member #573 Joined: Fri Mar 09 2007, 11:26AM
Location: Russia
Posts: 14

Do you have LARGE caps across the battery? Also try to add a gap into flyback core.

r3d

Fri May 11 2007, 01:05PM

Registered Member #532 Joined: Sat Feb 17 2007, 05:00PM
Location:
Posts: 11

Make ZVS driver :)

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