National Instruments ISM-7400 User manual

USER MANUAL
NI ISM-7400
Integrated Stepper
This manual describes the NI ISM-7400 integrated stepper. It describes electrical and
mechanical characteristics of the devices, as well as I/O functionality.
Contents
Getting Started .......................................................................................................................... 2
Mounting the NI ISM-7400...................................................................................................... 3
Connecting the Power Supply .................................................................................................. 3
Choosing a Power Supply.........................................................................................................4
Voltage.............................................................................................................................. 4
Current .............................................................................................................................. 5
Regeneration ..................................................................................................................... 6
Connecting Input Signals.......................................................................................................... 6
Connection Examples: STEP & DIR................................................................................ 8
Connection Examples: EN................................................................................................ 9
Connecting the Digital Output.................................................................................................. 10
Using the Optional Encoder ..................................................................................................... 11
Configuring the NI ISM-7400 .................................................................................................. 12
Setting the Current............................................................................................................ 12
Setting Idle Current .......................................................................................................... 12
Load Inertia....................................................................................................................... 13
Step Size ........................................................................................................................... 13
Step Pulse Type ................................................................................................................ 16
Step Pulse Noise Filter ..................................................................................................... 16
Self Test .................................................................................................................................... 17
Reference Materials.................................................................................................................. 18
Torque-Speed Curves ....................................................................................................... 18
Heating.............................................................................................................................. 18
Mechanical Outlines ......................................................................................................... 21
Technical Specifications........................................................................................................... 23
Amplifier .......................................................................................................................... 23
Motor ................................................................................................................................ 23
Digital Inputs .................................................................................................................... 24
Fault Output ...................................................................................................................... 24
Physical............................................................................................................................. 24
Incremental Encoder Specifications ................................................................................. 24
Mating Connectors and Accessories................................................................................. 25
Alarm Codes .....................................................................................................................2
5
Worldwide Support and Services ............................................................................................. 26

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Figure 1. Block Diagram
Getting Started
You will need the following items to get started with your NI ISM-7400:
12 VDC to 48 VDC power supply. NI PS-12 (NI part number 748906-01) or NI PS-13
(NI part number 748907-01) recommended.
Source of step signals, such as a PLC or motion controller.
Refer to Choosing a Power Supply for more information.

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Figure 2 shows an overview of the connectors on the NI ISM-7400 integrated stepper.
Figure 2. NI ISM-7400 Integrated Stepper Connectors
Mounting the NI ISM-7400
Mount your NI ISM-7400 using four M3 screws, the mounting hole depth is 4.5 mm. Securely
fasten the NI ISM-7400 to a smooth, flat metal surface to conduct heat away from the motor. To
prevent overheating, forced airflow from a fan may be required. Refer to the Heating section for
more information.
Caution Never use your NI ISM-7400 in a space where there is no airflow or where
other devices cause the surrounding air to be higher than 40 °C.
Caution Never put the NI ISM-7400 where it can get wet or where metal or other
electrically conductive particles can contact the circuitry.
Caution Always provide air flow around the drive. When mounting multiple NI
ISM-7400 integrated steppers near each other, maintain at least one half inch of space
between devices.
Connecting the Power Supply
Refer to Choosing a Power Supply for more information.
1. Use 0.65 mm diameter (22 AWG) stranded wire for connections.
2. Connect the power supply positive (+) terminal to the connector terminal labeled V+.
3. Connect power supply negative (-) terminal to the connector terminal labeled V-.
1 Status LED
2 DIP Switches (current, idle current, steps/rev, load inertia)
3 Power and I/O Connector
4 Mounting Holes (x4)
1
2
3
4

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The NI ISM-7400 contains an internal fuse that connects to the power supply positive (+)
terminal. This fuse is not user-replaceable. If you want to install a user-replaceable fuse in your
system, install a fast acting 2 A fuse in line with the positive (+) power supply lead. Figure 3
shows the NI ISM-7400 connections.
Figure 3. NI ISM-7400 Connector
Caution Do not reverse the wires. Reverse connection will damage your drive and
void your warranty.
When you rapidly decelerate a load from a high speed, much of the kinetic energy of that load
transfers back to the power supply. This transfer can trigger the overvoltage protection of a
switching power supply, causing it to shut down. Unregulated power supplies generally do not
have overvoltage protection and have large capacitors for storing energy coming back from the
drive. NI offers the SMD-7700 regeneration clamp, part number 748908-01, to solve this
problem.
Choosing a Power Supply
NI offers two power supplies for the NI ISM-7400:
• NI PS-12 (24 V, 6.3 A)
• NI PS-13 (48 V, 6.7 A)
Voltage
Your motor can provide more torque at higher speeds if you use a higher power supply voltage.
Refer to the speed-torque curves for more information.
Note If you choose an unregulated power supply, ensure the no-load voltage of the
supply does not exceed 50 VDC.

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Current
The following charts list the maximum current required for each motor at several common
power supply voltages.

