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Avalanche

Sun Sept 10 2006, 02:10PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

I thought it was about time I started a thread for this coil. I started building this coil a couple of months ago, and it has been one of those on and off projects, but today I have almost completed it except winding the secondary and finishing the topload (the secondary and topload you see are taken from one of my SSTCs, and the frequency is way too high!

Anyway, I wanted to build a portable demonstration coil that would always be ready to run, that was the main motivation behind this thing. It's powered by a large flyback taken from a Sony Triniton TV. A ZVS drives the flyback for quite a nice DC output, I can draw flaming white 4" arcs without anything complaining. So far, the power supply has been totally reliable. The supply charges a 10nF, 20Kv MMC, with 8M2 resistors fitted across each cap (finally, they arrived yesterday). No resonant charging inductor yet, but I will probably add this if i'm feeling brave. The secondary diameter is about 2".

Everything (just!) fits into a small pine box I constructed (about 165x165x90mm), with a 60mm fan blowing air through and over the gap.

Anyway, here's a few pics! First light pics will be added shortly, although the system is just about untunable at the moment with it's >1Mhz secondary and 10nF tank cap. The thing looks and sounds fierce when the spark gap lights up the internals of the case through the fan grill, it's exactly the effect I wanted

Marko

Sun Sept 10 2006, 02:22PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I don't think you need a resonant charger since you already have plenty of voltage available!

Just widen the gap for more power

Avalanche

Sun Sept 10 2006, 04:21PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

True, I don't think I will add it afterall, I just thought it might help charge the caps faster for more BPS.

That might not be necessary though. Currently I have all 5 sparks working on the spark gap, and it's still firing at like 3-400BPS

Getting about 4" sparks at the moment, can't wait to see what happens when the thing is tuned.

Edit - I've just shot a quick video (953KB, WMV). The topload is way too lossy, I definitely think this coil can do more! It does a maximum of about 4" to ground, or just a bunch of corona to air.

video

Marko

Sun Sept 10 2006, 04:54PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Oh, she's pretty.. Try giving her some more coupling if you can!

Some other improvments I can think off could be extending a gap a bit, but carefully not to blow the MMC.

I would make a tunable gap simply by putting two adjusting screws close to each side of nut-gap, so you can realign the gap for mm or two if needed.

Maybe making primary a bit thicker and with less turns, I guess you don't need that much of them for ~1Mhz coil (just speculating, I would have to calculate it).

Part Scavenger

Sun Sept 10 2006, 04:55PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

That's going to be really nice. I've been thinking about a project like that, but haven't got around to it. Your's is already nicer than mine would ever be though...

Avalanche

Sun Sept 10 2006, 05:43PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

I wouldn't say that

Build another case like your ring launcher uses, and it would look awesome!

Anyway I'm going to make a new secondary soon, but I won't be aiming for as high as 1Mhz, probably about 500Khz or something. I have some thinner wire ready, hopefully I'll be able to use some more of those primary turns that way.

Tetrafluoroethane

Wed Nov 01 2006, 04:57PM

Registered Member #127 Joined: Fri Feb 10 2006, 03:36PM
Location: Cincinnati, OH - USA
Posts: 44

I was just wondering where you routed your RF ground on this. I checked out the project page on your website and wasn't able to discern it. Just curious since this is quite in line with my next project. Thanks Avalanche.

Avalanche

Sat Nov 04 2006, 08:23PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

sorry I only just spotted your post!

RF ground just goes from the base and out of the side of the case, along with the supply cable (it isn't shown in the above pics) It then just has a crocodile clip so I can attach it to anything that can form a ground. Internally, I just tried to keep it away from all the HV stuff.

still need to wind a secondary for this coil, I should be able to get much more than 4" out of it.

Marko

Mon Nov 06 2006, 10:02PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Avalanche: on your site, there seems to be a flaw in schematic you drawn; you connected UF4008's between gates and drains of same mosfets, instead to each-others.

Probably obivous to most people, but you could take a look at it if you want.

Avalanche

Tue Nov 07 2006, 07:57AM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Doh, so I have, probably shouldn't draw schematics in the early hours

Thanks for pointing that out, I'll sort it out. Hope no-one has used that schematic...

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