"DoN. Nichols" wrote in message
...

On 2011-11-21, Martin Riddle wrote:

Why bother including an on off switch?

It is an off switch to turn the *display* (only) back on. They
sometimes make it also turn the display back off to make
people feel better. :-)

The auto-turn-off time of the display is usually good enough.

Still, there's no benefit to turning off the display, in this case. Might
just as well have it display "OFF".

I bought a high-end headlamp from Coleman a few years ago
http://www.coleman.com/coleman/Colem...id=2000000265#
and every time I went to use it the batteries (4 AA) were dead. I measured
the current draw when turned off, and it was something like 300 uA, which
should have provided 8000 hours (almost one year) for the 2500 mA-hr
batteries. But I was getting only a few weeks before finding them exhausted.
Maybe the current increased as the battery voltage dropped. I usually used
rechargeable NiMH and they might have been old and tired. But, still, there
is no reason for 300 uA standby current on a flashlight. Even if it had a
microcontroller, a typical PIC18F2420 draws only 11 uA while running, and
only 100 nanoamps in sleep mode! So, I just pop out one of the batteries
while I'm not using it. There's no easy place to install a switch.

Paul
www.muttleydog.com