page 0
A
C + B
C * B
B
T1 ST2 A⋅=
T1
T2
T3
T4
ST1
ST2
ST3
FS = first scan
ST1 ST1 T1+()T2⋅ FS+=
ST2 ST2 T2 T3++()T1 T4⋅⋅=
ST3 ST3 T4 T1⋅+()T3⋅=
T2 ST1 B⋅=
T3 ST3 CB⋅()⋅=
T4 ST2 CB+()⋅=
ST2 A
ST1 B
ST3 C B
T1
T2
T3
T4
ST2
C
B
ST1

vided.
Additional materials and updates for this work will be available at http://clay-
more.engineer.gvsu.edu/~jackh/books.html
page i
1.1 TODO LIST 1.3
2. PROGRAMMABLE LOGIC CONTROLLERS . . . . . . . . . . . . . 2.1
2.1 INTRODUCTION 2.1
2.1.1 Ladder Logic 2.1
2.1.2 Programming 2.6
2.1.3 PLC Connections 2.10
2.1.4 Ladder Logic Inputs 2.11
2.1.5 Ladder Logic Outputs 2.12
2.2 A CASE STUDY 2.13
2.3 SUMMARY 2.14
2.4 PRACTICE PROBLEMS 2.15
2.5 PRACTICE PROBLEM SOLUTIONS 2.15
2.6 ASSIGNMENT PROBLEMS 2.16
3. PLC HARDWARE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1
3.1 INTRODUCTION 3.1
3.2 INPUTS AND OUTPUTS 3.2
3.2.1 Inputs 3.3
3.2.2 Output Modules 3.7
3.3 RELAYS 3.13
3.4 A CASE STUDY 3.14
3.5 ELECTRICAL WIRING DIAGRAMS 3.15
3.5.1 JIC Wiring Symbols 3.18
3.6 SUMMARY 3.22
3.7 PRACTICE PROBLEMS 3.22
3.8 PRACTICE PROBLEM SOLUTIONS 3.25
3.9 ASSIGNMENT PROBLEMS 3.28

5.9 SUMMARY 5.10
5.10 PRACTICE PROBLEMS 5.10
5.11 PRACTICE PROBLEM SOLUTIONS 5.11
5.12 ASSIGNMENT PROBLEMS 5.12
6. BOOLEAN LOGIC DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1
6.1 INTRODUCTION 6.1
6.2 BOOLEAN ALGEBRA 6.1
6.3 LOGIC DESIGN 6.6
6.3.1 Boolean Algebra Techniques 6.13
6.4 COMMON LOGIC FORMS 6.14
6.4.1 Complex Gate Forms 6.14
6.4.2 Multiplexers 6.15
6.5 SIMPLE DESIGN CASES 6.17
6.5.1 Basic Logic Functions 6.17
6.5.2 Car Safety System 6.18
6.5.3 Motor Forward/Reverse 6.18
6.5.4 A Burglar Alarm 6.19
6.6 SUMMARY 6.23
6.7 PRACTICE PROBLEMS 6.24
6.8 PRACTICE PROBLEM SOLUTIONS 6.27
6.9 ASSIGNMENT PROBLEMS 6.37
7. KARNAUGH MAPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1
7.1 INTRODUCTION 7.1
7.2 SUMMARY 7.4
7.3 PRACTICE PROBLEMS 7.5
7.4 PRACTICE PROBLEM SOLUTIONS 7.11
page iii
7.5 ASSIGNMENT PROBLEMS 7.17
8. PLC OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1
8.1 INTRODUCTION 8.1

