PLC ,Introduction,Working ,Main components of a PLC,Programing Languages of PLC

Introduction to PLC
               A Programmable logic controller or PLC is a computer like structure used for industrial automation.It can control a specific machine or whole production line lighting in the building fire alarms ,CCTV cameras or lots of other things.
Working Of  PLC
               The PLC receives information from connected sensors or input devices processes the data and triggers the out puts based on pre-programmed parameters.
                Depending on inputs and outputs a PLC can monitor and record run time data such as machine productivity,Operation,Operating temperature ,automatically stop and start,generate alarms.
Now a days PLC is used in lots of application and due to its flexible features it become the part of almost all industries.
Main Components Of a PLC
  • Processor or central processing unit(CPU).
  • Rack or mounting.
  • Input assembly.
  • Output assembly.
  • Power Supply.
  • Programing Units device or PC/Software. 
Rack Assembly     
              Most medium to large PLC systems are assembled such that the individual components CPU,Input?output,Power Supply are modules that are held together with in a rack.
Power Supply
             The Power Supply provides power for the PLC system.The power supply provides internal DC current to operate the processor logic circuitry and input/output assemblies.Common power levels used are 24vDC or 120vDC.
Processor(CPU)  
              The processor,central processing unit or CPU is the brain of the PLC.The size and type of CPU will determine things like the programming functions available,size of the application logic available ,processing speed.  
Input/Output assembly
              Input carry signals from the process into the controller they can be input switches,pressure sensors,operator inputs etc.These are like the senses and sensors of the PLC.
               Output are the devices that the PLC uses to send changes out to the world .These are the actuator the PLC can change to adjust or control the process motors,lights,relays,pumps etc.
                Many types of inputs and outputs can be connected to PLC and they can be divided into two large groups analog and digital.Digital inputs and outputs are those that operate due to a discrete or binary change on/off,yes/no. Analog input and outputs change continuously are a variable range ,pressure,temperature,potentiometer.
Programming Device
                The PLC is programmed using a specialty programmer or software on a computer that can load and change the logic inside.Most modern PLCs are programmed using software on a PC or Laptop computer.older systems used a custom programming device.
Popular Programming languages
                 PLCs from manufacturers can be programmed in various ways .Popular programming languages for PLCs are 
  • Ladder Diagrams.
  • Function Block Diagrams(FBD).
  • Statement List.

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