Programmable logic controller

Automation

Power electronics

Closed Loop Controller

Sensors and Actors

Switchgear,Contactors and Relays

Pneumatic and Hydraulic

Electronic Controls and

Microcontroller

Motors

Programmable Logic Controller

Leading Brands of PLC AMERICAN EUROPEAN JAPANESE1 ALLEN BRADLEY SIEMENS TOSHIBA2 GOULD MODICON KLOCKNER & MOULLER OMRON3 TEXAS INSTRUMENTS FESTO FANUC4 GENERAL ELECTRIC TELEMECHANIQUE MITSUBISHI5 WESTINGHOUSE 6 CUTTER HAMMER 7 SQUARE D

PLC Programing Software’s1. Velocio Software2. Siemens Software3. Rockwell Automation (Allen-Bradley) So

ftware4. Schneider Software5. Mitsubishi Software6. Modicon Software 7. Panasonic Software 8. Keyence Software 9. Telemecanique Software 10. Beckhoff Software 11. GE Software 12. Automation Direct Software 13. IDEC Software 14. Opto22 Software

15. Omron Software 16. Sirea Software17. VIPA Software 18. Triangle Research International Softwar

e 19. SPLAT Software 20. Smart Software Solutions 21. LSIS Software 22. Control Microsystems Software 23. Teco Software 24. Unitronics Software 25. ABB Software 26. Horner APG Software 27. Crouzet Software 28. Xinje Software 29. Entertron Software 30. Delta Electronics Software

PLC Communications

Manufacturer Network1 Allen-Bradley Data Highway2 Gould Modicon Modbus3 General Electric GE Net Factory LAN4 Mitsubishi Melsec-NET5 Square D SY/NET6 Texas Instruments TIWAY

PLC Acronyms ASCII American Standard Code for Information Interchange BCD Binary Coded Decimal CSA Canadian Standards Association DIO Distributed I/O EIA Electronic Industries Association EMI ElectroMagnetic Interference HMI Human Machine Interface IEC International Electrotechnical Commission IEEE Institute of Electrical and Electronic Engineers I/O Input(s) and/or Output(s) ISO International Standards Organization LL Ladder Logic LSB Least Significant Bit MMI Man Machine Interface MODICON MOdular DIgital CONtoller MSB Most Significant Bit PID Proportional Integral Derivative (feedback control) RF Radio Frequency RIO Remote I/O RTU Remote Terminal Unit

SCADA Supervisory Control And Data Acquisition

Definition of PLCAccording to NEMA standard ICS3-1978• A digitally operating electronic apparatus

which uses a programming memory for the internal storage of instructions for implementing specific functions such as logic, sequencing, timing, counting and arithmetic to control through digital or analog modules, various types of machines or process.

Areas of PLC Applications• Annunciators • Injection Molding• Auto Insertion • Assembly• Bagging• Motor Winding• Baking • Oil Fields• Blending • Painting• Boring • Palletizers• Brewing • Pipelines• Calendaring • Polishing

• Casting • Reactors• Chemical Drilling • Robots• Color Mixing • Rolling• Compressors • Security Systems• Conveyors • Stretch Wrap• Cranes • Slitting• Crushing • Sorting• Cutting • Stackers

• Digesters • Stitching• Drilling • Stack Precipitators• Electronic Testing • Threading• Elevators • Tire Building• Engine Test Stands • Traffic Control• Extrusion • Textile Machine• Forging • Turbines• Generators • Turning

• Gluing • Weaving• Grinding • Web Handling• Heat Treating • Welding• Manufacturing/

Machining• Food / Beverage• Metals• Power• Mining• Petrochemical/Chemical

PLC in industry

PLC in traffic light

Relating the PLC

Traditional system PLC system

control function is modified by physically changing the wiring between the devices

This is costly and time consuming endeavor

Soft wiring control function is modified

by just changing the control program inside the PLC

These changes are easy and cheap

PLC and Computer• A PLC and a computer both are electronic processor

unit. The architecture of a PLC’s CPU is basically same as that of a general purpose computer; however, some important characteristics set them apart.

• Unlike computer, PLCs are specifically designed to survive the harsh conditions of the industrial environment. A well-designed PLC can be placed in an area with substantial amounts of electrical noise, electromagnetic interference, mechanical vibration, and noncondensing humidity.

Cont.… • Distinction of PLCs is that their hardware and

software are designed for easy use by plant electricians and technicians. The hardware interfaces for connecting field devices are actually part of the PLC itself and are easily connected.

• The modular and self-diagnosing interface circuits are able to pin point malfunctions and moreover, are easily removed and replaced.

Cont.… • Software programming uses conventional relay

ladder symbols, or other easily learned languages, which are familiar to plant personnel.

• A computer can execute a complex programming task and also multitasking. A standard PLC is designed to execute a single program in an orderly fashion. As PLCs are rapidly changing, modern PLCs have multitasking capabilities.

Why PLCs are so popular?• Programmable logic controller have made it possible to precisely

control large process machines and driven equipment with less physical wiring and wiring time than it requires with standard electro-mechanical relays, pneumatic system, timers, drum switches, and so on.

