One Controller - Any Bus
Connecting Programmable Automation
Controllers ,Measurements, Sensors, Networks
and PLCs
Ian Bell
National Instruments
Agenda
• Industrial Communications Overview
• Why Connect a PAC to Industrial Networks and
PLCs?
• 3 Methods to Connect to Any PLC or Device
Basic Analogue and Digital I/O
 Industrial Network Communication
 OPC

2
Industrial Communications Overview
Industrial communications connect
industrial devices such as PLCs, sensors
and actuators
Common Industrial Networks
•DeviceNet
•PROFIBUS
•Modbus TCP
•Modbus Serial
•CANopen
•FOUNDATION fieldbus
•Interbus
•CC-Link
•LonWorks
•HART
•PROFINET
•Ethernet/IP
3
PAC Architecture
Software Capabilities
• Ruggedness and reliability of PLC
• Software capabilities of PC
• Modular and diverse I/O
PAC
PC
PLC
Ruggedness and Reliability
4
Why Connect PACs to Industrial Networks
and PLCs?
High-speed analogue measurements
 High-resolution analogue measurements
 Advanced analysis (digital filtering, frequency analysis)
 Custom hardware performance with FPGA technology

• High-speed closed-loop control
• FPGA-based processing and analysis

Custom Sensors/Measurements
5
3 Methods to Connect to Any PLC
Basic I/O
Analogue/Digital
Industrial
Communications
OPC
PACs
PLCs
6
Basic I/O
Cheap, Easy, Fast and Effective
• Available on every platform
• Analog and digital I/O options
• PLC users can easily integrate analogue and
digital I/O into their code
• Allows PACs to act as intelligent devices
7
Basic I/O
• Advantages

Fast, deterministic, little or no software overhead
• Considerations
Doesn’t scale well
 Point-to-point wiring (parallel)
 Can’t communicate lots of data

8
Example
Automated Filling of Aerosol Cans
• Existing PLC system was being used to
automate the filling of aerosol cans
• PLC did not have the capability to do highspeed analogue for pressure measurements
• NI CompactRIO PAC was used for high-speed
pressure measurements on 8 channels (2 k per
channel)
• CompactRIO and PLC were integrated using
digital I/O
9
10
3 Methods to Connect to Any PLC
Basic I/O
Analogue/Digital
Industrial
Communications
OPC
PACs
PLCs
11
Methods for Industrial Communications
Plug-In
Interfaces
Gateways over
Ethernet, Serial
Ethernet/Serial
Performance/Determinism
Versatility
12
Plug-In Communication Boards
•
•
•
•
•
•
CAN and CANopen
DeviceNet
FOUNDATION fieldbus
Serial (RS232, RS422, RS485)
Third-party PROFIBUS (Comsoft)
Support for PXI, PCI, PCMCIA, and
CompactRIO
13
Plug-In
Interfaces
Plug-In Communication Boards
Plug-In
Interfaces
• Advantages
Direct, deterministic communication with the processor
 Timing and synchronisation with other I/O (DAQ)
 High-level API support for LabVIEW and other programming
languages

• Considerations
Many smaller buses and protocols are not supported
 Many only available on PC and PXI (real-time supported)

14
Example : PROFIBUS
• PROFIBUS master/slave for
PXI and PCI
• More than 2 million nodes
• Popular in Europe and Asia
• Recommended: Comsoft DF PROFI II
interfaces
15
cRIO-PBMaster/Slave and cRIO-PBSlave
cRIO PB Master/Slave module

Supports operation as DP Master or DP
Slave

Ships with configuration tool configurator
II for DP Master configuration

Ships with GSD file to configure any DP
Master system
cRIO PB Slave module

Supports operation as DP Slave

Ships with GSD file to configure any DP
Master system
16
Ethernet-based Industrial Protocols
•
•
•
•
Modbus TCP/IP
Ethernet/IP
EtherCAT
Profinet
17
Why Ethernet: Protocols
Modbus
Modbus TCP/IP
DeviceNet
EtherNet/IP
CanOPEN
EtherCAT
PROFIBUS
PROFInet
Traditional Industrial
Protocols
Ethernet Physical
Layer
18
Modbus TCP/IP Overview
•
First industrial protocol on Ethernet (introduced 1999)


