Rockwell Automation 1771-QA User Manual
Allen-Bradley
Stepper
Positioning
User
Assembly
(Cat. No. 1771–QA)
Manual
Important User
Information
Because of the variety of uses for the products described in this
publication, those responsible for the application and use of this control
equipment must satisfy themselves that all necessary steps have been taken
to assure that each application and use meets all performance and safety
requirements, including any applicable laws, regulations, codes
and standards.
The illustrations, charts, sample programs and layout examples shown in
this guide are intended solely for example. Since there are many variables
and requirements associated with any particular installation, Allen-Bradley
does not assume responsibility or liability (to include intellectual property
liability) for actual use based upon the examples shown in this publication.
Allen-Bradley publication SGI–1.1, “Safety Guidelines For The
Application, Installation and Maintenance of Solid State Control”
(available from your local Allen-Bradley office) describes some important
differences between solid-state equipment and electromechanical devices
which should be taken into consideration when applying products such as
those described in this publication.
Reproduction of the contents of this copyrighted publication, in whole or
in part, without written permission of Allen–Bradley Company, Inc.
is prohibited.
Throughout this manual we make notes to alert you to possible injury to
people or damage to equipment under specific circumstances.
ATTENTION: Identifies information about practices or
circumstances that can lead to personal injury or death, property
damage or economic loss.
Attention helps you:
Identify a hazard.
Avoid the hazard.
Recognize the consequences.
Important: Identifies information that is especially important for
successful application and understanding of the product.
Important: We recommend you frequently backup your application
programs on appropriate storage medium to avoid possible data loss.
Table of Contents
Introduction
Assembly and Installation
Chapter 1
Description 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Understand Compliance to European Union Directives 1–2. . . . . . . . . .
EMC Directive 1–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Voltage Directive 1–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2
General 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input Considerations 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Supply Considerations 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Power Supply 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Auxiliary Power Supply 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stepper Translator and Power Supply 2–3. . . . . . . . . . . . . . . . . . . .
Stepper Motor 2–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulse Output Expander Module 2–3. . . . . . . . . . . . . . . . . . . . . . . . . . .
Module Disassembly 2–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Format (S1) 2–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input Logic (S2) 2–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Expander Module Address (S3) 2–6. . . . . . . . . . . . . . . . . . . . . . . .
Expander Module Output (S4, S5, S6) 2–7. . . . . . . . . . . . . . . . . . . .
Diagnostic Indicators 2–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stepper Controller Indicators 2–8. . . . . . . . . . . . . . . . . . . . . . . . . .
Expander Module Indicators 2–9. . . . . . . . . . . . . . . . . . . . . . . . . . .
Installation 2–9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System Grounding Considerations 2–10. . . . . . . . . . . . . . . . . . . . . .
Cable Considerations 2–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shield Connection 2–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Module Keying 2–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Compatibility 2–1 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Module Specifications 2–11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programming and
Operation
Chapter 3
General 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Positioning Concepts 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Move Definition 3–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Moveset 3–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Positioning Modes 3–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Single-Step Mode 3–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jog 3–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous Mode 3–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Synchronization of Axes 3–5. . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Table of Contentsii
Independent Mode 3–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Block Concepts 3–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Moveset Block 3–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Moveset Control Word 3–9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Offset Word 3–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preset Word 3–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Initialization Preset 3–15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Move Preset 3–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Move Block 3–17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Single Move Control Word 3–17. . . . . . . . . . . . . . . . . . . . . . . . . .
Move Data 3–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ramp Time 3–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Final Rate 3–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Decel 3–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Position 3–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Status Block 3–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Status Word 3–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Status Bits 3–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Position Words 3–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Block Transfer Programming 3–25. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Block Transfer Overview 3–25. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bidirectional Block Transfer 3–25. . . . . . . . . . . . . . . . . . . . . . . . .
Data Address and Module Address 3–25. . . . . . . . . . . . . . . . . . . .
Block Length 3–27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Multiple Writes of Different Block Lengths to One Module 3–27. . . .
File Addresses 3–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Enable and Done bits 3–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Example Instructions 3–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programming Considerations 3–30. . . . . . . . . . . . . . . . . . . . . . . . . .
Programming Strategy 3–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Block Length 3–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programming Commands 3–32. . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Table Sizing Considerations 3–33. . . . . . . . . . . . . . . . . . . . . . .
Data Table Documentation Forms 3–34. . . . . . . . . . . . . . . . . . . . .
Data Table Expansion 3–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Handshaking 3–35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Block Transfer Timing 3–37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLC-2/30 (PLC-2/20) Remote System 3–38. . . . . . . . . . . . . . . . . .
