What Is a PLC?

A PLC is a Programmable Logic Controller. In its purest form it is an industrial computer used as a stand alone unit. It can also be used in a network of PLCs to automatically control a process or perform a specific function.
PLCs use different forms of connected sensors to take in information from the outside world such as speed of an object, level in a tank, temperature of a liquid just to name a few. These real world Potential Entry Of New Competitors signals are transformed into electrical signals by the external sensors and relayed to the PLC, which in turn processes the electrical signals and uses them to complete its per-programmed task.
During the late 60’s PLCs were initially used in the automotive industry. Their flexibility to be reprogrammed with pre made programs enabled an assembly line to handle different parts or perform different functions on these parts. Before PLCs came on the scene, once an assembly line was built and wired the only way to change the function of the assembly line was to rewire the hardware involved to change the process.
Some assembly lines had elaborate mechanical machinery that needed to be moved or adjusted in order to be able to handle a new part. This type of machinery was necessary to give some flexibility in handling a small change in parts. While it did give a degree of flexibility the cost was very high and the engineering involved was intense. After the machinery was built its limited flexibility only applied to a certain set of parts.
Currently PLCs are used in so many places you may not be aware of how prevalent they are. I personally have worked on PLCs in the Food and Beverage, Manufacturing, Pharmaceutical, Medical and in different Military applications. These are just a few of the ever growing applications where PLCs are being used.
Many of the previous automation processes that relied mostly on relay logic or the use of hard wired relays have been upgraded throughout the last 25 years. Heavy Industry Meaning This upgraded automation has more flexibility and is easier to modify. This in turn lends itself to have a more efficient and portable process.
PLCs come in many different varieties. Some are small and modular others are a medium size allowing for more flexibility in how and where they are used. Still their are larger units with the capability for much more expansion. The medium and large units not only have more flexibility in what they can interface with in the real world but also in how they can process the signals they receive.
PLCs are programmed using different types of languages. Currently the main languages used are:
-Ladder Diagram
-Sequential Function Charts
-Function Block Diagram
-Structured Text
-Instruction List
The process of selection, programming, installation and maintenance of PLCs has created many new opportunities in the Electrical and Engineering fields. Maintenance Electricians and Technicians now have to be well versed in the fundamentals of how computers work and how computers communicate. The sensors that are connected to the PLCs are much smarter than in previous years, this requires a shift in how one thinks if we are to keep up with the advancing technology. They have to develop new efficient ways of troubleshooting and constant research to sharpen their skills.

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