PIC Microcontroller with multi-voltage measurement, display (LCD) a good example for software pic basic prepared with pic18f4455 RE3, RA0, RA1, RA2, pins and the 4-channel voltage measurement can be made circuit as an example 5 …. 12V DC Voltage used higher voltages You may need to use a voltage divider resistors. Measuring DC voltage in the range from 30VDC 0VDC
PIC18F2550 Voltage Monitor Circuit
To measure the voltages higher then the VCC (supply voltage of the ?C) i was thinking of using the well-known and simple voltage divider using resistors. Discover the possibilities of measuring DC voltages in a range from 0VDC to 30VDC. Use the Onboard A/D converter from the PIC18F4455 or PIC18F2550 range. Measure different DC voltages at a time. Try to do the measurement without using an external ref voltage.