Ingeniero

Programmable Controllers
Theory and Implementation
Second Edition
L.A. Bryan E.A. Bryan

PROGRAMMABLE CONTROLLERS
T HEORY AND I MPLEMENTATION
Second Edition

L. A. Bryan E. A. Bryan

An Industrial Text Company Publication Atlanta • Georgia • USA

© 1988, 1997 by Industrial Text Company Published by Industrial Text Company All rights reserved First edition 1988. Second edition1997 Printed and bound in the United States of America 03 02 01 00 99 98 97 10 9 8 7 6 5 4 3 2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

Reproduction or translation of any part of this work beyond that permitted by Sections 107 and 108 of the 1976 United States Copyright act are unlawful. Requests for permission,accompanying workbooks, or further information should be addressed to: Industrial Text and Video Company 1950 Spectrum Circle Tower A-First Floor Marietta, Georgia 30067 (770) 240-2200 (800) PLC-TEXT Library of Congress Cataloging-in-Publication Data Bryan, L.A. Programmable controllers: theory and implementation/L.A. Bryan, E.A. Bryan.—2nd ed. p. cm. Includes index. ISBN 0-944107-32-X 1.Programmable controllers. I. Bryan, E.A. II. Title. TJ223.P76B795 1997 629.8'9—dc21 96-49350 CIP

Due to the nature of this publication and because of the different applications of programmable controllers, the readers or users and those responsible for applying the information herein contained must satisfy themselves to the acceptability of each application and the use of equipment therein mentioned.In no event shall the publisher and others involved in this publication be liable for direct, indirect, or consequential damages resulting from the use of any technique or equipment herein mentioned. The illustrations, charts, and examples in this book are intended solely to illustrate the methods used in each application example. The publisher and others involved in this publication cannotassume responsibility or liability for actual use based on the illustrative uses and applications. No patent liability is assumed with respect to use of information, circuits, illustrations, equipment, or software described in this text.

Industrial Text & Video Company 1-800-752-8398 www.industrialtext.com

Contents

C ONTENTS
Preface..................................................................................................... ix About the Authors .................................................................................... x How to Use this Book ............................................................................. xi

SECTION 1 INTRODUCTORY CONCEPTS
Chapter 1 1-1 1-2 1-3 1-4 1-5 1-6 1-7 Chapter 2 2-1 2-2 2-3 2-4 2-5 Chapter 3 3-1 3-2 3-3 3-4Introduction to Programmable Controllers Definition ................................................................................................. 4 A Historical Background .......................................................................... 5 Principles of Operation ........................................................................... 10 PLCs Versus Other Types of Controls................................................... 13 PLC Product Application Ranges .......................................................... 22 Ladder Diagrams and the PLC ............................................................... 24 Advantages of PLCs ............................................................................... 26 Number Systems and Codes Number Systems.................................................................................... 34 Number Conversions .............................................................................. 41 One’s and Two’s Complement ............................................................... 43 Binary Codes .......................................................................................... 46 Register Word Formats...