Minimize battery consumption on a 18F2550

[aratti]

Using a voltage regulator introduce some complication. You will feed 9 volts to your inputs and this will demage your pic. You need to isolate in same way your pic (both input and output) see the attached suggestion. (remember that all the input must be pulled up)

Cheers

Al.

[Fredrick]

Will this work then?
PORTB are using internal weak-pullups, and I keep RA0 high as long as I want the PIC to run.

[aratti]

When the push button is open you feed 9 volts to the pic input. Place a diode on each input to stop this current flow.

Cheers

Al.

[Fredrick]

Does it look ok now?
I assume the standby current now will be 0uA when no button is pressed and the RA0 is not high?

[amgen]

the input to pic pins (9 volt) is limited by the 100K r and those pins should have redirect diodes (inside pic) that protects pic from overvoltage.
The opto will shutdown power or the r-c on fet gate can be made to time out (any time you set) but the power to pic then just reduces slowerly? ,,,but the brownout setting also will shut down pic before too low voltage makes program unfunctional ..
don

[aratti]

With reference to your schematic of post #14, please note that if you can find a switch with two contacts (common; No & Nc) then connecting the common to ground and the Nc to pic input and No to the gate of Pchan mosfet you can eliminate all the diodes.

All you need now is to assemble the circuit on a proto-board and see if it works.

Cheers

Al.

[Fredrick]

The datasheet says this

Absolute Maximum Ratings
Voltage on MCLR and RA4 with respect to VSS .................................................. ..........................................-0.3 to +14V
Voltage on all other pins with respect to VSS .................................................. ..................................-0.3V to VDD + 0.3V

Does that mean that I can feed +9 into RA4?
And if not why should this be avoided?