Copyright © 2002 Delmar Thomson Learning Chapter 9 Putting Together a Modular PLC

Copyright © 2002 Delmar Thomson Learning

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 systems is configured.


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.


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.


Module Installation into a Four-Slot SLC 500 Chassis

Image courtesy of Allen-Bradley, a Rockwell Automation business


Module Installation into a Four-Slot SLC 500 Chassis

(cont’d.)

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.


Series 90-30 PLC Model 331 CPU

Image courtesy of GE Fanuc Automation


Removing a GE Series 90-30 I/O Module



Local I/O ExpansionWhen more I/O is required than a

single chassis can hold, additional chassis can be added.

Communications cable connects expansion chassis together.

No processor in expansion chassis.Power supply required in all chassis.Expansion cable distance limited.


SLC 500 3-chassis Local Expansion



Remote I/O

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.


SLC 500 Remote I/O Example



SLC 500 Remote I/O Example (cont.’d)

SLC 500 uses 1747-SN scanner in local chassis.

SN scanner communicates with remote chassis.

1747-ASB communication module required in each remote chassis.


SLC 500 Remote I/O Example (cont.’d)

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.


PLC NetworkingA single chassis PLC can be part of a

larger factory-wide communication network.

Each PLC has 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.


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.


Current SLC 500 Network Connectivity

Remote I/OData Highway-485Data Highway PlusControl NetDevice NetEthernet


AB SLC 500 Data Highway-485 Network



Selection and Placement of I/O Modules

Consider Input and Output SignalsModules 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.


Table for Determining Input and Output Types


I/O Module Selection from Input and Output Type


Power Supply Selection

Each modular PLC chassis, rack, or baseplate must have own power supply.

Power supply designed to handle specific load.

Power supply loading is dependant on modules installed.


Power Supply Selection (cont’d.)

Proper power supply sizing will help avoid intermittent problems or power supply shutdown due to an overloaded power supply.


SLC 500 Power Supply Specifications



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.


RSLogix 500 Power Supply Loading


Installing a SLC 500 Power Supply



Series 90-30 Power Supply


Documents

Copyright © 2002 Delmar Thomson Learning Chapter 9 Putting Together a Modular PLC