10.2 PROCESS SEQUENCE BITS 10.2
10.3 TIMING DIAGRAMS 10.6
10.4 DESIGN CASES 10.9
10.5 SUMMARY 10.9
10.6 PRACTICE PROBLEMS 10.9
10.7 PRACTICE PROBLEM SOLUTIONS 10.10
10.8 ASSIGNMENT PROBLEMS 10.14
page iv
11. FLOWCHART BASED DESIGN . . . . . . . . . . . . . . . . . . . . . . . 11.1
11.1 INTRODUCTION 11.1
11.2 BLOCK LOGIC 11.4
11.3 SEQUENCE BITS 11.11
11.4 SUMMARY 11.15
11.5 PRACTICE PROBLEMS 11.15
11.6 PRACTICE PROBLEM SOLUTIONS 11.16
11.7 ASSIGNMENT PROBLEMS 11.26
12. STATE BASED DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1
12.1 INTRODUCTION 12.1
12.1.1 State Diagram Example 12.4
12.1.2 Conversion to Ladder Logic 12.7
Block Logic Conversion 12.7
State Equations 12.16
State-Transition Equations 12.24
12.2 SUMMARY 12.29
12.3 PRACTICE PROBLEMS 12.29
12.4 PRACTICE PROBLEM SOLUTIONS 12.34
12.5 ASSIGNMENT PROBLEMS 12.49
13. NUMBERS AND DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.1
13.1 INTRODUCTION 13.1
13.2 NUMERICAL VALUES 13.2

15.2 DATA HANDLING 15.3
15.2.1 Move Functions 15.3
15.2.2 Mathematical Functions 15.5
15.2.3 Conversions 15.10
15.2.4 Array Data Functions 15.11
Statistics 15.12
Block Operations 15.13
15.3 LOGICAL FUNCTIONS 15.15
15.3.1 Comparison of Values 15.15
15.3.2 Boolean Functions 15.21
15.4 DESIGN CASES 15.22
15.4.1 Simple Calculation 15.22
15.4.2 For-Next 15.23
15.4.3 Series Calculation 15.24
15.4.4 Flashing Lights 15.25
15.5 SUMMARY 15.25
15.6 PRACTICE PROBLEMS 15.26
15.7 PRACTICE PROBLEM SOLUTIONS 15.28
15.8 ASSIGNMENT PROBLEMS 15.34
16. ADVANCED LADDER LOGIC FUNCTIONS . . . . . . . . . . . . . 16.1
16.1 INTRODUCTION 16.1
16.2 LIST FUNCTIONS 16.1
16.2.1 Shift Registers 16.1
16.2.2 Stacks 16.3
16.2.3 Sequencers 16.6
16.3 PROGRAM CONTROL 16.9
16.3.1 Branching and Looping 16.9
16.3.2 Fault Handling 16.14
16.3.3 Interrupts 16.15
16.4 INPUT AND OUTPUT FUNCTIONS 16.17

19.2.1 Elements of the Language 19.3
19.2.2 Putting Things Together in a Program 19.9
19.3 AN EXAMPLE 19.14
19.4 SUMMARY 19.16
19.5 PRACTICE PROBLEMS 19.16
19.6 PRACTICE PROBLEM SOLUTIONS 19.16
19.7 ASSIGNMENT PROBLEMS 19.16
20. SEQUENTIAL FUNCTION CHARTS . . . . . . . . . . . . . . . . . . . 20.1
20.1 INTRODUCTION 20.1
20.2 A COMPARISON OF METHODS 20.16
20.3 SUMMARY 20.16
page vii
20.4 PRACTICE PROBLEMS 20.17
20.5 PRACTICE PROBLEM SOLUTIONS 20.18
20.6 ASSIGNMENT PROBLEMS 20.25
21. FUNCTION BLOCK PROGRAMMING . . . . . . . . . . . . . . . . . . 21.1
21.1 INTRODUCTION 21.1
21.2 CREATING FUNCTION BLOCKS 21.3
21.3 DESIGN CASE 21.4
21.4 SUMMARY 21.4
21.5 PRACTICE PROBLEMS 21.5
21.6 PRACTICE PROBLEM SOLUTIONS 21.5
21.7 ASSIGNMENT PROBLEMS 21.5
22. ANALOG INPUTS AND OUTPUTS . . . . . . . . . . . . . . . . . . . . 22.1
22.1 INTRODUCTION 22.1
22.2 ANALOG INPUTS 22.2
22.2.1 Analog Inputs With a PLC-5 22.9
22.3 ANALOG OUTPUTS 22.13
22.3.1 Analog Outputs With A PLC-5 22.16
22.3.2 Pulse Width Modulation (PWM) Outputs 22.18

