[mircemk] shows how to create a simple non-contact proximity sensor using little more than an Arduino Nano board, and a convenient software library intended to measure the value of capacitors. The ...

This project is a simple modification of the LightGauge project. Instead of measuring light, we measure the ambient voltage field on pin A5 and use it to detect if someone is too close to our Arduino.

An Arduino can be used to test the life of any battery with less than 5 volts, Boxall says. So, for a quick way to see how much juice your AAA, AA, C, or D batteries have left, build this ...