12v car battery monitoring

[oldcarguy85]

Hi,
I have been working on what i call the "OBD2 LCD." it is basically an interface for a good portion of 96-up vehicles that displays all info about engine parameters on a 4x20 LCD. My question is this. Battery voltage is not a parameter i can poll the engines ECU for, so i need to read it directly from the 12v input. I am very new to circuit design, and have no idea how i can scale this 12v source (actually probably in the range of 10-16v) down to 0-5v to use the PIC ADC. i am using a pic16f877a, which i believe has a few ADC's.

Thanks for any help!
Jordan

btw- if interested, here is the web site for the OBD2 LCD http://www.obd2lcd.com

[mister_e]

what you need is a voltage divider made with 2 resistor, and then read the output of it. Once you have the reading, few maths to scale it in a readable mode.

have a look at Darrel's Pic voltage divider calculator
http://www.pbpgroup.com/modules/wfse...p?articleid=25

[oldcarguy85]

Thanks a lot! that is EXACTLY what i needed!