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Types of Allen-Bradley PLC

March 11th 2024

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All remaining Allen-Bradley SLC 500 controllers will be discontinued on March 31st 2024, but what other Allen-Bradley controllers are available, and are they still supported? Continue reading to learn more about the extensive Allen-Bradley PLC catalogue and its rich history.

Allen-Bradley coined the term Programmable Logic Controller (PLC) when it launched one of the first-ever programmable controllers in 1970, the Bulletin 1774 PLC.

It is also widely said that Dr. Odo Josef Struger, under the Allen-Bradley brand, invented the PLC. However, it should be noted that many others also believe that the credit lies with Dick Morley of General Motors, who released the Modicon 084 PLC at a similar time.

Either way, Allen-Bradley has produced innovative PLCs for over 50 years now.

PLC-2, PLC-3, PLC-5

After the release of its first functional controller, the Programmable Matrix Controller (PMC), Allen-Bradley released its first series of PLCs.

Allen-Bradley PLC-5 Timeline

Initially, PLC-5 used 6200 series programming software but now uses RSLogix 5.

SLC Series

In 1991, Allen-Bradley released the SLC 500 series.

SLC is an acronym for “Small Logic Controller” and, as implied, it was smaller than other PLCs on the market when introduced. Allen-Bradley achieved this using a “shoe block” configuration, where a compact PLC enclosure contains the CPU, the PSU and the IO.

Allen-Bradley SLC Series PLC

Later, a rack-based version of the SLC 500, the SLC5/01, would be released.

Other models, such as the SLC5/02 and SLC5/03, support proprietary Data Highway serial-based communication (DH-485), and the SLC5/04 supports a faster communication protocol called Data Highway Plus (DH+), which is also proprietary to Allen-Bradley.

SLC5/05 supports both DH-485 and Ethernet protocols.

Allen-Bradley SLC 500 PLCs will be discontinued on March 31st, 2024.


The MicroLogix family debuted in 1994 with the release of the MicroLogix 1000 PLC.

This compact line of inexpensive controllers opened the door for using RSLogix 500-based programs on smaller applications that were previously less cost-effective with the SLC 500.

Allen-Bradley MicroLogix 1400 Series PLC

The MicroLogix platform does not use a rack. Instead, MicroLogix modules can be added to the end of the PLC by using a ribbon cable.

MicroLogix PLCs also support 32 digital IO points and 6 analogue IO points, and supported communication protocols include RS-232, RS-485 and Ethernet.

This family of PLCs also comes with an integrated LCD screen.


Released in 1997, the ControlLogix family was faster and had better memory than other PLCs on the market at the time.

This rack-based system was designed for larger applications and does not have an integrated LCD screen.

Allen-Bradley ControlLogix PLC

Programming is input via RSLogix 5000 software, and supported communication protocols include Ethernet, DeviceNet, DH-485, and ControlNet.

Moreover, the Sercos interface module can link a ControlLogix controller to Sercos interface drives, providing more control over coordinated systems.


Designed for medium-sized applications, the CompactLogix family was released in 2008 as a lower-cost alternative to the ControlLogix system.

CompactLogix PLCs can support 30 IO modules and 16 motion axes. Supported communication protocols include Ethernet, ControlNet, DH-485, RS-232 and Modbus.

Allen-Bradley CompactLogix PLC Family

Like MicroLogix, ComptactLogix is not rack-based and lets users add modules to the end of the PLC body.

As standard, CompactLogix PLCs come with an onboard IO system, and programming is input via RSLogix 5000 software.

Which PLC is right for me?

Navigating the broader PLC market can be overwhelming, and that’s where a knowledgeable automation partner like Foxmere fits in.

Daily, we support companies of all sizes, from start-ups to Fortune 500s, in understanding and buying automation and control parts.

Whether you’re a manufacturer looking for a like-for-like PLC-3 module to get your line back up and running or a systems integrator planning your next big project, we can help — simply contact us today for more information.

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