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Tracking Thieves With 'Find my iPhone'
An anonymous reader wrote in to say "A friend of mine who just got an iPhone 3GS and has Mobile Me just used the "Find my iPhone" feature to track down his lost and subsequently stolen iPhone. This story involves three nerds wandering sketchy streets with a MacBook, and ends with a confrontation at a bus stop."
However home-built tasers are pretty good for short range.
You can get a reasonable jolt out of a battery connected to a relay which has been wired through itself so that it is normally on and turns itself off when it gets power. Connect prongs on either side of the relay coil. It gets power, the coil charges a magnetic field, flicks the relay switch, which breaks the circuit. The coil loses power, the magnetic field dissipates, through the coil, creating a several hundred volt (and low current) spike across the prongs I told you to connect to each side of the coil, or more importantly whatever you've plunged the prongs into. The spring in the relay then pushes the switch closed again, and everything repeats.
The low current means that it hurts like hell* but isn't that dangerous. Keep away from hearts and pacemakers, don't apply directly to eyes, etc etc. Don't have it active for too long or the battery could explode, you are shorting it after all...
* Actually the 9V version doesn't hurt much normally, but might if you use sharp pins and break the skin. Don't build one with three 9Vs and a 25V relay, or a 2A lab bench power-supply. Then you possibly cross the border into dangerous.
You can power it up by putting a second coil around the first with more turns, and connecting THAT to the danger prongs. It makes an impressive show, with a near constant visible spark between the prongs. My high-school physics teacher had built a contraption like that, can't remember what he was demonstrating.
actually, it raises the question.
http://begthequestion.info/
don't worry, you're in good company. the whole spectrum of major media get it wrong too, from NPR to Fox.
"If still these truths be held to be
Self evident."
-Edna St. Vincent Millay