Shake Flashlight?

Yesterday, I was given on of those rechargable flashlights that you shake to charge up (like I really needed one, with about dozen wind-up ones laying around). Anyway, pretty useless, but was wondering if it would take much to make it a shocker? Haven't torn it a part yet, but its coil looks pretty weak.
Figure a stronger magnet and wind a new coil, I might get some interesting results. Just wondering if anybody has done this yet, and about how much wire I'd need to wind to give someone (well actually my dog, and of course my little brother) a little tingle. Not wanting to get too carried away, and not wanting to do any self testing (really hate getting shocked myself). Figured I ask for some input.

Shake it and measure the voltage using a true-RMS meter or a scope.

Unwind the coil counting the turns.

Divide the number of turns by the measured voltage to get the volts per turn.

Rewind a new coil to the desired new voltage.


A stronger magnet should increase the volts per turn; I'd try this out before you unwind it.

You probably need about 24VAC minimum to get a tingle if the skin is damp but to shock someone properly you need >50VAC.

Adding a small capacitor/diode multiplier will increase the voltage but be aware that AC is more shocking than DC.

Also you should stop being just a wimp and test it on yourself.

Would more than one rare earth magnet give more voltage? Would it be best to just let them stick together, or put in spacers. Maybe flip every other one around so the repel, and the tube isn't large enough to allow the magnets to flip back around... So many experiments, almost feel sorry for the dog...

Also you should stop being just a wimp and test it on yourself.

Click to expand...

Sadist...

Well, it was easy to take apart, the top unscrewed like most flashlights, all the stuff just dumped out. Magnet is pretty damn strong, about an inch long, half inch in diameter. Battery is 3.6 volts, 40 mAH. Four diode bridge, resistor, and white LED.

Put 6 neodymium (5lb pull each) in, only shook it about 10 times, still waiting for it to go dim. Brighter LED, might not be such a bad flashlight. Coil is about 2 inches long, wire is hair thin. Would really suck winding a coil like that...

You want the magnets stuck together rather than repelling in which case their fields will cancel not add.

It sounds like the coil is already as long as it can be.

The magnets probably made the crapy torch into a decent torch.

I have two outwardly identical "shake" flashlights.

One has a magnet, coil, and charging circuit to a small NimH battery. Fine.

When we got the other one home, my friend's 10 year old daughter took it apart. She discovered a metal slug instead of a magnet, the coil isn't connected to anything, and a coin cell lights the LED. Hilarious!

mneary said:

I have two outwardly identical "shake" flashlights.

One has a magnet, coil, and charging circuit to a small NimH battery. Fine.

When we got the other one home, my friend's 10 year old daughter took it apart. She discovered a metal slug instead of a magnet, the coil isn't connected to anything, and a coin cell lights the LED. Hilarious!

Click to expand...

What will those chinese think up next... That's pretty good though, probably saved 3 cents per unit that way...

Probably a way to sell those units whose coils failed Q.C.