Positive Displacement Meters 23.25
Pitot Tubes 23.25
23.2.6 Temperature 23.25
Resistive Temperature Detectors (RTDs) 23.26
Thermocouples 23.26
Thermistors 23.28
Other Sensors 23.30
23.2.7 Light 23.30
Light Dependant Resistors (LDR) 23.30
23.2.8 Chemical 23.31
pH 23.31
Conductivity 23.31
23.2.9 Others 23.32
23.3 INPUT ISSUES 23.32
23.4 SENSOR GLOSSARY 23.35
23.5 SUMMARY 23.36
23.6 REFERENCES 23.37
23.7 PRACTICE PROBLEMS 23.37
23.8 PRACTICE PROBLEM SOLUTIONS 23.38
23.9 ASSIGNMENT PROBLEMS 23.40
24. CONTINUOUS ACTUATORS . . . . . . . . . . . . . . . . . . . . . . . . . 24.1
24.1 INTRODUCTION 24.1
24.2 ELECTRIC MOTORS 24.1
24.2.1 Basic Brushed DC Motors 24.3
24.2.2 AC Motors 24.7
24.2.3 Brushless DC Motors 24.15
24.2.4 Stepper Motors 24.17
24.2.5 Wound Field Motors 24.19
24.3 HYDRAULICS 24.23
24.4 OTHER SYSTEMS 24.24

27.1 INTRODUCTION 27.1
27.2 SERIAL COMMUNICATIONS 27.2
27.2.1 RS-232 27.5
ASCII Functions 27.9
27.3 PARALLEL COMMUNICATIONS 27.13
27.4 DESIGN CASES 27.14
27.4.1 PLC Interface To a Robot 27.14
27.5 SUMMARY 27.15
27.6 PRACTICE PROBLEMS 27.15
27.7 PRACTICE PROBLEM SOLUTIONS 27.16
27.8 ASSIGNMENT PROBLEMS 27.18
28. NETWORKING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1
28.1 INTRODUCTION 28.1
28.1.1 Topology 28.2
28.1.2 OSI Network Model 28.3
28.1.3 Networking Hardware 28.5
28.1.4 Control Network Issues 28.7
28.2 NETWORK STANDARDS 28.8
page x
28.2.1 Devicenet 28.8
28.2.2 CANbus 28.12
28.2.3 Controlnet 28.13
28.2.4 Ethernet 28.14
28.2.5 Profibus 28.15
28.2.6 Sercos 28.15
28.3 PROPRIETARY NETWORKS 28.16
28.3.1 Data Highway 28.16
28.4 NETWORK COMPARISONS 28.20
28.5 DESIGN CASES 28.22
28.5.1 Devicenet 28.22

