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Nichrome Ignition

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: Technician1002 » Tue May 24, 2011 9:31 pm

Many switches are not rated for 5,000 Amps. Pitting of the contacts would be an issue unless you took precautons to limit the inrush current. Either a properly sized switch, or inductor to limit the current rise time to allow the switch to settle, or a proper sized semiconductor switch will need to be used.

The energy you are trying to switch is quite high.
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Unread postAuthor: jimmy101 » Wed May 25, 2011 5:13 pm

What Tech said, except "many switches are not rated to 5,000 Amps" should read "there are nearly no switches (commonly available) that are rated at 5,000 Amp". :D A typical 120 VAC wall switch is rated at 20 Amps.

But don't fret, there is a cheap switch rated to the capacity of a typical photocap even if the entire energy content of the photocap is dumped in 1/1000 of a second.

It is called a flashtube.

Just wire your hot wire in series with the phototube of a flash unit. Trigger the flash unit and the phototube acts as the switch, triggered by the HV of the flash board.
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Unread postAuthor: saefroch » Wed May 25, 2011 8:01 pm

Well that might work...
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Unread postAuthor: mobile chernobyl » Wed May 25, 2011 10:23 pm

Just get a nice little SCR and trigger it. I use them on my capacitor banks dumping many more volts than a standard photo cap without any problem.

you can get one that you need for very little.
http://www.mouser.com/Search/ProductDet ... 576-S4065K
That will be adequate and all you need to trigger it is a little 12v lipo and a resistor.

I'm working with one now that's rated for 1500A (working) at 1200V and it takes a little more current to kick it but the concepts the same.
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