Basics of PLC Programming

Basics of PLC Programming

Basics of PLC Programming
Basics of PLC Programming 

What is a PLC?

A PROGRAMMABLE LOGIC CONTROLLER (PLC) is an industrial computer control system that continuously monitors the state of input devices and makes decisions based upon a custom program to control the state of output devices. 

Almost any production line, machine function, or process can be greatly enhanced using this type of control system. However, the biggest benefit in using a PLC is the ability to change and replicate the operation or process while collecting and communicating vital information. 

Another advantage of a PLC system is that it is modular. That is, you can mix and match the types of Input and Output devices to best suit your application.

How does a plc operate?

There are four basic steps in the operation of all PLCs; Input Scan, Program Scan, Output Scan, and Housekeeping. These steps continually take place in a repeating loop.

Four Steps In The PLC Operations
  1. Input Scan
    • Detects the state of all input devices that are connected to the PLC 
  2. Program Scan 
    • Executes the user created program logic 
  3. Output Scan 
    • Energizes or de-energize all output devices that are connected to the PLC. 
  4. Housekeeping 
    • This step includes communications with programming terminals, internal diagnostics, etc...
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