Digital Voltmeter with 3-Digit Output

The construction of the device uses PIC16F676 for reading analog signal such as voltage, and displaying the 3-digit output by using 7-segment LED.

On the hardware part, the PIC16F676 has 10-bits 8 channels since most of PIC microcontrollers has either 8-bit or 10-bit analog to digital converter module. In this project, only one channel is used for measuring the input voltages while the others pins are used for digital I/O. A voltage divider consisting of R1 & R2 is used for the voltage input. The appropriate display of full scale voltage is being adjusted by VR1 connected in parallel with R2. The analog input will come from the divided input voltage from AN3.
In scan display routine, the digital output RA0-RA2 turns ON/OFF the digits. The 7-segment display is driven by the RC0-RC5 and RA5 and will be decoded by a software using CCS C compiler to programming. The 7-segment code is a converted form of the input voltage on RA3. The interrupt of every 5 ms is set on the timer while scanning all digits around 66 Hz frequencies. This means that for every 5 ms, only one digit is turned ON