As an aside, you will find that batteries last much longer in LED flashlights than in comparable incandescent bulb flashlights. I've got one 3-LED cheapie flashlight that uses 3 AAA cells. They last at least four times as long, and the light stays bright throughout battery life. The brightness drops sharply near the end of battery life, rather than gradually.
Mark Shapiro
-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu on behalf of Eric Lane, Lane
Sent: Wed 3/5/2008 6:49 AM
To: phys-l@carnot.physics.buffalo.edu
Subject: [Phys-l] led flashlights
The newer led flashlights apparently have a voltage multiplier circuit along with a voltage regulator that boosts the battery voltage up to what the leds need. This means that you can use old batteries to power the flashlight and get almost the same intensity as with new batteries, although they don't last as long. I find this to be a great use for my used AAA bateries that are too weak to power my calculators. Old batteries work in small radios but they last so long that i've accumulated a small box full of weak, but still usable batteries. Mag-Lights@ with a tungsten filament that use AAA batteries also work well but the light starts dim and gets dimmer as the battery is used up. Leds keep the light level high for a shorter time. Great! I found mine at Harbor Freight on sale for under $2 apiece (not an advertisement, just a fact.)
Prof. Eric T. Lane eric-lane@utc.edu
Physics Dept. 2352 423-265-7804
The University of Tennessee at Chattanooga 37403-2409
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