Clive Mitchell wrote in
:

In message , Victor Roberts
writes
I don't think this has anything to do with temperature at all since LED
lamps tend to run almost cold due to their very simple capacitive power
supply and low output.

I agree that the heat rise above ambient of 20ma LEDs is minimal, but
your blanket statement certainly does not apply to high power LEDs such
as any of the Luxeons. These will all overheat if not connected to a
proper heat sink.

Most LED lamps use clusters of 5mm LEDs. There are a few Luxeon
versions, but I shudder to think what the circuitry is like inside them.

If it's the early Chinese white LEDs, then even using them in a fridge
wouldn't make them last longer.


A one watt Luxeon LED draws 300 ma at ~3.4V,all you need is a 3 terminal
regulator IC and a dropping resistor to limit the current,and properly
heat-sink the Luxeon LED.(and sufficient overhead on the supply.)
Not efficient,but it will work.

In a dark room,a 1W Lux LED is really bright,maybe too bright at close
proximity to a keyboard.

IMO,too much,I'd use a few 5mm bright-white LEDs.

--
Jim Yanik
jyanik
at
kua.net