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Registered Member #3785
Joined: Sat Mar 26 2011, 03:37PM
Location: Surrey, UK
Posts: 16
Hi Hellfire, welcome to the forum!
Most coilguns I have ever seen use capacitors rated between 200 and 600 Volts, although Barry at had some good results at 50V. You need a reasonably high voltage (>200) in order to get a large enough current through the coil. Beyond 600 Volts, capacitors with a decent capacitance become rare and massively cost prohibitive.
In simple terms, higher voltage capacitors release a faster, more intense pulse of current and are more suited to small, light projectiles, whilst lower voltage and higher capacitance ones cause a longer, less intense pulse of current and are more suited to heavier projectiles.
The energy stored inside a capacitor is equal to 1/2 x Capacitance (in Farads) x Voltage squared.
My advice would be pick a voltage that you are sure you will able to charge up to (dependant on your charging circuit), and work from there by picking an energy you feel safe using, and using the right number of capacitors to get there.
One final note, if you run two capacitors in parallel, you double the capacitance, and if you run 2 in series you double the voltage they can take, but halve the capacitance. (which is useful if you have trouble sourcing appropriate caps)
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
If it's for a first time coilgun project, i recommend camera flash capacitors. they're easy to salvage, easy to charge, and they won't kill you the first time you zap yourself. these can get you started
If your first project is a railgun well... just don't do a railgun for your first project. you'll either end up disappointed or in incredible danger.
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
Stare at Ebay/your local surplus store/whatever until you find capacitors that are priced appropriately, then build up from that. Most people use big electrolytic filter caps. Your bank's energy content is very very important in determining your coilgun's performance.
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Capatiance or voltage
