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

previous 1 2 3 next

Move Thread

LAN_403

Dr. Dark Current

Mon Dec 07 2009, 07:25AM

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

Killa-X wrote ...

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..

This really seems like some noise /interference problem to me. I often have these problems and it often has something to do with grounding.

Killa-X wrote ...
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.

So does it work with an antenna?

Are you sure your power supply (whatever it is) is supplying enough power? Tesla coils at CW draw HUGE power. You get just a few inch discharge with a kilowatt of power.

Killa-X

Mon Dec 07 2009, 09:08PM

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

Have school, so cant reply during day.

First statement, Yes that's right. It was a grounded stick. When i hold a screwdriver, its solid. But I didn't dare do this at that voltage. it WAS grounded.

Second statement, Yes it works with an antenna, I just rather use the CT. With CT i have no idea how to hook a oscillator. Also, Its running off a 198W stereo transformer, at the end of that video, 78V doubled (400V 470uf caps) then filted by 400V 1150uf cap bank. So, no, this power supply is far from enough power.

I took most apart to fix some stuff, but I will get back to you tonight, I'm going to try some 450V 2400uf caps I got in the mail today as my doubler. See if 2400uf works better than the 470uf.

Killa-X

Wed Dec 09 2009, 03:44AM

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

Just wanted to update you Kilovolt, I tryed the CW mode with no filter caps, and half wave. And it indeed was larger, but I need to fix my variac to fully see the results. Then I put it back together, and used a doubler of my newly ordered 2400uf caps, and it indeed was a lot better.

On 470uf doubler, when i did a topload, i would be lucky to get 4" at 78V doubled. With the 2400uf, I was able to get maybe 6" if not more...I feel my transformer is a bit llimited so again, need variac fixed. Fixing fuses.

teravolt

Wed Dec 09 2009, 04:52AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

if you can use circuit breaker insted of fuses is cheaper say 1A. I think that your strange ringing is real. what type of material are you useing for your gate driver transformer. maby if you put some resistance maby 100 to 1k in parallel with the tranformer winding to dampen the higher frequencys that will help. It depends on how much driving current you have will determin how much resistance you can hang on the gates or transformer windings. stray frequencies like that can be caused by long leads or stray inductances

Killa-X

Thu Dec 10 2009, 03:09AM

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

Well, The GDT leads are all smaller than 1 inch, and twisted.However, the wires to the primary (due to testing) is rather too long, it like C bands from the board to the actual primary.

The fets also have right now, 5 ohms of resistance. And the cores are from Electronic goldmine, the 5 for $1 deal.

Dr. Dark Current

Thu Dec 10 2009, 09:09AM

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

Does it ring only when you connect the bridge power, or also if just the gate driver is running? Does it ring with unconnected gates?

Killa-X

Thu Dec 10 2009, 04:13PM

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

Dr. Kilovolt wrote ...

Does it ring only when you connect the bridge power, or also if just the gate driver is running? Does it ring with unconnected gates?

Cant scope it now but from past, Id say no. When i scope the fets, I didnt have ringing, my square waves were just a little curved at the ends. And, like I said, Im scoping pin 1 and 3 of a fet. When I turn everything on, Its all what you see in those pictures. When i JUST turn the power supply off, i see a decent looking square wave (no ringing at all) that fades to 0v. so, I guess something in the lines of activating power..adds that ringng. I can however, give you scope feedback of the GDT...Just not with power on :P

teravolt

Fri Dec 11 2009, 06:22AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

how much capacitance do you have on the power pins to the drivers for the gate drive transformers?are you using any tantalum caps or bypass? does the fuzz apear at driver output? are all of your bridge fets good?

Killa-X

Sat Dec 12 2009, 01:01AM

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

teravolt wrote ...

how much capacitance do you have on the power pins to the drivers for the gate drive transformers?are you using any tantalum caps or bypass? does the fuzz apear at driver output? are all of your bridge fets good?

Well, I think I copyed the mini SSTC exactly.

I think I have my 18V 3A transformer going to a 2500uf capacitor, then the 12V regulator has 1000uf, and the 5V regulator has 1000uf. These filter capacitors are lytics. Then, on every chip, I have a 0.1uf film capacitor over + - to protect them, UCC output is then caped with 2uf (until i fix that) Both fets work fine, and have 12V zener diodes in --|>--<|--- connection, and the fets dont have the MUR1560s anymore.

Killa-X

Sat Dec 12 2009, 07:31PM

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

Ok, sorry for the delay gets busy with school + work. Still work today but I had time to get more help out here.

In the first part, you might ask "Whats that randomly placed square?" Well, That's the oscillator with a randomly picked 1nf capacitor. So, ignore it for now.

This video should help a lot. First, Spects.
Half-bridge at 38V, with no filter caps. Kizmo told me, with no caps and halfbridge, you get a lot larger CW output. compared to full bridge, it's just a fuzz. the other 2 sections of the video is interrupter.

The other 2 parts, make me think we have probe issue. As seen, the top breaks solid squares (I PURPOSELY set it to have a hard time starting, to show you guys this!!!) And the bottom, is a probe on my desk, picking up whats in the air, this was to show that ringing, is due to the coil, not the circuit. I had probe to pin 1, and probe gnd to pin 3 of the 2nd fet in the SSTC, the one that goes from middle, (pin 2) and to circuit ground. The only stuff around the probe, is the coil..The CT (current transformer to drive coil..1cm away) GDT, more tesla ground wires, and other stuff.

Any solutions to fix the (possible reason) Ringing due to coils interference? Also, the 2nd channel probe was 6 from coil base. When its by my scope..3ft away..its flat line.

previous 1 2 3 next

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