LED Based Flashlight




This flashlight was created for and field tested on my climb of Mt. Kilimanjaro. I needed something that could last a long time on one set of batteries, was rain / snow / cold and shock resistant and could be attached to my hat as a headlamp. Since nothing else quite fit the bill, I built my own bulb for use in an underwater flashlight case (oh yeah, I also wanted it to be waterproof, ideally to a few hundred feet of depth so I could even use it for scuba diving). The bulb consists of three white LEDs and resistors. Needless to say, the underwater flashlight (with clip I added for hat-mounting) fit most of my needs, but the power consumption was too high. The LED-based bulb consumes about a quarter as much power and lasts for more than 20hrs on one set of NiMH AA (unfortunately it does require 4) cells. [[Update: now lasts 40hrs on NiMH, due to advances in battery storage, or 100+hrs on Lithium]] It sheds as much uniform light as the underwater bulb, much more than most headlamps available on the market. Its only drawback is that it lacks the focussed center spot and is therefore only effective at looking at things up to 6m (20ft) away. As expected, this was not an issue for hiking/camping use, but didn't make it good for scuba (so I still use the halogen bulb there).