Embedded Systems and PLC

The world of automatic control surrounds us so completely that its workings largely escape notice. A washing machine faithfully sequences through its wash cycle, an automobile's engine control unit adjusts fuel injection thousands of times per minute, and an industrial bottling line fills, caps, and labels thousands of containers per hour — all governed by embedded computing intelligence that operates silently, reliably, and, for the most part, invisibly. This book was conceived to illuminate that intelligence: to explain, in a rigorous yet accessible manner, both the general-purpose embedded systems that pervade consumer and industrial products alike, and the specialised, industrially hardened class of embedded controller known as the Programmable Logic Controller (PLC) that governs the vast majority of the world's factories, process plants, and infrastructure.
The decision to treat embedded systems and PLCs within a single, unified volume, rather than as two entirely separate subjects, was deliberate and, I believe, pedagogically important. As Chapter 18 of this book argues at length, a PLC is not a fundamentally different technology from a general-purpose embedded system, but rather a specialised, ruggedised, and standardised category within the broader embedded-systems domain — sharing the same underlying microcontroller architectures, the same fundamental concepts of sensors, actuators, interrupts, and real-time scheduling, and, increasingly in modern industrial practice, converging technologies such as the soft PLC. A student or practising engineer who understands both domains, and appreciates their relationship, is far better equipped for a career in modern automation, mechatronics, or embedded product engineering than one who has studied only one in isolation.
This book is organised into three parts. Part I (Chapters 1–9) lays the foundation of embedded systems: their definition, classification, and application domains; hardware architecture, processors, and memory systems; sensors, actuators, and signal conditioning; communication interfacing; embedded software development; real-time operating systems; and design methodology. Part II (Chapters 10–17) turns to Programmable Logic Controllers in comparable depth: their history and architecture; the IEC 61131-3 family of programming languages, with particular emphasis on ladder logic; timers, counters, and sequencing; industrial communication networks; SCADA and HMI systems; and practical installation, troubleshooting, and maintenance. Part III (Chapters 18–20) draws the two domains together through direct comparison, a series of worked industrial case studies, and a forward-looking examination of Industry 4.0 and the Industrial Internet of Things.
Throughout the book, I have aimed to balance conceptual rigour with practical relevance. Each chapter concludes with a set of review questions intended to consolidate understanding and support use of this book in a formal academic course, while original figures, diagrams, and tables — prepared specifically for this book — are provided throughout to support visual as well as textual understanding of the material. Every effort has been made to verify technical claims, standards references, and historical facts against authoritative and current sources prior to inclusion in this text.
This book is intended primarily for undergraduate and postgraduate students of electronics, electrical, instrumentation, mechatronics, and industrial automation engineering, as well as for practising engineers and technicians seeking a structured, comprehensive reference spanning both embedded systems and PLC technology. No prior background beyond basic digital electronics and elementary programming concepts is assumed, though readers with some prior exposure to either subject will find the integrated treatment offered here a valuable complement to more narrowly focused texts.