Archive for July 10th, 2011
Some simple measurements using that Pololu driver in its default mixed decay mode and that Arduino sync generator. The captions give the operating conditions; basically, I’m varying the rotation speed by cranking the signal generator driving the Pololu board.
At 1 rev/s, it’s about as good as it gets:
At 5 rev/s, the driver has trouble getting current out of the winding:
At 10 rev/s, things are getting ugly:
At 20 rev/s, the back EMF has pretty much taken control of the current and the driver is going along for the ride:
At 25 rev/s, the driver produces only occasional dents in the waveform:
At 25.3 rev/s, the motor stalled. Even with no back EMF (what with the rotor being stopped and buzzing in frustration), the driver can’t force the current to behave:
I don’t have any way to measure the motor’s output torque, but at 1500 RPM there won’t be any worth mentioning.
For what it’s worth, 25 rev/s means the driver is handling 40 k steps/sec = 25 µs/step. The motors in a Thing-O-Matic run at 3 rev/s to move the XY stages at 100 mm/s, so scale what you see here accordingly.