Allen-Bradley 1756-L71 – ControlLogix 5570 Series Controller
The Allen-Bradley 1756-L71 is a high-performance controller in the ControlLogix 5570 series, designed by Rockwell Automation for demanding industrial control applications. This controller is ideal for large, complex systems that require significant processing power, fast communication, and tight synchronization across multiple control disciplines. Whether used in process automation, motion control, batch systems, or safety-critical applications, the 1756-L71 offers robust performance and advanced diagnostics in a modular, scalable platform.
Unlike compact or micro controllers, the 1756-L71 is part of the ControlLogix platform, which provides plant-wide integration, redundant capabilities, and a common development environment through Studio 5000 Logix Designer software. This allows engineering teams to standardize on a single platform for discrete, process, safety, and motion control — improving lifecycle management and reducing total cost of ownership.
Core Strengths
1. High-Speed Processing & Large Memory
The 1756-L71 features a dual-core processor and 2 MB of user memory, enabling it to handle complex tasks with short scan times. This is crucial in high-speed manufacturing where milliseconds matter.
2. Modular Architecture
ControlLogix controllers mount in a 1756 chassis, allowing users to add communication modules, I/O modules, or specialty modules as needed. This modularity supports system expansion and future upgrades without replacing the controller.
3. Extensive Communication Capabilities
The 1756-L71 supports multiple network topologies including:
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EtherNet/IP for standard plant networking
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ControlNet for deterministic control
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DeviceNet for legacy device integration
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Remote I/O and Safety Networks for distributed architectures
Communication modules can be added to support redundancy, fiber-optic networks, or third-party protocol gateways.
4. Integrated Safety & Motion
When paired with GuardLogix safety controllers or Kinetix drives, the 1756-L71 can coordinate safety-rated control and integrated motion over EtherNet/IP. This reduces wiring complexity and improves response times for applications like robotics, conveyors, and coordinated drives.
5. Redundancy & Reliability
The ControlLogix platform offers controller redundancy, hot-swappable modules, and advanced diagnostics to minimize downtime. The 1756-L71 supports online editing, firmware updates, and fault handling to keep production running even during maintenance.
Technical Specifications Table
| Category |
Details |
| Series |
ControlLogix 5570 |
| Controller Model |
1756-L71 |
| Processor |
Dual-core, high-speed CPU |
| User Memory |
2 MB |
| Non-Volatile Memory |
Optional 1784-SD1 Secure Digital card (1 GB standard, up to 2 GB) |
| Communication Options |
EtherNet/IP, ControlNet, DeviceNet, DH+/RIO (via modules), serial, third-party gateways |
| I/O Capacity |
Supports up to thousands of I/O points (depends on chassis size and network architecture) |
| Chassis Slots |
4-, 7-, 10-, 13-, or 17-slot 1756 chassis supported |
| Task Support |
Up to 32 tasks, 100 programs per task |
| Scan Time |
Sub-millisecond for typical applications |
| Motion Control |
Supports integrated motion over EtherNet/IP (up to 32 axes) |
| Redundancy |
Supports ControlLogix controller redundancy systems |
| Diagnostics |
Advanced system diagnostics, online editing, online program changes |
| Power Requirements |
Powered via 1756 chassis power supply (varies by chassis) |
| Operating Temperature |
0 °C to 60 °C (32 °F to 140 °F) |
| Storage Temperature |
−40 °C to 85 °C (−40 °F to 185 °F) |
| Certifications |
UL, CE, C-Tick, ATEX (Zone 2), SIL 2/3 capable (when used with GuardLogix) |
| Programming Environment |
Studio 5000 Logix Designer (formerly RSLogix 5000) |
| Mounting |
1756 ControlLogix chassis |
System Integration Benefits
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Seamless Plant-wide Integration: The 1756-L71 can be used as the core of a plant’s control system, integrating process, batch, safety, and motion control under a single platform.
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Future-Proof Design: Modular approach allows easy addition of new technology without replacing the controller, protecting your automation investment.
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Data & Analytics Ready: With EtherNet/IP, it can stream real-time data to SCADA, MES, or IIoT platforms for predictive maintenance and performance monitoring.
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Safety Applications: Paired with GuardLogix, it can achieve SIL 2/3 safety levels, reducing the need for separate safety PLCs.
Example Applications
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Automotive Assembly Lines: Coordination of robots, conveyors, and safety interlocks across large facilities.
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Process Industries: Batch control for chemical, pharmaceutical, or food production, requiring recipe management and data logging.
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Material Handling Systems: Coordinated motion for cranes, hoists, and automated storage/retrieval systems.
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Energy & Utilities: Turbine control, water treatment plants, or power distribution systems with redundant control requirements.
Why Choose the 1756-L71?
This controller strikes a balance between cost and capability — offering enough memory and performance for most mid- to large-scale applications without stepping up to the more expensive 1756-L73 or L75 models. It is a reliable workhorse for system integrators who need:
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