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# im building a tesla coil and have so many questions about one thing and one thing only, the capacitor bank! Answered

im building a tesla coil at my great uncles, my parts are limited, to make the capacitor bank i only have an unlimited supply of 100uf 330v capacitors, but they cannot charge in a 60hz cycle and i dont have a converter, could i put a diode so the sign wave never goes bolow 0 and make it work with the transformer capacitor and the coils? and to actually make the capacitor bank work with 7.5-10kv how would i have to wire them up? (like....... series or paralell and how many?)

thanks

update: ok now i only have an unlimited supply of capacitors that are all 330v but range from 80-120uf

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Best Answer 8 years ago

Having an unlimited supply of 100µF caps is good, but there's a better answer. Make your own.
Once you get up into a couple kV or more you're going to have arcing problems. The only solution is going to be to increase the spacing between the poles. You won't be able to do that with your 100µF caps. Also, you're going to want a couple of Farads of capacitance for a 10kV Tesla coil. Here's how you get it.
Get some ¼" plate glass panels of about 12" x 12". Ten should do. Also get some aluminum (or copper) sheet metal. 22 gauge (even heavy foil) should be fine.
Compute the distance to arc based on the voltage. (I couldn't find the formula or I would have provided it here). That is, if the thing is running a 7.8 kV, there's going to be a minimum arc length in inches. If it's running at 8.3 kV, that distance is going to be shorter.
Let's assume you determine the arc distance for your application to be 1". Cut your aluminum into 9" squares and glue it onto one side of each glass plate. This will give you a buffer of ½". Cut grooves into a bar of non-conductive plastic to separate the glass plates 1¼" - 1½". Build a stack of glass plates, all parallel to one another. Attach one side of your power to the first aluminum plate and the other side to the last aluminum plate. Encase the whole thing is an enclosure of 1" plexiglas because if you miscalculated anything and overload it, it will explode sending glass everywhere.
If you did everything right, and I apologize for not providing the formulae for figuring it out, this glass menagerie will be a capacitor of several FARADS.
Other materials could be used.

well making it out of 80-160uf 330v caps it the whole point of the project, although your awnser would work very well but the point it to show that you can build tesla coils out of things like flash cameras (and other things)
how could i make it with the capacitors i have?

If you can, try looking online for sites or if you have access, a bookstore. A good book to try is Electronic Gadgets for the Evil Genius (Tesla Coil Projects) or Homemade Lightning.

ok... but can you awnser how i make a lot of 330v 100uf caps be able to hold onto 10000-7500 volts?

you have to connect a bunch together. i don't know the math formula to calculate it.

I don't think you can. If the capacitor could hold more voltage without destroying itself, it would have been rated higher.

Have you looked at the instructables about tesla coils? It appears people are building their own caps.

i know its possible, my dad does it, he taught me almost all he knew. but before he taught me everything he knew he passed away. i saw him build a gigantic tesla coil for a museum when i was 6.  he had thousands of little tiny capacitors wired together.

The memory of when you were 6 could possibly (and very likely) be inaccurate. Think about it. Thousands of tiny caps would take up a whole lot of space. Like a room full.
Even as low as 3 kV, you're going to get arcing at distances as short as ¾" depending on humidity. He probably had a bunch of caps there for something, but it probably wasn't thousands and they may not have been used for what you intend now.
Can you go back to that museum now and have a look? It may be your best source of info.

i went there, the torroid and gnd are at the side of a wall and thw wireing is in the back room (usually people cant go in there) they let me see and there wer a LOT (about 600) caps about 1 inch tall and 1/2 inch diamater. so how would i wire this up?