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DiscoverCircuits.com -- Hobby Corner
"Hobby Circuits for
your Hobby Projects"
Last Updated on:
03/22/2010 03:34:03 AM
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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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