Quote Originally Posted by mister_e View Post
Diode are there to avoid conflict between your voltage source... with this, the higher voltage will win the race

Capacitor, 10 uF and more should be enough. For filtering purpose.

You could use 1N4xxx diode, bear in mind their voltage drop is around .6V so your 3V will be 2.4 volt when your battery is at full-charge.

The pic will work as long you haven reach the Brown-Out threshold voltage OR his voltage threshold depending on the osc speed you're using.

You could still use another much fancy system, this one work pretty well in many cases.
I didn't know that diodes had such use
What's wrong if both supplies are connected at the same time in parallel???

Filtering capacitors? What do they filter?

Voltage drop? Right... 2.4v is a little too low, knowing the PIC will be fine down to 2V but I can't use 8MHz anymore if using 2V... In this case I can use 3*1.5v batteries instead and use 1N4001 diodes, right?

I disabled Brown Oout Detect in the config words, do I still need to care about this feature?

What fancy system are you talkning about?