You know when you see something like this it’s just going to be awesome, and we weren’t disappointed by our first impression. [Davide Gironi] built a brushless motor controller from the ground up using an ATmega8 as the brain. If you want to understand every aspect of a subject this is how to do it. Lucky for us he explains what each portion of the prototype does.
Brushless motors have no brushes in them (duh). But what does that really mean? In order to spin the motor a very carefully crafted signal is sent through the motor coils in the stationary portion (called the stator), producing a magnetic field that pushes against permanent magnets in the rotor. A big part of crafting that signal is knowing the position of the rotor. This is often accomplished with Hall Effect sensors, but can also be performed without them by measuring the back EMF in the coils not currently being driven. The AVR-GCC compatible library which [Davide] put together can be tweaked to work with either setup.
Get a good look at the system in action after the break.
[via Dangerous Prototypes]