The Birth of Allen-Bradley: Pioneers in Industrial Automation
Almost all control engineers are familiar with the name Rockwell Automation or Allen-Bradley. Given the company's long history of innovation prior to the modern computer systems era, it is understandable that many early developments in digital automation took place here.
Allen-Bradley was founded in 1903, accumulating extensive experience in electronics even before the first PLC (Programmable Logic Controller) was released. The company became a global leader in the development of new components and technologies. In 1970, Allen-Bradley coined the term "PLC" when they launched one of the first programmable controllers, the 1774 PLC.
1774 PLC
Around the same time, the 1774 PLC (referred to as PLC-1) was developed, and Allen-Bradley subsequently introduced the concept of Data Highway, which was one of the earliest computer networks specifically designed for digital control systems! In 1985, the major manufacturing company Rockwell International acquired Allen-Bradley, forming Rockwell's industrial automation division. Today, the Rockwell and Allen-Bradley brand logos are almost interchangeable in the internal workings of control cabinet hardware and software.
Another significant milestone was the launch of the SLC500 PLC platform in 1990, which was more compact and affordable than its predecessor, the PLC-5. SLC stands for Small Logic Controller. The first product in this series was the SLC 5/01, equipped with a memory range of 1k to 4k and the ability to control 30 I/O slots, which was impressive at the time.
With the introduction of the SLC 5/02 and 5/03 models, Allen-Bradley launched the DH485 data highway. Based on the RS-485 standard, it was designed specifically for factory floor applications. The SLC 5/03 was the first to introduce common PLC features, such as run mode and online programming. It was also the first product to support firmware upgrades. The consecutive model, SLC 5/04, referenced an enhanced version of the data highway known as DH+.
SLC 5/05
The last model of the SLC 500 series is the SLC 5/05, which is the first Allen-Bradley PLC capable of Ethernet-based communication. The DH or DH+ ports from previous models have been replaced with Ethernet ports, now achieving transmission speeds of up to 100 Mbps. The SLC 5/05 is available in three memory sizes: 16k, 32k, and 64k. This PLC is the only one in the SLC series that is still supported by Allen-Bradley today.
In the latest major hardware revision of the chassis-based platform, Allen-Bradley released a new series of ControlLogix automation controllers. In the following years, the CompactLogix and MicroLogix series were introduced to target specific market sectors for various projects.
2. The ControlLogix Era: 1756-L75 and Scalable Architecture
The ControlLogix PLC was the first release in the Logix platform. These general-purpose controllers feature a modular and rack-mounted design, composed of processors, power supplies, I/O, and communication modules. The first controller released in this series was the 1756-L1 in 1999, and it has undergone multiple iterations. The platform replaced the SLC and PLC-5 series, offering significant advantages such as faster scan times and higher storage capacity.
ControlLogix
The release of the 1756-L75 ControlLogix in 2003 marked a leap in automation technology, setting the industry benchmark:
- Processing Power: 4 MB user memory, expandable via the 1756-MVI module.
- Network Integration: Native support for ControlNet (5 Mbps), EtherNet/IP (100 Mbps), and DeviceNet (500 Kbps), enabling seamless integration of HMI and vision systems.
Real-World Applications:
- Oil & Gas: The BP Whiting Refinery used the 1756-L75 to construct a Safety Instrumented System (SIL 3 certified) that monitors 12,000 I/O points, including pressure sensors and emergency shut-off valves.
- Pharmaceuticals: The Pfizer vaccine production line employs the 1756-L75 along with S88 batch control modules, reducing production cycle times by 18%.
- Performance Comparison: Independent tests in 2005 showed that the 1756-L75 backplane throughput (256 KB/s) outperformed Siemens S7-400 by 22% in multi-axis motion control tasks.
3. MicroLogix PLC Micro800 Series: A Flexible Choice for SMEs
In 1994, Allen-Bradley launched the MicroLogix series, a compact and cost-effective product line. These smaller controllers come with built-in processors, power supplies, and I/O designed specifically for small applications, with some models supporting both embedded and expansion I/O. Many models from 1000 to 1500 have been discontinued but are still widely used.
Micro800
The latest revision of the Micro series is the Micro800 series, which debuted in 2014. It includes many of the same design considerations, such as embedded I/O terminals on top and bottom, as well as integrated communication channels like USB and Ethernet. The Micro800 series also features front connections for additional modules, enhancing functionality.
1763-L16AWA Micro800:
Design Concept: Cost-effective PLC equipped with 16 points of I/O (10 DI/6 DO), USB programming port, and compatible with CCW software.
Case Study: A packaging machinery manufacturer in the American Midwest replaced a Siemens S7-1200 with the 1763-L16AWA, significantly reducing total ownership costs (TCO) by 15% due to lower licensing fees and simplified wiring.
4. Rockwell Automation Integration: IoT and Industry 4.0 Transformation
After being integrated into Rockwell International in 1985, Allen-Bradley PLCs became a core component of the Factory Talkecosystem:
IoT Integration:
1756-L75 Firmware v32: Supports MQTT protocol for real-time data streaming to Microsoft Azure IoT Hub, enabling predictive maintenance.
Collaboration with PTC ThingWorx: In a General Mills food plant, the 1763-L16AWA monitored motor vibration data, reducing unexpected downtime by 35%.
Cybersecurity: The 1763-L16AWA features CIP Security protocol to encrypt controller-HMI communications, intercepting 99.6% of ransomware attacks in a 2021 U.S. Department of Energy test.
5. Maintenance and End-of-Life Management Challenges
Legacy System Dilemmas:
Migration Tools: Rockwell's Studio 5000 Logix Translator automatizes 80% of PLC-5 code conversion to 1756-L75, but user feedback indicates compatibility issues with AOIs (add-on instructions).
Spare Parts Strategy:
After the discontinuation of the 1761-L32BWA in 2018, refurbishers provide a one-year warranty on parts at lower prices than the original manufacturer.
The 5069-L306ER replaces the 1763-L16AWA, upgrading Ethernet bandwidth from 100 Mbps to 1 Gbps, with dual-port switching support.
User Case: A Canadian automotive supplier extended the lifespan of the 1756-L75 by 7 years through Rockwell's lifecycle services, combining firmware upgrades with third-party I/O modules.
