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Question about stun guns

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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Question about stun guns

Unread postAuthor: Ragnarok » Tue Nov 06, 2007 8:03 pm

I'm planning to take advantage of the BCArms deal on the combustion "essentials", but I need to ask a couple of things about stun guns first, because I have some specific requirements for it.

- What's the "reaction time" like on them? Practically instant? A few fractions of a second?
- Could I reasonably control one using some form of relay circuit to replace the conventional control switch?
- How fast do they use batteries?

I'm assuming it's "Practically instant", "Yes, as long as you don't screw it up" and "Not too fast" in which case it's all more than fine, but I just want to make sure.
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Unread postAuthor: Fnord » Tue Nov 06, 2007 8:09 pm

Most of them react fast enough to be considered instant, but I don't know what BC is selling. It should work fine for even high-speed timing though.

I'm sure you could trigger it with a relay or a transistor. Are you going to try an automotive relay?

They eat batteries pretty fast. Mine lasted maybe a minute(?) with a new 9vt.

Edit: The only problem I can see is the stungun lifetime being limited. They aren't really made for this type of use, just for rare self-defence stuff.
Something like a flyback will last longer, but is a bit hard to get working.
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Unread postAuthor: Ragnarok » Tue Nov 06, 2007 8:30 pm

That should be fast enough. I'm not absolutely decided on what I'll use for switching, but it's possible. I need to get a few separate controlled bursts of sparks for a couple of seconds at a time, if it can handle that, that's great.

And I don't think batteries can actually be drained that fast, even directly shorted.

I do know a forum full of people who build flybacks for fun, but I'm cursed around HV stuff I've tried to build.
I either get shocked by it or it doesn't work. Truthfully, regardless of the voltage I use, one of those things happens - in order for anything to work, it must ground across into me, and I don't want to be an earth for a 100kV flyback in order to get it working.
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Unread postAuthor: sandman » Tue Nov 06, 2007 8:36 pm

can you point me in the way of this forum as i might want to try my flyback again :)
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Unread postAuthor: Fnord » Tue Nov 06, 2007 8:44 pm

Well, the battery was not drained completely, but below a certain voltage (about 7-8 volts) the stungun just stops working.
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Unread postAuthor: Ragnarok » Tue Nov 06, 2007 9:12 pm

sandman wrote:can you point me in the way of this forum as i might want to try my flyback again :)

Of course: http://www.4hv.org/
Home of Tesla coilers, Coilgun enthusiasts, and a few other people too. Watch out, spend too long around there and your keyboard will start arcing.

@_Fnord: In that case, I might just use a set of 8 AA NiMH rechargeable batteries. It'll take a lot more to drain that than a 9V, and the voltage will be a bit steadier.
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Unread postAuthor: jimmy101 » Wed Nov 07, 2007 1:08 pm

_Fnord got everthing pretty much correct.

The time delay from pulling the trigger to a spark is pretty small. My "100KV" sparks at about 10 times/second so the delay to the first spark is probably ~1/10 second.

Any small relay should be able to handle the power. The relay's delay time is probably more than the stungun's delay time. A moderate powered transistor or a small solid state relay will also work and would probably have essentailly zero delay. Figure a 9V battery can supply 10A for a very short length of time. You just need a device that'll handle that much power for short durations.

Battery life isn't great but if you are using the stungun to ignite a spudgun then the battery should last for a long time. You really don't want to be firing the stungun for more than a second or so at a time because it'll fry itself. With ~1 second pulses they battery should last for many tens to perhaps a few hundred of shots.

The stungun will continue to work across a small spark gap even after the battery voltage has dropped below the point where the default gap quits working. Since the default gap is typically an inch or so, compared to parhaps 1/2 inch total spark gap in a gun, the stungun will continue to work even when the battery is too weak to fire the default gap.
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Unread postAuthor: Ragnarok » Wed Nov 07, 2007 5:03 pm

Ok, I can work with that. Although I need it for an automatic, I can't fire too many shots in one go or the chamber will overheat - I'm making it out of copper though, and I'd bond it with something other than solder, as solder will melt and weaken if the temperature rises too much.
With those considerations it should stand the heat generated by short bursts of fire.

I'm hoping that problems won't come up, but there are about 300 J worth of energy in each combustion, and a lot of that will be absorbed by the walls, so it may heat quite fast, even with the cooling if it's firing more than a couple of times a second.
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Unread postAuthor: hi » Wed Nov 14, 2007 11:45 pm

i have a question about stun guns. i have a 500k stun gun (a bit over kill i know, but i got a good deal on it) and i was wondering if it would melt the chamber at all. i have never used on on a combustion and i don't know if it gets hot or if it damages the chamber at a all... its an ABS chamber.
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Unread postAuthor: jimmy101 » Thu Nov 15, 2007 1:00 pm

hi wrote:i have a question about stun guns. i have a 500k stun gun (a bit over kill i know, but i got a good deal on it) and i was wondering if it would melt the chamber at all. i have never used on on a combustion and i don't know if it gets hot or if it damages the chamber at a all... its an ABS chamber.

Nope, "500K" won't melt the chamber. It won't even significantly warm up the electrodes.

To generate heat with electricity you need two things; voltage and current. The power is the voltage x current. To generate a spark you only need high voltage (though high current will give a fatter spark).

Stun guns (and flybacks, and car ignition coils) work by trading current for voltage. Low voltage at moderate current in, very high voltage at miniscule currents out. The total power changes very little. Stun guns and photoflash circuits also sum (store) the input power over a length of time and then dump that power in a much shorter duration pulse. Again, the total power is the same (actually usually a fair bit less) than the input power.

Can the 9V battery of the stugun melt your chamber? If it can't, then there is nothing that can be done (flyback, stungun, photoflash) to get it to. You can't get more energy than what the battery had to start with.
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