I want to brainstorm about synchronizing two BLDC motors intended for R/C airplanes (although I am not using them for R/C). The controllers would presumably use the PWM protocol that servos use.
I am thinking that I would designate one of the motors as the 'master' and sync the other to it. I would also need some way to count RPM.
I am wondering if there is an easy way to sense one of the motor phases turning on and off to get RPM. Or am I'm better off with an optical or hall sensor looking at the rotor.
It seems straightforward to vary the speed of the motors using the servo-type PWM, though I wonder if it gives enough control.
The application involves using the motors with offset weights for vibration. They need to counter-rotate to cancel torque effects and obviously if they are not synchronized, the vibration will be weird.
As I write this, I am looking at how many timers I would need. I want to use an ATtiny26 or ATtiny261. The 261 has input capture whereas the 26 does not. I am not familiar enough to know the real advantage of this, but I suspect wanting two PWM outputs and two RPM timers may require the input capture.