“I’ve made fumes extractor from old Dell fan. It’s quite powerful: 110mm 12V 0,6A, but unfortunately it’s horribly noisy on full speed. I decided to make speed controller for it. I wanted it to be as simple as possible, mounted on fan, thus powered from it’s voltage line (12V), potentiometer controlled. I chose ATtiny45 because main circuit would consist only of ATtiny and potentiometer. Alternative was 555 timer, but I wanted it simpler! My fan had wire for PWM control, but there’s nothing stopping you from using it with any DC motor with additional transistor! I’ll show how to program any ATtinyX5 or ATtinyX4 with Arduino IDE, how I’ve done my controller, how to use it with any DC motor, and how tu use zener diode as simplest voltage regulator.”