What Is the Difference Between ControlLogix and CompactLogix?

ControlLogix and CompactLogix, which make up the Allen Bradley Logix 5000 product line, are each designed to meet specific needs. While both are known for their performance and reliability, they are suited for different scales and levels of complexity.

It is better to know that the Allen Bradley Logix 5000 product line is Rockwell Automation’s flagship range of PLCs.

Rockwell Automation made the Logix5000 series very flexible. These PLCs can handle almost any job you can think of, from simple tasks to big, complex projects.

If you want to learn more about the Logix 5000 product line PLCs and how to program them, remember to check out realpars.com/courses. We are constantly adding new courses to provide end-to-end training for Allen Bradley PLC systems.

In this article, we’ll compare these two PLC systems based on their design, features, and ideal use cases, so you can decide which one is the best fit for your project.

Ok… First, let’s take a look at each PLC. We’ll start with CompactLogix:

Overview of CompactLogix PLCs

CompactLogix PLCs are perfect for standalone machines or medium-sized systems that require flexibility and modularity, I mean a system that's not too big but still needs some flexibility to add more parts later.

The CompactLogix PLC system has a rackless design, meaning it doesn’t use a physical chassis to mount and connect its modules. Instead, CompactLogix modules are connected through an electrical connection on the side of each module.

A CompactLogix system consists of a single controller and several I/O and communication modules, all connected together on a bus.

Modern CompactLogix controllers support EtherNet/IP and have Ethernet ports at the bottom.

Projects can be downloaded via the Ethernet or USB port and are stored on an SD card behind a small door on the front.

If the controller fails, the SD card can be moved to a new controller to quickly restart the production line.

There are many different models of CompactLogix PLC available to use in applications. The choice of CompactLogix controller depends on factors like the memory required, the number of connected devices, and whether motion or safety control is needed.

The positioning of CompactLogix PLCs is shown here. From Left to right, controllers have more memory, support more devices, and include motion and safety control.

If you want to learn more about CompactLogix systems and the details of the 1769 CompactLogix 5370 Controllers, 1769 Compact I/O modules, and 1734 POINT I/O modules, we suggest checking out our course Learn Logix 2 - A Complete Guide to CompactLogix Systems.

Overview of ControlLogix PLCs

ControlLogix PLCs are designed for large, complex applications.

They have features needed to control large processes, and complete production lines including modular architectures, a range of IO options, and support for different industrial networks.

ControlLogix is the best choice for complex applications with process control or many axes of motion.

The ControlLogix PLC system is chassis-based. Controllers, I/O, and communication modules are installed in a chassis, which comes in different sizes to different various applications.

Once the modules are installed, they communicate with each other using the backplane of the chassis.

All modules are powered by a power supply connected to the left side of the chassis.

ControlLogix systems are multi-controller, meaning you can install more than one controller in a single chassis.

The remaining space can be filled with I/O modules, communication modules, and specialty modules.

There are specialty modules for ControlLogix that aren’t available for CompactLogix, such as redundancy modules for critical applications and Model Predictive Control modules for advanced tuning of process applications.

Also when choosing a ControlLogix controller, consider factors like memory requirements, the number of connected devices, and whether motion or safety control is needed.

These factors will help you select the right ControlLogix PLC for your application.

Differences Between ControlLogix and CompactLogix PLCs

Both ControlLogix and CompactLogix PLCs provide great performance, but they are built for different application sizes and complexities.

Let’s see what are the key differences:

Rackless vs. Chassis-Based

CompactLogix uses a rackless design, meaning it doesn't rely on a physical chassis to mount and connect its modules. This allows for compact, smaller applications.

ControlLogix, on the other hand, uses a chassis-based design. This allows for the installation of multi-controllers and I/O modules within a single chassis, making it ideal for larger, more complex systems. The modular design supports expansion, with backplane communication between modules.

Mid-Range vs. Large-Scale

CompactLogix is designed for mid-range applications, such as standalone machines or small to medium batch processes.

In contrast, ControlLogix is built for large-scale and complex applications. It is ideal for controlling large processes and complete production lines, especially those that require advanced process control or handle multiple axes of motion.

CompactLogix is designed for mid-range applications, like standalone machines or small to medium batch processes.

On the other hand, ControlLogix is built for large-scale and complex applications. It’s perfect for managing large processes and complete production lines, especially those requiring advanced process control or handling multiple axes of motion.

Specialty Modules and Expansion

The ControlLogix system offers many specialty modules that are not available for CompactLogix systems.

These include redundancy modules for critical applications and Model Predictive Control modules for advanced tuning of process applications.

A CompactLogix system is made up of one controller. In contrast, ControlLogix systems are multi-controller systems which means that more than one controller can be installed in a single chassis.

Wrap-Up

Ok, let’s review… In this article, I gave you an overview of ControlLogix and CompactLogix.

CompactLogix offers great value if you're working with standalone machines or a medium-sized project.

CompactLogix's smaller form is more suitable for applications where space is limited. They're designed to be rackless, meaning they don't require a physical chassis for module installation. With its compact design, integration into smaller control cabinets is easier.

However, for large-scale or complex applications that need advanced control, ControlLogix provides the robust features and scalability necessary to handle more intensive processes and production lines.

If you’re interested in PLC programming, make sure to check out our PLC Programming Skill Path at realpars.com/courses. We’re always updating our lessons to give you a complete and practical understanding of PLC systems.