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Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
I have more caps now, and my bank is at 400v 1147uF, which is about 90J, my old charger died and I can't charge them anymore, but can I use rectified mains to make this charge.
I also have 4 420v 100uF caps, can I add these to my current bank, no? because the voltage is uneven between them?
I was thinking, mains>60W bulb to limit current to 250ma>salvaged 1phase rectifier>to caps>coilgun ^^
Registered Member #3792
Joined: Sun Mar 27 2011, 06:07PM
Location:
Posts: 136
The voltage difference between the capacitors is not something you should worry about. But be careful when charging them, because the 400V capacitors will explode if charged beyond that voltage.
If you have both 400 and 420V capacitors in your citcuit, the maximum voltage that you can charge them is 400V (the voltage of the lower voltage rated capacitors). In my first coilgun i had used similar capacitors to yours and the voltage of them ranged between 400 and 450V. As far i charged them at 400V, these caps lasted forever.
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
It's working, I used a 60W bulb to limit the current, then into a single phase bridge rectifier, charger to 330v, so there's 70 volts in reserve, so they wont blow up.
I'm trying to make a coilgun, but most of the power is wasted by the switch. I made a coil from mains wwire, 10 turns in a loop and it shuts a Calculator off for about 2 seconds. But as for the gun it never works, The coil is from a PSU not alot fo turns, and thick wire (32amp).
Registered Member #3930
Joined: Sun Jun 05 2011, 07:27PM
Location: Sydney, Australia
Posts: 33
You can get a suitable scr on ebay. Just look for 600V scr - that can hadle a few hundred amps. That way it wont blow up. I have a hockey puck one, but you should be fine with one of the "stud" style ones. Also get a big power diode as well - that will protect your caps from reverse voltage coming back from your coil. Youput the diode across your coil (so it also protects your SCR), with the anode to the grounded end of your coil, and kathode to the + end of your coil. That way when the coil current reverses after a shot, the diode clamps the back emf pulse and protects your SCR and caps.
Wire your SCR in the ground leg; anode to bottom of coil, kathode to -ve of caps, and gate to your trigger circuit. In this way, the scr replaces your switch.
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Charging caps.