PLC-2/30 Local System 3–40. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mini-PLC-2/15 Controller 3–42. . . . . . . . . . . . . . . . . . . . . . . . . . .
Application Considerations 3–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Move Duration 3–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reversing Direction During a Continuous Sequence 3–48. . . . . . . . . .
Decel and Position Considerations for a 0Hz Rate Move 3–49. . . . . . .
Override Ramp Time Considerations 3–51. . . . . . . . . . . . . . . . . . . . .
Stepper Motor Acceleration Considerations 3–54. . . . . . . . . . . . . . . .
Publication 1771-UM002A–EN–P– May 2000
Table of Contents iii
Resonant Frequency 3–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accuracy of Ramp and Decel Times 3–55. . . . . . . . . . . . . . . . . . . . .
Minimum Move Time 3–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Example Programs
Troubleshooting
Specifications
Chapter 4
General 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-Axis Program 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programming a 1-Axis Profile 4–2. . . . . . . . . . . . . . . . . . . . . . . . . .
Preset and Jog Data 4–9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Move Data 4–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ladder Diagram 1-Axis Program 4–1 1. . . . . . . . . . . . . . . . . . . . . .
Operational Summary 4–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3-Axis Program 4–15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programming a 3-Axis Profile 4–18. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operational Summary 4–39. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 5
General 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Troubleshooting Tables 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Illegal Bit Combinations 5–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Appendix A
Pulse Output Expander Module Specifications (cat. no. 1771-OJ) A–1
Stepper Controller Module Specifications (cat. no. 1771-M1) A–2. . . .
CSA Hazardous Location
Approval
Appendix B
CSA Hazardous Location Approval B–1. . . . . . . . . . . . . . . . . . . . . . . .
Publication 1771-UM002A–EN–P– May 2000
Table of Contentsiv
Publication 1771-UM002A–EN–P– May 2000
Chapter
1
Description
Processor
PC
Bi–Directional
Block Transfer
The Stepper Motor Positioning Assembly (cat. no. 1771-QA) allows
programmable control of stepper motors by Allen-Bradley
programmable controllers. Data and commands set to the stepper
positioning assembly are converted to a pulse output for a
user-supplied stepper motor translator which in turn provides the
proper voltage and current to the stepper motor to produce the
desired motion. The stepper motor positioning assembly consists of:
• 1 Stepper Controller Module (cat. no. 1771-M1)
• 1 Pulse Output Expander Module (cat. no. 1771-OJ)
• 1 Field Wiring Arm (cat. no. 1771-WB)
One stepper controller module can control up to three pulse output
expander modules. The system can be expanded modularly from
one to three axes per I/O chassis by placing from one to three output
expander modules in the chassis (Figure 1.1). The pulse output
expander modules can be located in any slot except the left-most slot
and in any order in the I/O chassis.
Figure 1.1
Typical System Block Diagram
1771 I/O Rack
1771–OJ 1771–OJ 1771–OJ
1771–M1
Stepper
Controller
Module
Backplane
Communications
Pulse
Output
Expander
#3
Pulse
Output
Expander
#2
Pulse
Output
Expander
#1
Move
Data
Axis #1
Move
Data
Axis #2
Move
Data
Axis #3
Status
Data
Axis #1
Axis #2
Axis #3
Translator
Translator
Translator
Axis #2
•
Axis #3
Publication 1771-UM002A–EN–P – May 2000
Stepper
Motor
Axis #1
Stepper
Motor
Stepper
Motor
10509
1–2 Introduction
Stepper motor positioning assemblies can be used in applications
requiring more than three axes by using additional I/O chassis. The
stepper assemblies can be distributed throughout the plant using
remote I/O or data highway configurations.
Typically, each axis can control a linear slide although not limited to
that type of mechanical load. The axes can be controlled
independently or control of the axes can be synchronized.
Programming is based on a data block format where blocks of data
can be manipulated using block format instructions such as
file-to-file move and block transfer read and write instructions. The
stepper positioning assembly can be used with any Allen-Bradley
programmable controller that has block transfer capability and an
expandable data table except for Mini-PLC-2 (cat. no. 1772-LN3)
and PLC-2/20 (cat. no. 1772-LP1) Processors.
When using the PLC-2/20, programming will be more lengthy
because data must be transferred using repeated get/put (word)
transfer instructions.
Understand Compliance to
European Union Directives
The number of axes that can be controlled and the complexity of
motion will depend on the memory available for the positioning
program after the data table of the PC processor has been expanded
to store the data blocks.
If this product has the CE mark it is approved for installation within
the European Union and EEA regions. It has been designed and
tested to meet the following directives.
