The 555 is really only a few comparators, a voltage divider, one or two transistors, a flip flop and an inverter. The idea is you use a capacitor to charge and the comparators can set or reset the ...

Instead of going with a microcontroller he built the circuit around a 555 timer. What he really needed in this case is a flip-flop but lacking a chip for that he went with the 555 because it has ...