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. Now ...

The build relies on the classic Arduino Uno microcontroller, which talks to a HC-SR04 ultrasonic sensor module and two infrared sensors in order to track a human target and follow it around.

In the second phase, the logic operates two drive motors (left and right) as per the informed track status. The infrared sensor card contains infrared light emitting diodes and infrared photodiodes.

This is usually mounted at the bottom of a line following robot chassis. ... You will see the status LED wakes up instantly when your hand is close to the infrared sensor part. That’s it! HW-006 ...

The little robot, about half the size of a small egg, whirs along on invisible wheels, using a camera on its base to follow any line it's put on. When it meets a branching path, it picks one randomly.