EMC Directive
This product is tested to meet Council Directive 89/336/EEC
Electromagnetic Compatibility (EMC) and the following standards,
in whole or in part, documented in a technical construction file:
• EN 50081-2EMC – Generic Emission Standard,
Part 2 – Industrial Environment
• EN 50082-2EMC – Generic Immunity Standard,
Part 2 – Industrial Environment
This product is intended for use in an industrial environment.
Publication 1771-UM002A–EN–P – May 2000
Low Voltage Directive
This product is tested to meet Council Directive 73/23/EEC
Low Voltage, by applying the safety requirements of EN 61131–2
Programmable Controllers, Part 2 – Equipment Requirements and
Tests.
1–3Introduction
For specific information required by EN 61131-2, see the appropriate
sections in this publication, as well as “Industrial Automation Wiring
and Grounding Guidelines For Noise Immunity,” Allen-Bradley
publication 1770-4.1
Open style devices must be provided with environmental and safety
protection by proper mounting in enclosures designed for specific
application conditions. See NEMA Standards publication 250 and
IEC publication 529, as applicable, for explanations of the degrees of
protection provided by different types of enclosure.
Publication 1771-UM002A–EN–P – May 2000
1–4 Introduction
Publication 1771-UM002A–EN–P – May 2000
Chapter
Assembly and Installation
2
General
Rate
Fwd Dir
Rev Dir
+ DC Input Supply
+ DC Output Supply
Common
Stop Input
Jog Forward Input
Jog Reverse Input
Not Used
Not Used
Not Used
Not Used
Fwd Rate
Rev Rate
The stepper positioning assembly can be wired for 1-axis operation
with a stepper translator and motor as shown in Figure 2.1. One
stepper controller module can control up to three pulse output
expander modules installed in the same chassis. When the
application calls for 2-or 3-axis control, each additional expander
module should be wired as shown in Figure 2.1. No more than one
stepper controller module can operate in an I/O chassis.
Figure 2.1
Typical 1-Axis Connection Diagram
Pulse Output
Expander Module
Field Wiring Arm
1771–WB
1
2
3
4
5
6
7
8
9
10
11
12
Input
NEC Class 2
Power
Supply
+–+–
Rate Pulses/
Directional Signals
Output
NEC Class 2
Power
Supply
Stepper
Translator
and
Power
Supply
Mechanical
Load
Stepper
Motor
10510
Input Considerations
Pulse output expander modules can be controlled manually by the
use of switch inputs for stop, jog forward and jog reverse. The stop
switch will cause output pulses to the corresponding axis to cease
instantaneously. Jog switches are operational only when the
corresponding axis is at rest.
Publication 1771-UM002A–EN–P – May 2000
2–2 Assembly and Installation
Input switch contacts should be compatible with the voltage and
current levels of the input circuits. The pulse output expander
module will accept inputs from open collector logic devices or
grounded switch contacts, and inputs from the Allen-Bradley
Encoder/Counter Module (cat. no. 1771-IJ, -IK). Refer to section
titled “Module Specifications” for additional input specifications.
Power Supply
Considerations
Each module in the I/O chassis including the processor or adapter
module draws power from the I/O (chassis) power supply. Some
modules require an additional power source.
I/O Power Supply
Power is supplied through the I/O chassis backplane from the 5V DC
I/O power supply. The stepper controller draws all of its power
(1.75A, maximum) from the I/O power supply. Each pulse output
expander module requires a current of 0.80A maximum. These
amounts (4.15A maximum for a 3-axis system) should be totalled
with the current requirements of all other modules in the chassis so
as not to exceed the maximum output current of the I/O chassis
power supply.
Auxiliary Power Supply
Pulse output expander modules require an additional power source
for switch inputs to the module and for pulse outputs to the stepper
translator and motor. The power source can be separate input and
output power supplies for one, two or three axes, a combined power
source for each axis, or a combined power source for up to three
axes. The power supply must be NEC Class 2 listed. Each input
switch draws 11mA maximum when closed. The maximum output
current for the pulse output expander module is 100mA. Refer to
Appendix A, Module Specifications” for additional information
concerning the auxiliary power supply requirements.
Publication 1771-UM002A–EN–P – May 2000
The supply voltage can be any value chosen from 5V DC to 30V DC
required by the user-selected stepper translator and/or the switch
input circuits. The variation in the DC voltage level due to ripple
should not exceed the input specification for the stepper translator
because the supply voltage ripple appears at the output terminals of
the pulse output expander module. Power supplies with 15mV
peak-to-peak ripple can be used. However, check the translator input
specification to ensure that the power supply specifications meet
translator input requirements. The supply may require input filtering
to guard against electrical noise.
