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 Arduino ...

A tuning mechanism consisting of 10 stepper motors and a further 10 servo motors for plucking the strings—combined with an arduino controller and some clever MaxMSP and Pure Data programming ...