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PLL driver improvement

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Steve Ward

Thu Jun 22 2006, 05:34PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Steve's new PLL driver is a lot like my Mk2 driver, but simpler, which I guess is a good thing The sparks look great!

Thanks. Im coming to the conclusion though that there is indeed a slight trade-off with using my controller. The PC2 just seems too sensitive to low power ground strikes, so at low power, the ground hits are often thin. I wish i had a DSO so i could capture one burst from the PLLs VCO to see exactly what its trying to do. It may in fact just be a characteristic of my coil.

To me these are probably nicest SSTC arcs I seen, altough not the longest

I agree. I think maybe the higher operating frequency tends to make the arcs brighter in this case because of the higher currents (?). Also, since he used a camcorder to capture the sparks, it probably makes them look brighter than the pics i too with my camera. I think camcorders are particularly sensitive to TC sparks from when ive used them... they would make sparks on even little coils look extra thick.

Omg steve, that's 'pretty big' CW spark.

Sorry if i mislead, but the 3 foot sparks were with half-wave input. My longest CW sparks are about 21" so far.

Terry Fritz

Thu Jun 22 2006, 07:27PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Meh. I program DSPs for a day job, and I still chose analog circuitry for my PLL driver.

Since you do it for "work", that takes all the fun out of it

I think you mentioned once you like the analog circuits for Tesla coils because they aren't like work. In my case, I got ride of the "work", so now I like it all again

The big problem with processor based stuff is latency, ie the time it takes to suck data in through the A/D converters, do all the calculations, and spit it out again.

Consider if you "trigger" on "current reversal". Not the zero crossing, but the current peak. The inflection point where the primary current goes from positive to negative. The zero crossing is only 1/4 cycle latter. The time is short enough so the zero crossing can't "move" too far but long enough for the processing. Normally we would never consider that since it takes a computer... But with a computer, why consider anything else... You could still have ZCC detectors there just as a double check or to detect a problem. No A/D converion since simple comparitors give the digital transition used for timing.

Steve knows a million times more about all this stuff than I do and "nightmare wavforms" would require a "Cog" all by themselves!! You could also take IGBT temperature and at least try to shut the bridge down in the case of a fault. The computer could keep track of IGBT power dissipation as a pure calculation too... No reason to "waste" any of the CPUs :o)

Of course, one could do a full speed primary current A/D stream to the processor too! Then you could probably hit the ZCC every time.

Of course, this is all "more easily said that done stuff"

But I think all the technical tools are out there to do it if one wishes.

Oddly, someone WILL probably use a gameboy to do it... "why spend $25 on the CPU when you can just use one out of a busted gameboy"... But those are programmers who live in a world "I" can't comprehend"

One could also completely model the coil in the multi CPU and just display the coil on the color video screen without any coil hardware at all... But "i" might be the only one who would "appreciate" that :o) Yeah, I know.... "Terry, just a game boy could be programed to do that..." But the game boy could have all the coil parameters, timing, rail voltages, etc. on the buttons so you could sit there and play with it all day!!! The only thing I would need then would be for the guys in the white coats to bring me batteries %:o))

Cheers,
Terry

colin heath

Thu Jun 22 2006, 08:22PM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

The only way I'd be interested in trying for the DRSSTC record would be as part of a UK team, kind of like what Chris Hooper is doing with Ward and Jimmy.

Well Steve. That sounds like a job invite

Lets do it. I will be up for the mechanical building part and anything else you need. I have a 12" x 60" secondary here with a 12" x 48" toroid. 10 turn primary also. Only thing is secondary is around 80KHZ or so I think with topload. (will have to measure).

Sounds like some fun building this thing with a full bridge of cm600 and throwing some massive arcs!

If you don't fancy it then I could do with some cm600 bricks to finish mine

maybe I can talk the missus round

Cheers,

Colin

J. Aaron Holmes

Thu Jun 22 2006, 08:38PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

Terry Fritz wrote ...

Oddly, someone WILL probably use a gameboy to do it... "why spend $25 on the CPU when you can just use one out of a busted gameboy"... But those are programmers who live in a world "I" can't comprehend"

Perhaps when I get my DRSSTC book, I can play with this idea. I already created a Game Boy cartridge and add-on hardware to control my handheld radio for Radio Direction Finding hunts, shown here:

(sorry, pictures are pretty dark/lame)

I believe this was also one of the first amateur projects to use the link port for anything. Used Game Boys are cheap. The FLASH cartridges are the worst part. A cheap one is as much as the Game Boy itself. I'd hate to fry either! The HAM SDK has text output with built-in font, and I built a text menu system on top of it. If you can write C code, producing a cartridge that samples the link port and pumps out square waves is totally trivial.

Regards,
Aaron, N7OE

Terry Fritz

Fri Jun 23 2006, 03:24AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

I already created a Game Boy cartridge and add-on hardware to control my handheld radio for Radio Direction Finding hunts.......

Seeeee wadda I mean.... Color video, input switches, color displays, keybords, USB, "spins"... Then add "gammer processors" from "the really hot place"... The technology to "calculate" has far "outrun" the needs of Tesla coils

))

Even them DRSSTC's

))

We is real "slow"...

Beware analog folks!!!, the "digital kids" are going to run us over like "old frogs"!!! Jimmy and the Steves will be be feeling "old" now too :O))) Just like "me" :O))))

As "Tesla said"... See the excitment coming!!!!!!!!

BTW - When a DRSSTC is first fired up, it could fire a small "pre-pulse" as a "measure"... all the current crossings and such, Plenty of time to analize "that readback" for "problems"... Then predict and modify the drive signal based off that first "test of the world out there"... Real time feedback takes care of the streamer loading and such issues... That is in the first 10mS!!!!!

It's "gonna get wild now"

)) Aaron looks older... A "young mind with old knowledge"... That is the most dangerous weapon of all :o)))))))))))))))

Cheers,

Terry

Steve Conner

Fri Jun 23 2006, 09:32AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Wow, looks like a nice Gameboy project

I have one of the original GBs with the GBDSO cartridge, but I never got round to making my own flash cart and trying to load stuff into it. I did briefly think of trying to make a DRSSTC interrupter cartridge for it, but I just lay down and the feeling went away.

Colin, building the coil itself would be pretty easy. That big coil system you have sounds OK, although it would be nice if the frequency was nearer 20kHz than 80.

The real problem is finding an indoor venue with plenty of power, enough headroom for sparks, and "Tesla friendly" owners, that we could take over for at least two full days to allow for debugging. And sorting out transport for the people and equipment that have to be brought together from all over the UK. If you guys can do that, I'm happy to turn up with a full bridge of CM600s and a large tank cap.

This is off-topic and any further discussion should be done on the TCBOUK mailing list or a new thread.

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