# Rail Gun

Discussion in 'General Electronics Discussion' started by Pyromaniac1, Jan 23, 2014.

1. ### Pyromaniac1

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Jan 23, 2014
I am building a rail gun. I plan on using 3 400v 2200uf capacitors in series. Any suggestions on a supplier?

2. ### GreenGiant

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Feb 9, 2012
Digikey? Mouser?
Should be a fairly common value.

3. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,482
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Jan 21, 2010
Look for capacitors with the highest ripple current rating you can.

Even better, look for capacitors designed to be used with xenon flash as they are designed to handle the huge discharge currents.

4. ### Pyromaniac1

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Jan 23, 2014
Thanks. That was pretty helpful. Were kind of on a budget though. Do you think we could still get substantial power from 350 v capacitors, or only two 400 v capacitors?

5. ### Pyromaniac1

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Jan 23, 2014
What kind of speed should the projectile be going when it enters the barrel to avoid spontaneous welding.

6. ### Pyromaniac1

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Jan 23, 2014
How many 250 v 400 uf capacitors would i need to equal the power output of three 400 v 22000 uf.

Please give me any input you have so I don't melt my face off.

7. ### jcurrie

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Feb 22, 2011
divide 22000 by 400. they will still have a 250volt rating though.
jc

8. ### duke37

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Jan 9, 2011
The energy in a capacitor is C * V^2/2.
3 * 400 *400 * 22000E-6 /2 = 5280J

N * 250 *250 * 400E-6 /2 = 5280J
N = 5280 *2 /250/250/ 400E-6 = 422.4 say 420

This is all rather simplistic and the efficacy of the capacitors will depend on the resistances and inductances of the circuit.

9. ### jcurrie

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Feb 22, 2011
Duke is correct I was thinking of farad not power.
jc

10. ### Pyromaniac1

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Jan 23, 2014
Thanks guys. Fingers crossed I will not blow up my middle school.

11. ### eKretz

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Apr 8, 2013
Don't say that...the NSA will send the black helicopters!