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Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
This is easily the most impressive project I've seen here.
You've provided a lot of useful info, and I'm especially impressed by all the new tricks and techniques you've incoroprated into it.
Even though you've detailed the most important bits, I would be very interested in having a look at the code and the schematics for some inspiration if I get around to doing a similar project. It's extremely tempting, especially considering that I already have all the major parts, but I'm usually very slow on completing big projects.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I'm interested in the transformer combining scheme, because there's no reason (that I can see) to stop at two bridges. What did you use for DC block capacitors on the primary side?
Why yes, of course there is no reason to stop at 2, in fact i had originally planned on using 4 bridges. Ultimately, 2 bridges were enough to exceed the capability of my battery and power system, so i stopped at 2. I use a .68uF 1200V snubber cap for the DC blockers. The transformers dont even have to be all that great either, a little leakage inductance just adds to the primary L. I found that lowering the coupling helped keep the sparks straighter anyway, so if i ever made another one, the primary wouldnt be as tall.
I think if i make another one, im just gonna drive the TC with MOSFETs at ~130VDC with 6 of those LiPo's in series. That way there is no stupid DC converter to impede things . With the transformers, you can match the low voltage bridges to whatever coil setup you have. Id probably also go water cooled so that you could possibly use the 12kW of power available from such a battery... well until some other components melt .
Even though you've detailed the most important bits, I would be very interested in having a look at the code and the schematics for some inspiration if I get around to doing a similar project. It's extremely tempting, especially considering that I already have all the major parts, but I'm usually very slow on completing big projects.
Cool, i'll see about compiling it into some useful form. I have no doubt someone could replicate my work, or even make it better. Id just have to make the warning that with a system this complex, troubleshooting really requires you know your stuff. But, i guess ive de-bugged all the code and such, so any problems should just be due to assembly mistakes or something.
Does anyone else on this forum have a serious interest in building a QCW coil?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Me, me! :D
I'm rather intrigued by the idea of running directly off batteries. That would have been a joke when I started solid-state coiling, but the power and energy density of Lipos gets higher all the time. Maybe with direct battery power the system could be made small enough for a handheld "Tesla saber".
I also have a long-term project to make an all-digital Tesla coil controller on a FPGA (and a fiber optic multiplexed data format to go with it) and am looking for collaborators.
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
And me! I have most of a giant QCW bus modulator sitting right here, though I fear phase-shift modulation makes it completely obsolete How big is your transformer? Something capable of handling 120A peak must be quite bulky (though the 400 KHz operation helps handle that I suppose).
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I can see where Dr Spark is coming from, there is nothing quite like shooting a real gun.
Anyway, here's some design files (ehhh, minus the PCB layouts for now):
How big is your transformer? Something capable of handling 120A peak must be quite bulky (though the 400 KHz operation helps handle that I suppose).
The cores are about 2.5"x2.5"x1.25". They are in fact a lot bigger than they need to be, since i had plenty of room to fit the wire on the core with lots of space left. I mainly used these because i didnt have enough of anything smaller. The output (120A side) is wound with 10awg, and the input (60A) is wound with 12awg. With my low duty cycles, they do not warm up at all. For a real, mains powered thing, you'd probably have to use bigger copper, preferably some litz wire i think.
I also have a long-term project to make an all-digital Tesla coil controller on a FPGA (and a fiber optic multiplexed data format to go with it) and am looking for collaborators.
I guess for such a project to work out, we'd all have to have access to whatever IDE the chip maker has. I think an FPGA would be super cool, especially if you can just put a uC core in it, and still have some awesome peripherals that we can design. I think if you built in enough flexibility in the hardware, it should not be obsoleted for a really long time! . I know Marko wants to do such a project too. Maybe time to start defining some requirements/feature set?
By the way, ive had zero problems with both the Xmega and CPLD on this project, despite being 3.3V powered things (i think the CPLD might have a 1.8V core inside too). I remember years ago being afraid of having such hardware in the gate drive loop of a tesla coil, but it looks like it works fine.
Registered Member #61
Joined: Thu Feb 09 2006, 05:50AM
Location: Mountain View, CA
Posts: 43
I, too, have considered having an all digital FPGA-based controller. I've been going through a fair bit of pain with my most recent CD4046/74HCT4046-based coil (PC2 is very noise sensitive, and hence loses its mind when I take a ground strike; PC1 has an obnoxious phase shift, making it more or less unusable), and I've considered a few times using an FPGA instead of the '4046 to get more precise control. (I need to post a thread about my most recent coil; I think I first need to get some scope shots so that I can get ideas from others as to where I'm stuck.)
I also considered using just a CPLD as a tiny PLL; I think it would have just enough logic to do the job. Certainly an FPGA would be much more interesting, though; you would be able to integrate a micro, for instance, to do interrupter control.
So, if you're interested, Steves, let me know! I'm certainly on the IRC all the time...
edit: oh, and I failed to mention -- spectacular work, as always, SteveW! Very very neat packaging on it, and pushing the envelope as always. Bravo.
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ArcAttack! Tesla Gun
. With the transformers, you can match the low voltage bridges to whatever coil setup you have. Id probably also go water cooled so that you could possibly use the 12kW of power available from such a battery... well until some other components melt 
