Stepper Page (Axis Configuration)

LabVIEW 2018 SoftMotion Module

Edition Date: March 2018

Part Number: 371093W-01

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Use this page of the Axis Configuration dialog box to configure options for stepper axes.

This page includes the following sections:

Note Note  Not all options and pages are applicable for all axis types.

Output

  • Output Mode—Specifies the output mode for the stepper command signals.

    Valid options are:

    • Step/Direction—Configures the stepper outputs for step and direction mode. When step and direction mode is configured, each commanded step (or microstep) produces a pulse on the step output. The direction output signal level indicates the command direction of motion, either forward or reverse. The following image shows an example of step and direction output mode:

      step and direction

    • CW/CCW—Configures the stepper outputs for clockwise (CW)/counterclockwise (CCW) mode. CW and CCW mode produces pulses on the CW output for forward-commanded motion and pulses on the CCW output for reverse-commanded motion. The following image shows an example of CW/CCW output mode:

      CW/CCW

  • Output Type—Specifies the output type for the stepper command signal.

    Valid options are:

    • Single-Ended—Selects single-ended stepper signal configuration. In a single-ended configuration, the transmitter generates a single voltage that the receiver compares with a fixed reference voltage, both relative to a common ground connection. This configuration is less complicated but more sensitive to signal noise than differential signals. Refer to the Step and Direction Output Circuit section of the NI 951x User Manual for information about connecting the Step (CW) and Direction (CCW) signals to drives.
    • Differential—Selects differential stepper signal configuration. In a differential configuration, the information is transmitted electrically by means of two complementary signals sent on two separate wires. This configuration helps to protect the signal from the effects of noise. Refer to the Step and Direction Output Circuit section of the NI 951x User Manual for information about connecting the Step (CW) and Direction (CCW) signals to drives.
    • Sinking—Selects a sinking output type. Sinking outputs provide a path to ground for current flow.
    • Sourcing—Selects a sourcing output type. Sourcing outputs provide a path to a voltage source for current flow.
    • Simulated—Selects a simulated output. Use simulated output type when there is no physical output connection, but you want to configure the output for simulation purposes.
  • Active State—Specifies the active state of the stepper command signals. The stepper command signals are driven to their active state to generate a stepper command pulse. For example if the active state is set to Low, then the output will drive high when no pulses are generated and drive low to generate stepper pulses. When the stepper output mode is configured for Step/Direction, the active state on the direction signal is the state of the signal when the axis is moving in the forward direction. Refer to your drive documentation to determine the active state setting that matches the expected states on the drive inputs.
    NoteNote  Available active state selections depend on the Output Type selected.

    Valid options are:

    • High—Configures the signal to be active when there is a high signal on the pin.
    • Low—Configures the signal to be active when there is a low signal on the pin.
    • On—Configures the signal to be active when current is flowing through the circuit.
    • Off—Configures the signal to be active when current is not flowing through the circuit.

Drive

Configures stepper drive parameters.

  • Current Reduction Percentage—Specifies the percentage by which to reduce the maximum current when the motor is stopped after the specified Current Reduction Delay has passed. Valid options are between 0 and 99%. The default is 25%.
    Note For the NI 9501 stepper drive module, only the following options are available:
    • 0% (No Reduction)—Disables the current reduction functionality.
    • 25% (default)—Reduces the current by 25% of the maximum.
    • 50%—Reduces the current by 50% of the maximum.
  • Current Reduction Delay—Specifies the time to wait, in ms, after the electrical angle stops changing before the current is reduced to the reduced current level.
  • Minimum Pulse Width—Specifies the minimum step TRUE time. Valid options are between 0 s and 2.5 x 10^-6 s. The default is 1 x 10^-7 s.

Rates

Configures stepper rates.

  • Microstepping Rate—Specifies the current microstepping rate. Valid options are powers of 2 between 1 (full step, no microstepping) and 256. Microstepping provides higher positional accuracy and smoother motion at the expense of reduced torque.
    CautionCaution Updating this property while a move is in progress will increase or decrease the velocity of the axis.
    You can update the Microstepping Rate when the drive is enabled. This allows you to perform a move at higher speeds using a low microstepping rate, then perform a move using a much higher microstepping rate to achieve high precision when reaching the final target position.
    Note For the NI 9501 stepper drive module only the following options are available:
    • 1 (Full Step)—No microstepping.
    • 2 (Half Step)
    • 4
    • 8
    • 16 (default)
    • 32
    • 64
    • 128
    • 256
  • Spline Loop Period—Specifies the stepper spline loop period, which is the rate at which the step generation FPGA loop executes, in clock ticks. Valid options are between 0 s and 0.01 s. The default is 5 x 10^-5 seconds. The value specified must be an integer multiple of the NI Scan Engine Scan Period, configured on the Scan Engine Page of the Target Properties dialog box.

Units

Configures stepper base units and steps per Unit.

  • Units—Specifies the display units for move data. You must specify the appropriate steps per unit for proper scaling.
  • Steps Per Unit—Specifies the steps per unit ratio for the system. Steps can be full steps, half steps, or microsteps depending on the external stepper drive configuration. Valid options are between 0.000001 and 232 Units. The default is 1 Unit. For example, a 200 steps per revolution stepper motor configured for x4 microstepping has 800 steps per revolution.
    Note  Specify the units for your application using the Stepper page of the Axis Configuration dialog box for open-loop stepper axes, or the Encoder page for closed-loop stepper and servo axes. Specified units only apply when you perform moves and not when you are generating motion profiles.
    If you are setting up a stepper motor with encoder feedback, take into account the encoder counts per unit setting. For example, if the encoder is configured for 8,000 counts per revolution, setting steps per revolution to 8,000 means that NI SoftMotion generates one step per encoder count. A setting of 24,000 steps per revolution means that NI SoftMotion generates 3 steps per encoder count. Valid options are between 0 and 232. The default is 1.

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