What does ‘PLC’ mean?

A PLC (Programmable Logic Controllers)  is an industrial computer used to monitor inputs, and depending upon their state make decisions based on its program or logic, to control (turn on/off) its outputs to automate a machine or a process.

NEMA defines a PROGRAMMABLE LOGIC CONTROLLER as:

“A digitally operating electronic apparatus which uses a programmable memory for the internal storage of instructions by implementing specific functions such as logic sequencing, timing, counting, and arithmetic to control, through digital or analog input/output modules, various types of machines or processes”.

Traditional PLC Applications

• In automated system, PLC controller is usually the central part of a process control system.
• To run more complex processes it is possible to connect more PLC controllers to a central computer.

Disadvantages of PLC control

• Too much work required in connecting wires.
• Difficulty with changes or replacements.
• Difficulty in finding errors; requiring skillful work force.
• When a problem occurs, hold-up time is indefinite, usually long.

Advantages of PLC control

• Rugged and designed to withstand vibrations, temperature, humidity, and noise.
• Have interfacing for inputs and outputs already inside the controller.
• Easily programmed and have an easily understood programming language.