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Making my first coil gun

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jaysun92

Fri May 08 2009, 12:02PM

Registered Member #2114 Joined: Fri May 08 2009, 11:58AM
Location: London, Ontario
Posts: 36

I have 4 50v 2800 uf capacitors. will I be able to make a coil gun with this and what kind of switches will i need?

thanks to anyone who helps

Camel

Fri May 08 2009, 12:27PM

Registered Member #1694 Joined: Sat Sept 13 2008, 09:13AM
Location: Australia
Posts: 108

I reckon you should put those caps in series for 200V 700uF.
If you are just starting to learn electronics, I think maybe a large mechanical switch would be a good option . .

Bjørn

Fri May 08 2009, 01:23PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Start by reading this

and this

Almost everything you will need to know is there or in threads on the forum or the archives.

jaysun92

Fri May 08 2009, 07:51PM

Registered Member #2114 Joined: Fri May 08 2009, 11:58AM
Location: London, Ontario
Posts: 36

for series i connect positive on one to negative on the other right?

hotcrazyfruit

Fri May 08 2009, 08:35PM

banned on 5/26/2009
Registered Member #1877 Joined: Mon Dec 22 2008, 02:03AM
Location:
Posts: 147

jaysun92 wrote ...

for series i connect positive on one to negative on the other right?

yes. and parallel is all of the cathodes(positive) connected and all the anodes (negative) connected.
remember, as you add capacitors in series, voltage goes up, and capacitance goes DOWN by a factor of the number capacitors in that string. but in parallel the voltage is constant, but capacitance is added. be careful when your putting capacitors in series also, varying capcitances can cause one capacitor to overcharge and another to undercharge, which calls in the need for a balancing resistor. read up on the hv wiki.

jaysun92

Fri May 08 2009, 10:07PM

Registered Member #2114 Joined: Fri May 08 2009, 11:58AM
Location: London, Ontario
Posts: 36

to charge the capacitors do i just connect a 9v battery or is it more complicated then that

thanks to anyone who helps

jaysun92

Sat May 09 2009, 12:03AM

Registered Member #2114 Joined: Fri May 08 2009, 11:58AM
Location: London, Ontario
Posts: 36

i hooked it up like in this diagram
V= a 9volt battery
c= a capacitor bank of 200v 700uf
R= 390 ohm

but the capacitors wont charge beyond 9 volts
what am i doing wrong?

thanks to anyone who can help

Myke

Sat May 09 2009, 12:33AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

To charge the caps beyond 9V, you will need some boost converter or some other way to step up the voltage. The caps, in your configuration, will only charge up to 9V like you had said it had done.

Arcstarter

Sat May 09 2009, 12:48AM

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

It seems to me you are a beginner. I will at least try to persuade you to start a bit smaller. Capacitors are dangerous, and 200 volts will at least give you one heck of a shock, and in an extremely unlucky condition, you could even be killed. These capacitors would hold enough energy to stay charged long enough to shock you, so even though the total energy holding capacity is low, it will still be dangerous.

Also, if you overcharge just a bit, they could explode and mess your eyes up, or catch on fire. You only get one chance at life, why waste it on a coilgun that would not even shoot very well (your capacitor bank would be a bit too small to shoot hard)?

I might be in no place to say this, i may not be as careful as i could possibly be, but i have gotten better. And if the coilgun works, you could even get comfortable with it and not pay as much attention as possible, and then ZAP.

I started my electronics hobby with motors and such things like that. Maybe you could do some audio amplifier things, or mess with comparators and op amps and oscillators to get a sound out of a speaker or get an LED to blink. Get a feel for how electrical currents flow, and read up on Ohm's law a bit to understand what voltage it would take to get a certain current through a certain resistance (like what voltage it would take to get enough current across the human body's resistance to kill or fibrillate).

Once again, you have one chance at life. Don't become a darwin award winner and waste it on something like this!

Lem0nHead

Sat May 09 2009, 11:13PM

Registered Member #2096 Joined: Mon Apr 27 2009, 03:08AM
Location:
Posts: 18

that's a very good advice :)

I'm a begginer also, but I'm taking all kind of precautions
I check if the capacitors are discharged everytime before touching anything, put insulation tape on everything I can, put some weight on loose wires (when I'm testing voltage for example) so they don't slip and touch me (or some othe part of the circuit)
and I never do things I'm not sure (except shorting a 6V power supply and see a small capacitor flying, twice! :/)

but you really should take into consideration that you ARE risking your life to do a kind stupid (but ok, cool) thing... just make sure you keep your risk at minimum so it worth it

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