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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Tuesday, November 29, 2011 08:14 PM
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Shake to Charge Flashlight --
Page 1 of 4
designed by David A. Johnson, P.E. |
| Have you ever wondered
how some of those “Forever” flashlights work? These devices appeared several
years ago and are often sold on some TV home shopping networks. A company in
Colorado: (Applied Innovative Technologies
www.appliedinnotech.com) made the original device but knock-offs from China are
now popping up everywhere. That fact that some of those devices don’t even
work will be a topic for later discussions. |
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Shake & Charge Flashlight |
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| I
bought one of the cheaper counterfeit devices and took it apart. There were no
manufacture or country of origin markings anywhere on the device. I traced out
the circuit. It is not much more than a coil of wire, a magnet, a bridge
rectifier, super capacitor and white LED. A small magnet attached to an on/off
switch is used to turn on the light by activating an internal reed relay. This
method maintains a tight weatherproof seal and is about the only thing I found cleaver
about the device. Shaking the thing forces a large magnet slug to slide back and
forth inside the body of the device. Two rubber stoppers cushion the magnet at each
end. In some other more expensive shake to charge flashlights, they use two more
magnets as contact-less bumpers. |
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