Programmable Logic Controllers

Organization of the Presentation Introduction Components of PLC PLC Functioning PLC Programming Example Problems Applications PLC Selection

Introduction

Components of PLC

PLC Functioning

PLC Programming

Example Problems

Applications

PLC Selection

Introduction

PLC Defined Programmable Logic Controller (PLC) is a solid state device designed to perform logic functions. Essentially PLC is an assembly of solid state digital electronic elements designed to make logical decisions and provide outputs

Programmable Logic Controller (PLC) is a solid state device designed to perform logic functions.

Essentially PLC is an assembly of solid state digital electronic elements designed to make logical decisions and provide outputs

Why PLC Relay based Process or Machine Control is expensive and Rigid Need for programmable and reconfigurable control Move towards Flexible Automation

Relay based Process or Machine Control is expensive and Rigid

Need for programmable and reconfigurable control

Move towards Flexible Automation

Areas of Application Process control Control of Machinery Control of Equipments Certain Aspects of Control in CNC machines and Machining Centers

Process control

Control of Machinery

Control of Equipments

Certain Aspects of Control in CNC machines and Machining Centers

Components of PLC

PLC Components Any PLC Has 1. A Central Processing Unit (CPU) Microprocessor based system 2. Input / Output Section (I/O Section) Digital and analog I/O s 3. Programming Device Usually a Computer

Any PLC Has

1. A Central Processing Unit (CPU)

Microprocessor based system

2. Input / Output Section (I/O Section)

Digital and analog I/O s

3. Programming Device

Usually a Computer

PLC Components

PLC Functioning

PLC’s Perform Scans Sequentially and Cyclically

Typical PLC Scan Sequence

PLC programming

Typical Inputs and their Representation

Inputs (Continued )

Inputs (Continued )

Inputs (Continued )

Inputs (Continued )

An Electro Mechanical Relay

Typical Outputs and Their Representation

Timers On Delay Timers Off delay timers Retentive Timers

On Delay Timers

Off delay timers

Retentive Timers

Counters Up Counters Down Counters Up Down Counters

Up Counters

Down Counters

Up Down Counters

Relays Internal Relays External Relays Retentive Relays

Internal Relays

External Relays

Retentive Relays

Example Programs

Design a Control Program for a Water Pump Motor

Product in Position (LS1 Close) Start button on. Conveyer moves product to A (Limit switch LS1 returns to normal) Conveyer moves the Product to A and stops Distance to A counted by encoder (8 Pulses) Waits at A for 10 s Moves again to LS2 and stops Emergency stop Emergency stop resets counter and timer

Applications

Process Control Electroplating Heat Treatment Powder Coating Chemical Processing Refineries Control of Hydraulic and Pneumatic Circuits

Electroplating

Heat Treatment

Powder Coating

Chemical Processing

Refineries

Control of Hydraulic and Pneumatic Circuits

Control of Machinery and Equipment Control of Material Handling Equipments like Conveyer Belts Control of Flexible, Automated Assembly Lines Control of Special Purpose Machines like Bottling Machine etc.

Control of Material Handling Equipments like Conveyer Belts

Control of Flexible, Automated Assembly Lines

Control of Special Purpose Machines like Bottling Machine etc.

CNC Machines velocity, displacement and position control is being carried out by exclusive controllers (Hardware interpolators, Closed Loop Controllers etc..) Mostly all ‘M’ codes are transferred to PLC Control PLC Provides one more level of Protection in CNC Machines

velocity, displacement and position control is being carried out by exclusive controllers (Hardware interpolators, Closed Loop Controllers etc..)

Mostly all ‘M’ codes are transferred to PLC Control

PLC Provides one more level of Protection in CNC Machines

Machining Centers Automatic Tool Changers Automatic Pallet Changers Overall system protection

Automatic Tool Changers

Automatic Pallet Changers

Overall system protection

PLC Selection

Criteria for Selecting PLC Number of logical inputs and outputs. Memory Number of special I/O modules Scan Time Communications Software

Number of logical inputs and outputs.

Memory

Number of special I/O modules

Scan Time

Communications

Software

Typical PLC Specification

Commercial PLC Manufacturers Omron Electronics Inc. Allen Bradley Aromat GE-Fanuc IDEC Keyence Mitsubishi Modicon Omron Automation Direct Siemens Toshiba

Omron Electronics Inc.

Allen Bradley

Aromat

GE-Fanuc

IDEC

Keyence

Mitsubishi

Modicon

Omron

Automation Direct

Siemens

Toshiba

PLC Manufacturers Websites Aromat http://www. aromat .com Keyence http://www. keyence .com/ plc /start. htm Toshiba http://www. toshiba .com.au/ plc /index.html

Aromat

http://www. aromat .com

Keyence

http://www. keyence .com/ plc /start. htm

Toshiba

http://www. toshiba .com.au/ plc /index.html

Some Interesting PLC Websites http://claymore.gvsu.edu/~jackh/books/plcs/ http://www.plcs.net http://www.geindustrial.com/cwc/solutions ?

http://claymore.gvsu.edu/~jackh/books/plcs/

http://www.plcs.net

http://www.geindustrial.com/cwc/solutions ?

Reference Programmable Logic Controllers by Frank D Petruzella, McGraw – Hill Books Companey, 1989.

Programmable Logic Controllers by Frank D Petruzella, McGraw – Hill Books Companey, 1989.

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