Programmable Logic Controllers - Dogwood Valley …

1 Programmable LogicControllers:An Emphasis on Design and ApplicationSecond EditionKelvin T. EricksonMissouri University of Science and TechnologyDogwoodValleyPress,LLCC opyright 2011 Dogwood Valley Press, LLC. All rights portion of this book may be reproduced, stored in a retrieval system, or transmitted inany form or by any means, including electronic, mechanical, photocopying, scanning,recording or otherwise, except as permitted under the 1976 United States Copyright Act,without explicit, prior written permission of the publisher except for brief passagesexcerpted for review and critical book was set in Times New Roman and printed on acid-free in the United States of AmericaISBN 978-0-9766259-2-6 Dogwood Valley Press, LLC1604 Lincoln LaneRolla, MO 654011-573-426-3507 to Fran, Esther, David and AmandaCONTENTSP refaceviiChapter 1 Introduction to Control in System of the Versus Other PLC Summary20 References20 Chapter 2 Basic Ladder Logic Ladder Ladder Logic Logic Processor with NC Contacts and Summary66 References66 Problems67 Chapter 3 Memory Organization and 61131-3 Memory Unity ControlLogix/CompactLogix PLC-5 and SLC-500/MicroLogix S7 Summary144 References144 Problems147 Chapter 4 Input/Output Modules and Summary200 References200 Problems203 Chapter 5 Timers and Timers and Timers and ControlLogix Timers and PLC-5/SLC-500 Timers and S7 Timers and Timers and Timer and Counter Summary279 References280 Problems281 Chapter 6 Sequential Function Chart in Ladder Reset Questions in the Sequential Design and Single-Step Sequential When PLC

2 Has No Set/Reset Summary374 References379 Problems380 Chapter 7 Comparison and of Physical Comparison and Comparison and ControlLogix Comparison and PLC-5/SLC-500 Comparison and S7 Comparison and Comparison and Summary520 References520 Problems522 Chapter 8 Other Ladder Logic IEC Function Modicon Function ControlLogix Function PLC-5/SLC-500/MicroLogix Function Siemens S7 Function GE Function Summary678 References680 Problems682 Chapter 9 Other Function Chart Register-Based Function Summary769 References769 Problems771 Chapter 10 PID Control controller Control PID Function Summary864 References864 Problems866 Chapter 11 Function Block 61131-3 Function Block Function Block Function Block S7 Function Block PACS ystems Function Block Summary933 References933 Problems935 Chapter 12 Structured 61131-3 Structured Structured Structured Structured S7 Structured Control PACS ystems Structured Summary971 References971 Problems972 Chapter 13 Instruction 61131-3 Instruction Instruction S7 Statement List Instruction Summary991 References991 Problems992 Chapter 14 Sequential Function 61131-3 Sequential Function Sequential Function Sequential Function Sequential Function S7 Sequential Function Summary1082 References1082 Problems1083 Chapter Troubleshooting I/O Status for Fault Summary1109 References1109 Chapter 16 Sensors and Summary1184 References1184 Appendix - Thermocouple Conversion Polynomial Coefficients1186 Problems1192 Chapter 17 Communication (DP, PA, PROFInet)

3 Proprietary Proprietary Logic Communication Summary1276 References1276 Chapter 18 Human-Machine Panel HMI HMI Summary1305 References1305 Chapter 19 Control System Automation Network Processor Security1312 Contents Summary1325 References1325 Chapter 20 Selecting a Summary1337 References1338 Chapter 21 Control Control Design Control Requirements Summary1428 References1428 Problems1430 Chapter 22 Example Handling Chemical Summary1444 References1444 Appendix ANumber Systems and Conversions1445 Appendix BElectrical Diagram Symbols1451 Appendix CPiping and Instrumentation Diagram (P&ID) Symbols1454 Glossary1457 Index1473viContentsPREFACEThe field of automatic control has been undergoing a transformation over the pasttwenty years. Twenty years ago, the engineering undergraduate had a course in feedbackcontrol theory and those interested in control engineering secured a position in theaerospace or chemical industries.

4 Due to various factors, the number of control engineeringpositions in the aerospace industry has been declining, but the number of controlengineering positions in manufacturing has been dramatically increasing to the point thatthe majority of control engineering positions is now in manufacturing and involves book presents the subject of programming industrial Controllers , calledprogrammable Logic Controllers (PLCs) with an emphasis on the design of the texts teach one how to program the PLC in its languages, but little, if any, attention ispaid to how does one attack the problem: Given a set of operational specifications, howdoes one develop the PLC program? This book develops the design process: the tasksinvolved, breaking the program into manageable pieces, standard code for the various parts,and handling the sequential parts of the problem.

