The Future of Programmable Logic Controllers

Abstract

     The topic of this paper is The Future of Programmable Logic Controllers (PLC).  My objective is to explore the possible future uses of PLCs.  To achieve this objective I read several articles written over the past several years on the future uses of PLCs.  After performing this research I believe that PLCs have a bright future indeed.

 

Introduction

     “A Programmable Logic Controller (PLC) is an industrial grade digital computer that is capable of being programmed to perform control functions.” PLC’s are used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures.  Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact.  “PLC’s have eliminated much of the hardwiring associated with conventional relay control circuits.”  Some of the benefits of PLC’s include easy programming and installation, high control speed, network capability, troubleshooting and testing convenience, and high reliability.”[1]

The parts of a PLC

     The basic PLC has only a few parts.  “First, a central processing unit (CPU), the CPU is the brain of the whole operation.  A typical processor usually consists of a microprocessor for implementing the logic and controlling the communications among the modules.  The processor requires memory for storing the results of the logical operations performed by microprocessor.  Memory is also required for the program EPROM or EEPROM plus RAM.  The CPU controls all PLC activity and is designed so that the user can enter the desired program is relay ladder logic.”[2] Next, a power supply that supplies power to other modules that are plugged into the rack.  The input and output (I/O) portions are just that, the inputs and the outputs.  “The I/O system forms the interface by which field devices are connected to the controller.  The purpose of this interface is to condition the various signals received from or sent to external field devices.”[2] Finally we have a programming device which is used to enter the desired program into the memory of the processor.  “A personal computer (PC) is the most commonly used programming device.  Most brands of PLCs have software available to that a PC can be used as the programming device.  The PC communicates with the PLC processor via a serial or parallel data communications link, or Ethernet.  If the programming unit is not in use, it may be unplugged and removed.  A program is a user-developed series of instructions that directs the PLC to execute actions.  A programming language provides rules for combining the instructions so that they produce the desired actions.  Relay ladder logic (RLL) is the standard programming language used with PLCs.”[2]

Another use for PLCs

     PLC technology may very well be the future of multi-room audio systems.  “If you’re lucky enough to own a home pre-wired for audio, video, cable and network communications, you’re ready for a whole house music system. If you don’t own a networked home, and have no plans to retrofit your home with network wiring, PLC technology may be for you. PLC enables the distribution of music and control signals throughout your home via your home’s existing electrical wiring. PLC makes it easy to setup a multi-room audio system without installing any new wiring in your home.  PLC is based on Powerline Carrier technology that piggybacks audio and control signals over the alternating current or AC electrical wiring that almost all homes have. HomePlug is the name of the industry group whose mission is to promote PLC technology and adopt product standards.”[4]

 

A bright future for PLCs

     According to the many articles I read, the future of PLCs is bright indeed.  The following is taken from a June 2008 article published on the Engineering Talk website by the Arc Advisory Group.  The Arc Advisory Group is the leading research and advisory firm for manufacturing, energy, and supply chain solutions.  “PLCs, which are used across all major discrete and process industries, will continue to experience growth as robust, emerging economies create buoyant demand for increasing automation.  While a cooling off period is expected, automation demand is expected to continue to grow during the forecast period.  The market is demanding the programmable automation controller (PAC), a multi-disciplined controller capable of providing real-time logic, motion and process control, in addition to HMI and other functions, on a single platform.  Major automation suppliers have extended PLC functions beyond just logic, especially in higher end models.  The PLC-based PAC market growth is expected to be higher than the overall PLC market growth.  This growth will be driven by the logical extension of PLC functionality to a multi-disciplinary platform.  ARC predicts that most of the small and large PLCs of today, as well as some of the micro PLCs, will morph into PACs, and the pure PLCs will remain at the Nano and some of the micro level.  PLC applications cut across discrete, process and hybrid automation segments, and are poised for steady growth across all manufacturing.  Manufacturing companies, acutely aware of the need for more automation, and for both producing and saving energy to cope with rapidly rising energy demands and costs globally, are increasingly using PLCs.”[3]

Conclusion

     In writing this paper I have discovered that we have only begun to tap into the many possible uses of PLCs.  I believe it is only a matter of putting our imaginations to work and we may find many as yet unforeseen uses for PLCs.

References

[1]Dane E. Gilkey, (2011, April 6), EET 331 Programmable Logic Controllers, “LogixPro Relay Logic Introductory Lab”.

[2] Text Book by Frank D. Petruzella, “Programmable Logic Controllers”, 4^th Edition, Published by McGraw-Hill, 2005.

[3]Engineeringtalk, Initials. (2008, June 12). The future for programmable logic controllers. Retrieved from http://www.engineeringtalk.com/news/arb/arb201.html

[4]Gary Altunian, Initials. (2011). Is plc technology the future of multiroom audio?. Retrieved from http://stereos.about.com/od/advancedstereotopics/a/homeplug.htm