What is PLC?

What is a PLC?

What is PLC?

Control engineering has evolved over time. In the past humans were the main method for controlling a system. More recently electricity has been used for control and early electrical control was based on relays. These relays allow power to be switched on and off without a mechanical switch. It is common to use relays to make simple logical control decisions. The development of low cost computer has brought the most recent revolution, the Programmable Logic Controller (PLC). The advent of the PLC began in the 1970s, and has become the most common choice for manufacturing and automation controls.

The PLC has input lines where sensors are connected to notify upon events (e.g. temperature above/below a certain level, liquid level reached, etc.), and output lines to signal any reaction to the incoming events (e.g. start an engine, open/close a valve, etc.) (oh yes, there is obviously a ce)


Advantages of PLC

PLCs have been gaining popularity on the factory floor and will probably remain predominant for some time to come. Most of this is because of the advantages they offer.

  • Cost effective for controlling complex systems.
  • Flexible and can be reapplied to control other systems quickly and easily.
  • Computational abilities allow more sophisticated control.
  • Troubleshooting aids make programming easier and reduce downtime.
  • Reliable components make these likely to operate for years before failure.
  • Communication between other PLCs and computers is easy with lots of communication protocols.

 How to program a PLC?

PLC programming can be done mainly with the following methods

  1. Ladder Logic
  2. Mnemonic instructions


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