Book Image

Mastering PLC Programming

By : Mason White
Book Image

Mastering PLC Programming

By: Mason White

Overview of this book

Object-oriented programming (OOP) is a new feature of PLC programming that has taken the automation world by storm. This book provides you with the necessary skills to succeed in the modern automation programming environment. The book is designed in a way to take you through advanced topics such as OOP design, SOLID programming, the software development lifecycle (SDLC), library design, HMI development, general software engineering practices, and more. To hone your programming skills, each chapter has a simulated real-world project that’ll enable you to apply the skills you’ve learned. In all, this book not only covers complex PLC programming topics, but it also removes the financial barrier that comes with most books as all examples utilize free software. This means that to follow along, you DO NOT need to purchase any PLC hardware or software. By the end of this PLC book, you will have what it takes to create long-lasting codebases for any modern automation project.

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Table of Contents (25 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Download the example code files
Download the color images
Conventions used
Get in touch
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1
Part 1 – An Introduction to Advanced PLC Programming
Part 1 – An Introduction to Advanced PLC Programming
Free Chapter
2
Chapter 1: Software Engineering for PLCs
Chapter 1: Software Engineering for PLCs
Technical requirements
Software engineering for PLCs
Understanding the IEC 61131-3 standard
Introducing CODESYS
Testing CODESYS
Summary
Questions
3
Chapter 2: Advanced Structured Text — Programming a PLC in Easy-to-Read English
Chapter 2: Advanced Structured Text — Programming a PLC in Easy-to-Read English
Technical requirements
Understanding error handling
Understanding pointers
Understanding references
Understanding documentation
Understanding state machines
Summary
Questions
Further reading
4
Chapter 3: Debugging — Making Your Code Work
Chapter 3: Debugging — Making Your Code Work
Technical requirements
What is debugging?
Understanding debugging tools and techniques
Troubleshooting – a practical example
Summary
Questions
Further reading
5
Chapter 4: Complex Variable Declaration — Using Variables to Their Fullest
Chapter 4: Complex Variable Declaration — Using Variables to Their Fullest
Technical requirements
Auto declaring variables
Understanding constants
Investigating arrays
Exploring global variable lists
Understanding structs
Getting to know enums
Exploring persistent variables
Final project – motor control program
Summary
Questions
Further reading
6
Part 2 – Modularity and Objects
Part 2 – Modularity and Objects
7
Chapter 5: Functions — Making Code Modular and Maintainable
Chapter 5: Functions — Making Code Modular and Maintainable
Technical requirements
What is modular code?
Why use modular code?
Exploring functions
Examining return types
Understanding arguments
Final project – temperature unit converter
Summary
Questions
Further reading
8
Chapter 6: Object-Oriented Programming — Reducing, Reusing, and Recycling Code
Chapter 6: Object-Oriented Programming — Reducing, Reusing, and Recycling Code
Technical requirements
What is OOP?
Why use OOP?
Understanding function blocks
Getting to know objects
Getting to know methods
Getting to know properties
Understanding the purpose of a getter and setter
Understanding recursion and the THIS keyword
Final project – creating a unit converter
Summary
Questions
Further reading
9
Chapter 7: OOP — The Power of Objects
Chapter 7: OOP — The Power of Objects
Technical requirements
Understanding access specifiers
Exploring the pillars of OOP
Inheritance versus composition
Examining interfaces
Getting to know design patterns
Final project – creating a simulated assembly line
Summary
Questions
Further reading
10
Part 3 – Software Engineering for PLCs
Part 3 – Software Engineering for PLCs
11
Chapter 8: Libraries — Write Once, Use Anywhere
Chapter 8: Libraries — Write Once, Use Anywhere
Technical requirements
Investigating libraries
Guiding principles for library development
Building custom libraries
Final project – part computation library
Summary
Questions
Further reading
12
Chapter 9: The SDLC — Navigating the SDLC to Create Great Code
Chapter 9: The SDLC — Navigating the SDLC to Create Great Code
Technical requirements
