Allen-Bradley 1756-L81E ControlLogix 5580 Controller

Product Overview

The Allen-Bradley 1756-L81E is a member of the ControlLogix 5580 series programmable automation controllers (PACs) from Rockwell Automation, designed to deliver high-performance control for demanding industrial automation applications

. As part of the modern ControlLogix 5580 family, this controller replaces older legacy systems like PLC-5 and SLC 500, providing a powerful migration platform while enhancing processing capacity, connectivity, and functionality

. It is engineered to meet the complex requirements of modern manufacturing, process control, and large-scale machine automation, offering robust performance, scalability, and integrated security features.

The 1756-L81E is positioned as an entry-level model within the ControlLogix 5580 series but is still a highly capable controller

. It is equipped with 3 MB of user memory and includes 2 GB of non-volatile memory via a 1784-SD2 Secure Digital (SD) card, eliminating the need for battery-backed RAM and providing an environmentally friendly energy storage solution. This controller can handle up to 128,000 discrete I/O points and 4,000 analog I/O points, making it suitable for large-scale applications

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Key Features and Capabilities

Processing Power and Memory

The 1756-L81E controller provides substantial processing power for executing complex control algorithms, data handling, and communication tasks. With 3 MB of user memory, it offers ample space for user programs, data structures, and tag definitions

. The included 2 GB SD card ensures reliable non-volatile storage for program backups, firmware updates, and data logging, enhancing system reliability and simplifying maintenance procedures

.

Integrated Connectivity and Communication

A standout feature of the 1756-L81E is its comprehensive communication capabilities. It boasts a built-in USB 2.0 port for temporary local programming and a 1 Gb embedded Ethernet port that supports EtherNet/IP

. This high-speed Ethernet integration enables real-time I/O control, peer-to-peer messaging, and seamless integration with upper-level systems. The controller supports up to 100 EtherNet/IP nodes (depending on the firmware version), facilitating connection to a wide array of devices and networks

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The controller is compatible with various communication protocols through additional 1756 series communication modules, including:

• EtherNet/IP: For real-time I/O control and data exchange.

• ControlNet: Offers deterministic, high-throughput performance for real-time applications.

• DeviceNet: Connects simple industrial devices like sensors and actuators.

• Data Highway Plus (DH+) and Remote I/O: Supports legacy equipment integration.

• SynchLink: Provides time-synchronized data broadcast for coordinated motion control

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Scalability and I/O Capacity

The 1756-L81E is designed for scalability. It must be installed in a 1756 series chassis (such as 1756-A4, A7, A10, A13, or A17), which can accommodate multiple I/O modules and communication adapters

. The controller itself occupies a single slot in the chassis and can support a vast I/O configuration—up to 128,000 discrete points and 4,000 analog points

. This makes it ideal for extensive distributed control systems.

Safety and Security

Security is a critical aspect of modern industrial controllers. The 1756-L81E incorporates digitally signed and encrypted firmware to help prevent malicious intrusions and unauthorized code changes

. For applications requiring functional safety, the ControlLogix platform can be integrated with safety controllers and I/O modules certified for Safety Integrity Level (SIL) 3

.

Environmental Robustness

The controller is built to operate reliably in harsh industrial environments. Its standard operating temperature range is 0°C to 60°C (32°F to 140°F) when installed in a 1756 Series C chassis

. It can withstand shock ratings of 30G and vibration ratings of 2G at 10-500 Hz. For corrosive environments, a conformally coated version (designated by a "K" suffix, e.g., 1756-L81EK) is available, offering extended protection against contaminants, moisture, and chemical exposure

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Technical Specifications

The following table summarizes the key technical specifications of the Allen-Bradley 1756-L81E controller:

System Configuration and Programming

Hardware Configuration

The 1756-L81E is a modular controller that requires installation in a 1756 series chassis

. The chassis provides the backplane for communication and power distribution to the controller and other modules. Various chassis sizes are available, offering 4, 7, 10, 13, or 17 slots. The controller must be paired with a compatible 1756 power supply (such as 1756-PA75, PB75, etc.)

.

To form a complete control system, users must add 1756 I/O modules (digital, analog, specialty) and 1756 communication modules (for networks like ControlNet or DeviceNet) to the chassis

. This modular design allows for highly customized and scalable system architectures.

Software and Programming

The 1756-L81E is programmed using Rockwell Automation's Studio 5000 Logix Designer integrated development environment

. This powerful software supports multiple programming languages per the IEC 61131-3 standard, including Ladder Logic (LAD), Structured Text (ST), Function Block Diagram (FBD), and Sequential Function Chart (SFC)

. The controller's operating system is flash-upgradeable, allowing users to easily update firmware for new features and improvements.

The controller supports multiple tasks and programs, allowing for organized and modular code structure. It can handle up to 32 tasks, with each task containing up to 1000 programs

. This enables complex control strategies to be executed with deterministic performance.

Applications

The 1756-L81E is suited for a wide range of demanding industrial automation applications, including:

• Large-Scale Discrete Manufacturing: Controlling high-speed assembly lines, automotive manufacturing systems, and complex material handling systems requiring extensive I/O and fast processing.

• Process Control: Managing continuous processes in industries such as chemical, oil and gas, pharmaceuticals, and food and beverage, where analog I/O and regulatory control are critical.

• Infrastructure and Utilities: Monitoring and controlling water/wastewater treatment plants, power generation facilities, and other critical infrastructure.

• Integrated Motion Control: While the L81E itself does not have integrated motion, it can coordinate motion over EtherNet/IP for applications involving servos and drives

• .

• High-Availability and Redundant Systems: The controller can be configured in redundant or high-availability systems to ensure continuous operation in critical processes

• .

Comparison and Considerations

The 1756-L81E is the base model in the ControlLogix 5580 series. For applications requiring more memory, greater I/O capacity, or specialized functionality, higher-end models are available:

• 1756-L8xE Series: Models like L82E, L83E, L84E, and L85E offer increasing levels of user memory and EtherNet/IP node capacity

• .

• NSE (No Storage Energy) Models: Designed for specific energy consumption profiles

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• XT Models: Designed for operation in extreme temperature environments (-25°C to +70°C)

• .

• Process Controllers: Optimized for process applications with specialized function blocks