29.5 PRACTICE PROBLEM SOLUTIONS 29.11
29.6 ASSIGNMENT PROBLEMS 29.11
page xi
30. HUMAN MACHINE INTERFACES (HMI) . . . . . . . . . . . . . . . 30.1
30.1 INTRODUCTION 30.1
30.2 HMI/MMI DESIGN 30.2
30.3 DESIGN CASES 30.3
30.4 SUMMARY 30.3
30.5 PRACTICE PROBLEMS 30.4
30.6 PRACTICE PROBLEM SOLUTIONS 30.4
30.7 ASSIGNMENT PROBLEMS 30.4
31. ELECTRICAL DESIGN AND CONSTRUCTION . . . . . . . . . . 31.1
31.1 INTRODUCTION 31.1
31.2 ELECTRICAL WIRING DIAGRAMS 31.1
31.2.1 Selecting Voltages 31.8
31.2.2 Grounding 31.9
31.2.3 Wiring 31.12
31.2.4 Suppressors 31.13
31.2.5 PLC Enclosures 31.14
31.2.6 Wire and Cable Grouping 31.16
31.3 FAIL-SAFE DESIGN 31.17
31.4 SAFETY RULES SUMMARY 31.18
31.5 REFERENCES 31.20
31.6 SUMMARY 31.20
31.7 PRACTICE PROBLEMS 31.20
31.8 PRACTICE PROBLEM SOLUTIONS 31.20
31.9 ASSIGNMENT PROBLEMS 31.20
32. SOFTWARE ENGINEERING . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1
32.1 INTRODUCTION 32.1
32.1.1 Fail Safe Design 32.1

34.1.4 Compare 34.10
34.1.5 Calculation and Conversion 34.14
34.1.6 Logical 34.20
34.1.7 Move 34.21
34.1.8 File 34.22
34.1.9 List 34.27
34.1.10 Program Control 34.30
34.1.11 Advanced Input/Output 34.34
34.1.12 String 34.37
34.2 DATA TYPES 34.42
35. COMBINED GLOSSARY OF TERMS . . . . . . . . . . . . . . . . . . . 35.1
35.1 A 35.1
35.2 B 35.2
35.3 C 35.5
35.4 D 35.9
35.5 E 35.11
35.6 F 35.12
35.7 G 35.13
35.8 H 35.14
35.9 I 35.14
35.10 J 35.16
35.11 K 35.16
35.12 L 35.17
35.13 M 35.17
35.14 N 35.19
35.15 O 35.20
page xiii
35.16 P 35.21
35.17 Q 35.23
35.18 R 35.23

(PLCs). It is my personal hope that by employing the knowledge in the book that you will
be able to quickly write controls programs that work as expected (and avoid having to
learn by costly mistakes.)
This book has been designed for students with some knowledge of technology,
including limited electricity, who wish to learn the discipline of practical control system
design on commonly used hardware. To this end the book will use the Allen Bradley Con-
trolLogix processors to allow depth. Although the chapters will focus on specific hard-
ware, the techniques are portable to other PLCs. Whenever possible the IEC 61131
programming standards will be used to help in the use of other PLCs.
In some cases the material will build upon the content found in a linear controls
course. But, a heavy emphasis is placed on discrete control systems. Figure 1.1 crudely
shows some of the basic categories of control system problems.
Figure 1.1 Control Dichotomy
• Continuous - The values to be controlled change smoothly. e.g. the speed of a car.
• Logical/Discrete - The value to be controlled are easily described as on-off. e.g.
the car motor is on-off. NOTE: all systems are continuous but they can be
treated as logical for simplicity.
e.g. “When I do this, that always happens!” For example, when the power
is turned on, the press closes!
CONTROL
CONTINUOUS
DISCRETE
LINEAR NON_LINEAR
CONDITIONAL
SEQUENTIAL
e.g. PID
e.g. MRAC
e.g. FUZZY LOGIC
BOOLEAN
TEMPORAL

2. As the elevator approaches the correct position, slow down.
Non-linear:
1 Accelerate slowly to start.
2. Decelerate as you approach the final position.
3. Allow faster motion while moving.
4. Compensate for cable stretch, and changing spring constant, etc.
Logical and sequential control is preferred for system design. These systems are
more stable, and often lower cost. Most continuous systems can be controlled logically.
But, some times we will encounter a system that must be controlled continuously. When
this occurs the control system design becomes more demanding. When improperly con-
trolled, continuous systems may be unstable and become dangerous.
When a system is well behaved we say it is self regulating. These systems don’t
need to be closely monitored, and we use open loop control. An open loop controller will
set a desired position for a system, but no sensors are used to verify the position. When a
plc wiring - 1.3
system must be constantly monitored and the control output adjusted we say it is closed
loop. A cruise control in a car is an excellent example. This will monitor the actual speed
of a car, and adjust the speed to meet a set target speed.
Many control technologies are available for control. Early control systems relied
upon mechanisms and electronics to build controlled. Most modern controllers use a com-
puter to achieve control. The most flexible of these controllers is the PLC (Programmable
Logic Controller).
The book has been set up to aid the reader, as outlined below.
Sections labeled Aside: are for topics that would be of interest to one disci-
pline, such as electrical or mechanical.
Sections labeled Note: are for clarification, to provide hints, or to add
explanation.
Each chapter supports about 1-4 lecture hours depending upon students
background and level in the curriculum.
Topics are organized to allow students to start laboratory work earlier in the

