Explain how a center tap push - pull gdt works?

alec_t · Oct 16, 2013

Now I just have to pull out the waveform and I'm set. It would be great if someone could help me with that?

Just click and drag on a bit of the waveform to zoom in on it.

killivolt · Oct 16, 2013

I was clicking but not dragging. Thanks I fixed my last post. It's still not to pretty but it will do.

Thanks,
kv

dr pepper · Oct 17, 2013

I tried a plasma speaker a while back, wasnt impressed with it, but that might have been my rubbish build.

One benefit from the gate drive shown is that to get the gate voltage 4 or 5 volts higher than the source to get the min rds on you dont need a seperate power rail, the xformer adds the gate drive voltage to the source voltage.

killivolt · Oct 17, 2013

dr pepper said:
I tried a plasma speaker a while back, wasnt impressed with it, but that might have been my rubbish build.

One benefit from the gate drive shown is that to get the gate voltage 4 or 5 volts higher than the source to get the min rds on you dont need a seperate power rail, the xformer adds the gate drive voltage to the source voltage.

I understand that in a post somewhere in the many threads I've created, the Mosfets work better when on separate heat sinks, prevents knocking.

shortbus= turned me on to this, I like the box they put it in.......

dr pepper · Oct 17, 2013

What the heck is knocking, new one on me.

Interesting design, an acoustically loaded plasma arc, with transparant chamber.

killivolt · Oct 17, 2013

dr pepper said:
What the heck is knocking, new one on me.

Interesting design, an acoustically loaded plasma arc, with transparant chamber.

It was just someone else's term, Knocking?

Yeah, I thought it was pretty cool, I was thinking maybe a resonator sort of like in a guitar or something + add some boom boom to it as suggested on one design.

It might allow for the gases to escape.

dr pepper · Oct 17, 2013

Boom or bad transient response is something most designers dread, esp in bass cabs.

Know what you mean though.

killivolt · Oct 17, 2013

dr pepper said:
Boom or bad transient response is something most designers dread, esp in bass cabs.

Know what you mean though.

It had to do with ZVS driver circuits, of course you probably already new that, I'll hunt around to see if I can find the post with the full comment.

dr pepper · Oct 17, 2013

Zvs is an effective method, however modulating a zvs requires a few tricks, I'd be interested to see such a circuit.

killivolt · Oct 17, 2013

dr pepper said:
Zvs is an effective method, however modulating a zvs requires a few tricks, I'd be interested to see such a circuit.

Here's one I've been working on, I kept this design because I have like 20 of the SG3525's...https://adammunich.com/oldstuff/Plasma_Speaker_2_files/schem.png

Here is the Spice Transformer help I got from ETO folks. https://www.electro-tech-online.com/threads/building-lt-spice-transformer-help.138524/

This is what started it all. I'm going to put it on a Development Board first this time, then I'll build it. https://www.electro-tech-online.com/threads/plasma-speaker-halloween-project.136126/

ChrisP58 · Oct 17, 2013

KV

I have to confess to a major mistake way back when. I was thinking of the SG3524 (which has open collector outputs) when I said you needed a CT on your GDT. As mentioned above, the SG3524 does indeed have totem pole outputs, so it can drive a single GDT transformer primary directly.

I sincerely apologize for misleading you, and for the time you have spent following my stupid error.

killivolt · Oct 17, 2013

ChrisP58 said:
KV

I have to confess to a major mistake way back when. I was thinking of the SG3524 (which has open collector outputs) when I said you needed a CT on your GDT. As mentioned above, the SG3524 does indeed have totem pole outputs, so it can drive a single GDT transformer primary directly.

I sincerely apologize for misleading you, and for the time you have spent following my stupid error.

Nah, your awesome

I look at this as a learning curve, this hole thing was geared around that, and to have a little fun. The good thing is, I have proven this circuit will work. Which makes me happy.

On the other hand, your mistake will only increase your brain, they say mistakes, builds new dendrites. I know it's hard to believe, but it's true. Plus while your teaching on ETO builds both memory and aptitude.

It's a win, win, for all of us.

I'm glad to know I have someone to back me up, I sure need it.

