Small Bi-polar SSTC

Dr. Drone, Tue Nov 21 2006, 04:25AM

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Re: Small Bi-polar SSTC
Dr. Drone, Mon Nov 27 2006, 03:36PM

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Re: Small Bi-polar SSTC
Dr. Drone, Wed Dec 06 2006, 01:06AM

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Re: Small Bi-polar SSTC
Dr. Drone, Fri Dec 08 2006, 02:41AM

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Re: Small Bi-polar SSTC
Dr. Drone, Wed Dec 20 2006, 10:00PM

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Re: Small Bi-polar SSTC
Dr. Drone, Mon Jan 08 2007, 03:34AM

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Re: Small Bi-polar SSTC
Marko, Mon Feb 12 2007, 08:52PM

It's simply so perfect.. I had little to say about it.

Audiomodulation by frequency shifting seems hard on FET's since they go out of soft switching. This can ofcourse be solved with external diodes.

If you want to experiment (you would be the very first to do that on such bi coil) you could try to use a modulated buck/buck/boost converter/class D amp to modulate the supply rails directly.. I guess only imagination limits you there. smile
Re: Small Bi-polar SSTC
Avalanche, Mon Feb 12 2007, 09:12PM

wrote ...
you could try to use a modulated buck/buck/boost converter/class D amp to modulate the supply rails directly.. I guess only imagination limits you there.

Definitely the way forward for serious sstc audio modulation - a few months ago when I was playing around with making my own inverter it turned into an audio modulated power supply for that purpose. I wasn't going to mention anything about it until I got it beyond the breadboard and to the 'impressive' stage, but that never happened. I think it was more impressive with a function generator hooked up, to produce insanely loud triangle waves. Maybe one day I'll get it running again and revive the project thread!
Re: Small Bi-polar SSTC
ragnar, Tue Feb 13 2007, 01:24AM

You wouldn't be the first to modulate the rails -- even for my really old audio-modulated current-fed push/pull flyback mess, I used a FET, source-follower, for audio modulation. I also used it on my very first ever coil, but quickly learned that I didn't have any heatsinks big enough. wink

The great thing about a pulse-width modulator supply is it can serve two purposes; A) to step down the voltage from the mains, if you're running a resonant switching topology (e.g. class-E amplifier, where voltage across the MOSFET is equal to pi * Vin, MINIMUM) and B) of course, proper rail modulation for audio.

Re: Small Bi-polar SSTC
Marko, Tue Feb 13 2007, 12:34PM

you wouldn't be the first to modulate the rails

I didn't say that, but he would be the first to do it on really big coil (afaik, waverider also sucessfully modulated his 6Mhz coil that way).

I'm not sure wich topology would be best, maybe a buck/boost since it can also give higher output voltage (if more power is wanted).

I would just modulate the comaprator input of a PWM IC, without any feedback and use small smoothing capacitor.

Big input filter cap would worsen the PF, if anyone actually cares about it...
Re: Small Bi-polar SSTC
Dr. Drone, Tue Feb 13 2007, 05:17PM

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Re: Small Bi-polar SSTC
Dr. Drone, Wed Nov 07 2007, 01:36AM

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Re: Small Bi-polar SSTC
Dr. Drone, Sat Nov 10 2007, 06:48PM

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Re: Small Bi-polar SSTC
Spedy, Sat Nov 10 2007, 08:16PM

That looks great. It's hard to believe its a TC making that noise. Great job!
Re: Small Bi-polar SSTC
Dr. Drone, Mon Nov 26 2007, 06:09AM

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Re: Small Bi-polar SSTC
Tom540, Mon Nov 26 2007, 07:21AM

Awesome! Except one thing...... THAT SONG!!! ! ill
Re: Small Bi-polar SSTC
Dr. Drone, Mon Nov 26 2007, 03:55PM

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Re: Small Bi-polar SSTC
Tom540, Mon Nov 26 2007, 04:14PM

Maybe something that will push its limits. Techno or trance. Damn I want one now. hehe. I would store that one in the house for sure.
Re: Small Bi-polar SSTC
Marko, Mon Nov 26 2007, 08:37PM

Looking around all the time now... I've just never actually seen an audio modulated coil doing big, I mean really big singing sparks. Everyone seems not to be able to do more than few cm sparks. I wonder if anyone will manage to break 1 foot mark... but I think not with the topology that is currently used.

The main problem apparently isn't hard switching, but the massive amount of reactive current you have in your primary - and exceeding your mosfet rating is to easy.


I was thinking about the hypothetical modluateable power converter (class D amp) which you could use to drive the coil in tune without need for FM modulation or hard switching.

Still, that would mean large piece of ferrite to process all the power, and still your SSTC switches would be very stressed.

Since there is no way you could get without a hard switched converter anyway, I thought there could be simpler way around:

- Some LARGE ferrite. Like this. Link2


You build a normal coil, and use FM or PWM audio modulation; but, instead of your primary coil, you wind a step-up transformer onto the core and run it into magnifier mode, through base feed.

You will be hard switching, but current stress on your switches should be many times smaller and allow you to give out some real audio-modulated output.

Those inverter welders work well with hard switching and your circuit would now be nothing but one such an inverter with a resonator stuck onto end. You could get rid of all the control loop problems associated with class D amps.

I know it's a huge project, but you are definitely by far biggest candidate for something like that! Getting things like large ferrites and mosfets isn't a problem for you, so it depends on how much you like big audiomodulated sparks!


Awesome! Except one thing...... THAT SONG!!! !

Well... Where is that chrunching sound coming from?

Chris:
To show the coil off.. I wondered if you could just play something very well known, neutral, classical and liked-by-all?

