Allen-Bradley 1756-L71S GuardLogix 5570 PAC Installation & Maintenance Guide
Product Introduction
The Allen-Bradley 1756-L71S serves as a high-performance safety PAC within the Logix5000 family. This processor module delivers both standard control and safety functions on a single platform. The 1756-L71S requires a 1756-L7SP safety partner module to achieve SIL 3 or Category 4/PLe safety ratings. The system automatically configures the safety partner, which significantly simplifies project setup. You can install this controller in any slot within a ControlLogix 1756 chassis.
Core Value
The 1756-L71S controller provides substantial memory resources for complex automation tasks. It offers 2 MB of standard user memory, 1 MB of dedicated safety memory, and 0.98 MB of I/O memory. A pre-installed 1 GB Secure Digital card (1784-SD1) supplies non-volatile storage, with expansion options up to 2 GB using the 1784-SD2 card. The controller supports up to 128,000 digital I/O points and 4,000 analog I/O points. This capacity makes the 1756-L71S suitable for large-scale discrete and process applications requiring integrated safety.
Furthermore, the controller supports up to 100 motion axes and 500 controller connections. It handles up to 31 standard tasks and one dedicated safety task, with 100 programs permitted per task. The 1756-L71S eliminates the need for lithium batteries by using the 1756-ESMCAP Energy Storage Module. This design choice reduces maintenance requirements and enhances reliability in critical applications.
Technical Insights
The 1756-L71S controller operates with a dual-processor architecture, where the primary processor handles standard logic while the safety partner manages safety functions. The system supports multiple programming languages, including Relay Ladder Logic for safety tasks and Structured Text, Function Block Diagram, and Sequential Function Chart for standard tasks. The controller features a USB 2.0 port (Type B receptacle) for local programming and configuration. This port connects directly to the Studio 5000 Logix Designer application through RSLinx software.
The 1756-L71S supports three primary industrial networks for safety communication: EtherNet/IP, ControlNet, and DeviceNet. For EtherNet/IP communication, the controller supports up to 256 connections using the 1756-EN2x adapter. The front display provides runtime diagnostic information for quick troubleshooting. The controller draws 5 mA at 1.2V DC and 800 mA at 5.1V DC, with a power dissipation of 2.5W and thermal dissipation of 8.5 BTU/hr. The isolation voltage is rated at 30V continuous for basic insulation.
Installation & Maintenance
Proper installation of the 1756-L71S begins with chassis selection and mounting. The controller installs into a ControlLogix 1756 chassis by aligning the circuit board with the top and bottom guides. Slide the module until it sits flush with adjacent modules, then engage the top and bottom latches. You can perform insertion or removal while chassis power is active, but observe caution in hazardous locations due to potential arcing.
The Energy Storage Module (ESM) installation requires attention. Slide the 1756-ESMCAP unit into the chassis until it snaps into place. For applications requiring residual energy depletion before transport, use the 1756-ESMNSE(XT) module for the primary controller and the 1756-SPESMNSE(XT) for the safety partner. The SD card installation involves unlocking the card door, verifying the lock position, and inserting the card before closing the door.
Firmware updates for the 1756-L71S require the ControlFLASH tool. Connect the controller via USB and select the desired firmware revision. Allow the update to complete fully before cycling power to prevent firmware corruption. The key switch on the front panel provides three operating modes: Program, Remote, and Run.
Buyer’s Guide FAQ
Q: What memory capacities does the 1756-L71S controller offer?
A: The 1756-L71S provides 2 MB of standard user memory, 1 MB of safety memory, 0.98 MB of I/O memory, and a 1 GB Secure Digital card for non-volatile storage.
Q: Does the 1756-L71S support controller redundancy?
A: No, the 1756-L71S does not support controller redundancy.
Q: What safety certification does the 1756-L71S hold?
A: The 1756-L71S meets SIL 3 per IEC 61508 and Category 4/PLe per ISO 13849-1 when used with the 1756-L7SP safety partner.
Q: Which programming languages work with the 1756-L71S?
A: The 1756-L71S supports Relay Ladder Logic, Structured Text, Function Block Diagram, and Sequential Function Chart.
Q: What communication ports are available on the 1756-L71S?
A: The controller includes one USB 2.0 port for local programming and supports optional EtherNet/IP, ControlNet, and DeviceNet communication adapters.