Based on Modbus developed by Modicon in 1979
Widely adopted and open Ethernet standard
• Advantages


Uses standard Ethernet (hardware and TCP/IP transport
layer)
Open and relatively simple
• Disadvantages


Not a hard real-time protocol
Does not deliver determinism
19
Ethernet-based Industrial Protocols
•
•
•
•
Modbus TCP/IP
Ethernet/IP
EtherCAT
Profinet
20
EtherNet/IP Overview
• Dominant bus for Rockwell Automation
Managed by Open Device Vendors Association (ODVA)
 Extends DeviceNET concepts to Ethernet

• Advantages

Uses Ethernet transport layer (TCP and UDP)
• Disadvantages

Can overload networks with UDP messages if not correctly
configured, recommend managed switches with IGMP
snooping
21
Ethernet/IP Terminology
Explicit Messages
• TCP/IP
• Used to set parameters and initiate
implicit communication
Implicit Messages
• UDP/IP multicast
• Used to communicate I/O data
• Normally set-up for cyclical updates
22
Communication from NI PAC to
ControlLogix and ComapctLogix PLCs
Ethernet/IP
Uses explicit messaging
Available for download from NI Labs
23
Gateways over
Ethernet, Serial
Third-Party Gateways
• Wide variety of communication buses and
protocols supported
• Ethernet or serial-based
• Perfect for non-PXI, PCI, and PCMCIA systems
PROFIBUS
DeviceNet
EthernetIP
ControlNet
Ethernet
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Example
Adding Vision for Food Processing Optimisation
• Needed NI Compact Vision System to calculate the
mass/volume of the food item coming through on the
conveyor belt
• Ethernet/IP connectivity was a requirement
Modbus TCP
EthernetIP
27
3 Methods to Connect LabVIEW to Any PLC
Basic I/O
Analogue/Digital
Industrial
Communications
OPC
NI PACs
PLCs
28
What Is OPC?
• Universal language for
reading and writing
data
• OPC Client: Read
and write to OPC
• OPC Server:
Translates between
OPC and devicespecific protocols
Windows PC
English
English
Speaker:
Speaker:
“Hello!”
“Hello!”
English
Spanish
Translator
Spanish
Speaker
German
Translator
German
Speaker
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French
Translator
French
Speaker
OPC Client
Windows PC
PLCs
Ethernet/IP
Allen-Bradley
OPC Server
PROFINET
Siemens
OPC Server
CCLink
Mitsubishi
OPC Server
OPC
Driver
Device-Specific
OPC Server
OPC
Client
OPC Client
30
NI OPC Servers for Third-Party PLCs
• OPC support for more than 100 PLCs
• Connects with LabVIEW DSC OPC client

Evaluation version included with DSC
• Servers included for:
•Allen-Bradley
•AutomationDirect
•Cutler-Hammer
•GE
•Hilscher
•Modbus
•Omron
•Philips
•Siemens
•Toshiba
•WAGO
•Yaskawa
•Yokogawa
•…and more!
• ni.com/opc
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OPC
• Advantages
Most universal
 Least device-dependent
 Ideal for HMI and SCADA applications

• Considerations
Slower, not deterministic, single-point only
 Can require PC-based OPC servers
 Not for safety or critical communications

32
ABCO Adds LabVIEW to PLC System
“The ease by which NI can speak to the
• ABS brake testing system
Allen-Bradley hardware saved me
valuable time on this delivery-critical
• PXI for high-speed encoder job.”
-Arif Bustani, electrical engineer ABCO
measurements
• Added to existing Allen-Bradley PLC
assembly line
• OPC used for communication
between PXI and Allen-Bradley PLCs
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Summary
• PACs add flexibility to connect to anything
• Use PACs to add any measurements to existing
system
• 3 Methods to Connect PAC to Any PLC:
Basic Analogue and Digital I/O
 Native Industrial Communications
 OPC

34
Online Resources
ni.com/comm
ni.com/pac
ni.com/labs
www.modbus.org – Modbus TCP/IP
www.odva.org – Ethernet/IP
www.ethercat.org – EtherCAT
www.profibus.com/pn - PROFINET
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