but we do know her Arduino does. Her build uses the ubiquitous HC-SR04 SONAR sensor and a servo. This is a great use for a servo since a standard servo motor without modifications only moves ...

This solar tracker system uses the Arduino UNO board, a servomotor, 2 LDRs and 2 resistors to rotate the solar panel towards the Sun or a source of light. Here https ...

Some readers may recall building a line-following robot during their school days. Involving some IR LEDs, perhaps a bit of LEGO, and plenty of trial-and-error, it was fun on a tiny scale.