I am missing a way to control the duty cycle, because the higher the on time, the higher the output voltage. But all of this can be done with the good old 555 instead of a microcontroller.

Four small coreless motors are used for propulsion, driven by tiny MOSFETs, and the whole assembly is run via a teeny 220 mAh lithium-polymer battery. Oh, and there’s an FPV camera so you can ...

The machine uses a ‘grbl’ controller, which has an Arduino-based circuit that includes multiple outputs, including a powerful 24V pwm signal that is generally used to drive a 60-80W spindle motor..