Allen Bradley CompactLogix PLCs

The CompactLogix PLC system is designed for medium-sized applications. Typically, a CompactLogix system is used to control a machine or small process.

In this post, I'll talk you through the features of the CompactLogix system and the CompactLogix modules that are available to use.

Let's start by looking at the structure of a CompactLogix system.

Structure of a CompactLogix System

A CompactLogix system is made up of a power supply, controller, and I/O modules

Unlike ControlLogix systems, a CompactLogix system can only have one controller and there are some limitations on how modules can be arranged in the rack. Tools like Rockwell Automation’s Integrated Architecture Builder (IAB) can help you to design legal CompactLogix configurations.

All CompactLogix part numbers begin with 1769 or 5069.

Bank

A CompactLogix system does not use a chassis to connect modules.

Modules clip together using a sliding bus connector to form a bank. This bank can be mounted on a DIN rail.

For larger applications, multiple banks can be connected together using a special bank-to-bank connector.

Power Supply

The power supply used for a CompactLogix system depends on the type of CompactLogix controller being used.

1769-L3 CompactLogix controllers must be powered by a dedicated power supply like the 1769-PA2 shown here.

Other CompactLogix controllers can be powered by any power supply that meets the application’s requirements. The power supply is connected to the controller via terminals on the controller.

Controllers

CompactLogix controllers are available in different models. These models have different combinations of memories and capabilities. Some models have different form factors which impacts the type of I/O modules that are used with them.

Some CompactLogix controllers support motion control. The part number for these controllers end in “M”. For example, a 1769-L33ERM controller supports motion control, but a 1769-L33ER does not.

All CompactLogix controllers, regardless of their form factor, have some common features including;

SD Card

CompactLogix controllers have an SD card that provides nonvolatile memory for project storage.

USB Port

CompactLogix controllers have an embedded USB port. This is used to create a temporary point-to-point connection with a computer

Energy Storage Module

CompactLogix controllers use an embedded Energy Storage Module, or ESM, for project retrieval from non-volatile memory after power loss and to keep a wall clock running without power for up to 5 days.

This ESM replaces the lithium batters that were used in older CompactLogix controllers. This reduces environmental issues and safety concerns that come from using lithium batteries

Ethernet Ports

CompactLogix controllers have an embedded two-port 10 or 100 MB Ethernet switch. This switch supports a single IP address and allows a CompactLogix controller to an EtherNet/IP network without a communication module.

5069 Controller Enhancements

5069 CompactLogix 5380 are the latest series of CompactLogix controllers. These controllers are an enhanced version of the previous 1769 CompactLogix 5370 controllers.

The 5069 CompactLogix controllers include a scrolling four-digit display that allows for enhanced diagnostics and troubleshooting.

The embedded switch on a 5069 CompactLogix controller is also upgraded to support speeds up 1000 MB and two unique IP addresses.

The memory capacity of 5069 CompactLogix controllers is up 20 percent larger than 1769 CompactLogix.

Finally, security for the L8 controller has been enhanced through controller-based changed detection and logging, digitally signed controller firmware, and role-based access controller (RBAC).

RBAC is a method of controller access to a computer or network resource based on the roles of individual users within an enterprise. Only specific users are allowed to perform a specific task such as view, create, or modify a file

I/O Modules

Different types of CompactLogix controllers use different I/O modules.

1769-L1 CompactLogix controllers use 1734 POINT I/O modules. I will talk about these I/O modules when I explain the range of distributed I/O modules available for Allen Bradley systems.

1769 Compact I/O Modules

1769-L2 and 1769-L3 Compact Logix controllers use 1769 Compact I/O modules to add local I/O to a CompactLogix system.

These I/O modules feature;

• a movable bus connector that the modules together and to a controller. This bus connector connects the module to the CompactBus backplane. This backplane provides power to the module and allows it to communicate with other modules in a CompactLogix system.
• A DIN rail latch. This is a movable piece of plastic that helps secure the module to a DIN rail for mounting in a control panel.
• A Removable Terminal Block (RTB). An RTB is used to connect field wiring to an I/O module. The RTB for Compact I/O modules is secured with two screws. To ensure the best connection between the RTB and an I/O module, it is important to alternatively tighten the two screws.

5069 Compact 5000 I/O

5069 CompactLogix controllers use 5069 Compact 5000 I/O modules to add local I/O to a CompactLogix system. These are high-performance I/O modules with 200 microsecond update rates for very precise process control.

These I/O modules feature;

• Status indicators. These indicators indicate the health of a module and the status of each I/O point.
• Interlocking side pieces that allow modules to clip together and form a bank.
• An RTB that connects the I/O modules to field wiring.

Wrap Up

In this post, I have introduced the CompactLogix PLC system.

For more details on this system and the modules that are available for it, check the CompactLogix Selection Guide published by Rockwell Automation.

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