/diy/ - Do It Yourself

>>1392648
Technically you could run one as the other, provided you drive it correctly. The distinction to make is that an induction motor is asynchronous; the magnetic field in the squirrelcage slowly rotates in the opposite direction to that the rotor is spinning. The net effect is that while the magnetic field stays perfectly in sync with the switching electromagnets, the rotor itself moves a little slower, depending on the load. I believe this makes them harder to stall than a BLDC, not to mention easier to start and drive.

To run an induction motor as a BLDC you'd first need to ensure you're putting enough of a voltage across it, they're probably made for mains and running them even at 48VDC will result in a severe lack of torque, if it even gets up to speed, which is unlikely. But you won't need any feedback to run it, meaning you'd just need to supply it with 3 out-of-phase square waves (preferably with filtration), probably ramping up in frequency. A frequency ramp isn't necessary if you're running it at the intended voltage. Might struggle finding the right 3-way H-bridge IC though.

>>1392652
A BJT transistor has a current amplification ratio, emitter_current = hFE * base_current. Putting two in an arrangement like that squares this ratio. That circuit is bad because there's no base resistor to limit current out of the microcontroller, and the valve won't actuate on 5V, and there's no freewheel diode, and that it literally shorts Vcc to GND. A MOSFET will do the same thing as a darlington without requiring any current from the microcontroller. Pic related will work, provided you pick an appropriate MOSFET.