2–3Assembly and Installation
Stepper Translator and Power Supply
The stepper translator and power supply convert digital information
from the pulse output expander module into the proper voltage and
current for the precise control of a stepper motor. For compatibility
with the pulse output expander module, the translator must accept
low true logic. The programmed maximum pulse rate from the pulse
output expander module to the translator can be any value up to
20,000 pulses per second.
Stepper Motor
The stepper motor converts electrical pulses into mechanical
movements. The motor shaft rotates through a specific angular
rotation for each pulse. The movement is repeated precisely with
each pulse and the shaft rotates in fixed, repeatable increments.
When a threaded shaft is used to drive a linear slide, the velocity,
distance and direction of the slide can be precisely controlled.
Pulse Output Expander
Module
The stepper motor, stepper translator and translator power supply
should be grounded to guard against electrical noise interference in
accordance with the manufacturer’s specifications and guidelines.
Improper grounding can result in unwanted extra pulses occurring at
the stepper translator and/or stepper motor.
Prior to installation, a pulse output expander module must be
configured to correctly interface with the corresponding stepper
translator.
Adjustments are made using six switch assemblies. The functions of
the switches are summarized in Table 2.A and described in
subsequent paragraphs.
Module Disassembly
The switch assemblies are located on the module printed circuit
board. They are accessed as follows:
1. Remove the four screws from the upper and lower edges of the
labeled cover.
2. Remove the printed circuit board from the covers and set it
solder-side down.
3. Locate the switch assemblies labeled S1 through S6 as shown in
Figure 2.2.
Publication 1771-UM002A–EN–P – May 2000
2–4 Assembly and Installation
Table 2.A
Summary of Internal Switch Functions
Switch
Assembly Function Description
1 Output Format Separate forward and reverse pulse outputs,
or Pulse out, direction output
2 Input Logic low = true or
high = true
3 Expander Module
Address
Each expander module must have a different
binary address, either 1, 2 ,or 3.
4, 5, 6 Module Output Push-Pull or Current Source (open emitter), or
Current Sink (open collector).
Figure 2.2
Location of Dip Switch Assemblies
S1
S2
Publication 1771-UM002A–EN–P – May 2000
S3
S4 S5 S6
OFF
OFF
OFF
ON
ON
ON
10511
2–5Assembly and Installation
4. Set the switches as described in the following sections. Some
switches are labeled on/off. Others may be labeled open for the
off position.
5. Reassemble the module. Start all four screws before tightening to
facilitate alignment of the covers and printed circuit board.
Output Format (S1)
The output format that determines forward or reverse motion differs
between translators. Therefore, the output terminals of the pulse
expander module are user-selectable to match the required pulse
input configuration of the translator. There are two basic translator
input configurations.
Some translators are designed to receive a pulse train at either one of
two terminals, depending on the direction of rotation desired in the
stepping motor. With this type of translator, a pulse train sent from
the pulse output expander module to one of the translator terminals
causes the stepping motor to rotate in the forward direction. An
identical pulse train sent from the module to the other translator
terminal causes the stepping motor to rotate in the reverse direction.
Output terminals on the pulse output expander module can be
selected in accordance with Table 2.B.
Table 2.B
Output Format (S1)
Switch Assembly S1
Switch 1 Switch 2
either ON
or OFF
OFF ON 10
ON ON 10
Note: Low = true logic
OFF 10
Output
Terminal
11
12
11
12
11
12
Active Output
Configurations &
Logic Levels
High
Forward Pulse train
Reverse Pulse train
Pulse train
Low High
(Forward) (Reverse)
High Low
Pulse train
Low High
(Forward) (Reverse)
High Low
Logic
Level
When
Stopped
High
High
High
High
Last State
Last State
High
High
High
Publication 1771-UM002A–EN–P – May 2000
2–6 Assembly and Installation
Other translators are designed to receive only one pulse train at a
single “pulse” terminal. These translators usually have a separate
terminal for direction information. If a high (or low) signal is sent to
the “direction” terminal, the stepping motor rotates in the reverse
direction. If a low (or high) signal is sent to this terminal, the
stepping motor rotates in the forward direction. The rate of rotation
(in either direction) is controlled by the pulse train at the “pulse”
terminal.
The status of the pulse output expander module’s outputs when
motion has stopped is also user-selectable.
The settings of switch assembly S1 for the output format are
summarized in Table 2.B.
Input Logic (S2)
The choice of low true or high true logic for manual control of the
pulse output expander module’s hardware inputs is user-selectable.
The S2 switch assembly settings are summarized in Table 2.C.
