Take a look at http://ww1.microchip.com/downloads/en/DeviceDoc/40040b.pdf under 
tip #11
basically a n channel fet with it's gate powered by the cpu's clock that bridges 
a momentary switch used to power up the pic. a very clever design that uses 
virtually no power when idle.

Peter

----- Original Message ----- 
From: "kravnus wolf" <kravnus@yahoo.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Monday, August 29, 2005 10:41 PM
Subject: RE: [PIC] 16F84A power savings....


>I have currently completed a door bell by using 16F84A
> MCU. Now comes the question of power....
> It is possible to run 16F84a in low power for a door
> bell solution? How long would it run on batteries?
> Is there any pic with PDIP that can run longer?
> This is my first real project........ Please bear with
> me.
>
> Thanks,
> John Chung
>
>
>
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