Need help with charging capacitors!

[magicmaze]

Hey all,

I am currently making a railgun, where I have 3x 2200uF at 400v capacitors. There are two aluminum 'planks' in parallel, that is screwed down on top of the capacitors, positive and negative. However, I only have access to a 12vdc power pack. I was wondering how to go about charging the capacitors with the equipment I have now?

All help is appreciated,
magicmaze

 

[chris.mourad]

Hi

You probably need a voltage multiplier like a charge pump, or even a step-up dc-dc.
What is the voltage you want to charge your capacitors?

 

[magicmaze]

Hey Chris,

Thanks for the reply. I don't know much about electronics, so I don't really know how to operate a charge pump. If I only have that power pack, what is the extent of my capabilities? (like what I could do with only this powerpack)

Thank you

 

[chris.mourad]

Hello Magic

With the 12V powerpack, you will need an electronic circuit to boost the voltage, i.e. generating voltages above the available 12V out of the pack.

This can be done with different type of circuits, here are 2 of them:

1. A charge pump or voltage multiplier. This converts an AC input voltage into a higher DC output voltage

2. A step-up DC-DC, that converts a DC input voltage to a higher DC output voltage. This is what you probably need, and it is similar for example to a camera flash circuit generator, which generates very high voltage on a capacitor (>300V), starting with a 1.5V or 3V battery voltage


With only your powerpack, you can't do much. You are stuck with a 12V voltage and need an additional circuit to generate high voltages!

Cheers

 

[betwixt]

I doubt a charge pump would raise 400V from 12V. You need a fairly powerful inverter to charge 6,600uF to 400V, The initial charge current will be quite high, something like a camera flash HV would probably take several hours to charge up if it could manage at all.

As a non-electronics person, your simplest solution is to buy a 12V to 240V inverter, the kind used to generate mains AC from a car battery. Then use a bridge rectifier wired across the AC outlet to convert it back to DC. With a sine wave inverter it will give you ~350V with enough current to charge the capacitors in a few seconds. With a modified sine inverter the voltage will be a little lower but otherwise it should work the same.

Brian.

 

[ads-ee]

I am currently making a railgun, where I have 3x 2200uF at 400v capacitors.

Hasn't anyone else responding to this thread thought about how they are helping someone to build potentially a weapon? :thumbsdown:
https://www.youtube.com/watch?v=rGk2vGttCmY

What is the plan for this railgun, kill the neighbors dog that keeps pooping in their yard? 8-O

 

[betwixt]

I agree we shouldn't promote the use or design of weapons but with component values like that it won't pack much punch. I imagine it would give the dog a fright but it would only fire a small projectile, more of a sting than pegging it to the ground.

The video is misleading, a rail gun uses magnetic 'push' to launch the projectile so where does the tail of flames and smoke come from?

Brian.