PLC learning Series 1: What is PLC? Functions of PLC

What is PLC?

PLC stands for Programmable Logic Control.

Definition: PLC is electronic systems that operate digitally and are designed for use in industrial environments, where the system uses programmable memory for internal storage instructions that implement specific functions such as logic, sequences, timing, enumeration and arithmetic operations to control machines or processes through digital or analog I/O modules

One can clearly explain what is PLC from it’s name:

  • Programmable, shows the ability in terms of memory to store programs that have been made that can easily be changed functions or uses.
  • Logic, shows the ability to process input in arithmetic and logic (ALU), which is conducting operations comparing, summing, multiplying, dividing, subtracting, negation, AND, OR, and so forth.
  • Controller, shows the ability to control and regulate the process so as to produce the desired output.

Why PLCs are used?

This PLC is designed to replace a sequential relay circuit in a control system. Besides being programmable, this tool can also be controlled and operated by people who do not have knowledge in the field of computer operation specifically.

This PLC has a programming language that is easy to understand and can be operated if a program that has been made using software that matches the type of PLC used has been included.

Programmable Logic Control is ideal to be operated in critical industrial conditions, since it was designed and conceived for use in the environment industrial.

PLCs offer many advantages over other devices of control such as relays, timers electronic devices, meters and mechanical controls of the drum type.

Main functions of PLC:

Sequential Control:

PLC processes binary signal input into output used for sequential processing of techniques, here PLC maintains that all steps in sequential processes take place in the right order.

Monitoring Plant:

PLC continuously monitors the status of a system (such as temperature, pressure, altitude) and takes the necessary actions in connection with the process being controlled or displays the message to the operator.

Shutdown System:

The working principle of a PLC is to receive a controlled process input signal and then perform a series of logical instructions on the input signal in accordance with the program stored in memory and then produce an output signal to control the actuator or other equipment.

Programming Languages of PLC:

Applications of PLC:

PLC was originally designed as a device industrial control replacement, today they are used in countless applications so that they meet the needs of the users.

It is important that the application of a PLC can be considered the benefits of future expansions.

Its application ranges from manufacturing processes industrial of any kind to that of industrial transformations, control of facilities, etc.,

The communication tools integrated into the PLCs not only improves the possibility of operating the control systems, but also opens its Applications to integrated manufacturing and production systems such as: CIM, CAM, etc.

PLCs have several languages through which you can create the
applications in question, but of them the most widely used is the language to contacts or ladder diagram since it is most familiar to professionals who are involved in operations with PLCs.

Related contents:

PLC learning Series I: What is PLC? Functions of PLC
PLC learning series 2: PLC programming languages
PLC learning series 3: PLC Architecture and wiring of PLC
PLC learning series 5: 8 Rules for ladder diagram programming
PLC learning series 6: PLC process Scan basics
PLC learning series 8: Instruction List programming
PLC learning series 9: PLC selection criteria.
PLC learning Series 10: PLC timers
PLC learning series 11 : How to interface PLC with SCADA?
PLC learning series 12: Troubleshooting PLC
PLC learning Series 13: Counters in PLC


Instrumentation Engineer

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