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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
radiotech wrote ...
Your diagram shows a SPDT switch. How do you know that during the switch transition there is not an arc over connecting the battery to the gate?
2Spoons wrote ...
If the cap is charged, there is no current is flowing and there is no arc on contact opening.
I think radiotech means switch bounce with power flowing in the other direction. Incomplete triggering, when the charge is zero and the gate should be held on, but then flickers off and on.
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615
Well, TBH a mechanical switch is never going to be the best answer. The best option is probably a baby thyristor dumping the cap charge into the gate of the big thyristor . I'm not about to go designing proper gate drive circuits - this sketch was only meant to convey the general idea.
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Thanks for the help all, first time Ive really even used an SCR for anything since a basic high school circuit class. Never really knew much about their requirement for a proper turn on. But unfortunately after receiving a replacement I managed to break it by being ham-handed.
With ~30 minutes to come up with a working solution I put in an 300A 600V IGBT brick I had laying around, added a 2nd 9v battery for 18V of gate drive, and a 1k pull down resistor so it wouldnt float. It worked for one shot, I still havent had a chance to see if the IGBT survived or not, just glad the in class demo worked.
I'd like to play around with the launcher more, but polyprojectitis has me at my limits right now. (2 rifles, a 30k lumen light, a terrarium water cooler and a new pc in the work makes for a whole lot of being spread thin)
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SCR failure modes
