This is a digital voltmeter project based on PIC12F683 microcontroller. It measures and displays input voltage from 0 to 20V with high accuracy. You cannot feed 20V directly to PIC port, so a simple resistor divider network is used for this purpose. A 5.1V zener diode is used to prevent any damage to PIC port in case the input voltage goes way above 20V.
Since PIC12F683 does not have sufficient pins to drive a LCD, 3-wire serial discussed before is used to display the measured voltage.