This is a simple application of internal 10-bit ADC (analog to digital converter) of PIC16F676 microcontroller.you can use this circuit to measure up to 30 v dc. the possible applications are on bench top power supply or as a panel meter in various system.
MICROCHIP’S PIC16F676 is the heart and brain of this circuit .the internal adc of the mcu with a resistor network voltage divider is used to measure the input voltage . then 3 digest of comm anode 7 segment display is used to display final converted voltage. as you can see in the schematic the displays are multiplexed with each other . means we switch on one display and put the corresponding digit on this while other two displays are off this cycle go for each of the display.
Panel Voltmeter Using PIC16F676 – [Link]