Table 2.C
Input Logic (S2)
Switch
Number Motion Control Input Logic
1 STOP OFF = High true
ON = Low true
2 JOG
FORWARD
3 JOG
REVERSE
OFF = High true
ON = Low true
OFF = High true
ON = Low true
Expander Module Address (S3)
Each pulse output expander module must have its own (binary)
address for communication with the stepper controller module.
Allowable addresses are 1 (001), 2 (010) or 3 (011). They can be set
using switches 1 and 2. Switch 3 is always off. No other
combinations of the S3 switch assembly settings are valid. Refer to
Table 2.D.
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2–7Assembly and Installation
Table 2.D
Expander Module Address (S3)
Switch Assembly S3 Expander
Switch 1 Switch 2 Switch 3 Address
ON OFF OFF 1
OFF ON OFF 2
ON ON OFF 3
Expander Module Output (S4, S5, S6)
The choice of pulse output expander module output, either push-pull,
current source (open emitter) or current sink (open collector), is
user-selectable to best match the input characteristics of the stepper
translator.
PUSH-PULL-OPEN The push-pull output is compatible with many
stepper translators. The expander module output is wired to the
translator input as shown in Figure 2.1.
3
10
11
12
Expander Module
Common
Direction
CURRENT SOURCE or CURRENT SINK-OPEN When using the
expander module as a current source or sink for the output pulses, it
may be necessary to use a pull-down or pull-up resistor, respectively
(Figure 2.3) Refer to the translator input specifications and
installation instructions for correct use of this resistor if it is required.
Figure 2.3
Output Source or Sink Connections
+Supply
Pull–Up
Resistors
(Current Sink)
or
Pull–Down
Resistors
(Current Source)
–Supply
Translator
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The positive (+) and negative (-) terminals of the output power
supply must be connected to the + DC OUTPUT SUPPLY and
COMMON terminals, respectively, of the module field wiring arm
regardless of the choice of module output.
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2–8 Assembly and Installation
ATTENTION: Avoid shorting any of the output
terminals to ground, to the common terminal, or to the
!
positive (+) terminal of a power supply. Damage to the
module could occur.
The settings of switch assemblies S4, S5 and S6 for the desired
module output are summarized in Table 2.E.
Set all switch positions in assemblies S4, S5 and S6 to the same
output configuration.
Table 2.E
Expander Module Output (S4, S5, S6)
Diagnostic Indicators
Switch
Assembly
S6
S5
S4 ON
Set all switch positions in assemblies S6, S5, and S4 to the same output configuration.
Switch 1Switch2Output
ON
OFF
ON
ON
OFF
ON
OFF
ON
OFF
ON
ON
OFF
ON
ON
OFF
ON
ON
Terminal Module Output
10
11
12 Current Source (Open Emitter)
Current Source (Open Emitter)
Current Sink (Open Collector)
Push-Pull
Current Source (Open Emitter)
Current Sink (Open Collector)
Push-Pull
Current Sink (Open Collector)
Push-Pull
The stepper controller and pulse output expander modules have LED
indicators. Their color and function are described in the following
paragraphs.
Stepper Controller Indicators
Publication 1771-UM002A–EN–P – May 2000
Three LED indicators are located on the upper front panel of the
stepper controller module. They perform the following functions.
• PC COMMUNICATIONS FAULT (Red)
This indicator is normally off. If a communications fault between
the stepper controller module and the PC processor is detected, or
a stepper controller module hardware fault is detected, this
indicator will illuminate.
• EXPANDER COMMUNICATIONS FAULT (Red)
This indicator is normally off. If a communications fault between
the stepper controller module and any one of the pulse output
expander modules is detected, or a hardware fault in any one of
the pulse output expander modules is detected, this indicator will
illuminate.
Important: If both red indicators illuminate simultaneously at
power-up, the stepper controller module has a hardware
fault.
• ACTIVE (Green)
This indicator illuminates unless a hardware fault on the stepper
controller module is detected causing it to turn off. At power-up
this LED will not illuminate until the PC processor is in run
mode. This indicator will flash on/off if, after power-up, an
invalid expander address is detected, no expander module is
present and/or another stepper controller module is detected in the
same I/O rack.
2–9Assembly and Installation
Expander Module Indicators
Five LED indicators are located on the upper front panel of the pulse
output expander module (Figure 2.4). They perform the following
functions:
• MODULE FAULT (Red)
This LED is normally off. If an expander module hardware fault
is detected, it will illuminate.
• OUTPUT PULSE RATE (Green)
This LED is normally on or flashing at the output pulse rate
whenever an output is present.
• STOP INPUT (Orange)
This LED illuminates when a hardware stop input is asserted.
