Difference between revisions of "Mechanically powered flashlight"
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Revision as of 13:44, 28 March 2007
A mechanically powered flashlight is one of several varieties of flashlights that do not use batteries, but rather depend on mechanical movement by the user to generate enough electrical current to power a miniature incandescent bulb or light-emitting diode.
A dyno torch is a flashlight or pocket torch which stores energy in a flywheel. The user squeezes a handle to operate a small dynamo, supplying electrical current to a miniature incandescent bulb. Dyno torches were very popular in Europe during World War II because the power supply was not very reliable.
Dyno torch design
In the photo, the L-shaped handle spins a gear, which in turn spins the dark grey magnet mounted on a flywheel, seen on the left. The magnet induces an electrical current in the red copper winding, seen on the right. The current from the copper winding flows through the incandescent bulb filament (not shown). Because electrical power is only produced when the handle is squeezed, a switch is not needed. The flywheel makes sure the light is fairly constant, despite the fact that the power supply (the squeezing) is intermittent.
The Faraday flashlight contains a super capacitor and charging mechanism that uses induction to power a high-intensity white LED array. Simply shaking the light for about thirty seconds provides about five minutes of light. Shaking the unit for 10 to 15 seconds every 2 or 3 minutes as necessary permits the device to be used continuously. This particular design of flashlight is documented in United States patent #6729744.
Inside the flashlight, a sliding magnet moves back and forth inside a solenoid, or a spool of copper wire. Current is induced through the loops in the copper wire to create a current per Faraday's law of induction. This charges a capacitor, which essentially acts as a short-term battery. To produce light, the capacitor powers an array of LEDs.