NEMA 23 - Stepper Motor - Continuous Rotation Issue

Other Hardware Motors, Mechanics, Power and CNC
1

I will preface this post by highlighting that I understand that a stepper motor is not ideal for running continuously, but it is the current use case and what I have available for a conveyor system I am trying to run.

Below is a breakdown of the hardware I am currently using:

My current issue is that I cannot continuously run the stepper motor, regardless of the various stepper motor libraries available (i.e. AccelStepper, ContinousStepper, BasicStepperDriver)

Below is a further explanation of my current approach to the problem:

0J4344.600

Based on the schematic above, I am supplying approximately 3.1V (Measured) to VMOT with the 100uf capacitor in parallel with VMOT and GND. The motor power supply is a 24VDC 5A (Output) power supply, but converted down to 3.3V by the K7803-2000R3.

As mentioned above the stepper motor has 8 windings but with bipolar serial connections.

I am able to get the motor to run for a quarter to half rotation but with the command of rotating 360. I also used the following code to try and run continuously using the AccelStepper library example. This also causes the motor to run a few steps and jitter.

#include <AccelStepper.h>

AccelStepper myStepper(AccelStepper::DRIVER, stepPin, dirPin);           // works for a4988 (Bipolar, constant current, step/direction driver)

void setup()
{  
   myStepper.setMaxSpeed(200);   // this limits the value of setSpeed(). Raise it if you like.
   myStepper.setSpeed(-200);	   // runSpeed() will run the motor at this speed - set it to whatever you like.
}

void loop()
{  
   myStepper.runSpeed();   // This will run the motor forever.
}

My current guess is that it is an issue with the current draw causing the overcurrent protection in the DRV8834 to kick in at 2A. Originally the stepper was wired for a parallel connection but changed to series to help with this issue. I would appreciate any guidance in this and would be happy to share more information where needed.

2

That's far to low for your stepper. Why do you use a Low voltage stepper driver?
Using the standard DRV8825 and connect the 24V directly to VMot would be more appropriate.

1 Like
3

Thank you for pointing this out. I did not read the data sheet properly and read the voltage for unipolar winding. I am new to stepper motors and just getting familiar with them. I will attempt this next.

4

Stepper drivers regulate motor current.
To do that, driver supply voltage must be significantly higher than motor voltage.
A higher supply voltage gives you more torque at high step rates.
So a 24volt supply is fine for a 3volt motor, as long as the driver is ok with 24volt.
Leo..

5

Thank you for the reply and feedback @MicroBahner and @Wawa

I wanted to try and still use the low voltage stepper driver, so I was able to find a 10V supply laying around that I could use. The DRV8834 has a max operating voltage of 10.8V.

After I supplied the 10V directly to the driver, the motor barely moves now, I only see it jittering. This should be enough voltage to cover for the required motor 5V (Bipolar series winding)? Or maybe I am missing something?

I wanted to try and still use the DRV8834 but if the low voltage driver is the cause I will have to order the DRV8835, which will delay my project. I would appreciate any insight, thank you!

6

I've used the drv8834 in a project running off 9v with no problems though with NEMA 8 motors. What have you set the current to? Have you read the instructions for setting current? Obviously you can't use the full 24v cos the chip is only specified to 10.8v. what microstep setting do you have?

7

ALWAYS think CURRENT, Amps, when dealing with motors.

8

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