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Regeneration
If you plan to use a regulated power supply you may encounter a problem with regeneration. If
you rapidly decelerate a load from a high speed, much of the kinetic energy of that load is
transferred back to the power supply. This can trip the overvoltage protection of a switching
power supply, causing it to shut down. Unregulated power supplies are better suited for
applications with significant regeneration as they generally do not have overvoltage protection
and have large capacitors for storing energy coming back from the drive. Refer to Connecting
the Power Supply for more information.
Connecting Input Signals
The NI ISM-7400 has three inputs:
•STEP—High-speed digital input for step pulse commands, 5 V to 24 V logic
•DIR—High-speed digital input for the direction signal, 5 V to 24 V logic
•EN—5 V to 24 V input for commanding the removal of power from the motor
Note To convert STEP and DIR inputs to STEP CW and STEP CCW, move switch
#8 to the ON position. Refer to Step Pulse Type for more information.

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Figure 4. Connector Pin Diagram
Figure 5. Internal Circuit Diagram

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Figure 6. Mating Cable Diagram
Connection Examples: STEP & DIR
Figure 7. Connecting to Indexer with Sourcing Outputs
Figure 8. Connecting to Indexer with Sinking Outputs

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Figure 9. Connecting to Indexer with Differential Outputs
Connection Examples: EN
Connecting the Enable input as shown in Figure 10 causes the drive to disable when the relay is
closed and enable when the relay is open.
Figure 10. Connecting an Input to a Switch or Relay
Connecting the Enable signal as shown in Figures 11 and 12 causes the drive to disable when the
proximity sensor activates.
Figure 11. Connecting an NPN Type Proximity Sensor to an input
Figure 12. Connecting a PNP Type Proximity Sensor to an input

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Connecting the Digital Output
The NI ISM-7400 has a digital output labeled OUT. This output closes to signal a fault condition.
Figure 13. Internal Circuit Diagram
Use this output to drive LEDs, relays, and the inputs of other electronic devices like PLCs. The
positive collector and negative emitter terminals of the output transistor are available at the
connector. This allows you to configure the output for current sourcing or sinking.
Diagrams of each type of connection follow.
Caution Do not connect the output to more than 30 VDC. The current through the
output terminal must not exceed 80 mA
Figure 14. Sinking Output
Figure 15. Sourcing Output

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Figure 16. Driving a Relay
Using the Optional Encoder
There are three versions of the NI ISM-7400: the NI ISM-7400 has a single shaft, the
ISM-7400D has a dual shaft, and the ISM-7400E has a dual shaft with a 1000-line, incremental
encoder assembled to the rear shaft of the unit. The A, B, and Index (Z) channel signals of this
encoder can be connected to the external controller for position verification and enhanced
performance. To facilitate connecting the encoder signals to your external controller, you should
purchase cable part number 748995-01.
Note Maximum noise immunity is achieved when the differential receiver is
terminated with a 110 Ωresistor in series with a 0.0047 μF capacitor placed across
each differential pair. The capacitor simply conserves power; otherwise power
consumption would increase by approximately 20 mA per pair, or 60 mA for 3 pairs.
Note If making your own cable to connect the encoder signals to your controller,
NI recommends using a shielded cable with four or five twisted pairs for improved
noise immunity.
Figure 17. NI ISM-7400 Encoder Connector

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Configuring the NI ISM-7400
Setting the Current
Set the current to 100% to achieve maximum torque. However, under some conditions you
might want to reduce the current to save power or lower motor temperature. This is important if
the motor is not mounted to a surface that will help it conduct heat away or if you expect the
ambient temperature to be high.
Step motors produce torque in direct proportion to current, but the amount of heat generated is
roughly proportional to the square of the current. If you operate the motor at 90% of rated
current, you will get 90% of the rated torque and approximately 81% as much heat. At 70%
current, the torque is reduced to 70% and the heating to about 50%.
Switches 1 and 2 on the front of the NI ISM-7400 control the percent of rated current that will
be applied to the motor. Set them according to the illustration below.
Figure 18. Configuring Current on Switches 1 and 2
Setting Idle Current
You can also reduce motor heating and power consumption by lowering the motor current when
it is not moving. The NI ISM-7400 automatically lowers the motor current when it is idle to
either 50% or 90% of the running current. The 50% idle current setting lowers the holding torque
to 50%, which is enough to prevent the load from moving in most applications. This reduces
motor heating by 75%. Some applications, such as those supporting a vertical load, require a
high holding torque. In such cases, set the idle current to 90% as shown in the following figure.
Figure 19. Configuring Idle Current on Switch 3

