Rockwell Automation  РFour PLC Programming Languages

My name is Shane Welcher, I have put together a few helpful videos to show anyone willing to learn how to program using structured text an easy way to get a base foundation of how things work. Having over 18 years of working with Rockwell Automation software but enough about me, let’s discuss the four plc programming languages.

If you are new to PLC programming or just looking to sharpen your skills then you came to the right place. PLC programming is a logical-based system that interacts with a processor to control a machine or machinery when put in a very general statement, meaning, they do much more than what I just described. Most well-known PLC software has four code-written languages.

Four PLC Programming Languages:

  • Ladder Logic
  • Function Block
  • Structured Text
  • Sequential Function Chart


This is a lot of information to cover over text or being read through an article so I have made four videos to show each one of these programming languages in use to give a clear understanding.

Starting out, we will cover Function Block first then show Ladder Logic, Structured Text, then finally Sequential Function Chart.

Function Block PLC Programming

The video below shows function block programming for a conveyor to run a box back & forth, a very simple yet real application to give the foundation of how to get a base understanding.

Throughout the video, I will give you a detailed reason why I showed the system the way I did, and believe me when I say if you want to see more then I will be glad to show you a more advanced method but this video is designed to give a base foundation.

In this video, I show the function block for a simple conveyor system being written on Rockwell Automation’s Studio 5000 software platform to give a base implementation to give a clear view of each plc programming language. As you can see as I build the function block logic, it is much different than standard ladder logic with the one constant being the fact of programming in a logical method.

Function block programming is generally used more in process controls rather than simple controls as a conveyor system. In the videos above, just making a simple conveyor system control a box move back & forth gets to be a rather hard-to-read logic. With that being said, there are many control systems that function block makes things very easy.

Ladder Logic PLC Programming

The video below shows ladder logic programming for a simple conveyor which is the same exact example we will be using throughout this article to give a solid foundation of how to get a base understanding.

If you have been following along & have watched both the video on function block & the video on the ladder logic, you can easily see that the ladder logic was much more practical for this logical use of plc programming. Although we aren’t done yet because we are going to show two more plc programming languages.

Ladder logic is one of the most commonly used logical programming methods used. Largely because it is very simple to read while still accomplishing the goal of making the machine achieve its scope of work. Using ladder logic is often where most people start their introduction to plc controls & is very helpful in learning a logical way of thinking which will help you throughout your journey of learning the other three plc programming languages.

Sequential Function Chart PLC Programming

The video below shows sequential function chart programming for the simple conveyor example, following a step & transition method to achieve the goal of making the machine per design. (AKA -Scope of Work)

After watching this third video about sequential function char, you can now start to understand that there are other ways than ladder logic that can be used & still be easy to read as a person troubleshooting. Sequential function charts work in a step & transition model which makes it very easy to see what state the machine is in & also what is the coming state of the machine.

In the example above, we had a scope of work to move a box back & forth on a simple conveyor which used a sequential function chart as the plc programming language. As from the above video, you can see that structured text programming is part of the SFC design with the way the commands are written.

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Structured Text PLC Programming

The video below shows structured text programming for our simple conveyor box transfer example, structured text is commonly used for all different machine applications so it is probably second on my list if you asked me what should I learn first.

In our final video in this article, we show how structured text can be another easy-to-read & understand plc programming language as we continued to use the simple conveyor system. By now you should have a base understanding of each plc programming language along with starting to understand which one to use in your future system if you happen to be the one writing them.

I will be putting together more programming videos and articles upon request, I already have several ideas and will be starting to add more videos to my YouTube channel which is Shane Welcher RSlogix 5000 Programming

I would love to hear what you guys think so far as I am trying to get this website whipped into shape.

Drop me a comment here or on my YouTube channel.



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PLC Programming Languages