If you ever need assistance with Appliance Related Equipment, FYI, I did it for the better part of 25yrs. But, what I'm seeing these day's is they'er all going electronic too!

Back in my day we said. Thanks man, much appreciated.

kv

Edit: I worked for Action Target in the Electronics Department R&D. I hand wound many, many Transformers just like that one. But, it's a little harder at my age, no problem.

killivolt · Oct 17, 2013

dr pepper said:
What the heck is knocking, new one on me.

Interesting design, an acoustically loaded plasma arc, with transparant chamber.

In my 3rd reference in post #30 is my Halloween Project, you asked what was "knocking"?

I found it in the 18th post from Dr_doggy the sound "knocking" is what he was referring too! I think I will adopt pretty much anything, to make a really good Plasma Speaker.

I do think a resonator is the way to go, however, it's time for me to look into that, I don't know the actual construction yet. I really like the horns on the evaluation of a Plasma Speaker, it was very telling.

killivolt · Oct 22, 2013

ChrisP58 said:
KV

I have to confess to a major mistake way back when. I was thinking of the SG3524 (which has open collector outputs) when I said you needed a CT on your GDT. As mentioned above, the SG3524 does indeed have totem pole outputs, so it can drive a single GDT transformer primary directly.

I sincerely apologize for misleading you, and for the time you have spent following my stupid error.

Ok. Forget about the other stuff. It suddenly hit me? should I try a SG3524A with that Transformer I wound, or is it a completely different circuit and to complicated?

Is there that much difference, I really don't care if it can produce sound or not?

Would I have to recreate the hole circuit or is their a simpler solution?

Just curious.

Thanks Chris,

kv

Edit: I already have a wound Trans, why not?

ChrisP58 · Oct 22, 2013

Simplest would be to remove, or ignore, the fourth winding winding and use it as a three winding GDT like the original circuit shows.

killivolt · Oct 22, 2013

ChrisP58 said:
Simplest would be to remove, or ignore, the fourth winding winding and use it as a three winding GDT like the original circuit shows.

:Wink: Got it.

Thank you, I'm sure there will some other stuff, I will for sure ask about. This one, well on my part, sadly ends. No matter I will just re-wind

Thanks again, Man.

kv

dr pepper · Oct 23, 2013

How did you get zvs with a sg3525?, zvs implies resonant whereas the '3525 isnt, there are some quasi resonant controllers but I didnt think the '3525 could do it.

killivolt · Oct 23, 2013

I'm not sure if this answers your question of not, but in the first post of the "Thread" is the circuit I used, I pulled it from the Instructables Website "thinking" name "Reliable Plasma Speaker" spoke for itself! The reality may not be so.

Thats why I'm here and why I've spent so much time making sure it's not a complete waist of time, I'm going to try again on my development board this time, maybe this weekend. I'm going to Wind a new GDT and go from there, I may end up scrapping the hole thing in the end, not sure yet. If it won't play music I may just set up correct resistances and just see if I can get an arc, I bought like 15 or 20 of them? Me and these SG3525 are going to be intimate eventually.

I may end up frying them all!!!! Just kidding.

killivolt · Oct 23, 2013

alec_t said:
Actually my sim used a square wave to represent the output from the SG3525.

Edit: Btw, if you have a cap in series with the GDT primary, as shown in the original circuit (why is it there??), you will get strange waveforms. My sim excluded the cap.

I just re-read this and found that it was your simulation that I needed and it didn't belong to Adam. I also need to include you into the credit for finding the Cap issue.

Thank you,

kv

dr pepper · Oct 23, 2013

I've no reason to think the circuit is unreliable, however from what you say I dont think this is a zvs design.
Zvs or zero volt switching requires the primary of the step up to be made resonant with a parallel capacitance, then the switching of the circuit is controlled via the resonance of the cap/coil, the sg3525 circuit operation isnt the same, you can still make the circuit resonant by putting a cap across the coil and tuning the freq of the '3525 till resonance is achieved, the drawback from this kind of circuit is that load on the ht, temperature changes and various other factors can change the resonant freq of the transformer misaligning resonance of the transformer with the drive freq.
Still doesnt mean to say you cant make a good plasma speaker out of it though.

Explain how a center tap push - pull gdt works?

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