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Shakin' Fake Flashlights

I bought a motion-powered flashlight from a Chinese vendor at a flea market in Harpers Ferry last year. It was only about $2, and it had a fairly bright blue/white LED that came on when I turned the switch. I could see that there were two coin cell batteries inside, but there was also a coil through which a magnet would pass when the light was shaken, and a little PC board connected to the coil. It appeared that the light got brighter when I shook it. I used it for a while, and I misplaced it.

I returned to the flea market last Sunday, and they had what appeared to be the same flashlight, three for $5. So I bought three of them, along with other things. When I got home and looked more carefully, I saw that the PC board was not populated. I took the light apart, and found that (1) the leads from the coil were tied together to one point on the board, and (2) what I thought was a magnet was just a slug of steel. The lights actually work fairly well, and not too bad a price for a disposable LED flashlight and wrist exerciser (if I decided to shake it).

They had other flashlights for about $4 that seemed to have a larger battery pack, and possibly a PC board with components. I'm sure there are some of these lights that actually work, but I don't know if this vendor sells them. They are probably all fakes. They do have some dual LED hand powered lights for $4 that work by squeezing a lever which operates a small clockwork dynamo, and they function properly. They also have an internal battery and a switch in case your hand gets tired. Probably the gears will soon wear out and it will also become a disposable flashlight, but it is amazing what you can get for a few dollars.

I do wonder what it takes to make a good hand powered light using a sliding magnet and coil. It would probably take several hundred turns of wire to get 3 to 4 volts for a white LED. You would probably need diodes to get DC for the LED, and they would need to be Schottkey or Germanium for efficiency. It might be necessary to have a capacitor or inductor to smooth out the pulses from the coil. There is probably an optimal coil design to get the most usable output from the variable motion of the magnet.

Maybe I'll try a Google search, but I am curious if anyone knows any more about these devices. Also, maybe some ideas on how I can get even with these vendors of fakes!

Paul

Reply to
Paul E. Schoen
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I got one which did include a 0.1F supercapacitor etc. to make it work 'properly', but also had 2 lithium cells..!

You can tell the really good ones, as instead of the rubber bumpers at the ends of the tube, they have additional magnets to repel the main one, preserving the energy at the end of the stroke instead of turning it into heat. You can easily 'feel' the difference - the good ones feel 'springy' instead of thumping at the end of the travel. These ones are good :

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Reply to
Mike Harrison

Watch out-- I got one of these flashlights for xmas. Very interesting insides. A quick peek and my dubiousness-meter pinned. The coil had about 40 turns of wire on it. The PC board had NO components on it. Opening it up, the moving "magnet" turned out to be non-magnetic.

I guess what happens is if the factory runs out of supercapacitors or diodes or runs low on coil wire, they switch over to making "fake" flashlights. Well, they're flashlights all right, but "shake to charge" in looks only.

If you look closely at the pictures of these flashlights on eBay, a good 20% of them have no parts on the PC board. Hard to rectify and store shake energy without rectifiers or capacitors.

Reply to
Ancient_Hacker

[snip]

I got one from a fleamarkey too. It had the components and it worked, still works. While the clear plastic case allows to follow the magnet and have a look at the coil, I would have appreciated if they made a sheed of iron to the outside. The field is rather strong, and I wouldn't recommedn to have it beside a floppy for example. A sheet of iron would have increased the magnetic flux and thus the efficieny.

Rene

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Reply to
Rene Tschaggelar

Now I'm going to go take a good look at mine...

Isn't this a matter for the Federal Trade Commission? Some importer is going to get busted.

Reply to
mc

I have one of the LED flashlights that has a crank to turn that charges a battery. It's still doing fine after a year and a half, and it would be an odd application where I couldn't stop to crank it rather than simply shake a shaking flashlight. It is more expensive than the shaking flashlights being talked about. And it's not as bright as the LED adaptor I bought for my Maglite.

ON the other hand, I once bought an LED flashlight that was in a package similar to the cheap laser pointers, and when the batteries ran out (the switch kept activating while in my pocket), I just bought a $1.99 laser pointer and used the batteries from that. It seemed cheaper than buying batteries separately (and I have the laser pointer to run from an external supply if I ever get around it). Actually, the laser pointers turned out to use the same batteries as a number of items I have around, so they become a good source of batteries.

Michael

Reply to
Michael Black

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