Help with tesla coils wave forms / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Help with tesla coils wave forms

1 2 3 next

Move Thread

LAN_403

Killa-X

Sun Dec 06 2009, 03:48AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Hey all, I been having some issues with my mini SSTC thats been here for awhile. Anytime i go to CW more, 90% of the time, i turn power on, nothing. I turn the poewr off, POP. 1 burst, usually 4". 10% of the time, it stays on, but its only 3mm... Also, I wanted to make sure the wave forms i get are correct. I see there's a LOT of ringing...but...Hopes to fix things, and get some feedback on its behavior. Any questions / pictures that the video doesnt show, please as, and i will try my best to get them.

Video info: Top = Probe to Pin 1, Gnd to pin 3 of the fet. This is the 2nd fet in the halfbridge of the mini SSTC.

bottom = Primary. Scope probe to the first ring of the primary, and to ground.

Thanks for your time and help!

Dr. Dark Current

Sun Dec 06 2009, 01:49PM

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

You tried to change the phasing of the primary right?

Killa-X

Sun Dec 06 2009, 04:40PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Dr. Kilovolt wrote ...

You tried to change the phasing of the primary right?

I'm sorry I cant think right now! What do you mean phasing? Flip the connections to the Primary connections on my Fet power board?

Things you should know about the primary also:
6.5" diameter PVC pipe (form)
1/8" copper tubing as wire
6 windings (And its using the full 6 in that video)
about 1cm spacing between windings.
The first winding I THINK is about 1" lower than the first secondary winding. Rig wasnt made to adjust, but if I must, i will.

Secoondary:
4.5" diameter
30awg wire..and well..its not needed :P

When I zoom in with the zcope in that video, where you see the square wave with lots of ringing, My scope is set to about 1uS..so at least its tuned, with the Current transformer :)

Dr. Dark Current

Sun Dec 06 2009, 05:18PM

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

Killa-X wrote ...

Dr. Kilovolt wrote ...

You tried to change the phasing of the primary right?

I'm sorry I cant think right now! What do you mean phasing? Flip the connections to the Primary connections on my Fet power board?

Yes, just change its "polarity".
What is your estimated/calculated secondary resonant frequency? How much us/div is the scope set to when you display the ringing waveforms? Does the running frequency match the calculated one?

Killa-X

Sun Dec 06 2009, 05:33PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Well i have no exact count. And my old tuner isn't here any more. But last i checked it, it was around 358khz. I guess I will have to recheck the scope with that.

As for the rest of the questions I'll get back to you soon. Scope and all is off desk because the fan wouldn't start (at least by ear) apparently its just on so little due to room temp. So, I will reply before 2 hours seeing its near lunch. Thanks! (Secondary is 4.5", flashlight wire (30awg i believe) and 10" tall.

Killa-X

Sun Dec 06 2009, 09:12PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Well, As i said i dont fully know the exact ratings of my coil in terms of frequency. But i did somewhat what you said then.

Picture 1:
Here, I left the primary as it was in the youtube video.
Time/Div = 1uS
Votls / Div channel 1 (Mosfet) 20
Volts / Div channel 2 (Primary coil) 50

I then did as you said, Fliped the primary connections. Didnt work (as expected) then changed the CT as well, so it works.

Picture 2:
I left EVERY thing on the scope the SAME. All I did was change the primary and CT connections. Same Time / Div, same volts.

Should mention also, the power input was 38V doubled. The doubler consists of 2X 400V 470uf capacitors, and that feeds into my SSTC, where i have 400V 1200uf filter cap.

Dr. Dark Current

Sun Dec 06 2009, 09:50PM

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

Isn't the noise being picked up by the scope probes by any chance? Try to short the probes to the ground clips (leave the clips in the circuit) and see if you get any ringing on the scope.

Killa-X

Sun Dec 06 2009, 10:12PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Dr. Kilovolt wrote ...

Isn't the noise being picked up by the scope probes by any chance? Try to short the probes to the ground clips (leave the clips in the circuit) and see if you get any ringing on the scope.

Well, i have my scope at 1uS, with the probe to nothing (not shorted) and its flat line. when shorted, flat line. not wiggly at all, solid flat. 100mhz scope. even when i got it to 5mv / div, shorted probe, its solid flat.

anyways. My scope was calibrated and tuned by professional when it was shipped. Also, my scope has these 2 black marks that i thought was my time frame. maybe not. Because actually, the black | | marks where saying 1uS. BUT the plastic markrer was to 10uS. So actually must be 10uS, not 1uS. Sorry!

Also, nothing in my SSTC is shielded, and my ucc board maybe has 4uf of DC blocking caps, and 4 coils on GDT. with 5 ohm resistors on the gates of the fets.

Dr. Dark Current

Sun Dec 06 2009, 10:39PM

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

Well if it really is 10us/div, then you only have there 25kHz.
Have you tried running it without the scope? Maybe the probe capacitances are doing funny things.
What is the cross section of the GDT? And is it wound on a black core (ferrite)?

And forgot to ask, what is your schematic, is it the mini SSTC or did you make any changes to it? What confuses me is that you say you go CW, and the original mini SSTC circuit really cannot do CW without a start-up oscillator.

Killa-X

Sun Dec 06 2009, 10:57PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

I'm using the mini SSTC diagram with 4uf blocking cap to the one link of the GDT. both fets have 5 ohm resistors.

Heres the odd part. When its on, its ringing as youu see. But the SECOND i turn it off, i see a no-ring SQUARE wave that fades to a line..

Thats when i leave the GDT power circuit on, aka the driver, but turn off the 38V power supply.

Also, i have a switch that enables (pin 3?) high, to go CW. The issue is i cant make it work. Maybe i need to build that starter than...Because i cant make it work no matter what i do. Issue is I use a CT, and im not sure how to connect it...Isn't like the antenna.

No scope. just test.

EDIT I took boards off, I actually only have 2uf of DC blocking..which isn't a lot.

1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob