I’m new to stepper motors and I’m experimenting with the DRV8825 controller and the model 1200 stepper motor (both from Pololu). I can get the motor to work using one of the minimal wiring diagrams supplied on the Pololu site. So far I’ve just been using full steps, and I run the motor at 12V. My problem is, I can’t get the motor to run beyond about 1 kHz on the STEP pin. At this frequency the motor is spinning (I’m guessing) at about 50 RPM. Increasing the STEP frequency beyond 1 kHz causes the motor to sort of stutter and then stop (though it hums in tones proportional to the STEP frequency). I’ve confirmed the controller continues sending (seemingly) valid waveforms as I increase the frequency, and I’ve verified the current limit (via the Vref method) is within the motor’s spec. Given inertia, I don’t expect the motor to run at the full 250 kHz the DRV8825 is capable of handling, but it seems like it should be able to run faster than 1 kHz/50 RPM. Is this a reasonable limit, or am I doing something wrong? Thanks for your help.
You didn’t say whether you are using microstepping. However, if you try to start up a stepper from standstill at a fixed step rate, you can’t expect it to spin very rapidly. The maximum rate depends on a lot of factors but 50 rpm sounds about right.
You can get much higher speeds if you slowly ramp up the step rate from a standstill, but don’t expect much power out of the motor shaft at high step rates. Use of the microstepping feature may allow you to achieve even higher rpms. Steppers are best used at low rpms, where accurate and repeatable turn angles are desired.
I’m using full steps, but I have the same problem (proportionately) if I micro-step. Anyway, if ~50 RPM is the norm, that’s what I needed to know. Thanks.
I measured the RPM now and I’m actually getting around 250 RPM at a pulse frequency of 27 kHz with 1/32 microsteps. I’m just posting this for the benefit of any future readers looking for this type of info.