On Tue, Mar 21, 2017 at 4:44 PM, 'woody stanford' via BeagleBoard <beagleboard@googlegroups.com> wrote: > Ok so little angry now about the possibility of having to use 6 MOSFET's to > control a single motor (how the HELL did someone come up with the idea of > using a 3-phase motor for these toys...what was it some CAD/CAM guy...and > what i the whole difficulty with brushes anyways?). Brushes are unreliable, lossy and result in torque ripple. 3phase motor torque is flat, and they're so efficient that practically all high end motors are 3phase, and there's a trend to put 3phase in smaller and smaller appliances, like dishwashers, washing machines and refrigeratos. What is your issue with 6 mosfets? They cost less than fancy carbon brushes :) > > How is this for an idea of how to use 3 MOSFET's to control one of these > drone motors? I figure that its the voltage that the motor "sees", I can > feed it a 50% PWM signal that my motors will think is zero volts (silly > things). Then I can go down to 0% PWM for the negative voltage eliminating > the need for the additional 3 MOSFETs. Run 100% for max positive voltage. For 50% PWM to result in zero current through your motors you need to reference it to a half-Vcc, so you'll need some sort of circuit anyway. Just welcome your new 6-legged 3-phase overlords and be done.
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