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Secondary base feedback

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LAN_403

KresoLiubov

Tue Dec 11 2007, 04:47PM

Registered Member #1153 Joined: Mon Dec 03 2007, 07:27PM
Location: Croatia
Posts: 213

Im two steps to completing my demo coil and since im trying something new i want to discuss about
this type of feedback and experince of You with it?

MY first tests were not promising because coil worked fine until i tried to draw ground arcs.

I wound this two today for testing. Round one come from Nixie PSU and cubic one come from line filter.

Dr. Dark Current

Tue Dec 11 2007, 05:05PM

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

I never got secondary base feedback to work with ground arcs. I think antenna does much better here.

KresoLiubov

Tue Dec 11 2007, 05:12PM

Registered Member #1153 Joined: Mon Dec 03 2007, 07:27PM
Location: Croatia
Posts: 213

jmartis wrote ...

I never got secondary base feedback to work with ground arcs. I think antenna does much better here.

Problem is in verry compact coil. Antena works okay but coil "hickup", work 5 seconds then stops for 2...
However antena feedback works perfectly when distanced.

Zum Beispiel

Tue Dec 11 2007, 05:33PM

Registered Member #514 Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295

You don't really have to have a real ground connection to get ground arcs.

You can use a chicken stick with a small toroid and a breakout point on it to draw arcs. The capacitance should get enough current to flow (if I place an incandescent lamp between the toroids, the filament starts to glow brightly

)

I don't know how these compare to "real" ground arcs, but I can draw really hot flaming arcs off my Mark II coil (input 1kW, sec. base feedback) with no problems.

Just my 2c

KresoLiubov

Tue Dec 11 2007, 06:06PM

Registered Member #1153 Joined: Mon Dec 03 2007, 07:27PM
Location: Croatia
Posts: 213

Zb wrote ...

You don't really have to have a real ground connection to get ground arcs.

)

I don't know how these compare to "real" ground arcs, but I can draw really hot flaming arcs off my Mark II coil (input 1kW, sec. base feedback) with no problems.

Just my 2c

I never draw "real" ground arcs with grounded wire. Always with insulated stick wich on end has terminated toroid. Well il decide to play with antena.

And by the way i still use interpter some thing similiar from Steves mini SSTC. Should i convert to ome of DRSSTC interupters ? Any suggestions

...

Tue Dec 11 2007, 07:09PM

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

What kind of driver are you using?

In my coil using steve's pll driver it was actually much more stable when pulling ground arks using the base transformer than with an antenna.

I was using a 'goldmine' dohnut core with the secondary ground wire passed through once, and with a 50 turn secondary, loaded with a 390r resistor and a a pair of 1n4148's to clamp it to the rails.

KresoLiubov

Tue Dec 11 2007, 07:15PM

Registered Member #1153 Joined: Mon Dec 03 2007, 07:27PM
Location: Croatia
Posts: 213

... wrote ...

What kind of driver are you using?

In my coil using steve's pll driver it was actually much more stable when pulling ground arks using the base transformer than with an antenna.

I was using a 'goldmine' dohnut core with the secondary ground wire passed through once, and with a 50 turn secondary, loaded with a 390r resistor and a a pair of 1n4148's to clamp it to the rails.

Im using my modification of Steves MINI SSTC.

I will try PLL, eventually. Im looking scopeboys driver for some time and just want to try

Bauerb2

Wed Dec 12 2007, 12:00AM

Registered Member #973 Joined: Tue Aug 28 2007, 07:32PM
Location: Pittsburgh, PA
Posts: 66

i use base feedback with no problems, even with ground arcs. the xformer sec. is clamped using 1n4148s like always, with 270R load. the secondary is 65-70 turns and primary is one turn from the tesla secondary. the actual transformer is a j material ferrite toroid (Al~4500) covered with electrical tape. it apparently works great, much more reliable than the antenna feedback style that i've tried before, IMO.

The base feedback signal then goes into a fast logic 'buffer' (74f04pc for now). this signal goes into the gate drive chips and to the fets... its not my final circuit setup, cause i am still working on it, and i'm sort of an idiot with this stuff so work is slow

. Ground arcs are very hot, and the fets run cool (tuning is off abit though) at 70V, 12 amp with smoothed DC. the scope shows the base feedback signal dip down far when an arc is grounded, but still not enough to deplete the signal to the drive.

im not too sure as to why others have trouble with base fb, maybe its the feedback transformer your using, i've never seen one of those used for sstc's....

Fo'shizzle

-Andrew

Tom540

Wed Dec 12 2007, 06:03PM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617

I also have used base feedback a lot and have never had any trouble with it. I will never go back to antenna feedback for any coil. I don't use a resistor in series with the CT though. Try making it smaller or removing it completely.

I would have to agree with Bauerb2 guess that that weird transformer you have could be the problem. I think a toroidal core would be much much better. Or try reducing the turns on the green wire.

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