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Stepper Motor unable to exceed 4(ish) RPMs at any microstep


Hello Pololu Community,

My setup consists of the following:

[ul]Stepper Motor: Unipolar/Bipolar, 200 Steps/Rev, 57×76mm, 8.6V, 1 A/Phase (Purchased through Pololu)
DRV8825 (Current Limited to 0.3V on VRef or 0.6A if I am not mistaken)
Function Generator or Arduino supplying the step
Desktop Variable Power Supply or 48V 7.2A Power Supply[/ul]

Motor Wiring to DRV8825:

Black - A1
Green - A2
Red - B1
Blue - B2

I am new to stepper motor control and a novice, in general, for electronics. When looking at torque curves, for example the pololu motor listed above, the curve suggest being able to maintain a minimal torque at pulse rates in excess of 6,800 pps when half stepping. My understanding is that a half step is 400 pulses per revolution. Therefor: 6,800 pulses/second / 400 pulses/revolution = 17 Revolutions per Second (RPS)

My problem is, loaded or bare motor shaft, I am unable to achieve anything over 4 RPS at any microstepping level. The motor shaft siezes up (or slips, not sure on terminology). On one occasions I was able to break through this barrier while 32x microstepping and exceed 160k pps (25 rps) with no load but I have been unable to recreate the event since. Increasing the current to 1A will move the ‘slip point’ to 4.25 or 4.5 RPS, but it still occurs premature nonetheless.

My project goal is to achieve a minimum of 10 rps in either direction with a load suitably under the torque curve. Admittedly, my work with a soldering iron is nothing short of a massacre, but I do not believe it would cause the consistent results across all microstepping levels. The same results are experience on different DRV8825 carriers. My hope is that the problem lies in the motor wiring, but my crude understanding is that the stepper either steps or it doesn’t. I honestly do not know the operating difference in a properly running stepper vs. a bad one.

Any guidance would be greatly appreciated! I am hoping this is not simply the nature of all stepper motors.



Hello, Brent.

Your calculations seem correct, and since the motor is stepping, I do not think your wiring or soldering is a problem. However, it sounds like the power supply you are using is supplying too high of a voltage for that motor driver. We recommend a maximum of 45V and the torque curve was generated with a supply of 30V. I don’t expect lowering the voltage to within the driver’s recommended range to help the motor step any faster, but you will be less likely to damage the driver.

In general, it can be difficult to achieve high step speeds with stepper motors, and the maximum speeds you mentioned seem reasonable. However, the posts in this thread by kevin and Ben might help you increase the speed of your stepper motor.