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Party cup capacitors. Has anyone used them on tesla coils?

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LAN_403

Arcstarter

Fri Apr 18 2008, 03:56AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Thanks to Ultra7,I have now decided upon using party cup capacitors. So has anyone had any experience with them? Im sure they would work well because they are the exact same thing as saltwater capacitors. I have tested mine at up to 20-30kv dc with my flyback without a single failure. They should be exposed to some 16kv peak on what i am using them for. I am using two mots with a doubler and then 4 mot's as a choke. I do not want to have to use more than 50 capacitors.

Also,about what would the capacitance be for a cup that is made from Jack Frost and is 16 ounces or 473 ml? The physical dimensions are 4 3/4 inches tall, 3 1/2 inches wide at the top and 2 inches wide at the bottom. None of the measurements are exact,but close.

Thank you!

Ultra7

Fri Apr 18 2008, 02:24PM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

Yeah, I used them before I got MMC caps.
No issues with them whatever but the mess.
It was fun building them with my kids, as well.
I'll post pics of them later.

Mark said with 10 cells, he got 5nf rated at 50KV.

So with 4, ten cell units, you'd get 20nF rated for 50Kv

That would be a peachy capacitor.
Add another 4 units in series for 40nF.

flannelhead

Fri Apr 18 2008, 03:52PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

Huh, that'd be a lot of work. It would take up a lot of space, too. I will probably prefer commercial caps for my coils.

Arcstarter

Fri Apr 18 2008, 04:38PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

spark wrote ...

Huh, that'd be a lot of work. It would take up a lot of space, too. I will probably prefer commercial caps for my coils.

Well i posted a...post and noone told me were i could get commercial caps. Ultra7 suggested i used these because i am on a low budget (of approximately 0 bucks). If i can find some good caps for about 20-40 buck that can withstand 20kv and is 40 nf than i will be good!

flannelhead

Fri Apr 18 2008, 04:52PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

Look at ebay, you can often find plenty of good things... For example these:

Ultra7

Fri Apr 18 2008, 06:17PM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

Those 600 Volt caps probably wouldn't work, and the yellow caps are $3.50 apice

Arc is broke like a teenager.

I was giving him options to "make" a cheap cap rather than spending money he doesn't have.

J. Aaron Holmes

Fri Apr 18 2008, 06:33PM

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

spark wrote ...

Look at ebay, you can often find plenty of good things... For example these:

Wow, $3.50/piece for nameless Chinese caps when Richardson sells the CDE942's for $2.87? I'll pass. Granted, the minimum order from Richardson is 50 pieces, so that's ~$150. I'll still pass.

Cheers,
Aaron, N7OE

Arcstarter

Fri Apr 18 2008, 07:01PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

How about this capacitor? It is rated a little low on voltage but do you think it would be good for tesla coil duty? Because if i have to i will just use two mots for 4kv and use a ballast until the capacitance is right.

J. Aaron Holmes

Fri Apr 18 2008, 09:07PM

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

Arcstarter wrote ...

How about this capacitor? It is rated a little low on voltage but do you think it would be good for tesla coil duty? Because if i have to i will just use two mots for 4kv and use a ballast until the capacitance is right.

Hard to say. There isn't enough data there to convince me that it wouldn't just pop.

When you start thinking about trade-offs like this, it usually helps to have some kind of performance goal in mind. Then you can work backwards through the various formulae to determine what parts will get you there. 4kV with a .03uF cap is only 120W coil power at 120bps on the gap (about 1J/bang). That might make ~18" streamers if your quench is good, but at 4kV AC I'm going to bet against you unless you're building an RSG. Is this what you're looking for? If not, perhaps we can help you to explore other options. Just focusing on the cap may not be that helpful.

Cheers,
Aaron, N7OE

Ken M.

Fri Apr 18 2008, 09:11PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

The old Beer bottle caps work ok also >.>

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