• JOG FORWARD (Orange)
This LED illuminates when a hardware jog forward input is
asserted.
• JOG REVERSE (Orange)
This LED illuminates when a hardware jog reverse input is
asserted.
Installation
The stepper positioning system is susceptible to electrical noise
unless the equipment is properly grounded, the cabling is properly
shielded and the power supply(ies) is properly filtered. If not, an
incorrect number of position pulses could result.
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2–10 Assembly and Installation
System Grounding Considerations
The following should be connected to earth ground:
• Ground prong of all AC line cords
• Negative (-) or common terminal of the I/O power supply(ies)
• One I/O chassis mounting stud
Ground the drain wire of the cable connecting the pulse output
expander module to the stepper translator. This cable should be
grounded either at the translator or at the I/O chassis, but not both.
See Shield Connection below.
The stepper translator, power supply and motor should be grounded
in accordance with the manufacturer’s instructions.
ATTENTION: Improper system grounding can result
in additional unwanted pulses occurring at the stepper
!
translator and/or stepper motor. Unpredictable
machine motion could occur with possible damage to
equipment and/or injury to personnel.
Cable Considerations
The stepper translator should be wired to the field wiring arm using a
twisted 3-conductor shielded cable (Belden 8771). The cable
distance between the pulse output expander module and the stepper
translator generally should not exceed 40 feet.
Shield Connection
Belden 8771 cable has a foil shield with a bare drain wire. The
shield should be connected to earth ground at one end of the cable
only. This can be at the customer end of the cable or at an I/O
chassis mounting bolt or stud. At the other end of the cable, the
shield should be cut short, bent back and taped to insulate it from any
electrical contact. This practice helps to guard against unwanted
radiated electrical noise and ground current loops.
Module Keying
Plastic keying bands shipped with each I/O chassis provide an easy
method for keying an I/O slot to accept only one type of module. Use
of the keying bands is strongly recommended.
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2–11Assembly and Installation
The module is slotted in two places on its rear edge. The position of
the keying bands on the backplane connector must correspond to the
slots to allow insertion of the module so that only the desired module
will fit in this slot.
Refer to Figure 2.4. Snap the keying bands on the upper backplane
connectors between these numbers printed on the backplane:
Stepper Controller
2 and 4
8 and 10
Expander Module
8 and 10
22 and 24
Needle-noise pliers can be used to insert or remove keying bands.
Figure 2.4
Keying Diagram
Stepper Expander
Controller Module(s)
Keying
Bands
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
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Compatibility
An I/O chassis that contains a stepper controller module may not
contain another “master” intelligent I/O module.
Module Specifications
The pulse output expander module specifications and stepper
controller module specifications are listed in Appendix A.
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2–12 Assembly and Installation
Publication 1771-UM002A–EN–P – May 2000
Chapter
Programming and Operation
3
General
The desired motion of the stepper motor can be accelerated,
decelerated or maintained at constant rate by controlling the pulse
rate from the pulse output expander module. Motion can be
rotational such as used to position an indexing table, or can be linear
such as obtained when a linear slide is driven forward or backward
by turning a threaded shaft. In either case, the position at any given
moment is defined by the number of pulses sent to the stepper motor.
It can result in some number of degrees of rotation or linear units of
travel.
The motion can be programmed by manipulating data table words
(control blocks) arranged in a convenient format. Blocks of data are
also used to indicate that commands were received and desired
motion was implemented (status block). Control and status blocks
are communicated bidirectionally between the PC processor and
stepper controller module by block transfer programming.
The task of programming requires that control and status block be
assigned in the data table and that control data be entered using the
industrial terminal. Control blocks sent to the stepper controller
module by write block transfers govern acceleration, deceleration,
final rate and final position. Control blocks also contain control
words. Bits in control words must be set according to the particular
application and desired motion.
Positioning Concepts
The stepper controller module sends status blocks of data to the PC
processor using read block transfers. Status blocks contain current
position information and diagnostic bits set by the stepper
positioning assembly.
The format of the data blocks and the function of status and control
bits will be covered later in this chapter.
There are three stepper positioning concepts which should be
understood before learning how the stepper positioning assembly is
programmed. They are:
• Move Definition
• Moveset
• Positioning Modes
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3–2 Programming and Operation
Move Definition
A move in its simplest form consists of an acceleration of the stepper
motor axis, a final rate, a deceleration to zero and a final position
(Figure 3.1). The value for an acceleration is the time required to
achieve a final rate. Values can be chosen from 0-9.99 seconds. The
final rate determines the constant speed of machine motion. The
final rate value can vary from 1 to 20,000 pulses per second. The
decel value, any value from 0-9.99 seconds, is the time required to
decelerate to zero pulses per second from a final rate.
