In this tutorial, we will build a circuit with Arduino Uno that can read voltages from 0 to 30V DC and display them on the 16×2 display, the ideal project to build our DIY voltmeter.
Thanks to the analogue inputs, that can be used to measure voltages from 0 to 5V. For higher values we will use a voltage divider formed by 2 resistors in series, and we will measure the voltage of the central node connecting it to the analog input A0.
Sketch for I2C LCD:
16×2 LCD sketch