Ladder Logic vs. Other Programming Languages: A Comparison

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⌚Timestamps:
00:00 - Intro
01:05 - Ladder Diagram
02:37 - Structured Text
04:01 - Function Block Diagram
05:07 - Sequential Function Chart
06:06 - Instruction List
06:40 - Recommendations
07:43 - Conclusion
In today’s video, we are going to talk about Ladder Diagram and how it compares to other PLC programming languages.
As you may be aware, PLCs are special-purpose computers that are designed to monitor and control automated processes. PLCs are programmed using programming languages defined in the IEC 61131-3 standard.
This standard defines 5 programming languages called Ladder Diagram, Function Block Diagram, Structured Text, Sequential Function Chart, and Instruction List that are supported by almost all PLC manufacturers.
- Ladder Diagram is the most popular PLC programming language because it was the first one introduced.
When PLCs were first invented as a programmable alternative to hardwired relays in control panels, Ladder Diagram was the only programming language available.
Ladder Diagram is a high-level, graphical programming language that is designed to look like electrical schematics.
Because it is a visual language, it is very easy to understand and debug Ladder Diagram code. Ladder Diagram makes it easy to program and monitor complex Boolean logic which is exactly what it is designed for.
- Structured Text (ST) is a text-based PLC programming language. It is generally preferred by people with traditional programming backgrounds because of its similarity to higher-level programming languages like Python.
Structured Text is much better than Ladder Diagram for specific tasks, such as complex calculations on a single line and looping over sections of logic.
- Function Block Diagram (FBD) is another high-level graphical programming language.
It is commonly used in the process industry because its appearance is similar to P&IDs that define how process equipment is laid out.
FBD is easy to program, monitor, and troubleshoot. Function Block Diagram can make implementing continuous process control using PID loops easier.
- Sequential Function Char (SFC) is another high-level language that looks like a flow chart.
It is a great programming language for modeling sequential processes on a high level, and should only be used to model processes, not to write control logic.
- Instruction List (IL) is a text-based programming language similar to assembly languages.
Instruction List is harder to write and debug than Ladder Diagram, or any of the other IEC 61131-3 programming languages.
If you are working on new projects, you should not use the Instruction List programming language. I recommend using Ladder Diagram instead.
I recommend that every PLC programmer learns how to program with the Ladder Diagram programming language and uses it as their default programming language.
I make this recommendation because Ladder Diagram is the most widely used, understood, and accepted PLC programming language right now.
In specific situations, use the other IEC 61131-3 programming languages:
- For continuous process control, consider using Function Block Diagram,
- For heavy computation, data processing, and looping, consider using Structured Text,
- For modeling sequential processes on a high-level and implementing sequencers, consider using SFC
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Пікірлер: 38

@Donnner93 10 ай бұрын

Started my 2 year Automation-Engineer education today, and have been following you guys a while now - Very excited to become one of the people!

@JKTCGMV13 10 ай бұрын

3:30 Thank you for addressing maintainability. Too many people don’t think about that aspect of programming.

@realpars 9 ай бұрын

Our pleasure!

@tommyhuffman7499 10 ай бұрын

Very excited that you made this video! Fascinating topic.

@realpars 9 ай бұрын

Glad to hear that, Tommy! Happy learning

@livingsafarillc 9 ай бұрын

I have worked as an Automation Engineer for 40+ years. this is a great review and evaluation of PLC programming. Very thorough and truthful. I agree with everything they have shown you.

@realpars 9 ай бұрын

Thank you very much!

@klebermarcio1317 10 ай бұрын

Your explanation is amazing! Congrats!!

@realpars 9 ай бұрын

Glad it was helpful!

@BeeFree_BK 10 ай бұрын

Thank you and it is really helpful to understand PLC languages~

@realpars 10 ай бұрын

You're very welcome!

@atrbulldog5955 9 ай бұрын

I have been working as an automation engineer for almost two years. Our company uses B&R PLCs. We have been straying away from using IEC languages, ladder logic is completely gone with only some structured text still present in some projects. We have almost completely moved to C/C++. I find it interesting how many still use these older languages, I guess it is fine for simple projects. I can't imagine trying to implement something like a neural network in anything other than C/C++. These older languages just can't keep up with the amount computation we are doing for some of these systems from a performance standpoint too. C/C++ also offers control of the PLC at the lowest level, allowing for some of the most dynamic and versatile programs. But with great power comes great responsibility. Anyways I wanted to see if anyone else has been seeing a shift in languages as automation advances.

@realpars 9 ай бұрын

Thank you for sharing that! Hopefully others in the community can chip in on that.

@matty9217 10 ай бұрын

Thanks for your coolest videos! It's really helpful.

@realpars 9 ай бұрын

You're very welcome! Glad to hear that our video courses have been helpful

@syufrijal 10 ай бұрын

Nice information about comparation ladder diagram and other programming languange...very helpful

@realpars 9 ай бұрын

Glad it was helpful!

@876_FIRE 10 ай бұрын

Clear and concise

@yukreszi1994 9 ай бұрын

Hi, can you explain about End of Line Resistor ?

@realpars 9 ай бұрын

Hi there, Thanks for your question! It's a bit off-topic for this video, but we have covered the topic a bit in our explanation of DeviceNet. You can check that post out here: realpars.com/devicenet/?fbclid=IwAR12d7sqdLCuBBD1EC0anQXKt4epCUsh41Weqp0hrbItEcx764Y39yHlFOE. Hopefully it helps!

@IngDzib 10 ай бұрын

many thanks realpars

@realpars 9 ай бұрын

Our pleasure!

@johnneenee5847 5 ай бұрын

Good explanation

@realpars 5 ай бұрын

Thank you very much!

@MarsShare123 9 ай бұрын

Can i know what the meanings as "looping "

@realpars 9 ай бұрын

Hi there, Thanks for your question! Looping is repeating the same piece of code multiple times. In PLC programming, imagine that you have to move the value 0 to every element in an array of 100 elements. You could write a program with 100 move instructions or you could write a loop which executes the same command 100 times to move the value 0 to each element of the array. Does that make sense?

@tricky778 9 ай бұрын

How does this compare to Frege's logic?

@realpars 9 ай бұрын

Hi there, I'm not familiar with Frege's logic. Would you be able to elaborate a bit more?

@tricky778 9 ай бұрын

@@realpars it's a historical logic for formal reasoning, but it looks a lot like a ladder diagram. Maybe it's just that both represent some kind of information flow so no surprise they look similar

@GuyFromJupiter 9 ай бұрын

3:30 Careful now! You don't want to upset the true PLC gurus! This is 100% true though. You have plenty of tools at your disposal, and limiting yourself to a single one for all situations is dumb. Use the right tool for the job!