The final position of a move is the number of pulses between 0 and
999,999 to be achieved by the move. The physical location will
depend on the resolution (pulses per degree of rotation or pulses per
inch of travel, etc.) of the stepper translator/motor configuration and
the specific application (gearing threads per inch of the linear axis,
etc.).
Figure 3.1
Move Definition
Rate
Ramp (Accel)
(0-9.99 Sec)
Final Rate
(1–20,000 Pulse/Sec)
Decel
(0-9.99 Sec)
Final Position
0–999,999 Pulses
Position
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Moveset
A moveset refers to the data used to control from 1 to 10 moves.
Sequential moves can be blended to form a continuous move profile
or can be implemented one move at a time where motion stops
between moves. A moveset can be executed using a minimum of
ladder diagram programming.
Publication 1771-UM002A–EN–P – May 2000
Two or more movesets can be implemented sequentially as if they
were a single large moveset. The stepper positioning assembly can
store two movesets simultaneously for up to three axes. When one
moveset is in operation (working moveset), the next moveset is in
storage (storage moveset). In the continuous mode, the last move of
the working moveset is blended with the first move of the storage
moveset.
3–3Programming and Operation
In any mode, when the working moveset is finished, the storage
moveset automatically becomes the next working moveset. Then
another (storage) moveset can be block transferred to the stepper
positioning assembly.
In the continuous and independent modes of operation, the storage
moveset must be received by the stepper controller module before
the third from last move of the working moveset is complete (for
example, move 8 of 10 moves). In the single-step mode, the storage
moveset must be received before the second from last move of the
working moveset is completed. Skipped moves (section titled
“Move Block,” Bit 02) are not counted. The use of multiple
movesets allows long and complex positioning profiles or long
sequences of single moves to be performed with little additional
programming. The moveset is further defined in section titled
“Moveset Block.”
Positioning Modes
The stepper positioning assembly can be programmed for operation
that is tailored to the application requirements. The positioning
modes determine the type of positioning profile and the manner in
which the axes of two or three stepper motors can be coordinated.
The stepper positioning assembly can also be operated manually
using hardware or software jog inputs.
Single-Step Mode
In the single-step mode, a moveset allows the individual moves to be
controlled one at a time. A start command from the PC processor
starts the first move of the sequence. After the move is completed,
the stepper motor axis stops and a done bit is set. In order for the
next move to begin, the PC processor must transfer another start
command to the stepper controller module (Figure 3.2).
Figure 3.2
Single Step Mode
Rate
Final
Rate
Start
Command
Final
Rate
Ramp
Decel
Ramp
Move 1 Move 2 Move 3
Final
Position
Start
Command
Decel
Final
Position
Ramp
Final
Rate
Start
Command
Decel
Time
Final
Position
Done Bit
is set
Note: Jogging between moves causes a system fault..
Done Bit
is set
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Done Bit
is set
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3–4 Programming and Operation
Jog
A jog allows an axis to be manually controlled by an operator
independent of other axes in the system. This can be done at any
time except when a positioning profile is in progress. A jog can be
initiated by a hardware or software input to the stepper positioning
assembly.
Jog data is one move block that controls one axis. The job move
block typically is contained in a separate 1-move (10-word) moveset.
The jog move block can also be contained in a moveset with other
moves. If so, the jog must be the first move of the moveset. The
remaining moves will be ignored as a result of the stepper controller
module processing the jog move block. After the jog has been
executed as needed, the remaining moves can be initiated by again
transferring the same moveset to the stepper controller module. This
time a skip bit must be set in the jog data and the jog load bit must be
cleared. (These bits are described in section titled “Move Block,”
Bit 02 and 03). The positioning profile will then start with move two
and ignore the jog data.
The jog can be initiated by jog forward or jog reverse user-supplied
input switches or by ladder diagram logic. An axis must be at rest
before a jog can be initiated. As long as the jog input is asserted, the
jog will continue at the specified rate.
Once released (off) the jog will decelerate to a zero rate over the time
defined by the decel value programmed in the jog move. If desired,
the final position value can serve as an upper (or lower) limit of jog
travel. The jog will automatically decelerate to reach a zero rate at
the programmed final position if the jog input is held on.
If the final position value of the jog is programmed as zero, the limit
of travel will be 999,999 pulses. If the decel value is programmed as
zero, the jog rate will cease instantly when the jog input is turned off.
ATTENTION: Avoid damage to the stepper motor
and machine by selecting jog final rate and decel
!
values which are compatible with the stepper
motor/machine dynamics.
