How to monitor battery level that is running the PIC itself?

[capfelix]

Hi,

Did anyone have any experience with designing a battery monitoring system that monitor the PIC controller battery level?

I have a PIC controller running on 2 AA size battery (3V in total). Is there a way for the controller itself to monitor its battery level? Code and circuit will be very much appreciated.

Thanks!

[Ttelmah]

This has been answered only a day or so ago, in the thread:
"ADC Vref and ISCP-CLK on PIC16F68x need some input"

The 'key' is to have some known reference voltage feeding into an analog input, use the supply as Vref, and read this. As the supply drops, the reading will rise. So if (for instance), you had a 2.5v reference, and 3.3v supply the reading would be (for a 10bit ADC), 776. If the supply fell to 3.1v, the reading would rise to 826.
The supply, is (2.5*1024)/reading.

Best Wishes

[ljbeng]

I have used the MCP100-xxx (normally holds micro in reset) to indicate when the battery level falls below a certain level. Connect the MCP100 to supply and it's output to a micro input pin. You can even use an output pin to turn on the device for low current consumption, then check the input pin after .3s or so to see if the battery is above or below the voltage of the device.

see:http://www.electronicdesign.com/Articles/ArticleID/11609/11609.html

[kender]