What Is Allen-Bradley? Introduction to Rockwell Automation PLCs
Key Takeaway
Allen-Bradley is Rockwell Automation's industrial PLC brand. The product line includes ControlLogix for large systems, CompactLogix for mid-size applications, MicroLogix for legacy small controllers, and Micro800 for entry-level automation.
Quick Answer
Allen-Bradley is Rockwell Automation's brand of industrial PLCs and automation hardware. The product line spans from entry-level Micro800 controllers to enterprise-scale ControlLogix systems with redundancy and high I/O counts, all supported by Studio 5000 or dedicated programming software.
History of Allen-Bradley and Rockwell Automation
Allen-Bradley was founded in 1903 in Milwaukee, Wisconsin, manufacturing motor starters and rheostats. The company became a pioneer in programmable logic controllers in the 1970s and 1980s with the PLC-2 and PLC-5 families. Rockwell International acquired Allen-Bradley in 1985, and the automation division was later spun off as Rockwell Automation in 2001. Today, Rockwell Automation is the world's largest company dedicated to industrial automation, with Allen-Bradley as its primary hardware brand.
PLC Product Family Breakdown
ControlLogix (1756 Series)
The ControlLogix platform is designed for large, complex applications. Key characteristics:
- Modular backplane chassis (4, 7, 10, 13, 17 slot options)
- Multiple processors per chassis for partitioned control
- Controller redundancy with automatic failover (1756-RM2)
- Up to 120,000+ I/O points per controller
- Motion control for up to 256 axes
- Best for: compressor stations, large processing facilities, pipeline control centers, and manufacturing lines
CompactLogix (1769 / 5069 Series)
CompactLogix delivers ControlLogix-class programming in a smaller footprint:
- Integrated processor with built-in EtherNet/IP ports
- 1769 (legacy) and 5069 (current) I/O form factors
- Same Studio 5000 programming environment and instruction set
- Code portability between CompactLogix and ControlLogix
- Best for: wellsite automation, tank batteries, pump stations, small water treatment plants, and OEM machines
MicroLogix (1100, 1400)
MicroLogix is a legacy small PLC platform:
- Fixed I/O with limited expansion
- Programmed with RSLogix 500 (different instruction set)
- Discontinued — replaced by Micro800 series
- Still widely installed and maintained in existing systems
Micro800 (820, 830, 850, 870, 880)
The Micro800 series targets entry-level and OEM applications:
- Programmed with Connected Components Workbench (free software)
- Plug-in modules for communications, I/O expansion, and storage
- No RSLinx required — direct USB or Ethernet connection
- Best for: standalone machines, simple pump controls, HVAC, and small building automation
GuardLogix (1756-L7SP, 5069-L3100ERMS2)
GuardLogix adds safety-rated control to the ControlLogix and CompactLogix platforms:
- SIL 2 and SIL 3 safety certification (IEC 61508)
- Integrated standard and safety control in one program
- Safety I/O modules for E-stop, light curtains, and safety interlocks
- Eliminates the need for separate safety relay systems in many applications
Choosing the Right Platform by Application Size
- Under 20 I/O — Micro800 with CCW
- 20-200 I/O — CompactLogix 5380/5480
- 200-2000 I/O — CompactLogix 5380 or ControlLogix
- 2000+ I/O or redundancy required — ControlLogix
- Safety functions required — GuardLogix
Allen-Bradley vs Siemens vs Mitsubishi
Allen-Bradley dominates North America due to integrator availability and parts supply chain. Siemens (S7-1200, S7-1500) is the leading platform in Europe and is gaining share in North American process industries due to cost advantages and TIA Portal engineering tools. Mitsubishi (MELSEC iQ-R, iQ-F) is dominant in Asia-Pacific and common in automotive manufacturing globally. All three platforms are technically capable — the best choice depends on geographic support, existing infrastructure, and integrator expertise.
Typical Industries
- Oil and gas — Wellsite control, pipeline monitoring, compressor management, tank farm automation
- Manufacturing — Assembly lines, material handling, packaging, and quality inspection
- Water and wastewater — Treatment plant control, distribution pump stations, lift station automation
- HVAC and building automation — Chiller plants, air handling units, and building management systems
Frequently Asked Questions
ControlLogix uses a modular backplane chassis supporting multiple processors and I/O modules with high scalability. CompactLogix integrates the processor and I/O in a more compact form factor suited to smaller systems with lower I/O counts.
Studio 5000 Logix Designer is used for ControlLogix and CompactLogix. RSLogix 500 for legacy MicroLogix. Connected Components Workbench for Micro800 series.