From the MAKE Flickr pool
Windell of Evil Mad Scientist Laboratories shares some thoughts from his investigation into the electrical properties of LED throwies. Particularly interesting are his results when using a red LED -
Lithium coin cells aren’t designed to source nearly that much power– and aren’t lithium batteries a fire hazard? And why does my LED– rated for 25 mA continuous current survive this? I’ve certainly seen enough LEDs destroyed by overcurrent, and this one was over 25 mA for ten minutes solid. But, and perhaps against my better judgement, I do believe that this actually *is* safe in practice. With all of the throwies and similar things out there — don’t forget the keychain flashlights — they just don’t seem to be exploding or catching on fire. (Breaking, falling apart, running out of photons, yes– but those modes of failure are usually not as dangerous.)
Head over to EMSL for more observations and a working solution.