Wednesday 7 December 2005

Pic of the day: Behold the bright light of the future! Or perhaps not.

My first LED lamp

Bought a head lamp today. That is, a lamp to wear on my forehead when I am in the dark. This has the benefit that I don't need to hold it, so can hold other things or keep my hands warm. The lamp is a very new model, which uses LEDs: Light Emitting Diodes. These convert electricity to light much more efficiently than glow bulbs, and have an almost unlimited lifetime. Or that's what I have heard until now.

An LJ-friend informed me that this is only the case for small red LEDs. The white ones are actually blue but convert blue light to white using phosphor. Blue LEDs use more electricity, and large LEDs overheat and don't last long. Well, that's what he told me. The text on the package said 100 000 hours, but I suspect I'll lose track before that. And anyway, it isn't one large LED, it is a row of small ones. I also seriously doubt overheating will be a problem in the part of the year where I'll be using it.

Be that as it may, the thing gives off a cool bluish-white light. It is not particularly strong, but makes the difference when it is otherwise dark. It also has two blink modes, one fast and one slow. When I walk outside in the dark, I can use the blink mode to be noticed by cars and bikes. It would be pretty hard to ignore. I suppose blink mode uses less power too, and since there is barely any temperature difference, it won't wear out the lamp like it would a bulb.

Speaking of power use, I have read that LEDs in flashlights make the batteries last a lot longer. Even a modern battery does not have peak performance till it dies. After a while it starts to run weaker. At this point a glow lamp will loser its luster really fast, because it depends on the high temperature to give off white light at all. If the power fades, the temperature shift down and the light shifts to red. In a LED, the light remains the same color, and loses intensity only very gradually. LEDs are more efficient the less power they are given, at least within reasonable bounds. That doesn't mean they glow stronger given less power, but they lose output less than they lose input, so to speak. So I expect those batteries to last for a long winter.

Popular science magazines have for some time predicted that LED will completely replace all other forms of lighting once the production cost comes down. I have to wonder now. This lamp was the cheapest in the shop. Perhaps there are, after all, some technical difficulties? Please stand by ...