"Donwill" wrote in message
...
I purchased a string of 10 Leds powered by 2 AA batteries connected in
series giving 3 volts or thereabouts presumably.
I was a bit sceptical about the life of the batteries so I left them on 24
hrs to check, I was surprised that they lasted over a month which makes
them very useful as party lights in a damp conservatory, let's say running
them for 4hrs a day which should make them last for 6 months perhaps.

I got to thinking about dimming them, a series resistor would surely do
that, but it would reduce the battery life by warming up the resistor.
Now you can dim filament bulbs by using an astable multivibrator and
varying the mark to space ratio, relying on the chopping frequency and the
time constant of the filament to provide a non flickering and dimmable
light.
Doing that to an led would cause flickering of the light but would the
relativly slow response of the eye smooth out the flicker? as in film
movies which I think have to be in excess of 25 fps in order to fool the
eye.
In the interests of battery life, are there any dimmers of this type
available for leds?

Cheers
Don

A 555 timer will prolly do the job
http://www.kpsec.freeuk.com/555timer.htm
Of course, the cost of your time in making it would buy a good few batteries