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MicroBoxer SSTC working

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KresoLiubov

Fri Jun 06 2008, 07:34PM

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

I was writing about such idea long time ago.

So a coil very small...
So a coil powered from 12 V (rechargable batteries included)
Coil palm size
Coil exceeding secondary size sparks by 2 X

So i finally cached time to test it and play with my new Fluke scope.

Principe is simple. The small transformer on photo is pulsed by 555 and charging a photo flash capacitor, and coil is interrupted to 1 bps.

Now i need to push it in some stand or box, add 3.6 V 18650 2000 mah in series for 14.4 V. Coil is currently making 6 inch sparks. However im using 800 V fets so i need to make voltage doubler and it will run on 600 VDC.

Soon to continue

KresoLiubov

Fri Jun 06 2008, 10:30PM

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

Almost 1 AM :)

So i build half bridge, doubler and all on PCB.

I have on problem, my GDT has racing sparks

I had problem with logic starting to wander off until i grounded - pole of board. However even if i remove it my GDT arcs everywhere.

Any suggestions? On it there is CAT5 wire

flannelhead

Sat Jun 07 2008, 09:08AM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

Nice to see it finally working!

I'll try something similar.

WTF, Racing sparks on GDT? Are your insulations OK?

KresoLiubov

Sat Jun 07 2008, 10:10AM

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

Dr. 2N3055 wrote ...

Nice to see it finally working!

I'll try something similar.

WTF, Racing sparks on GDT? Are your insulations OK?

Yesterday i continued to play with coil and didn't pay attention to it. Today i put evrything on board and im just rewinding a little more powerful step-up transformer. Still i need to solder battery pack together and coil is finished. Its amazing performer for battery powered coil.

I will spray GDT today with 10-20 coats of enamel and pot it in hot plastic. I hope it will help. I think its because on my half bridge there is 700 VDC. Too much voltage for CAT wire?

The only thing i regret now is i didn't solder there a full bridge, but there is no place on board

. Second my voltage divider caps on half bridge are 400 VDC rated, but its still fine

flannelhead

Sat Jun 07 2008, 11:21AM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

Just curious, where do you ground the secondary base? Also what kind of a driver are you using (PLL, 74HC14, or what?)

KresoLiubov

Sat Jun 07 2008, 01:14PM

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

Dr. 2N3055 wrote ...

Just curious, where do you ground the secondary base? Also what kind of a driver are you using (PLL, 74HC14, or what?)

I just connect it to - of battery

. There is a yellow alligator clip to connect to ground, but it works fine without it too.

I disassembled circuit now again. I will make 12 - 600 V converter with a ferrite transformer, the iron core really is not that good at 200 Hz. I upped frequency to 25 kHZ and set duty cycle to 50 %.

Going back to work

flannelhead

Sat Jun 07 2008, 02:01PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

*Hmm, makes me thinking...* Maybe I'll build a Class E version of this one...

Secondary/primary parameters? Any other details? Aww, this project is so cool

Hopefully you get it cased up. It would be a really nice display piece when properly finished!

KresoLiubov

Sat Jun 07 2008, 03:20PM

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

Dr. 2N3055 wrote ...

*Hmm, makes me thinking...* Maybe I'll build a Class E version of this one...

Secondary/primary parameters? Any other details? Aww, this project is so cool

Hopefully you get it cased up. It would be a really nice display piece when properly finished!

I like more this way than class E.

Secondary is 50 mm diameter, 1000 turns of 39 AWG. It is totaly pervert to wind this, this wire is like made of air. Sphere is small copper sphere 8 cm diameter i think. There is now 40 primary turns, isolated from secondary by HV insulating sheet, few layer. )my friend has HV transformer production so i get such goodies there)

So STEP-UP SMPS works fine. I tried inserting a transformer from ATX PSU but that gave me too little voltage. So instead of that im just winding my one, 4th time. The coil draws for now 1 A at 14 V complete (logic, interupter, SMPS).

I allready read "cashed up" :). I sell my coils to museums, even one my big SGTC is in Nikolas Birth house in Croatia. However i dont have extremly big desire to spent 4 days of like machining acrlyic case for it, so it will be on circular wodden stand.

I will post som photos soon, just need to finish the SMPS transformer.

And regarding driving circuit. I was playing on this board with PLL and self resonanto 74HC and without it, and with TL494 so its a "hybrid" circuit of all this circuits :)

Little edit

I finished the SMPS transformer. I dont know why was i even bothering with pulsing a iron cored transformer

This one charges caps to 700 V in less than 1 second

KresoLiubov

Sat Jun 07 2008, 07:25PM

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

I obviously need help.

I finished SMPS, boxed coil and everything. Coil works, but spark length is only 1 cm.

I noticed if disconnect power from logic when bridge capacitors are still charged and connect the logic back on i get 1-2 streamers (coil is running extremly low BPS) like they should be 5-8 inch and then again 1 mm.

I scoped, probed, re soldered everything i could but i cant trace it

Its 74hc with UCC drivers and 555 as interrupter. SMPS (12-600 V) is a 555 driving a BD139/140 which are driving the IRFP064 mosfet which is driving step up transformer

KresoLiubov

Sun Jun 08 2008, 05:32PM

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

I got the circuit to work. I dumped the voltage doubler and use single capacitor for 400 V. Also changed to IRFP460 just to be more robust.

Coil works, happy 5-8 inch sparks.

I will post photos of compelte coil next weekend. Secondary is drying in varnish and then i will "compact it"

Proof it works and final driver

3 A X 13 V

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