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Chapter 9

Chapter 9. Putting Together a Modular PLC. Objectives. Define rack, chassis, and baseplate and tell how or why they differ. Select the proper type of I/O to interface a specific input signal. Explain why power supply loading must be determined as a PLC system is configured.

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Chapter 9

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  1. Chapter 9 Putting Together a Modular PLC

  2. Objectives • Define rack, chassis, and baseplate and tell how or why they differ. • Select the proper type of I/O to interface a specific input signal. • Explain why power supply loading must be determined as a PLC system is configured.

  3. PLCs Come in Two Styles • The I/O of a fixed PLC is built in and not changeable. • A modular PLC consists of user-selected I/O modules, a processor, a power supply, and a chassis.

  4. Rack, Chassis, or Baseplate? • Depending on the modular PLC manufacturer, the term used to identify the hardware device that holds all the modules, processor, and power supply may vary. • Some use rack, chassis, or baseplate.

  5. Module Installation into a Four-Slot SLC 500 Chassis (1 of 2) Image courtesy of Allen-Bradley, a Rockwell Automation business

  6. Module Installation into a Four-Slot SLC 500 Chassis (2 of 2) • The General Electric Series 90-30 incorporates the processor into the baseplate for the low-end modular PLCs. • Baseplates come in five-slot and ten-slot models.

  7. Series 90-30 PLC Model 331 CPU Image courtesy of GE Fanuc Automation

  8. Removing a GE Series 90-30 I/O Module Image courtesy of GE Fanuc Automation

  9. Local I/O Expansion • When more I/O is required than a single chassis can hold, additional chassis can be added. • Communications cable connects expansion chassis together. • There is no processor in expansion chassis. • A power supply is required in all chassis. • The expansion cable distance is limited.

  10. SLC 500 3-chassis Local Expansion Image courtesy of Allen-Bradley, a Rockwell Automation business

  11. Remote I/O • Allows greater cable distance between chassis • Typically a serial link • SLC 500 remote I/O maximum cable length 10,000 feet • Baud rate of 57.6 K bits per second

  12. SLC 500 Remote I/O Example (1 of 3) Image courtesy of Allen-Bradley, a Rockwell Automation business

  13. SLC 500 Remote I/O Example (2 of 3) • SLC 500 uses 1747-SN scanner in local chassis. • SN scanner communicates with remote chassis. • 1747-ASB communication module is required in each remote chassis.

  14. SLC 500 Remote I/O Example (3 of 3) • Remote I/O allows I/O to be “distributed” around the plant floor. • PanelView operator interface terminals as well as variable frequency drives can be connected on a remote I/O link.

  15. PLC Networking • A single chassis PLC can be part of a larger factory-wide communication network. • Each PLC has its own processor. • Each device on the network is a node or station on the network. • Each node must have a unique identifier known as the node address.

  16. Advantages to Networking • Multiple stand-alone PLCs networked together • Share information between processors • Share control of the process • Operator interface devices input or display information from multiple PLC processors • PLC control of other devices such as VFDs

  17. Current SLC 500 Network Connectivity • Remote I/O • Data Highway-485 • Data Highway Plus • Control Net • Device Net • Ethernet

  18. AB SLC 500 Data Highway-485 Network Image courtesy of Allen-Bradley, a Rockwell Automation business

  19. Selection and Placement of I/O Modules • Consider input and output signals • Modules are divided into family groups. • The appropriate input or output module is selected by determining incoming and outgoing signals. • Match I/O signals to proper module.

  20. Table for Determining Input and Output Types

  21. I/O Module Selection from Input and Output Type

  22. Power Supply Selection (1 of 2) • Each modular PLC chassis, rack, or baseplate must have its own power supply. • Power supply is designed to handle specific load. • Power supply loading is dependent on modules installed.

  23. Power Supply Selection (2 of 2) • Proper power supply sizing will help avoid intermittent problems or power supply shutdown due to an overloaded power supply.

  24. SLC 500 Power Supply Specifications Image courtesy of Allen-Bradley, a Rockwell Automation business

  25. Determine Power Supply Loading • Proper size power supply is selected to handle load placed upon it by the I/O module mix. • Power supply loading can be manually calculated using manufacturers’ tables and module loading data. • PLC programming software can provide power supply loading calculation feature.

  26. RSLogix 500 Power Supply Loading

  27. Installing an SLC 500 Power Supply Image courtesy of Allen-Bradley, a Rockwell Automation business

  28. Series 90-30 Power Supply Image courtesy of GE Fanuc Automation

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