-----Original Message-----
From: Ricardo Seixas <rseixas@CICLONE.COM.BR>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Tuesday, 14 October 1997 3:35
Subject: Sensing Low Battery Condition


>Hi PICers
>
>        Does anyone know a quick and dirty way (no Op Amp) to measure a low
>battery condition ?
>        Let's me explain:
>        I've built a portable camber meter using a 16F84 that's powered by
>a 9V battery and regulated down to 5V with a 7805, now I'm thinking to
>implement a simple low voltage indicator that drives a pin (High or Low)
>when battery reachs 5.5V.
>        This pin must be shared, since all pins are already used :(
>        It's no funny when you're in the middle of a camber adjustment and
>the battery dies ...
>        Any sugestions ?
>


Measuring terminal volts may not be a good way of indicating low battery,
becuase you will get so little warning of impending dead battery that it is
meaningless (nicads are a good example).
How about storing 'battery used' time?  This works well with rechargables.
Microchip make a dedicated chip for battery management that includes this -
you interrogate it for battery life.

MikeS
<mikesmith_oz@relaymail.net>