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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Coherent wrote ...
I wonder if a rectified 3kv NST would do a better job.
Yes it will. But you should still use a charging resistor in front of such a big capacitor, but a much smaller value will do. When the capacitor is totally discharged, it 'looks' to the power supply like a dead short, so there is a high inrush current which you want to avoid. A charging resistor will limit the inrush current to a manageable size.
As a man who now understands about RC Time Constants, you'll be able to calculate all this yourself! Good luck!
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Not too sure, but you may not need the resistor. NST's are current limited, made for a continuous short. The capacitor is too large to have any resonating effects, so if should pull what it normally would in the event of a short.
Registered Member #1886
Joined: Sun Dec 28 2008, 02:55AM
Location:
Posts: 73
Well rather than screw around with resistors I decided to just make a mini spark gap to charge it. I used two nails with the tips just barely not touching and it works great now. The power supply is already limited to 5ma so it really shouldn't need any additional current limiting. Either way the cap works great. Diodes turn into firecrackers, wires explode and it can instantly vaporize small strips of tin foil. There's an extremely loud bang, bright flash and nothing left of the foil but a white cloud of smoke. When it gets nicer outside I can try blowing fruit to bits ;)
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Strange cap charging issues
