Everything you need to know about PLC's 2022

22/03/2022

What does PLC stand for?


PLC stands for Programmable Logic Controller.


So then what is a PLC?


A uniquely designed computer that efficiently and effectively operates in severe industrial environments. This may include extreme temperatures between wet and dry conditions or even dusty environments.

The programmable is customisable, which means that we can program it ourselves. You can buy a PLC for a process and have someone who knows how to come in and program it for your process or your machine.

How does it work?


A programmer writes a PLC code from scratch that can function in any platform you use.


Where do you get a PLC from?


There are various PLC manufacturers that both manufacture the hardware and also the software. This is crucial as typically you would have to use the software made by the same manufacturer of the hardware.

Advice: This is changing.

What components make up a PLC?


Each PLC offered by different vendors are contrasting in appearance but made from the same components. PLCs often include a central processing unit (CPU), input/output cards (also called specific expansion modules), and backplanes to place the input/output cards into. Another component is a power supply.


Ways to program a PLC


Much like any automation solution, there are a variety of ways to program the robot. What programming does is it creates a sequence of action in the program. This will be elaborated further below.

PLC programming can be broken down into two various categories.



  • Textual language

Textual language which consists of instruction lists and structured text.

  • Graphical form


This consists of ladder logic (LD) and function block diagram (FBD) and sequential function chart (SFC).


In this case, there are a range of methods to program a PLC. It is keen to note that programming a PLC doesn’t require such complex programming. The three most common PLC programs are Ladder Logic (LD), Function Block Diagram (FBD) and Structured Text (ST). This article will break these three PLC programming down.

Structured Text (ST):


Compared to ladder logic or function block diagram, structured text is just text. Simply text.


Structured Text programming is basically a high-level language primarily utilised to solve complex arithmetic operations. Examples of this are math functions, conditional functions and also loops.

Ladder Logic (LD):


A visual language that is based on the circuit diagrams or relay logic hardware. In other words, it is based on the electrical control wiring. This method consists of numerous predetermined functions that have to contain a limit dependent on the designated applications.


Advice: Ladder Logic is typically the easiest programming language to learn to program a PLC.
Function Block Diagram (FBD):


This method of programming utilises sequences of logical blocks to understand between input variables and output variables. Simply the PLC will function using true and false conditions thus proceeding with the next action on the sequence.

Advice: The manufacturer that offers the PLC hardware often offers softwares to program the PLC’s. There aren't any missing functions if you were to choose from a different vendor. As previously mentioned in the earlier point, this method of action is changing.


An example of an easy to learn PLC is the Fanuc PLC Motion Control.

PLC applications:


A PLC can be designated for a range of applications. This includes:

  1. Civil applications: machines, elevators, and even traffic signal controls.

  2. Process automation: mining, oil & gas

  3. Batch processes: cement, chemical, food, paper, and more dependent on time or even based decisions.


These are just a few examples of PLC applications.


To learn more about cobots at PLC’s.


Updated 05/05/2022