Programmable Logic Controller (PLC) is microprocessor based industrial control system. It monitors inputs, makes decisions based on its program, and regulates outputs to automate a process or machine. As computer based system PLCs are typically programmed in an IEC 61131 programming language, and are designed for real-time use in rugged, industrial environments. Connected to sensors and actuators, PLCs are categorized by the number and type of input-output (I/O) ports they provide and their I/O scan rate. In addition PLCs can communicate with other process control components through data links. In the late 1960s, PLCs were first used to replace the hardwired networks of relays and timers in process assembly lines, which were partially automated at that time. Nowadays, the functionality of the PLC has enormously evolved and includes typical relay control, sophisticated motion control, process control, distributed control systems and complex networking. In general, the line between a general purpose programmable computer and a PLC is thinning.
This book is designed to provide information on successfully integrating a PLC into actual process control system. It not only deals with the PLC hardware and software, but all the surrounding building blocks that must be compatible in order to achieve a safe and reliable PLC industrial control system. The book has total 17 chapters, organized into two parts, two appendices, and a comprehensive Index. It comes with CD ROM in which reference material from Allen-Bradley is provided with the text. The book covers the following subjects: