SKU: 1771-IB

Allen-Bradley 1771-IB PLC-5 Digital Input Module

The Allen-Bradley 1771-IB is an 8-point digital DC input module for the PLC-5 platform. It provides reliable 12/24V DC sinking inputs with optical isolation and integrated LED diagnostics, ensuring high-performance signal acquisition in 1771 Universal I/O environments.

Technical Overview

The Allen-Bradley 1771-IB serves as a foundational discrete input interface for the PLC-5 system. This module converts high-level DC signals from field-level sensing devices into logic-level signals that the controller can process. Operating within a nominal 12V to 24V DC range, the 1771-IB features eight (8) independent input circuits. Because it utilizes a sinking configuration, the module requires the connected field devices to supply the current to the input terminals.

Operational Features and System Integration

This digital input module manages signal integrity through internal filtering and optical isolation. By decoupling the field wiring from the sensitive backplane electronics, the 1771-IB protects the PLC-5 processor from electrical noise and voltage transients. Furthermore, the unit incorporates front-panel LED status indicators. Consequently, maintenance personnel can visually verify the status of each input point at a glance, which significantly simplifies the diagnostic process during system troubleshooting.

The hardware design prioritizes durability and ease of installation. Since the 1771-IB installs directly into a 1771 Universal I/O Chassis, it eliminates the need for complex mounting hardware. Moreover, the use of a swing-arm wiring assembly allows users to replace the module without disconnecting individual field wires. This feature minimizes downtime and reduces the risk of wiring errors during hardware maintenance or system upgrades.

Key Technical Characteristics

Manufacturer: Allen-Bradley / Rockwell Automation
Model Number: 1771-IB
Module Type: DC Discrete Input Module
Number of Inputs: 8 Points
Voltage Category: 12–24V DC (Sinking)
Operating Voltage Range: 10V to 30V DC
Backplane Current Load: 75 mA
Signal Delay (Off to On): 1 ms (±0.5 ms)
Signal Delay (On to Off): 1 ms (±0.5 ms)
Isolation Voltage: 1500V RMS
Product Family: PLC-5 / 1771 I/O

Primary Applications

Monitoring limit switches and proximity sensors on high-speed conveyor systems.
Interfacing with push-button stations for manual operator control.
Collecting discrete state feedback from motor starters and circuit breakers.
Managing digital logic signals in vintage manufacturing and assembly environments.