Programmable Logic Controllers

Widely used across industrial and manufacturing automation, Programmable Logic Controllers (PLCs) perform a broad range of electromechanical tasks with multiple input and output arrangements, designed specifically to cope in severe environmental conditions such as automotive and chemical plants.

Programmable Logic Controllers: A Practical Approach using CoDeSys is a hands-on guide to rapidly gain proficiency in the development and operation of PLCs based on the IEC 61131-3 standard. Using the freely-available* software tool CoDeSys, which is widely used in industrial design automation projects, the author takes a highly practical approach to PLC design using real-world examples. The design tool, CoDeSys, also features a built in simulator/soft PLC enabling the reader to undertake exercises and test the examples.

Key features:

• Introduces to programming techniques using IEC 61131-3 guidelines in the five PLC-recognised programming languages.

• Focuses on a methodical approach to programming, based on Boolean algebra, flowcharts, sequence diagrams and state-diagrams.

• Contains a useful methodology to solve problems, develop a structured code and document the programming code.

• Covers I/O like typical sensors, signals, signal formats, noise and cabling.

• Features Power Point slides covering all topics, example programs and solutions to end-of-chapter exercises via companion website.

No prior knowledge of programming PLCs is assumed making this text ideally suited to electronics engineering students pursuing a career in electronic design automation. Experienced PLC users in all fields of manufacturing will discover new possibilities and gain useful tips for more efficient and structured programming.

• Register at www.codesys.com

www.wiley.com/go/hanssen/logiccontrollers

Autorentext
Dag H. Hanssen works as an Assistant Professor in automation at the Institute of Engineering and Safety at the University of Tromsø. During the course of his 18 year long career with the university he has taught many different courses, but he now focusses on control technique, process automation and Application Development.

Inhalt

Preface xiv

Part One Hardware 1

1 About PLCs 3

1.1 History 4

1.1.1 More Recent Developments 6

1.2 Structure 7

1.2.1 Inputs and Outputs 10

1.3 PLC Operation 13

1.3.1 Process Knowledge 14

1.3.2 Standard Operations 16

1.3.3 Cyclic, Freewheeling, or EventControlled Execution 18

1.4 Test Problems 19

2 Digital Signals and Digital Inputs and Outputs 20

2.1 Introduction 20

2.2 Terminology 21

2.2.1 Discrete, Digital, Logical, and Binary 21

2.2.2 Sensors, Transducers, and Transmitters 22

2.3 Switches 24

2.3.1 Limit Switches 24

2.3.2 Safety Devices 24

2.3.3 Magnetic Switches 25

2.4 Logical Sensors 26

2.4.1 Inductive Sensors 27

2.4.2 Capacitive Sensors 29

2.4.3 Photocells 30

2.4.4 Ultrasonic Sensors 33

2.4.5 Rotating Sensors (Encoders) 34

2.4.6 Other Detection Principles and Sensors 37

2.5 Connection of Logical Sensors 39

2.5.1 Sink/Source 41

2.5.2 Selecting a Sensor with the Proper Type of Output 43

2.6 Properties of Discrete Inputs 44

2.7 Discrete Actuators 45

2.7.1 Relays and Contactors 46

2.7.2 Solenoids and Magnetic Valves 47

2.7.3 Transistor Outputs versus Relay Outputs 49

2.8 Test Problems 50

3 Analog Signals and Analog I/O 52

3.1 Introduction 52

3.2 Digitalization of Analog Signals 53

3.2.1 Filtering 53

3.2.2 A/D Conversion 55

3.3 Analog Instrumentation 58

3.3.1 About Sensors 58

3.3.2 Standard Signal Formats 59

3.3.3 On the 420 mA Standard 59

3.3.4 Some Other Properties of Sensors 61

3.4 Temperature Sensors 61

3.4.1 Thermocouple 61

3.4.2 PT100/NI1000 62

3.4.3 Thermistors 64

3.5 Connection 64

3.5.1 About Noise, Loss, and Cabling 64

3.5.2 Connecting Sensors 67

3.5.3 Connection of a PT100 (RTD) 68

3.5.4 Connecting Thermocouples 72

3.6 Properties of Analog Input Modules 72

3.6.1 Measurement Ranges and Digitizing: Resolution 72

3.6.2 Important Properties and Parameters 74

3.7 Analog Output Modules and Standard Signal Formats 75

3.8 Test Problems 76

Part Two Methodic 79

4 Structured Design 81

4.1 Introduction 81

4.2 Number Systems 82

4.2.1 The Decimal Number Systems 82

4.2.2 The Binary Number System 82

4.2.3 The Hexadecimal Number System 83

4.2.4 BinaryCoded Decimal Numbers 85

4.2.5 Conversion between Number Systems 86

4.3 Digital Logic 87

4.4 Boolean Design 91

4.4.1 Logical Functional Expressions 91

4.4.2 Boolean Algebra 93

4.5 Sequential Design 97

4.5.1 Flowchart 97

4.5.2 Example: Flowchart for Mixing Process 99

4.5.3 Example: Flowchart for an Automated Packaging Line 101

4.5.4 Sequence Diagrams 107

4.5.5 Example: Sequence Diagram for the Mixing Process 110

4.5.6 Example: Batch Process 112

4.6 StateBased Design 113

4.6.1 Why Use State Diagrams? 114

4.6.2 State Diagrams 114

4.6.3 Example: Batch Process 117

4.6.4 Example: Level Process 118

4.6.5 Example: Packing Facility for Apples 121

4.7 Summary 124

4.8 Test Problems 125

Part Three IEC 611313 131

5 Introduction to Programming and IEC 611313 133

5.1 Introduction 133

5.1.1 Weaknesses in Traditional PLCs 134

5.1.2 Improvements with IEC 611313 136

5.1.3 On Implementation of the Standard 137 5.2 Brief Presentation of the Languages 1...