Maybe something like this? Link2

Or you just wouldn't try to play anything classical at all? ill

Marko
Re: Small Bi-polar SSTC
Dr. Drone, Mon Nov 26 2007, 09:31PM

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Re: Small Bi-polar SSTC
Marko, Mon Nov 26 2007, 09:40PM

Yes, I do have a big Audio coil on the Horizon. I wanted to understand what it requires to ensure audio is clear, so played with this one for a year or so.

Hard switching these FET’s really is no big deal; just ensure you can get the heat out of the die.

The issues I had was the gate drivers. I ended up having use eight drivers to keep the signal from clipping. Big focus on next coil is trying to use newer FETs with lower gate drive requirements. Also try putting an Equalizer, Subwoofer Amp and cassette player under a coil, talk about RF issues, wheeeeeeeeeeeeeeeeeeeeee!


But we want 1-2 foot audiomodulated arcs, not these tiny ones, right?

Hard switching is not exactly a killer alone, massive reactive current (because of poor primary to secondary coupling) is a killer. You probably figured out to what can you push those ''too small'' 50 amp mosfets.

I'd really want to see a big-sparking audiomodulated SSTC (not DRSSTC!) - that's one of things that need to be acheived yet. wink


Re: Small Bi-polar SSTC
Dr. Drone, Mon Nov 26 2007, 10:40PM

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Re: Small Bi-polar SSTC
Steve Ward, Mon Nov 26 2007, 11:53PM

2 foot of CW spark needs like 5kVA+, its surely no easy feat.

Ive developed a high quality class D amp for a semester project, and with that experience id say its certainly possible to use a class D front end on a SSTC, but the real question is why? The SSTC itself closely resembles a "clocked" class-D amp, so i dont see the point in adding another switching stage. From what ive learned with my self-oscillating class D design, i wonder if a similar operation could be implemented with self-oscillating SSTCs to modulate them.
Re: Small Bi-polar SSTC
Dr. Drone, Tue Nov 27 2007, 01:55AM

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Re: Small Bi-polar SSTC
Dalus, Tue Nov 27 2007, 12:50PM

Steve Ward wrote ...

2 foot of CW spark needs like 5kVA+, its surely no easy feat.

Ive developed a high quality class D amp for a semester project, and with that experience id say its certainly possible to use a class D front end on a SSTC, but the real question is why? The SSTC itself closely resembles a "clocked" class-D amp, so i dont see the point in adding another switching stage. From what ive learned with my self-oscillating class D design, i wonder if a similar operation could be implemented with self-oscillating SSTCs to modulate them.

Guess what I was planning to build next month, a self oscillating class-D teslacoil.
Re: Small Bi-polar SSTC
Marko, Tue Nov 27 2007, 01:52PM

The SSTC itself closely resembles a "clocked" class-D amp, so i dont see the point in adding another switching stage. From what ive learned with my self-oscillating class D design, i wonder if a similar operation could be implemented with self-oscillating SSTCs to modulate them.

Steve, and that *was* the point of my post!

5kVA and an achievement, hmmmmmmmmmm please send contributions by paypal to my email account, hee hee!

Still think a SSTC magy with primary and first secondary in oil housed by plexy with some big fat FETs at 240 volts @ 50 amps on doubler would make some really nice CW audio……………………..! Of course the oil is lit up with LED’s like my Quad MOT’s @ .

Cheers,
Ch

Chris, I don't think you'll achieve anything with air-cored transformer magnifier, simply because your coupling gets too low and magnetizing current way too high.

You can have many times the input DC current circulating through your mosfets and with hard switching, fr that power level, things just don't look good.


That's where large ferrite transformer skips in - at least in my theory, it should ensure efficient energy transfer, and although audio-modulation would cause hard switching, keep the mosfets happy.

That is, necessarily a ferrite transformer.

I don't think that should be any harder than designing a class D amp for the same power level, but I'm no expert.

That's probably something that would need some ugly prototyping before plexing it up.

I'd really like to see Steve W.'s thoughts on that!



Re: Small Bi-polar SSTC
Dr. Drone, Tue Nov 27 2007, 02:52PM

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Re: Small Bi-polar SSTC
Dr. Drone, Mon Dec 03 2007, 04:21AM

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Re: Small Bi-polar SSTC
Chris Russell, Thu May 21 2009, 03:28PM

I just featured this project on the front page, so I wanted to break the ice in case nobody wanted to be the first to post in over a year.

Congrats, Dr. Spark! Another stunning project.
Re: Small Bi-polar SSTC
quicksilver, Thu May 21 2009, 04:45PM

I did indeed accept the gracious offer of Dr. Spark to witness this and many other projects several months back in the "garage of wonder".... It was the final seed to get me hooked.

The meticulous nature of the gentleman's construction was really what sealed the deal for me. I love seeing something DONE RIGHT!

Plexiglas is not too difficult to "clean-up" if a scratch exists, etc and it really allows an element of creativity to a project that makes the piece a keeper. I have made a few little toys here and there but they didn't "look" attractive; regardless of the clean solder points, layout, or what have you.

There is a Hell of a lot of creativity in the good doctor's work - but there is also style. And that can make the difference between working on a project and then let it go after a great amount of effort - And KEEPING that project alive!
In my opinion, that has great impact in the HV hobby.
Re: Small Bi-polar SSTC
Dr Hankenstein, Thu May 21 2009, 09:54PM

Chris,

That bi-polar coil sure is a dandy! (Being that you hammered that thing together in just a few weeks is even more incredible!!!!)

Very nice,
Hank
Re: Small Bi-polar SSTC
Dr. Drone, Fri May 22 2009, 04:34AM

shades