P
Paul E. Schoen
- Jan 1, 1970
- 0
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
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