Understanding the SDLC
Investigating the general steps of the SDLC
Final project – creating a simple library
Summary
Questions
Further reading
13
Chapter 10: Advanced Coding — Using SOLID to Make Solid Code
Chapter 10: Advanced Coding — Using SOLID to Make Solid Code
Technical requirements
Introducing SOLID programming
Benefits of SOLID programming
The governing principles of SOLID programming
Final project – a painting machine
Summary
Questions
Further reading
14
Part 4 – HMIs and Alarms
Part 4 – HMIs and Alarms
15
Chapter 11: HMIs — UIs for PLCs
Chapter 11: HMIs — UIs for PLCs
Technical requirements
Understanding HMIs
HMIs versus SCADA
How the SDLC applies to HMIs
Exploring wireframing
Final project – creating an HMI
Summary
Questions
Further reading
16
Chapter 12: Industrial Controls — User Inputs and Outputs
Chapter 12: Industrial Controls — User Inputs and Outputs
Technical requirements
Exploring common HMI controls
Final project – creating a simple HMI
Summary
Questions
Further reading
17
Chapter 13: Layouts — Making HMIs User-Friendly
Chapter 13: Layouts — Making HMIs User-Friendly
Technical requirements
The importance of colors
Understanding grouping/position
Best practices for blinking
Organizing the screen into multiple layouts
Final project – creating a user-friendly HMI
Summary
Questions
Further reading
18
Chapter 14: Alarms — Avoiding Catastrophic Issues with Alarms
Chapter 14: Alarms — Avoiding Catastrophic Issues with Alarms
Technical requirements
What are alarms?
Alarm configuration – I, Warning, and Error setup
Alarm HMI components
PLC alarm logic
Alarm acknowledgment
Final project – motor alarm system
Summary
Questions
Further reading
19
Part 5 – Final Project and Thoughts
Part 5 – Final Project and Thoughts
20
Chapter 15: Putting It All Together — The Final Project
Chapter 15: Putting It All Together — The Final Project
Technical requirements
Project overview
Getting the requirements
HMI design
HMI implementation
PLC code design
Implementing the PLC code
Testing the application
Summary
Questions
21
Chapter 16: Distributed Control Systems, PLCs, and Networking
Chapter 16: Distributed Control Systems, PLCs, and Networking
Technical requirements
What are computer networks?
Common IT protocols
PLC/automation device communication
Understanding distributed control systems
The differences between DCSs and PLCs
Summary
Questions
Further reading
22
Assessments
Assessments
Chapter 1: Software Engineering for PLCs
Chapter 2: Advanced Structured Text — Programming a PLC in Easy-to-Read English
Chapter 3: Debugging — Making Your Code Work
Chapter 4: Complex Variable Declaration — Using Variables to Their Fullest
Chapter 5: Functions — Making Code Modular and Maintainable
Chapter 6: OOP — Reducing, Reusing, and Recycling Code
Chapter 7: OOP — The Power of Objects
Chapter 8: Libraries — Write Once, Use Anywhere
Chapter 9: The SDLC — Navigating the SDLC to Create Great Code
Chapter 10: Advanced Coding — Using SOLID to Make Solid Code
Chapter 11: HMIs — UIs for PLCs
Chapter 12: Industrial Controls — User Inputs and Outputs
Chapter 13: Layouts — Making HMIs User Friendly
Chapter 14: Alarms — Avoiding Catastrophic Issues with Alarms
Chapter 15: Putting It All Together — The Final Project
Chapter 16: Distributed Control Systems, PLCs, and Networking
23
Index
Index
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24
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Understanding state machines

As a software engineer, especially one that writes PLC code, you must understand what state machines are. State machines to PLC programmers are what the Model-View-Controller (MVC) pattern is for web developers. To be a quality PLC programmer, you must understand what a state machine is and how to implement one.

The most simplified way to think of a state machine is as a series of states that can transition from one state to another. A simple example of a state machine is a lightbulb connected to a switch. The following diagram represents the state of a lightbulb:

Figure 2.14 – Lightbulb state machine

Figure 2.14 – Lightbulb state machine

As can be seen with the arrows, if the lightbulb is on, it can transition to off when the switch is flicked down. If the lightbulb is off, it can transition to an on state when the switch is flicked up.

The majority of state machines that you are going to work with as a PLC programmer are called finite state machines...

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