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Programmable Logic Controllers:
Programming Methods
and Applications
by
John R. Hackworth
and
Frederick D. Hackworth, Jr.

Table of Contents

Chapter 1 - Ladder Diagram Fundamentals
Chapter 2 - The Programmable Logic Controller
Chapter 3 - Fundamental PLC Programming
Chapter 4 - Advanced Programming Techniques
Chapter 5 - Mnemonic Programming Code
Chapter 6 - Wiring TechniquesChapter 7 - Analog I/O
Chapter 8 - Discrete Position Sensors
Chapter 9 - Encoders, Transducers, and Advanced Sensors
Chapter 10 - Closed Loop and PID Control
Chapter 11 - Motor Controls
Chapter 12 - System Integrity and Safety

Preface
Most textbooks related to programmable controllers start with the basics of
ladder logic, Boolean algebra, contacts, coils and all the other aspects oflearning to
program PLCs. However, once they get more deeply into the subject, they generally
narrow the field of view to one particular manufacturer's unit (usually one of the more
popular brands and models), and concentrate on programming that device with it's
capabilities and peculiarities. This is worthwhile if the desire is to learn to program that
unit. However, after finishing the PLCcourse, the student will most likely be employed
in a position designing, programming, and maintaining systems using PLCs of another
brand or model, or even more likely, many machines with many different brands and
models of PLC. It seems to the authors that it would be more advantageous to
approach the study of PLCs using a general language that provides a thorough
knowledge of programmingconcepts that can be adapted to all controllers. This
language would be based on a collection of different manufacturer types with generally
the same programming technique and capability. Although it would be impossible to
teach one programming language and technique that would be applicable to each and
every programmable controller on the market, the student can be given a thorough
insight intoprogramming methods with this general approach which will allow him or her
to easily adapt to any PLC encountered.
Therefore, the goal of this text is to help the student develop a good general
working knowledge of programmable controllers with concentration on relay ladder logic
techniques and how the PLC is connected to external components in an operating
control system. In the course ofthis work, the student will be presented with real world
programming problems that can be solved on any available programmable controller or
PLC simulator. Later chapters in this text relate to more advanced subjects that are
more suitable for an advanced course in machine controls. The authors desire that
this text not only be used to learn programmable logic controllers, but also that this textwill become part of the student’s personal technical reference library.
Readers of this text should have a thorough understanding of fundamental ac
and dc circuits, electronic devices (including thyristors), a knowledge of basic logic
gates, flip flops, and Boolean algebra, and college algebra and trigonometry. Although
a knowledge of calculus will enhance the understanding of PID controls,it is not
required in order to learn how to properly tune a PID.

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Chapter 1 - Ladder Diagram Fundamentals

Chapter 1 - Ladder Diagram Fundamentals
1-1.

Objectives

Upon completion of this chapter, you will be able to
” identify the parts of an electrical machine control diagram including rungs,
branches, rails, contacts, and loads.
” correctly design and draw a simpleelectrical machine control diagram.
” recognize the difference between an electronic diagram and an electrical machine
diagram.
” recognize the diagramming symbols for common components such as switches,
control transformers, relays, fuses, and time delay relays.
” understand the more common machine control terminology.
1-2.

Introduction

Machine control design is a unique area of engineering...