=20
> Not higher voltage (measured using DC multimeter) - stable 4.5 VDC...

A fresh alkaline is 1.65V, so 3 would be as high as 4.95V (something
you learn when powering logic off of batteries)

Perhaps measure the battery voltage during operation and after the
unit stops working, also the current draw

Some designers are fiendishly clever, and can make a circuit work
within a narrow window but don't give a hoot about battery life

Similar to what Sean mentioned, I've seen a lot of people over at
the laser LED sites using 2 batteries without active current limiting
("just stick 3V on it, you'll be fine"). There's 3V, and then there's
3V

Ideally you'd want to characterise your tapestry with a PSU that
has voltage and current settings. You can make a basic one with
a couple of LM317s. One sets the voltage, another sets the current

http://www.ti.com/lit/ds/symlink/lm117.pdf

Worth having a few in the parts box. Figure 36 shows how you use
one as a current limiter - as an alternative to a resistor - to simulate
the battery impedance

Joe
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.