programming a plc

8/12/2019 Programming a PLC

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Day 3Programming a

ProgrammableController


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Objectives Describe the available options for programming a PLC.

Explain what online is in comparison to offline.

List the advantages of software programming with a

personal computer over a hand-held programming

terminal.

Explain the differences when interfacing a notebook

personal computer to a PLC.

Discuss open or soft PLC programming.

Provide an overview of the IEC 1131-3 standard.


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PLC Run Mode (1 of 2)

The PLC can do nothing without someone developing a

program and loading it into the PLC processors memory.

Once the program has been loaded into PLC memory, the

processor is put into run mode.

While in run mode, the processor is solving the ladder

program.


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PLC Run Mode (2 of 2)

While in run mode, the processor reads field device input

signals and stores them in memory.

There is one memory location for each input screw

terminals ON or OFF state.

Field device status information is stored in the input status

table.


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PLC Programming

The oldest programming method is the hand-held

programmer.

Most popular programming method is IBM-compatible

personal computer using either DOS or Windows software.

Higher-end PLCs can only be programmed using software.


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Allen-Bradley SLC 500Programming Options

Image courtesy of Allen-Bradley, a Rockwell Automation business


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Allen-Bradley SLC 500

Hand-held Terminal (HHT)



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Hand-held Programmer andSLC 500 Modular Processors

Hand-held are used only on fixed SLC 500, 5/01, and 5/02 processors.

5/03, 5/04, and 5/05 modular processors allow software programmingonly.

MicroLogix 1000 PLC has own hand-held programmer.


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Smart Hand-held ProgrammingTerminal Advantages

Compact size

Easy to use and learn, no software required

Low cost; cheaper than notebook computer

Easy to transport a program to the field

Easy to transfer PLC program to HHT for editing or

troubleshooting


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Smart Hand-held Programming TerminalDisadvantages

Holds one program at a time

Newer more complex processors do not support

Limited capability to display ladder rungs

Documentation not displayed

Many keystrokes needed to program or edit ladder program

Dead battery means program lost


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Software ProgrammingUsing PC Advantages Newer software Windows-based

View or monitor multiple ladder rungs

Documentation displayed

Easy to scroll through rungs for troubleshooting

Programs stored on computers hard drive

Programs transferred to floppy or CD-ROM

Easy editing and programming, drag and drop, cut andpaste, etc.


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Software ProgrammingDisadvantages

Maintenance personnel must learn Windows programming software.

Notebook computers are expensive.

Interface cards are expensive.

Personal computers are not designed for factory use.

There are frequent software upgrades.


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Allen Bradley 1747-PIC Interface

1747-PIC communication box used to communicate from aPCs serial port to a SLC 500 family data highway 485 PLC

Connects to any PC with a serial port

Communicates with fixed SLC 500, and 5/01, 5/02, and

5/03 modular processors


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AB 1747-PIC InterfaceConverter Interface



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Connecting a GE RS-422/RS-485to a RS-232 to a PC (1 of 2)

Image courtesy of GE Fanuc Automation


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Connecting a GE RS-422/RS-485to a RS-232 to a PC (2 of 2)

Easy connection between personal computer and Series 90-30 or 90-70

PLC

Connects to computer serial port

Connects up to 50 feet away


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Desktop or IndustrialComputer Interface to PLC

Allen Bradley 1784-KTX interface card

PC ISA expansion slot card

Connects to data highway plus or data highway 485 processors

Set up RSLinx software drivers to communicate


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Allen-Bradleys1784-KTX Interface Card



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1784-KTX Card andNetwork Interface

Easy network connectivity between personal computer and up to 64

data highway plus PLC 5 or SLC 5/04 processors (nodes) on DH+

network

Up to 32 data highway-485 SLC 500 family processors on network


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Node Addresses

Each device on the network will require a unique identifiercalled a node or station address.

Data highway plus network will support up to 64 nodes,

using octal addresses.

Data highway-485 network will support up to 32 nodes,

using decimal addresses.


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Communicating to

Multiple SLC 500s



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Notebook PC Interface to PLC

Direct serial connection

Hardware interface device such as 1747-PIC

PCMCIA card


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PCMCIA Interface Card

Notebook PCs do not have expansion slots for installationof KTX card.

PCMCIA card is a credit-card sized plug-in interface card.

Allen-Bradleys PCMCIA card is called the 1784 PCMK card.

1784 PCMK card serves as an interface between a PLC and

a PC used as a programming terminal.


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1784 PCMK Card Installation

Interface between notebook PC and either DH+ or DH-485

Interface PLC 5 or SLC 500 family processors

Insert card into notebook computer PCMCIA slot


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PCMK Card Insertion

into a PCs PCMCIA Slot



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Interface Cable Attachment

to PCMK Card (1 of 2)



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Interface Cable Attachmentto PCMK Card (2 of 2)

One cable to communicate to SLC 500,

DH-485 processors

One cable to communicate to SLC 5/04, DH+processor

Same DH+ cable will communicate to PLC 5 processors


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Interface Cable fromPCMK Card to PLC Processors



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Industrial Computers

Notebook and desktop personal computers were notdesigned for continuous use in the manufacturing

environment.


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Industrial Computers

Are Designed to Withstand:

Dirt

Shock

Vibration

High temperatures

Wash downs


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Industrial Computer Features

Shock-mounted hard drives

Air filters with air intake fans

Hazardous environment rating

NEMA 12, 4, and 4X ratings

Integrated mouse on front panel

Air-conditioned enclosure not required

Modular for easy repair


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Two Styles of Industrial Computers

Panel-mount

Computer and monitor built into one integrated unit

Rack-mount

Computer either separate component mounted in standard

19-inch rack or embedded inside enclosure

Separate monitor or touchscreen display


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Rockwell Automations RAC 6181

Computer Connections



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Connecting Industrial Mouse and Keyboardto the RAC 6181



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IEC 1131-3Programming Standard

Defines a consistent set of programming languages for PLCs:

Ladder diagram

Function block diagram

Instruction list

Structured text

Sequential function block


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Sequential Function Chart (2 of 2)


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Sequential Function

Chart OR Logic


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Sequential Function ChartIllustrating a Simultaneous Branch

programming a plc

Documents