method for controlling a system. More recently electricity has been used for control and
early electrical control was based on relays. These relays allow power to be switched on
and off without a mechanical switch. It is common to use relays to make simple logical
control decisions. The development of low cost computer has brought the most recent rev-
olution, the Programmable Logic Controller (PLC). The advent of the PLC began in the
1970s, and has become the most common choice for manufacturing controls.
PLCs have been gaining popularity on the factory floor and will probably remain
predominant for some time to come. Most of this is because of the advantages they offer.
• Cost effective for controlling complex systems.
• Flexible and can be reapplied to control other systems quickly and easily.
• Computational abilities allow more sophisticated control.
• Trouble shooting aids make programming easier and reduce downtime.
• Reliable components make these likely to operate for years before failure.
2.1.1 Ladder Logic
Ladder logic is the main programming method used for PLCs. As mentioned
before, ladder logic has been developed to mimic relay logic. The decision to use the relay
Topics:
Objectives:
• Know general PLC issues
• To be able to write simple ladder logic programs
• Understand the operation of a PLC
• PLC History
• Ladder Logic and Relays
• PLC Programming
• PLC Operation
• An Example
plc wiring - 2.2
logic diagrams was a strategic one. By selecting ladder logic as the main programming
method, the amount of retraining needed for engineers and tradespeople was greatly
reduced.

Figure 2.2 A Simple Relay Controller
The example in Figure 2.2 does not show the entire control system, but only the
logic. When we consider a PLC there are inputs, outputs, and the logic. Figure 2.3 shows a
more complete representation of the PLC. Here there are two inputs from push buttons.
We can imagine the inputs as activating 24V DC relay coils in the PLC. This in turn drives
an output relay that switches 115V AC, that will turn on a light. Note, in actual PLCs
inputs are never relays, but outputs are often relays. The ladder logic in the PLC is actually
a computer program that the user can enter and change. Notice that both of the input push
buttons are normally open, but the ladder logic inside the PLC has one normally open con-
tact, and one normally closed contact. Do not think that the ladder logic in the PLC needs
to match the inputs or outputs. Many beginners will get caught trying to make the ladder
logic match the input types.
115VAC
wall plug
relay logic
input A
(normally closed)
input B
(normally open)
output C
(normally open)
ladder logic
AB C
plc wiring - 2.5
Figure 2.3 A PLC Illustrated With Relays
Many relays also have multiple outputs (throws) and this allows an output relay to
also be an input simultaneously. The circuit shown in Figure 2.4 is an example of this, it is
called a seal in circuit. In this circuit the current can flow through either branch of the cir-
cuit, through the contacts labelled A or B. The input B will only be on when the output B
is on. If B is off, and A is energized, then B will turn on. If B turns on then the input B will

be some device outside the PLC that is switched on or off, such as lights or motors. In the
top rung the contacts are normally open and normally closed. Which means if input A is on
and input B is off, then power will flow through the output and activate it. Any other com-
bination of input values will result in the output X being off.
Note: When A is pushed, the output B will turn on, and
the input B will also turn on and keep B on perma-
nently - until power is removed.
A
B
B
Note: The line on the right is being left off intentionally
and is implied in these diagrams.