Author Options:

When building a Coilgun, do i want higher capacitance or voltage? Answered

What is needed in the capacitor bank. For example could i use a group of 8,000uF 80v or would i need higher voltages up to around 400v?



Best Answer 9 years ago

You will generally want a capacitor with a high voltage ( 200+ volts ). You can find these especially easy in disposable flash cameras. ( But be careful, short these out with a screwdriver, they keep a nasty shock ) You don't want ridiculously large capacitors as they tend to have a high ESR ( Equivalent Series Resistance ), which is what you want to avoid when building coilguns.

I can't say either way: Higher voltage will give more physical oomph to your projectile. More capacitance will give a longer impulse and higher current (takes longer to discharge, thus longer impulse applied to projectile) Both have the effect of increasing velocity. My verdict is to build it as big as you can :D then make it bigger!

The problem here is that more capacitance will take longer to discharge, and you're really looking for an initial surge with this kind of application. Unless you want to get into some ridiculous assortment of caps, I'd stick with the moderate capacitance, high voltage caps. Just my two cents.

totally agreed - although larger caps should still be able to totally discharge before the projectile even gets far into the coil. isn't it a matter of nanoseconds on a complete short circuit?

Its subjective. Larger caps and supercaps take more time to discharge. Some of them have an intentionally high internal ESR. Its just a matter of the capacitor's original application. If it was put in place to be used in a fast discharge operation with HV, its going to be best for coilgun use. There are naturally exceptions to this, but, eh. I'm just reporting on my best results. Statistically I've had better luck propelling large projectiles ( 3" washers) using high voltage, moderate capacitance, low ESR caps.

okay. so i probably shouldn't run it off 10,000uF 100v?