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Registered Member #1694
Joined: Sat Sept 13 2008, 09:13AM
Location: Australia
Posts: 108
Hey all,
Im working on an electrothermal gun. The cap bank is around 180J @ 450V. Use all probably know how an electrothermal gun works . . . the caps dump a massive amount of current through Aluminium powder, Al powder vaporises and the expanding gas pushes the projectile.
I'm trying to decide what to use to fire/discharge the cap bank in this thing. I would like to use a nice, pretty push button. But nice pretty push buttons generally do not take massive pulses of power. I was thinking about relays, but they are to big and bulky to fit into a smallish pistol. I don't know a great deal about solid state devices.
Registered Member #90
Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301
Maybe a ton and a half.
Still, I'm in favor of high-current mechanical switches. They have lower contact resistance than a silicon device, and are easy to debug. For 180J it will require a rapid closure time to reduce arcing, and of course decent copper surface area.
I wonder if a big mercury-wetted switch might be available. Too bad (for us) they don't build anything with mercury these days.
Registered Member #1694
Joined: Sat Sept 13 2008, 09:13AM
Location: Australia
Posts: 108
Yes, I've read a lot about SCRs on various websites. I'm a little unsure of how to use them.
In this schematic, there is a 9v battery triggering the gate. If I was to just use the power from my main battery pack for this, would it be at all detrimental to my NiMh cells? Would it be better if I just connected the positive from the cap bank to a resistor to a switch to the gate?
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
it will be fine with the NiHh cells, i do it all the time. Make sure you have a good voltage (5-20v depending on SCR) to give the gate a good kick to make it open faster. Do you have a SCR in mind?
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Electrothermal gun
