1771-A3B | Allen Bradley | PLC 5 Universal I/O Chassis

Product Overview

The Allen Bradley 1771-A3B serves as the structural and electrical foundation for the PLC-5 platform. This 12-slot universal I/O chassis houses and powers a wide array of 1771-series digital, analog, and specialty modules. It facilitates high-speed communication between the processor and field interfaces through a heavy-duty backplane. We supply this unit as 100% Brand New, ensuring factory-original structural integrity and electrical performance for your critical automation infrastructure.

Technical Specifications

The 1771-A3B provides extensive expansion capacity with high current thresholds for demanding industrial racks.

Engineering Advantages

• High-Capacity Backplane: The 1771-A3B supports up to 24 Amperes of backplane current. This allows engineers to populate all 12 slots with power-intensive modules—such as high-density AC outputs or sophisticated motion control cards—without risking voltage drops or communication instability.

• Rugged Mechanical Construction: Built to withstand harsh factory floors, the chassis resists vibration up to 2 g and survives non-operating shocks up to 30 g. These ratings ensure the chassis maintains secure physical contact between module gold pins and backplane connectors, even in proximity to heavy stamping presses or rotating machinery.

• Flexible Installation Geometry: The design supports both standard 19-inch rack mounting and direct panel mounting. This versatility enables technicians to install the chassis in traditional server-style cabinets or directly onto the backplates of compact NEMA enclosures.

• Thermal Management: The open-style enclosure promotes natural convection cooling. By maintaining a steady airflow across the 12 slots, the 1771-A3B prevents localized heat buildup, thereby extending the MTBF (Mean Time Between Failures) of the installed electronic modules.

FAQs

• Can I use the 1771-A3B for stand-alone applications or remote I/O?

  Yes. You can install a PLC-5 processor directly into the first slot for a stand-alone controller configuration, or install a Remote I/O Adapter (like the 1771-ASB) to use the 1771-A3B as a remote rack connected to a central processor.

• Does this chassis include a power supply?

  No. The 1771-A3B requires an external 1771 power supply module (such as the 1771-P4 or 1771-P7) that mounts either to the left side of the chassis or in a standard slot, depending on the specific power supply model chosen.

• What is the benefit of the 12-slot configuration compared to smaller racks?

  The 12-slot design provides a "sweet spot" for medium-to-large scale automation. It offers enough density to handle complex machine lines while remaining compact enough to fit into standard industrial control panels, reducing the need for multiple interconnected smaller racks.

• Is this chassis compatible with older 1771 modules?

  Yes. The 1771-A3B is a "Universal" chassis. It maintains full backward compatibility with the entire legacy 1771 I/O module family, allowing you to upgrade your rack hardware while retaining your existing trusted I/O cards.