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LAN_403

Dr. H.

Thu Oct 04 2007, 11:34AM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Hi Marko

The PLL is working. It is traking the exact frequency (about 500khz) . This are pictures of the output of the half bridge (top - no load, middle with lamp as load, third primarry with secondary for load.

So the question is for the 3rd. Should the voltage in the primary look like that (i don think so

)

Dr. H.

Sat Oct 06 2007, 06:27AM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

**UPDATE**

Hi guys, after a lot of fiddling i finaly got it to work properly. It si producing about 13sm of streamers (5.2 inch ) and about 15-16sm to grounded target

. Thanks for your help guys. Hire are some pictures of the streamers (i don't know why but on the picture they look shorter than they actulay are.

Zum Beispiel

Sat Oct 06 2007, 10:40AM

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

Good job! Now the real fun begins.

What kind of power are you using (Fullwave/Fullwave + filtering/Halfwave)? Experiment with different inputs. Halfwave rectification usually gives longer sparks than fullwave. Try taking some turns off the primary, try moving it up and down. Try putting a topload on it.

Push it till it blows, then back up a little

Bauerb2

Sat Oct 06 2007, 04:41PM

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

that is awesome huben. are the mosfets still overheating or do they run cooler now? You should definitely try a topload, i want to see how much power you'll get from this coil, it looks promising.

as a side question related to earlier in the thread, does anybody know where i can buy a ferrite gdt toroid that has a high permeability? i've checked everywhere but i can't seem to find the right one (there's so many different materials and sizes). im planning on powering a full bridge with one, but if i can get two toroids, i'll seperate the gdt into 2 parts. Where have you all bought your gdt toroids?
Anyway..once i get the gdt completed i can finish the whole coil in a few hours.

thanks for the help, nice coil ruben

pz - Andrew

Zum Beispiel

Sat Oct 06 2007, 04:47PM

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

Bauerb2 wrote ...

as a side question related to earlier in the thread, does anybody know where i can buy a ferrite gdt toroid that has a high permeability? i've checked everywhere but i can't seem to find the right one (there's so many different materials and sizes). im planning on powering a full bridge with one, but if i can get two toroids, i'll seperate the gdt into 2 parts. Where have you all bought your gdt toroids?
Anyway..once i get the gdt completed i can finish the whole coil in a few hours.

I bought the ones Thedatastream recommends on his site from Farnell. They don't cost that much and perform very well. You can ask from some eletronics shop if they have an account there and if they can order some for you.

Failing that, good ferrites can be salvaged from most broken eletronics thingies. If you have a scope you can check that it gives clean waveforms, just needs more work than buying a core that is known to work.

Dr. Dark Current

Sat Oct 06 2007, 05:09PM

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

I got two big ferrite toroids great for gdt from old switching power supply from a photocopier, some good ones are also sometimes in old tv's and you can always use the core from an atx power supply transformer, it works well for a gdt

Dr. H.

Sat Oct 06 2007, 05:25PM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Hi to all end thenks fot the help guys, if weren't you i woudn't have gone so far

So for the torroids i get them from microwave ovens - they have a some sort of filter. The toroids are great for gtds. In this coil i actualy use the same, and you can see tha waveforms on the previous page.

So now for the coil. Today i spent about 4 hours of experimenting with the primary and i found some interesting thing.
1st - when i use helical style primary i get smaller streamers and my tranzistor get very warm, so now i use something like a bunch of wires tightened togheter with straps.
2nd - when i increase the coupling, the streamers become shorter, but hotter, more like flame, i had to change the breakout point to tungsten, and the transistors are getting very hot.
3rd - when i use smaller coupling, and 6 turns i get the longest streamers and the tranzistors are only slightly warm

BUT hire comes the most strange to me problem. In the 3rd situation when i turn on the coil i get about 17-18sm of streamers

but for about 3-4 seconds, after that they become shorter and fatter, more like flame (i am using half way rectified, so i find this strange

). Also i noticed that this happens (according to me, but if anyone has other informatio PLEASE write it ) when the breakout point become hot.

Please tell what you think about that. And one last question - how do you guys determine coupling

???

Bauerb2

Sat Oct 06 2007, 05:36PM

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

maybe the heat from the breakout is creating a little 'pocket' of heat around it, and current likes to travel through this heat region. a few years back i arced a flyback xformer, run at a low duty cycle, which normally is just a sequnece of sparks *taptaptapta*, but when i short it out through a candle flame the seperate sparks combined into a fat little arc.

i could be wrong, but w/e.

anyway, thatnks for the help guys abotu the toroids. i've checked through pretty much all my electronic junk pile and found nothing. i had a few toroids from a couple of computer psu's but according to some people, this is not ferrite, but powdered iron, which apparently is not good for gdt use. ill look on the internet more, or find some junk to tear apart

thanks all

-Andrew

Dr. H.

Sun Oct 07 2007, 03:49PM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

So i complited the coil interely and tested it. It ran for 5 min without any problems, the transistors were slightly warm, but then, in the exact moment i turned it off the fuses blown and the two transistor went dead. Previously a had the same problem - they died in the moment i turned on the coil, but at that time i thought that this was caused by me. So the question is why they die

HELP

Bennem

Sun Oct 07 2007, 04:06PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

When turning off your supply voltages,
I sometimes think its a good idea to turn off the bridge supply
voltage first and if you have storage caps, make sure they are discharged,
then secondly turn off the drivers voltage.
Reverse the procedure when turning on your coil.
as sometimes when you just turn off all voltages at once may cause
your driver to inadvertantly turn on your bridge and blow IGBT's.
Just a thought.

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