Programmable Logic Controllers
by W. Bolton, Published by Newnes (Fourth Edition)
ISBN 0-7506-8112-8, paperback,292 pp, $29.95
EN-Genius Reviewer: Dennis L. Feucht

This book, printed and bound in the UK, offers a reasonably complete coverage of the technology underlying programmable logic controllers (PLCs), which are rugged computers typically used in industrial automation and process control applications. They are controllers with a programming interface based on ladder logic and ladder diagrams. The concepts are tailored for technicians who maintain and adapt such systems, and are easily grasped. The author does a good job of explaining the basic concepts involved in combinational logic, state machines, number systems of different bases, and how the programming instruction-sets of PLCs relate to ladder logic design. Various components familiar to digital designers appear, such as chapters on counters and shift registers. As for analog, the author does a reasonable job in presenting a useful amount of detail on a wide variety of I/O devices, including sensors and actuators of various kinds.

This book has problem sets at the end of each chapter and it would make a good textbook not only for teaching technicians PLC technology, but also the rudiments of embedded systems, electromechanics, and even robotics. I do not care for the boxy European style of circuit-diagram symbols, but this can be worked around easily enough. Realistic programming examples of PLC designs are given in the last chapter.

Overall, I would rate this book as somewhat brill (British). It can be a versatile book in that engineers could provide copies to technicians working amongst them (as the Brits might also say) to increase competency in various technologies, or at least provide an introduction to new technologies they will encounter on a new project. In this sense, the book is for the section of an engineer's bookshelf holding loan copies. This one would be good to loan, whether one is working on industrial automation or on ordinary programming, logic, and sensor-actuator interfacing, or to read over high tea:

"Yes, well it's tea, you know, with cocoa and scones, and eggs if you've got hens and bacon if you've killed a pig, and marmalade and Bovril and kippers, and you have it late for tea, about six."
"How terrible this must be!"
"Oh no -- high tea is absolutely smashing. Until you come to suppertime, and then I must say you do rather long for supper."

From Nancy Mitford's novel The Blessing -- while dining in Paris.