5 The emphasis is toward those who will beprogramming of its popularity (now and in the future), ladder Logic is the language that isused for the majority of the text. The industry trend is toward using the IEC 61131-3(formerly IEC 1131-3) standard, and so it is the primary language. However, IEC 61131-3is only a voluntary standard and individual manufacturers have some freedom in theimplementation. Therefore, the Allen-Bradley ControlLogix, Modicon, Siemens S7, andGE implementations of the 61131-3 standard are covered. Because of their large installedbase, the Allen-Bradley PLC-5/SLC-500 PLC languages are also to the limitations of ladder Logic , the IEC 61131-3 standard defines four otherlanguages: function block diagram, structured text, instruction list, and sequential functionchart. These four languages will become more popular in the future.

6 Therefore, this text alsocovers these a typical manufacturing plant may contain discrete, continuous, and batchprocesses, all of these applications are treated in this text, although the emphasis is ondiscrete and continuous processes. The emphasis is on a methodology that can be applied toany automation project, regardless of the , the book contains example problems demonstrating good design addition, these problems are solved with each PLC covered in the book. The textculminates in two full-length case studies where the application of the design techniques toa large problem is book takes a practical approach to the design of PLC control systems. Somemathematical theory is used to backup the presentation on PID Controllers . However, thetheory is not detailed and can be for Chapters 1 and 13, every chapter begins with a scenario that reflects theexperience of the author and his colleagues in the challenging world of factory scenarios present a small problem and the solution and are intended to illustratetroubleshooting main objectives of this text are to teach: PLC programming languages (with emphasis on IEC 61131-3) Approach to sequential problems Good program design practice Simple PID control tuning Introduction to sensors and actuators Factory communications Human-machine interface (HMI) conceptsContent OverviewThe book starts by introducing Programmable Logic Controllers (PLCs) and theirdistinguishing characteristics.

7 Chapters2 5 cover basic ladder Logic programming:contact, timer, and counter instructions. As part of the basics, the memory structure of thefive particular PLCs and installation topics are treated. Chapter 6 covers ladder logicprogram design for sequential applications, probably the most significant contribution ofthe text. Chapters 7 and 8 treat computation, comparison, and advanced ladder logicinstructions. Alternate sequential implementations in ladder Logic are covered in Chapter 9and PID controller tuning is covered in Chapter 10. Chapters 11 14 cover the other fourIEC programming languages: function block diagram, statement list, instruction list, andsequential function chart. PLC troubleshooting is covered in Chapter 15. Sensors andactuators appear in Chapter 16. Chapter 17 introduces factory communication interface, often called human-machine interface (HMI), issues are treated inChapter 18.

8 Control system security is addressed in Chapter 19 and PLC selection isintroduced in Chapter 20. Chapter 21 presents the perspective of an entire automationproject, bringing together the various pieces of PLC control design. Chapter 22 outlines twofull-length project case studies. One case study is for a process that is primarily discrete andthe other case study is for a process that is primarily continuous in nature. Details aboutnumber systems and drawing symbols are included as appendices, rather than interrupt theflow of the text AudienceThis book primarily serves the academic market, at the junior or senior undergraduateelectrical, mechanical, or industrial engineering or engineering technology level. This textis also suitable for the two-year technical school market. There is nothing in the materialthat requires a college degree, though the material will be more challenging than the typicalPLC textbook for this level of addition, this text serves the professional market.

9 Economic and regulatory pressuresin the manufacturing, chemical, petrochemical, pharmaceutical, and food industries haveforced control engineers to design new systems or retrofit existing control systems. Hence,there are many control engineers (primarily chemical and electrical) who need to rapidlyviiiPrefaceeducate themselves in an area of technology in which they are probably only somewhatfamiliar. This book is valuable to this EditionThe second edition primarily updates the Modicon, Siemens, and GE Controllers to thecurrent processors, but there are other changes throughout. The Modicon sections focus onthe Modicon Unity processors. For the older Modicon Quantum/Momentum processors,see the first edition of this text. The Allen-Bradley material has been updated to focus on theControlLogix processor, though the PLC-5/SLC-500/MicroLogix processors are alsocovered.

10 Coverage of the ControlLogix add-on instruction (AOI) has been added. TheSiemens S7-1200 has been added to the Siemens sections and the material on theS5-compatible timers and counters has been removed. The GE PACS ystems processor hasbeen added and the material focuses on this processor with references to the earlierprocessors as appropriate. The PLC history in Chapter 1 has been updated. In Chapter 2, thesection about converting relay Logic to ladder Logic has been removed and replaced with asection on using the transitional contacts and coils. The examples in sections , now utilize user-defined data types and user-defined function blocks. In addition, all ofthe chapter problems have been replaced with new problems. Lastly, the accompanying CDcontains the PLC projects for each example problem and has an additional set of author wishes to acknowledge the beneficial suggestions and comments of manycolleagues.