Types of Allen Bradley PLC

In this article, I will discuss the types of Allen Bradley PLC used from smaller applications to higher ones.

While designing a control system it is important to know about the PLC type you require.

The larger the project is, the higher end PLC requires to fulfill needs.

Types of Allen Bradley PLC

Types of Allen Bradley PLC

There are three types of PLC you can use,

  1. MicroLogix
  2. CompactLogix
  3. ControlLogix

These three types of PLC have the capability of handling the process. They are greatly differentiated by their software, expansion module limitation, memory space, and communication protocol.


This type of PLC is used for the small control system.

Allen Bradley MicroLogix PLC

We can use where less I/O’s is required.

Cost-effective solution for small-scale applications.

Use rslogix500 software for the programming.

It comes with fixed I/Os (onboard I/O).

No physical rack is required. The input and output cards are connected using a ribbon cable.

The supported communication port is RS-232/485, an Ethernet port.

The controller supports 32 discrete I/O points and 6 analogs I/Os.

It comes with an LCD display.


This type of PLC is used for the medium control system.

CompactLogix PLC

This type of PLC is used in machine control and packing system.

It comes with an inbuilt I/O system (onboard I/O).

We can use an expansion module to add additional I/Os, but there is a limitation of an expansion.

Rslogix 5000 software is required for the programming.

No physical rack is required.

The supported communication protocol is Ethernet, ControlNet, DH-485, RS 232, Modbus.

The controller supports 30 I/o modules and 16 motion axes.

No LCD display.


This type of PLC is used for a large control system.

ControlLogix PLC

This is also known as modular PLC as it uses separate I/O modules.

These types of PLC are used in processing, batching, and in a motion control system.

Rslogix 5000 software is required for programming.

It uses rack-based I/O modules.

Supported communication protocol are EtherNet/IP, ControlNet, DeviceNet, DH+.

The controller supports 32 points per module for digital I/O. For analog I/o it supports RTD and Thermocouple modules. Cn support 16 channel module.

No LCD display.

CompactLogix Versus ControlLogix

Apart from all the above mention things, there are some similarities between compact and Control Logix.

Both use a symbolic name, can create user-defined data types in both types of the PLC.

Both use Ethernet/IP, DeviceNet, ControlNet, DH communication protocol to transfer data.

Both require rslogix5000 software.

Still, anything misses out here? Then share your thought in the comment section.

Author: Suhel Patel

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2 thoughts on “Types of Allen Bradley PLC”

  1. Good evening, sir,

    I write to make enquiry of the prices of PLC PRODUCTS.

    I am an Electrical Engineering student from Nigeria. I need a small size PLC for programming. What are the prices of small size PLC products or what advice can you give me on getting a small size PLC Products for building projects?

    I await your apt reply graciously.
    Thank you.

    Sunday Ayeomoni


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