Additional information
by Rosario Cirrito (Author)
This booklet is the first of a series dedicated to automation recipes created with the PLC (Programmable Logic Controller) and HMI (Human Machine Interface) binomial. The series is aimed at an audience of readers with an elementary knowledge of PLC programming, eager to learn advanced solutions, extensively tested on real systems. In modern computer programming, generally oriented to the development of "object-oriented" software, the developer strives, as much as possible, to resort to so-called "Design Patterns", standard solutions for frequently recurring problems. A design pattern describes a problem, particularly recurring in a given context, and then provide the heart of the solution to this problem. It is therefore possible to successfully reuse this solution, thousands and thousands of times, with the certainty of using an efficient and well-tested solution. Patterns can ultimately be considered as "elegantly formalized" best practices, which the programmer is quick to use to simultaneously achieve both an exponential decrease in development time and greater robustness and reliability of the generated code. In the present series, which deals exclusively with development on PLC-HMI, the term "design pattern" has been replaced by the term "automation recipe" for an easier understanding by the non IT reader. In the chapters of this book we will show in detail an automation recipe that can be reused in any PLC-HMI automation project that uses "electric motors". The recipe has also been optimized for operation with Scada supervision systems. In detail the book illustrates the automation recipe for the automation of electric motors powered by three-phase alternating current. The first section, dedicated to a brief introduction to the application domain, illustrates the physical structure of an electric motor and the main types of starting: direct at full voltage and with reduced voltage, obtained with a star - delta switching. The second section deals with the development of combined software for both PLC and HMI. The logic of the main functional block (UDFB), ElectricMotor, as well as the HMI monitoring and local control screens, are analyzed in detail. An auxiliary function block, the twin sequencer Mot2Seq, is then introduced, to explain the pratical usage of ElectricMotor in a real application for twin-pumps automation. The HMI solutions have been extensively tested on the OCS, Operator Control System, manufactured by Horner Apg. OCS combines a Controller, Operator Interface, Network and I/O into a single product. While the author, has been widely using Siemens, Allen Bradley, GE Fanuc PLCs he has focused the books of this series on the Horner OCSs because Horner provides Cscape, an integrated development environment, extremely easy to use and above all completely free. All the logics, published in the book, have been developed using the IEC61131-3 compliant Ladder language; therefore it is extremely easy to migrate them on almost all the PLCs of other manufacturers. The same applies to HMI screens whose graphic controls are very similar on the different equipment offered on the market. The reader who already has experience with other manufacturers' equipment can therefore continue to use what he knows best.
