Ok, I have one of these: http://www.radioshack.com/product/index.jsp?productId=2062565. 1.2V, 100ma rating, but not much in the way of other specs available.
I'm trying to build a replacement control for a remote. The remote that I am replacing has no identifying marks about the LED in it. It's a darker blue bulb than the Radioshack one I have, and it appears to have just a 6.8 ohm resistor in series (running off 3x AAA batteries, so I assume that means it's getting a LOT of power thru it. If it's the same 1.2v as mine, that'd be like 600ma, right?)
I currently have mine running off the 5V rail of the arduino via a transistor. It's got about 50 ohm resistance on it (what I had handy...). It works, but the range is way lower than the original remote.
I looked at both systems via my cell camera. The original is MUCH brighter than mine.
So, how hard can I really push these LEDs before I'd burn them out? Since it's a remote, it's just being used for brief bursts of signal.
(secondly, how much wattage do you really need in the resistor to go with that? The 6.8 ohm in the original remote is a beefy thing - online calculators say it'd need to be 2W to put 500ma thru the LED. But would a lesser resistor really burn out in such short bursts of power?)