Allen-Bradley 1771-IAD 16-Point AC/DC Input Module for PLC-5

June 10, 2026 • 3 min read • wayne • Guide

Reliable Input Acquisition for Critical Industrial Control

The 1771-IAD module interfaces discrete field devices directly with your PLC-5 system. It accepts both 120VAC and 125VDC signals from pushbuttons or limit switches. This module offers sixteen input channels in a single, space-saving unit. Engineers value its robust 79 to 138 Volt operating range. This module provides a reliable bridge between your plant floor and controller.

Technical Configuration and Operational Precision

Selectable signal delay times allow you to tune the 1771-IAD for specific applications. The module offers a 5ms or 20ms delay for AC Off-to-On transitions. For DC signals, it provides a 3ms or 10ms selectable On delay. All Off-to-On transitions use a fixed 25ms delay for noise immunity. This flexibility helps you filter out electrical noise and contact bounce effectively.

Streamlined Installation with Removable Wiring

The 1771-IAD uses a 1771-WH field wiring arm for simplified maintenance. This arm functions like a removable terminal block for modular wiring. You can replace the entire module without disconnecting any field wiring. This design dramatically reduces downtime during component swaps. It also simplifies initial installation and system commissioning tasks.

Chassis Compatibility and Physical Integration

This module fits into several standard 1771 I/O chassis from Rockwell Automation. It is compatible with the 1771-A1B, A2B, A3B, A3B1, and A4B models. It also installs into the 1771-AM1 and AM2 chassis for flexible mounting. The module requires specific keying positions for correct slot alignment. Set keying bands between pins 10 and 12 or 14 and 16.

Power Consumption and Thermal Management

The module draws a backplane current of 195 milliamperes at 5 Volts DC. It dissipates a maximum power of 8.8 Watts during full operation. This translates to a maximum thermal dissipation of 30.1 BTU per hour. Proper ventilation ensures the module operates within its thermal limits. This efficiency helps maintain system reliability inside your control cabinet.

Visual Status Indicators for System Diagnostics

The front panel provides essential status indicators for quick system checks. One green LED confirms the module is active and receiving power. Sixteen red LEDs show the On/Off status for each individual input channel. This allows technicians to troubleshoot field wiring issues immediately. It provides a clear window into the logic side of the system.

Procurement and Application Value

This module supports ½, 1, and 2-slot I/O addressing modes. It offers a cost-effective way to add high-density inputs to your system. The module interfaces with pilot lights, motor starters, and annunciators. It provides a pocket-friendly means to expand a PLC control system. Choose the 1771-IAD for proven, reliable performance in demanding environments.