Publication 1771-UM002A–EN–P – May 2000
Continuous Mode
The continuous mode allows moves of the moveset to be blended
continuously into a move profile with fully programmed
accelerations and decelerations. One start command is required for
the entire positioning profile. A done bit is set at completion. Each
move is defined as having a ramp, a final rate and a final position.
The last move of the profile, in addition to the ramp, final rate and
final position, contains a deceleration to zero (Figure 3.3). The decel
value does not affect the positioning profile in any move except the
last move.
Figure 3.3
Continuous Mode
Rate
3–5Programming and Operation
Final
Rate 3
Decel 3
Done Bit
is set
Start
Command
Final
Rate 2
Final
Rate 1
Ramp 2
Ramp 1
Move 1 Move 2 Move 3
Final
Position 1
Ramp 3
Final
Position 2
Synchronization of Axes
All axes (up to three) can be synchronized move-by-move in the
single-step and independent modes. Each axis must complete a
given move before any axis is allowed to begin the next move.
Coordination is independent of PC processor scan time. If two axes
are synchronized, then the third axis, if used, must also be
synchronized. Synchronized axes must operate in the same
positioning mode.
Position
Final
Position 3
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A start command can be programmed for only one of the
synchronized axes. In the single-step positioning mode, this must be
done for each move of the moveset. Start commands received during
a move will be ignored. Done bits for all axes must be set before a
start command is executed. In the continuous and independent
modes, one start command is required at the beginning of the
synchronized profiles.
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3–6 Programming and Operation
A done bit is set for each axis at completion of each positioning
profile. If all axes (up to three) are not synchronized, then the
control of any axis is completely independent of the other(s). Three
different single-axis machines could be controlled by one stepper
controller module and three pulse output expander modules in one
I/O chassis.
Independent Mode
The independent mode allows a chain of single-step moves to be
sequentially executed. Each move is defined as having a ramp, final
rate, decel (to 0Hz rate) and a final position. Typically there is a
pause of 10-30ms from the end of one move to the beginning of the
next (dwell at 0Hz rate). Refer to Figure 3.4. One start command is
required for the entire positioning profile. A done bit is set at the
completion of each move.
Important: Done bits which are set between moves in the
independent mode should not be used because they
remain set for too short a time. Only the done bit of the
last move should be examined. This can be achieved by
examining the number that identifies the last move
(status bit 10-13) and the done bit in the same rung.
Figure 3.4
Independent Mode
Rate
Final
Rate
Final
Rate
Ramp
Decel
Ramp
Move 1 Move 2 Move 3
Start
Command
1
The done bit remains set until the start of the next move (10msec dwell time, nominal)
1
Decel
Ramp
1
Final
Rate
Decel
Done Bit
is set
Position
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When using the independent mode and the axes are synchronized, all
but the last axis to finish the move in process will stop motion when
finished and wait for the last axis to complete its move. All axes will
then begin the next move simultaneously as soon as the last axis has
finished its move. The process then repeats for each move in the
positioning profile (Figure 3.5).
Figure 3.5
Synchronized Axes (Independent Mode)
Rate
Done Bit
is set
Expander
# 1
1
3–7Programming and Operation
Expander
# 2
Expander
# 3
Rate
Rate
Start
Command
Move 1 Move 2
Done Bit
is set
1
Move 1 Move 2
Done Bit
is set
2
Move 1 Move 2
1
Done bit remains set until start of next move.
Done bit dwell time, 10msec, nominal.
2
Time
Time
Time
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3–8 Programming and Operation
Data Block Concepts
Words that control the motion of the stepper motor axis, record
position or monitor move diagnostics are stored in data table files.
These words are grouped into the following three kinds of data
blocks.
• Moveset Block
• Move Block
• Status Block
In addition to move data, the blocks contain special control or status
words. The bits in these words affect how the motion is controlled
or verify that the move commands and the move data were received
and implemented.
Moveset Block
The moveset block is a data table file for storing data and controlling
the motion of one stepper motor axis. It allows move data to be
stored in consecutive data table words to control up to 10 moves of a
positioning profile. Each axis must have at least one moveset block.
A moveset block must contain the following move data (Figure 3.6).
64–Word Moveset Block in
Data Table
Moveset Control Word
Offset word
MS Preset Word
LS Preset Word
Move Block # 1
Move Block # 2
Move Block # 3
• Moveset Control Word
• Offset and Preset Words
• One or more Moves
Figure 3.6
Moveset Block and Positioning Profile
1
The 64-word moveset block may
contain from 1 to 10 move blocks. If using less than
Rate
10 move blocks, fill all unused words with zeros or
a programming error results.
Move # 1 Interim Moves Move # 10
1
Position
Move Block # 9
Move Block # 10
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1
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