Programmable Logic Controllers

This is the introduction to PLCs for which baffled students, technicians and managers have been waiting. In this straightforward, easy-to-read guide, Bill Bolton has kept the maths to a minimum, avoided detailed programming instructions and presented the subject in a way that is not device specific - increasing its applicability to courses in electronics and control systems. Having read this book, you should be able to: * Identify the main design characteristics and internal architecture of PLCs. * Describe and identify the characteristics of commonly used input and output devices. * Explain the processing of inputs and outputs of PLCs. * Describe communication links involved with control systems. * Develop ladder programs for the logic functions AND, OR, NOR, NAND, NOT and XOR. * Demonstrate use of internal relays, timers, counters, shift registers, sequencers and data handling. * Identify fail/safe methods. * Identify methods used for fault diagnosis, testing and debugging programs. The third edition has been expanded to contain new material on fail / safe operating conditions, Sequential Function Charts, floating point numbers and dummy rungs, with discussion of commercial PLCs. There is also extended coverage on the programming of PLCs for fault diagnosis, as well as distributed systems and program documentation. Each chapter is followed with a Problems section, for students to put the theory they have learnt into practice. Appendices contain further problems, and answers to all questions from each chapter are included at the back of the book.