When I started learning Programmable Logic Controller PLC programming, I found it very difficult to understand the actual difference between compact PLC and modular PLC.
So, to make this simple for everyone, I am writing this tutorial with detail explanations.
As we all know, the programmable logic controller (PLC) (hardware) has two main categories as follows.
- Compact PLC
- Modular PLC
Now, let’s compare two PLCs.
Difference between Compact PLC and Modular PLC
| # | Content | Compact PLC | Modular PLC |
| 01 | Name | Compact PLC is also known as Fixed PLC. | Modular PLC is also known as Rack-Mounted PLC. |
| 02 | I/O | In Compact PLC, the number of inputs and outputs are fixed. Because I/O capabilities are decided by the manufacturer but not by the user. | In Modular PLC, the number of input and output are not fixed. Inputs and outputs can be added to the modular PLC systems by the user. |
| 03 | Module | It has inputs and outputs modular fitted with CPU. | In this PLC, several components are fitted on chassis or rack or bus with different slots. |
| 04 | Repair | Compact PLC is not easily repaired. | Modular PLC is easy to maintain and repair as compared to compact PLC. |
| 05 | Memory | It has fewer memory capabilities to store data/information. | It has more memory and capabilities to store more data. |
| 06 | Use | It is useful for smaller applications and most suitable for domestic purposes. | It is used for industrial purposes and also for future industrial expansion and growth. |
| 07 | Size | It is smaller in size. | It occurs in a large size with i/o connectivity, power supply, computing capabilities, etc. |
| 08 | Cost | It is an economic model. | It is costlier than Compact PLC. |
09. Block Diagram
Compact PLC block diagram: It includes input, output along with power supply and CPU.
Modular PLC block diagram: It consists of Power Supply, CPU, and Input/Output Modules, Interface Module.
In the modular PLC, one rack consists of nine or eighteen slots.
Out of 9th or 11th slots,
- the power supply connects with the slot number-one,
- the central processing unit (CPU) is fixed in slot number two and
- the interface module is fixed in slot number three.
Remaining slot numbers fourth to eleventh is used for the input and output modules, signal module, a communication module, an interface module, a peripheral module, a function module, etc.
Mostly, modular type PLC is used in automation industries. The more different brands of modular PLC are available in the market with their manufactured brand.
Hopefully, this difference between compact PLC and modular PLC gives you a better understanding. If you have any point to discuss, feel free to write in the comment.
If you are interested in learning PLC programming, here is PLC programming related tutorial from beginner to end.
It is simple to start with…
- Logic gate for PLC programming
- PLC Programming Languages
- PLC Brands and their Softwares
- PLC Programming Learning Procedure
- PLC Interview Questions and Answers
- 8 Safety precautions for PLC programmers
Ready for Test:
If you are ready for online test, click on the PLC Automation Quiz.
Happy PLC Programming!
I have completed master in Electrical Power System. I work and write technical tutorials on the PLC, MATLAB programming, and Electrical on DipsLab.com portal.
Sharing my knowledge on this blog makes me happy. And sometimes I delve in Python programming.
Nice explanation about both plc. Thanks a lot!
You’re welcome, Manish!
You are providing very good information for us. Thanks a lot.
You’re welcome! Glad you fond it informative.
Your explanation is very good. Thank you for sharing.
Thank you, Veeraj.
In the official site of OMRON I saw 3 categories Compact PLC, Modular PLC and Rack PLC……can u tell me whats the difference between Modular PLC and Rack PLC
Btw thanks for sharing this !
The Rack PLC is the mounting base plate of the Power supply, CPU, Interface module and I/O modules. I think, there is not much difference between them.
I didn’t get the chance to work on Rack PLC.
Thank u very much .
You are most welcome, Qassim.
Thanku very much madam
it’s very helpful
You are welcome, Vijay:)
can you help me to get plc simulator software for finished my learning task please…
Hi, Kacung Jongos.
Yeah,Sure! In the before tutorial ([Step-by-Step] How to Learn PLC Programming at Home for Free?), I shared the PLC software link of free basic version for practicing and learning PLC programming.
If you are new and learning PLC, I guess using those free version of any PLC software brand is sufficient for your need.
You can download Delta PLC software from its official website for free. Choose the version suitable based on your computer system. Install it.
You can also download WPLSoft PLC software and install it. I am working on this PLC Software.
I am a new plc learner. Loved the explanation. I wanted help from your end in the project where I am stuck. Can it be discussed further for a solution as required at present for the progress of it?
Hi Supinder. I’m glad you like the explanation. Regarding your project, please fill this contact form by adding your project requirement. I will reply back to you.
Very good work out there. Really like every bit of your well explanatory.
Thank you very much, Emmanuel Konney.
Thanks a million for sharing your knowledge. This has been immensely helpful.
Thank you, David Igoche for giving feedback. I am very glad when I hear a few words for my contribution and effort.
Thank you so much Dipali.
You are most welcome.
I needs elaboration of how these two types of PLCs operates.
Hi Michael, I will try as early as possible to share the working role of both Compact and Modular PLC.
Thanks for suggesting this point.
Well defined. Good for the beginners.
Thank you, Maneesh 🙂
Madam, you have explained in a much simpler sentence, very helpful for me. Because, I’m a Hindi medium student.
Yup, Uttam. Enjoy the PLC learning with easy and simple explainations:)
Waoooh، like seriously, you are great woman! I wish I could be your successful trainee on PLC programming (software skill).
Thanks for this and I pray that your knowledge will never depreciate
Thank you very much, Saliman Osunniran. Really, you made my day very special 🙂
Ma’am, please provide Delta PLC and Allen Bradley PLC Contents or blogs.
Thank you.
Sure, Mohd.
Dear madam,
Firstly I want to say thank you to you because you did explain it so easily formats. Ma’am, I want learn more about electronic devices. Can you teach me personally, If it possible so.
Thanks, Deep to reach out to my blog and to finds useful it. I have created DipsLab group for electrical & electronics engineers. If you are interested to join the group. Here is a link to join- https://www.facebook.com/groups/dipslab.