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AceTachyon
11-04-2010, 12:39 AM
Just wanted to check something...

Bad guy is wearing a suicide vest hooked up to a deadman's switch. He activates the switch.

If the wire(s) connecting the switch to the vest is severed, the vest still goes kablooey, right?

lbender
11-04-2010, 12:52 AM
Depends how it's hooked up. If the detonator, etc. is in the vest itself, then probably. The part I don't understand is that most deadman switches would be rigged to explode almost immediately when triggered. After all, the guy holding it may be dead anyway. Why the delay?

AceTachyon
11-04-2010, 12:55 AM
The part I don't understand is that most deadman switches would be rigged to explode almost immediately when triggered. After all, the guy holding it may be dead anyway. Why the delay?
Wait one. I thought on a deadman's switch, depressing it would arm the vest (in this case) and letting go would detonate it?

Or have I got the mechanics wrong?

lbender
11-04-2010, 01:04 AM
Sorry. Misunderstood the word 'activate'. If you meant 'armed', then it goes back to it depending on how it's rigged. If you have it rigged so release completes a circuit, then cutting the wire will permanently prevent that. If you have it rigged so that release breaks the circuit and that sets it off, then it doesn't matter how the circuit is broken...cutting the wire will set it off also.

Drachen Jager
11-04-2010, 02:43 AM
Mostly it depends on how good the people who made the bomb are at electronics. It's very easy to make a switch that goes on and off. It's more difficult to rig it so that having the wires cut will activate the bomb rather than disabling it.

I can't think of a reason why you would go to the effort of creating such a failsafe for a deadman switch. I mean, you're going to be there, holding the switch, you'd think you'd notice if someone with a pair of wire cutters started snipping around.

thothguard51
11-04-2010, 02:48 AM
I could tell you, but then I would have to shoot you to keep DHS from finding me...

Carry on...

Anaximander
11-04-2010, 06:27 PM
It's fairly simple to set up a deadman det. The simplest way is to build the physical part so that letting go connects the contacts, rather than pushing the button. If the wires are cut on one of these, the bomb is safe because the circuit that fires the detonator won't be completed. However, it's not much more complicated to build a system that triggers when a circuit is broken, rather than when it's completed (simplest way is with a bypass switch, possibly using a voltage divider). Basically, the circuit is actually two circuits linked in some way (you can do it with some kind of processor, but a voltage divider is way easier). When one circuit (the one to the switch) turns off, the other (the one to the detonator) turns on. With this one, cutting the wires to the detonator handset would detonate the bomb in exactly the same way as releasing the button would. If you want to have it arm when pressed and detonate when released, then the voltage divider alon wouldn't do it - you'd need an extra (flip-flop, maybe) to stop it from firing the moment you hooked up the battery if you'd left the button un-pressed. Or you could just have a seperate arming switch, so you hold the button before you arm it. If you were using the slightly more complex processor-based method then it'd be easy to add the push-to-arm; it'd be a simple debounce.

AceTachyon
11-04-2010, 06:34 PM
lbender, Drachen, Anax--thanks for the input.

Julie Worth
11-04-2010, 06:36 PM
lbender, Drachen, Anax--thanks for the input.

See you at the bank.

Kathie Freeman
11-06-2010, 07:04 PM
Correct me if I'm wrong, but it seems to me that on any device with whatever kind of trigger, cutting the wire to the battery would kill it.

Lhun
11-06-2010, 07:34 PM
Correct me if I'm wrong, but it seems to me that on any device with whatever kind of trigger, cutting the wire to the battery would kill it.Unless there's more than one battery.

lbender
11-06-2010, 10:52 PM
How would someone on the outside know where the battery is? It would also frequently be placed right up against the explosive. There's no reason or point to put it out in the handheld part.

Anaximander
11-07-2010, 01:44 PM
Correct me if I'm wrong, but it seems to me that on any device with whatever kind of trigger, cutting the wire to the battery would kill it.
It would, but the battery would probably not be in the trigger device. The most likely place for the battery would be right by the charge, so there would be no wire, or at least a very short one that would be near-impossible to cut without the co-operation of the person carrying the bomb. And it wouldn't be too difficult to set up a circuit with two batteries, in separate locations so you can't get them both at once, and rigged to blow if either battery is disconnected.