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    PLCs - Programmable Logic Controllers

    A PLC (programmable logic controller) is an industrial digital computer control system designed for the continuous monitoring, control and automation of manufacturing processes or robotic devices. Programmable Logic Controllers are used where reliability control, simple programming and fault diagnosis are necessary. They were originally built to replace electromechanical relay systems in industrial automation.

    A CPU (central processing unit) forms part of the PLC system. PLC CPUs are microprocessor-based control systems and act as the electronic circuitry within an industrial computer. They are usually built-in to carry out instructions from the computer programme via programming languages, performing basic mathematical, logical, control, input and output operations. These intelligent and communicative logic controllers are key players in smart factories, and almost every application in the industry uses a PLC or logic controller to act as the brains, facilitating communication within the system and to a wider network.

    PLC Applications

    PLC controllers are incredibly useful and have many applications across several industries such as manufacturing, food & beverage, and building control. PLC's control the automation process in the machinery used for:

    • Production plants
    • Traffic light controls
    • Packaging machines
    • Lifts and escalators
    • Medical applications
    • Automatic gate systems
    • Heating control systems

    How do PLC's work?

    These automation and control gears respond to inputs from programming software and give the desired output. Programmable Logic Controllers can also include human-machine interfaces.

    Different models use varying PLC Programmes based on the programming languages used in the software. Programming languages that are used in PLC programming include:

    • ST: Structured Text (text-based)
    • FBD: Function Block Diagram (graphic-based)
    • LAD: Ladder logic (graphic-based)
    • STL: Statement List (text-based)
    • SCL: Structured Control Language (graphic-based)

    Types of PLCs

    Programmable Logic Controllers can be categorised in multiple ways, each with different functions, features and capabilities. For example, Soft PLCs are software-based and use their own operating system but do not have their own CPU. Whereas, Hard PLCs are hardware-based and typically only include the essential control functions. The full range of programmable controllers includes:

    • Hard PLCs
    • Soft PLCs
    • Compact PLCs
    • Slot PLCs
    • Unitary PLCs
    • Modular PLCs

    Programmable Controllers can also be made more efficient by using equipment such as HMI displays, DIN Rails, and Communication modules (such as MODBUS) which can be enhanced into a highly functional automated control system with PLC accessories

    RS boasts the RS PRO range of logic controllers, which offer affordable basic control for applications such as packaging machines, light control, home automation and filling systems. If you are on the search for companies that supply Programmable E-Logic Controllers, look no further than RS as your trusted distributor

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