In January, I reviewed a book that really didn’t further the cause of PLC training or information delivery. I have better news this month.
I picked up another book at the ISA show (actually they mailed it to me, and at a price of 75 “loonies” and five pounds shipping weight, I’m sure it cost them a bundle to get it across the border) to see if there was anything “new.”
This book is a brute—more than 1,400 pages. No, I didn’t read them all. However, I read enough to tell you that it’s part of the evolution of data transfer in print.
Programmable Logic Controllers: An Emphasis on Design and Application, from Dogwood Valley Press, was written by Dr. Kelvin Erickson, a professor at the University of Missouri–Rolla campus. The book makes nothing of his Ph.D, which is a really good start!
The first page of the preface reads, “The industry trend is toward using the IEC-61131-3 standard.” I almost cried (refer to my January column about that) with joy. This guy is on the ball.
I swear Erickson must have attended one of my courses, seminars or presentations, or he mind-melded with me somewhere. I couldn’t believe what I was reading. It was totally how I think. I might sound biased from here on, but not too biased, since I’m writing my own take on the subject.
The book covers four vendors: GE Fanuc, Rockwell Automation, Schneider Electric, and Siemens E&A. Ideas and examples are given for five different PLC types, so in a year or so the examples will be dated. But it’s useful to absorb the concepts he delivers, rather than all of the intimate details. Many drawings populate the pages, showing application examples, as well as sectional questions and problems.
Twenty-two chapters deal with all topics surrounding automation projects using PLCs. While the vast size might be intimidating, Erickson has written a reasonable dissection of the PLC models. So, if you are not interested in the Siemens PLC, for instance, then turn the page.
His examples are real. If you’re unfamiliar with process P&ID drawings, some might seem foreign to you. The same could be said for process people who wish to learn a bit about discrete.
Most of the examples are shown in the PLC vendors’ nomenclatures. So, for the maintenance electrician who has to deal with more than one vendor, the comparison is invaluable. The I/O addressing and memory-mapping comparison is worth the price of admission.
The coverage of IEC-61131 is complete, and rivals standalone books on the subject. Erickson not only covers the languages, but also the application of those languages and where the big benefits come from.
The PID (proportional–integral-derivative) treatment gives you a lesson on what it is, as well as the implementations in each controller.
I don’t agree with the way the author treats basic ladder logic instructions, but that could be just differences in personal habits. His statement that the reader needs to diverge from relay thinking to PLC thinking presumes that you’re electrically minded, and the book takes that for granted. However if you were mechanically minded, or process-centric, you will find many reasons to read portions of the text.
With Rockwell Automation, he addresses both the PLC-5 family and the new PAC family of ControlLogix processors. The ControlLogix family hasn’t been around for long, and this is the first non-Rockwell-originated text I know of dealing with any portion of that PLC family.
Erickson’s knowledge of the hardware and software and the application of these devices comes through loud and clear. The depth to which any topic is drilled sometimes isn’t necessary for the target market. Not everyone wants to know everything, which could make the general reading a bit on the tedious side. The security settings on a PLC-5 processor, for instance, are well documented in RSLogix (the PLC-5/ControlLogix programming software), and probably could have been left out, although he does give examples of how it could be implemented.
This book might not be a starting point for just anyone, though instructor-led training with this text would be great for beginners. It is a good entry point for control engineering people, maintenance electricians, and anyone wanting to learn more about various types of PLCs.
At 15 bucks a pound, it will feed you for some time.
|About the Author|
Jeremy Pollard, CET, has been writing about technology and software issues for many years. Publisher of The Software User Online, he has been involved in control system programming and training for more than 20 years. He’ll be pleased to hear from you, so e--mail him at firstname.lastname@example.org.