Nema 23 Motor Driver Options

Peter Boreland

Currently I am successfully driving a smaller nema23 motor using the TMC5160. I have set the IRUN current to 1800mA. I'm not sure this is a valid value for the particular driver, or even the correct value for a Nema 23 motor?

The motor is connected inline with the Dec worm on Losmandy G11. This arrangement works OK, but I have to  keep the slew rate quite low else the motors stalls, or looses steps. I have also set the Slew_Accerelartion_Distance = 35. Further, the motor also does not like run slowly and sometimes judders and/or looses steps at the end of the slew cycle. Not so while tracking. It works OK.

The telescope weights in at around 75 lbs. The motor has 400 steps and is microstepped 16/32. Both work. 

I think I'm pushing the limits of what is doable with the TMC5160, and I would like a higher slew rate. I was thinking of using and exterior motor driver. StepperOnline has this one available that connects to the back of the motor:

To use this I would have to use step/dir signals. I already do the for a Clearpath servo motor I have connected directly to the Ra worm. Its works great, but it is an expensive motor. 

Any advise or related experience with this style of exterior motor driver would be appreciated.


George Cushing

The 5150 is good for a maximum of 3A (3000mA). So 1.8A is OK, but generally we run the drivers a 40-50% of max. Your pusing the motor at 60% of max.

What is the max amperage of the motor? 

Have to set the Vref pots to max output? 

Alexander Varakin

Peter, You need to figure out the motor specs before you do anything about drivers. I've seen Nema23 with nominal current from 0.4A all the way up to 6A.
In case if you don't have specs for the motor, you can measure the resistance and then based on the resistance and size of the motor, try to find something similar on stepperonline site.
Most people use Nema 17 for your mount, something like this:

Peter Boreland


I have two motor sizes. 2.0A and 2.7A. What would you recommend the config.h motor setting be?

Where are the Vref pots, and what do they do?


Peter Boreland


I have the Oriental nema 17 400 step motor. These are being used to directly drive the end of the worm. I need the higher torque of the nema23 to make this work well and achieve higher slew rates.

The motors are from stepperonline. 

Electrical Specification

  • Manufacturer Part Number: 23HM22-2804S
  • Motor Type: Bipolar Stepper
  • Step Angle: 0.9 deg
  • Holding Torque: 1.26Nm(
  • Rated Current/phase: 2.8A
  • Phase Resistance: 0.9ohms
  • Inductance: 4.5mH ± 20%(1KHz)


Mike Ahner

On Wed, Apr 20, 2022 at 08:05 AM, Peter Boreland wrote:
I have two motor sizes. 2.0A and 2.7A. What would you recommend the config.h motor setting be?

Where are the Vref pots, and what do they do?
There are no Vref pots on TMC5160, only software settings via the config.h file. On other drivers, the Vref voltage translates into a maximum current for the driver, many TMCxxxx/s can use either Vref for external/voltmeter adjustment or simply use changes in the config.h.

The motor will probably give best performance somewhere between 30%~60% of the max stepper motor current (or maybe peak current). Start low then test the results and move up until the mount doesn't stall. Howard's testing shows the best performance and highest torque usually occur at less than full power to the stepper.

Here's the Wiki:

George Cushing

As mike says you want  600mA-1200mA for motor A and 780mA-1560mA for motor. These outputs are easily with the 5160's range. Also note that these are not out of the range of the TMC2130. The 2130 has the pot to set the Vref the 5160 does not.
voltage reference is an electronic device that produces a fixed (constant) voltage irrespective of the loading on the device, power supply variations, temperature changes, and the passage of time. Such a device is an op amp comparator.