Your 7805 regulator needs at least 7 volts to operate properly !
Use a low drop out regulator with an on board low input indicator. See
Maxim !
Jean

Ricardo Seixas wrote:
>
> 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 ?
>
> Thanks
>
> Ricardo Seixas
>
> -------------------------------------------------------------------------
> Ricardo Seixas
> Mechanical Engineer
> rseixas@ciclone.com.br
>
> ... Smile, tomorrow will be worst ...
>
> -------------------------------------------------------------------------