Quote Originally Posted by lerameur View Post
I am using a pic16F88 and I amnot sure whcih pins to use. Right now I am using pins 1, 2, 17, 18 for my lcd out and also pin 6,7 for control. Pin 5 and 14 for powering. Pin 8 for input.
If I use the Vref, then i need to move my lcd out pins to pin 10 through 13 ( I wanted to us these for led out, piezo and other outputs i needed. I never had luck outputting on port A. Shouln't be hard to get it going.
Also I dont have any MCP1525, I only have 7805 chips maybe use this chip for now and replace it when I get another ?...
and use a voltage divider on the 7805 to obtain 2.5 v ?
I assume the MCP1525 is an LDO chip ??

also instead of using 40k and 10 K resistors, can I use 400k and 100K ? would that take up even less power ?
Well, if you can't change the Vref pins around, then maybe use 2 A/D converters and compare your fixed reference against the total applied? In other words, if you're battery ever got down to 2.5v, then the A/D input would be at maximum. Just takes a bit of math I supose...

And since you don't have any MCP1525 or anything like it, I know one thing you do have that does have a fixed reference...

Or do you?
I'll give you a little bit to think about it, then I'll give you the answer.

And also since you don't have a fixed voltage (or do you? )...you won't need to worry about the resistors for now.