What Is a Programmable Logic Controller?

A Programmable logic controller is a device that we all take for granted. We use them in all areas of our lives and virtually everything that has been manufactured has been on a production line that has got at least one programmable logic controller in it.  In everyday life the buzz word for programmable logic controller is, smart, as in phone, tv, house and anything else that we input data into.

Programmable Logic Controller

Input And Output Device

Essentially a programmable logic controller is an electronic computer that processes inputted data that produces an action. In manufacturing, programmable logic controllers are used to control the speed of conveyor belts within a modular system. PLCs are also programmed to be reactive and can maintain systems automatically.

Improving Manufacturing Processes

Programmable logic controllers have revolutionised manufacturing because they have become much easier to incorporate into systems.  Recent programmable logic controllers can be programmed using a variety of input devices and no longer require hard wiring every time the instructions have to be changed.  It is also much more economical storing spares because the internal programming means that many different devices and components are required.

First Programmable Logic Controllers

The first commercially successful programmable logic controller was developed by Michael Greenburg in 1973.  Dick Morely invented the first programmable logic controller in 1969 and every single PLC that has been developed since then is based on his initial design.

Programming language

Programmable Logic Controller

The language used to programme a programmable logic controller is often the aspect that makes them seem to be complicated.  This is no longer the case because input devices have user friendly interfaces so that the user can input information without having to write a complicated programme.  Ladder logic is the most commonly used language however the following languages are also used; Function Block Diagram, Structured text, Instruction List and Sequential Function Chart.  

Keeping Control Of Your System

If we remember that a programmable logic controller is fundamentally an input/output device it makes understanding how they work much easier.  For example if all of the doughnuts are flying off the conveyor belt before they can be packed, all that is necessary is to programme a slower speed into the programmable logic controller and your packing problems are over.  Obviously programmable logic controllers are slightly more complex than that as they can also respond to different possibilities by activating the part of the programming that controls them.

Programmable logic controllers can be retro - fitted into systems allowing upgrades to be affordable and fit in with the long term plans of your business.