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Configure and Test a Stepper Motor

Hardware: Motion Control>>Controllers

Problem:
How do I configure my NI 73XX motion controller to control my stepper motor?

Solution:

1. Open the Measurement & Automation Explorer (MAX)
   
   
2. Configure your stepper settings
   
   1. Go to the Axis Configuration tab
   2. In the Axis Configuration tab, set Type to Stepper.
   3. In the Stepper Settings tab, select your Stepper Steps Per Revolution, Stepper Loop Mode, Stepper Polarity, Stepper Output Mode, and Pull-in Tries
      
      Note: For P-Command motors, select P-Command for Stepper Loop Mode
   
   
3. For now, disable your inhibit, home, and limit signals
   
   1. Go to the Motion I/O tab
   2. Disable all the signals in this tab (Limit Filters, Forward Limit Switches, Reverse Limit Switches, Home Switch, Forward Software Limit, Reverse Software Limit, Inhibit Output)
   
   
4. Initialize your motion controller with your current MAX settings
   
   1. Click on the Initialize button
   
   
5. Test your stepper settings with your stepper motor
   
   1. Go to the 1-D Interactive’s Main tab
   2. Set Stepper Loop Mode to Open Loop
   3. Set Velocity, Acceleration, and Deceleration to values slow enough for your motor to handle
   4. Set Operation Mode to Relative Position
   5. Set Target Position to the number of your Stepper Steps Per Revolution (see step 2c)
   6. Click the Start button
      1. Your motor should move one full revolution. If the motor moves but goes over or under one revolution, then most likely your Stepper Steps Per Revolution is incorrect.
      2. Your motor should rotate in the forward direction (if your Target Position is a positive value). If the motor rotates in the wrong direction, then you probably need to switch either phase A and A- or B and B- (effectively reversing directions) leads from your drive to your motor. (See KnowledgeBase 2DKB1MYJ: How Can I Determine My Stepper Motor Wiring without the Stepper Motor Pinout?)
   
   
6. If you are using feedback in your motion system, follow steps 7 and 8. If you are not using an encoder, you are done configuring and testing your open loop stepper system.


7. Configure your feedback settings
   1. Follow the instructions below if you are using a two-phase quadrature encoder for feedback
      
      1. In the Axis Configuration tab, set Type of Feedback to Encoder
      2. Go to the Encoder Settings tab
      3. Enter your encoder counts per revolution.
         Note 1: If you can kill your motor and rotate the motor manually, then you can determine the correct encoder counts per revolution by following the steps in KnowledgeBase 2FDCRSLT: Determining the Encoder Counts Per Revolution in NI-Motion
         
         Note 2: To increase feedback accuracy, NI motion controllers read every edge of an encoder feedback signal. With a quadrature encoder, this results in four edges (rising and falling on lines A and B) for every quadrature pulse of the encoder. Thus, if your quadrature encoder is rated at 2000 quadrature pulses per revolution, the controller will actually read 8000 edges per revolution – and each of these is considered a “count”.
         
         When setting the Encoder counts per revolution input in MAX, it is common to mistake this value for the encoder’s physical resolution. Instead, this setting needs to hold the corresponding number of counts read by the controller, which is four times that resolution. (See KnowledgeBase 3QGEF7D3: Following Error in a Motion System)
         
   2. Follow the instructions below if you are using analog feedback
      1. See KnowledgeBase 3VMMB7AJ: Analog Feedback with a Stepper Motor
   
   
8. Initialize your motion controller with your current MAX settings
   
   1. Click on the Initialize button
   
   
9. Test your encoder settings
   
   1. Go to the 1-D Interactive’s Main tab
   2. Set Stepper Loop Mode to Closed Loop
   3. Set Velocity, Acceleration, and Deceleration to values slow enough for your motor to handle
   4. Set Operation Mode to Absolute Position
   5. Click the Reset Position button to reset the Current Trajectory Data Position to 0.
   6. Set Target Position to the number of your Stepper Steps Per Revolution (see step 2c)
   7. Click the Start button
      1. Your motor should move one full revolution
      2. The Current Trajectory Data’s Position should match the Target Position
   
   
10. Re-enable the inhibit, home, and limit signals that you will be using
    1. Go to the Motion I/O tab
    2. Enable the signals that you will be using and configure the correct polarity for each
    
    
11. Configure the rest of tabs in MAX as is necessary
    
    1. Click on the Show Help button to display the MAX Help sidebar
    2. Use the MAX help for more information on the rest of the settings. Hover your mouse over a setting to populate the MAX Help with a description.
       
       Note: You do not need to configure anything in the Control Loop Settings tab for a stepper motor.
    
    
12. Initialize your motion controller with your final MAX settings
    1. Click on the Initialize button

Related Links:
KnowledgeBase 2DKB1MYJ: How Can I Determine My Stepper Motor Wiring without the Stepper Motor Pinout?
KnowledgeBase 2FDCRSLT: Determining the Encoder Counts Per Revolution in NI-Motion
KnowledgeBase 3QGEF7D3: Following Error in a Motion System
KnowledgeBase 3VMMB7AJ: Analog Feedback with a Stepper Motor
KnowledgeBase 2U4GA0OV: How Do I get the 73xx Controller and UMI 7764 to Drive a Third Party Stepper Motor?

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Report Date: 02/07/2007
Last Updated: 04/25/2008
Document ID: 466HEDS4

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