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.
Table of Contents (25 chapters)
1
Part 1 – An Introduction to Advanced PLC Programming
6
Part 2 – Modularity and Objects
10
Part 3 – Software Engineering for PLCs
14
Part 4 – HMIs and Alarms
19
Part 5 – Final Project and Thoughts

Understanding error handling

Errors can kill the execution of a program, which, in turn, can lead to injury or death. A fatal error will halt the execution of a program. These fatal errors are typically called exceptions. Essentially, an exception occurs when the PLC encounters a problem that it cannot handle at runtime. The ultimate fate of the PLC when an unhandled exception occurs is the program locking up and the PLC needing a reboot. On top of all that, if the condition that caused the error originally occurs again, the program will crash again, and the system will need to be rebooted. In essence, the only safe way to handle the condition is to modify the code to ensure that the condition does not happen again.

Exception errors will not show up during the compilation process. Instead, exceptions occur when the program is running. Due to their nature, it is often difficult or impossible to fully predict when an exception will occur. To make matters worse, some exceptions can...