LED driver circuits are common these days, all done in a single IC.

Check the usual IC mfrs sites... :- )

_-_-bear

Ole-Hjalmar Kristensen wrote:

"jr" == jim rozen writes:

jr In article , Ian Stirling says...
And then you quote the brightness at the start.

jr And they quote it with the absolute max. current
jr in the diode, such that it will fail shortly
jr after the intensity measurement is finished!!

jr Jim

jr ==================================================
jr please reply to:
jr JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
jr ==================================================

It shouldn't be to difficult to build a circuit which would give
essentially constant (and adjustable) brightness for the whole battery
life.

Just charge a capacitor, and dump the charge into the LED when the
voltage exceeds a threshold, then repeat the cycle. You modulate the
intensity by changing the threshold.

For a de luxe version of this scheme, see for example

http://www.fairchildsemi.com/ds/FA/FAN5609.pdf

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