• The programmability allows for fast and easy changes in the relay ladder logic to meet the changing needs of the process or driven equipment without the need for expensive and time consuming rewiring process.

• Modem PLCs are "electrician friendly", PLC can be programmed and used by plant engineers and maintenance electricians without much electronic and computer programming background. They can programmed by using the existing ladder diagrams.

Advantage and disadvantage of

PLC

Advantage of PLC No Advantage Description 1 Flexibility Universal Controller

Can replace various independent/ standalone controller.

2 Implementing Changes and Correcting Errors

Do not have to rewiring relay panel. Change program using keyboard.

3 Large Quantity of Contact Large number of' Soft Contact' available 4 Lower Cost

Advancement in technology and open architecture of PLC

will reduce the market price.

5 Pilot Running (Simulation Capability)

A program can be simulated or run without actual input connection.

6 Visual Observation.

Can observe the opening and closing of contact switch on CRT.

Operator message can be programmed for each possible malfunction.

7 Speed of Operation

Depends on scan time -millisecond. Asynchronous operation.

8 Ladder or Boolean Programming Method. Easy for 'Electrician , 9 Reliability In general -very reliable 10 Simplicity of Ordering Control Sys.

Components One package with Relay, Timers, Control Block, etc.

11 Documentation Printout of ladder logic can be printed easily 12 . Security Software lock on a program (Password) 13 Ease of Changes by Programming Ability to program and reprogram, loading and

down loading

14 Highly versatile (universal applicability) 15 Simple troubleshooting

Simple installation

16 Quick modification of the program (highly flexible)

17 Capable of task not possible with relays before as indicated by the following:

Calculation, information exchange, text and graphic display, data processing, networking

18 Low space requirement 19 Low power consumption 20 High processing speed 21 No moving parts, hence no wearing parts

Disadvantages of PLC N

oDisadvantages Description

1 New Technology Change from ladder and relay to PLC concept

2 Fixed program Application

Not cost effective for single- function application

3 Environment

Consideration Not adapted for very high temperature, high

humidity level, high vibration, etc.

4 Fail-safe operation

Does not start automatically when power failure ( can be programmed into ) Not "Fail-safe" -Fail-shorted rather than OPEN

5 Fixed-circuit operation Fixed control system -less costly

What Is Inside A PLC?

Cont.…• The Central Processing Unit, the CPU, contains an internal

program that tells the PLC how to perform the following functions:

• Execute the Control Instructions contained in the User's Programs. This program is stored in "nonvolatile" memory, meaning that the program will not be lost if power is removed

• Communicate with other devices, which can include I/O Devices, Programming Devices, Networks, and even other PLCs.

• Perform Housekeeping activities such as Communications, Internal Diagnostics, etc.

How Does A PLC Operate?• There are four basic steps in the operation of all PLCs; Input Scan, Program

Scan, Output Scan, and Housekeeping. These steps continually take place in a repeating loop.

1. Input Scan • Detects the state of all input devices that are connected to the PLC

2.Program Scan • Executes the user created program logic

3. Output Scan • Energizes or de-energize all output devices that are connected to the PLC.

4.Housekeeping • This step includes communications with programming terminals, internal diagnostics, etc...

What Programming Language Is Used To Program A PLC?

• While Ladder Logic is the most commonly used PLC programming language, it is not the only one. The following lists of some of languages that are used to program a PLC.

1. Ladder Diagram (LD) • Traditional ladder logic is graphical programming language. Initially

programmed with simple contacts that simulated the opening and closing of relays, Ladder Logic programming has been expanded to include such functions as counters, timers, shift registers, and math operations.

2. Function Block Diagram (FBD) A graphical language for depicting signal and data flows through re-usable function blocks. FBD is very useful for expressing the interconnection of control system algorithms and logic.

3. Structured Text (ST) A high level text language that encourages structured programming. It has a language structure (syntax) that strongly resembles PASCAL and supports a wide range of standard functions and operators. For example;

If Speed1 > 100.0 then Flow_Rate: = 50.0 + Offset_A1;Else Flow_Rate: = 100.0; Steam: = ONEnd_If;

4. Instruction List (IL)A low level “assembler like” language that is based on similar instructions list languages found in a wide range of today’s PLCs.

LDMPCLDSTRESET:ST

R1RESETPRESS_1MAX_PRESSLD 0A_X43

5. Sequential Function Chart (SFC) A method of programming complex control systems at a more highly structured level. A SFC program is an overview of the control system, in which the basic building blocks are entire program files. Each program file is created using one of the other types of programming languages. The SFC approach coordinates large, complicated programming tasks into smaller, more manageable tasks.

What Are Input/output Devices of PLC?

Input device 1. Switches and Pushbuttons2. Sensing Devices• Limit Switches• Photoelectric Sensors • Proximity Sensors 3. Condition Sensors4. Encoders• Pressure Switches• Level Switches• Temperature Switches• Vacuum Switches• Float Switches

OUTPUTS• Valves• Motor Starters• Solenoids• Actuators • Horns and Alarms• Stack lights• Control Relays• Counter/Totalizer • Pumps • Printers• Fans