[Andrea] built this LED chaser ... out how the circuit works? We already know that it’s using a CD4017 decade counter/divider chip. This gets its clock signal from a 555 timer circuit.

Rather than choosing any number of circuits to turn a strip of discrete lights on and off, [Johannes] took inspiration for his chaser lights from factory automation mechanisms that move parts ...

The 555 adjustable timer circuit starts timing when switched on. The green LED lights to show that timing is in progress. When the time period is over the green LED turns OFF, the red LED turns ON and ...