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Load Inertia
The NI ISM-7400 includes anti-resonance and electronic damping features which improve
motor performance. To perform optimally, the drive must understand the electromechanical
characteristics of the motor and load. Most of this is completed automatically in the factory
during motor and drive assembly. To further enhance performance, you must set a switch to
indicate the approximate inertia ratio of the load and motor. The ranges are 0 to 4X and 5 to 10X.
Divide your load inertia by the NI ISM-7400 rotor inertia (82 g-cm2) to determine the ratio, then
set switch 7 accordingly, as shown below.
Figure 20. Configuring Load Inertia on Switch 7
Step Size
The NI ISM-7400 requires a source of step pulses to command motion. This may be a PLC, an
indexer, a motion controller, or another type of device. The device must be able to produce step
pulses with a frequency proportional to the desired motor speed. The source must also be able
to smoothly ramp the step speed up and down to produce smooth motor acceleration and
deceleration.
Smaller step sizes result in smoother motion and more precise speed, but also require a higher
step pulse frequency to achieve maximum speed. The smallest step size is 1/25,600th of a motor
turn. To command a motor speed of 50 revolutions per second (3000 rpm), the step pulses
frequency must be 50 × 25,000 = 1.25 MHz. Sixteen different step size settings are provided, as
shown in Figure 21.

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Select the steps per revolution setting that best suits your system capabilities.
Figure 21. Configuring Step Size on Switches 1, 2, 3, and 4

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At lower step resolutions such as 200 steps per revolution (full step) and 400 steps per revolution
(half step) motors produce more audible noise than when they are microstepped (2000 steps per
revolution and beyond). The NI ISM-7400 includes a feature called microstep emulation, also
called step smoothing, that can provide smooth motion when using full and half steps. Set switch
6 to the ON position, as shown in the figure below, to provide the smoothest possible motion
when using full and half steps.
Figure 22. Configuring Step Smoothing on Switch 6
The step smoothing process uses a command filter which causes a slight delay, or lag in the
motion. The following graph shows an example of the delay that can occur from using the step
smoothing filter.
Figure 23. Delay Due to Filtering

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Step Pulse Type
Most indexers and motion controllers provide motion commands in the Step and Direction
format. The Step signal pulses once for each motor step and the direction signal commands
direction. However, a few PLCs use a different type of command signal where one signal pulses
once for each desired step in the clockwise direction (STEP CW), while a second signal pulses
for counterclockwise motion (STEP CCW). Set switch 8 as shown in the following figure to
allow the NI ISM-7400 to accept this type of signal. In STEP CW/STEP CCW mode, connect
the CW signal to the STEP input and connect the CCW signal to the DIR input.
Figure 24. Configuring Step Pulse Type on Switch 8
Step Pulse Noise Filter
Electrical noise can negatively affect the STEP signal by causing the drive to interpret one step
pulse as two or more pulses. This results in extra motion and inaccurate motor and load
positioning. To solve this problem, the NI ISM-7400 includes a digital noise filter on the STEP
and DIR inputs. The default factory setting of this filter is 150 kHz, which is suitable for most
applications. This is set by moving switch 5 to the ON position.
Note If you are operating the NI ISM-7400 at a high number of steps per revolution
in combination with high motor speeds, you may be commanding the drive at step
rates above 150 kHz. In such cases, you should set switch 5 to the OFF position as
shown below.
Figure 25. Configuring Step Noise Filter on Switch 5

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Your maximum pulse rate equals the highest motor speed multiplied by the number of steps per
revolution. For example:
Consider the maximum pulse rate when deciding whether you must increase the filter frequency.
Self Test
If you are having trouble getting your motor to turn, you may want to try the built-in self test.
Anytime switch 4 is moved to the ON position, the drive will automatically rotate the motor back
and forth, two and a half turns in each direction. This feature can be used to confirm that the
motor is correctly wired, selected, and otherwise operational
Figure 26. Configuring Self Test on Switch 4
40 revs
ondsec
------------------20 000steps
revs
-------------,× 800kHz=

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Reference Materials
Torque-Speed Curves
Figure 27. Torque Curve for NI ISM-7400
Heating
Step motors convert electrical power from the driver into mechanical power to move a load.
Because step motors are not perfectly efficient, some of the electrical power turns into heat on
its way through the motor. This heating is not so much dependent on the load being driven but
rather the motor speed and power supply voltage. There are certain combinations of speed and
voltage at which a motor cannot be continuously operated without damage.
The drive electronics of the NI ISM-7400 also dissipate power. The heat produced by the
electronics is dependent on power supply voltage and motor speed.
The following figure show the maximum duty cycle versus speed for each motor at commonly
used power supply voltages. Refer to these curves when planning your application. Charts
depicting typical power dissipation are also provided for use in planning the thermal design of
your application.
A step motor typically reaches maximum temperature after 30 to 45 min of operation. Running
the motor for one minute and then idling for one minute results in a 50% duty cycle. Running
the motor for five minutes on and five minutes off also results in 50% duty. One hour on and one
hour off results in 100% duty because the motor will reach full and possibly excessive
temperature during the first hour of use.

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Note National Instruments tested the NI ISM-7400 in a 40 °C (104 °F)
environment with the motor mounted to an aluminum plate sized to provide a surface
area consistent with the motor power dissipation. Your results might vary.
Maximum Duty Cycle
Figure 28. Duty Cycle for the ISM-7400
Power Consumption
Figure 29. Power Consumption for the NI ISM-7400

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Power Dissipation
Figure 30. Power Dissipation for the NI ISM-7400