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RAIL GUN capacitor size/power questions???

supak111

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Apr 29, 2012
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Hey everyone, I'm thinking about building a mini mini rail gun, got a few questions about capacitors.

QUESTIONS:

1. Whats better for a rail gun: using higher voltage capacitor or higher uF? example: is it better to us 1 x 1,000,000uF 5volt cap, OR say 1,000uF 5000v cap?? Power comes out the same but what better?

2. Which of the two above would charge faster if I have MAX rate voltage coming in both? Anyone know how fast?

3. Safety, if a capacitor is only 5volt x 1,000,000 is it safe to touch both leads since its only 5v?? I would or would NOT get shocked? And the 5000v I KNOW NOT TO TOUCH but if I did could it kill me?

(I like higher uF because capacitors are cheaper and smaller, I'm thinking they got to charger way slower tho)
 
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BobK

Jan 5, 2010
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A capacitor charged to 5V could only kill you if you try to swallow and choke to death.

A large enough capacitor charged to 100V could give you a fatal shock.

One charged to 5000V (you won't find any at a reasonable price) will likely kill you unless you are very cautious.

Bob
 

supak111

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Thank for the answer, any input on my question #1?
 

(*steve*)

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Energy = 1/2 x C x V^2

Power does not come out the same!
 

supak111

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Energy = 1/2 x C x V^2

Power does not come out the same!

Thanks for the formula, I needed that. Say those two were the same power output, whats better High V or High uF?
 

supak111

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I get that they are not the same now. You are still missing my question. Take 2 that are same, I just want to know what is better, high F or high V.
 

(*steve*)

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It depends on the impedance of the device you're driving.

You do realise what happens when you discharge a capacitor into an inductor, right?

You can't design one part in isolation from the others.
 

supak111

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railguns doesn't use any inductors.
 

supak111

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I'm a newbie man I'm not here to argue about what they use but I'm here hoping to get help on best parts to use to build one lol
 

jackorocko

Apr 4, 2010
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wait, is C a value of Farads? Isn't microFarads 0.000001 of a Farad? Then how is it 25kj and 25j? My calculator says 12.5 ;)

supak111, as steve has pointed out. Power is not the same, so the price point for smaller voltage caps is moot because you will need more to get the same power output. Maybe you should first figure out how much power you require first?
 
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