Rockwell / Allen-Bradley 1771-IAD 120V AC/DC Input Module

The Rockwell / Allen-Bradley 1771-IAD is a 16-channel digital input module for PLC-5 systems and the 1771 I/O platform. It accepts 120 VAC (50/60 Hz) or 125 VDC signals from discrete field devices including pushbuttons, limit switches, selector switches, and relay/contactor auxiliary contacts. The module features selectable input signal delays optimized for AC and DC sources, enabling stable signal processing in electrically noisy industrial environments while maintaining fast response to state changes.

Technical Specifications

Input Characteristics

• 16 discrete inputs at 120 VAC / 125 VDC nominal


• On-state voltage range: 79 to 138 VAC or VDC


• Nominal input current: 9.9 mA @ 120 VAC 60 Hz, 8.7 mA @ 120 VAC 50 Hz, 2.56 mA @ 125 VDC


• Maximum off-state current: 2.8 mA AC, 0.8 mA DC Signal Delays (Selectable)


• AC on-state: 5 ms (±3 ms) or 20 ms (±5 ms)


• DC on-state: 3 ms (±0.1 ms) or 10 ms (±1 ms)


• AC/DC off-state: 25 ms (±5 ms) Power & Thermal


• Backplane current draw: 195 mA @ 5V


• Maximum power dissipation: 8.8 W (30.1 BTU/hr)


• Minimum power dissipation: 1.0 W (3.42 BTU/hr) Physical


• Dimensions: 89 × 165 × 51 mm (3.5 × 6.5 × 2.0 inches)


• Weight: 1.00 lbs (0.45 kg)


• Module indicators: 1 green active LED; 16 red status LEDs

Key Features

• Dual voltage compatibility (AC and DC) in single module


• Independently selectable signal filtering for AC and DC inputs


• Screw terminal connections via 1771-WH wiring arm


• Maximum conductor gauge: 14 AWG stranded

Typical Applications Discreet industrial signal monitoring, machine safety circuits, process control interlocks, equipment status indication, and automation systems requiring mixed AC/DC input sources.

Compatibility & Integration Compatible with Allen-Bradley 1771 chassis platforms (1771-A1B through A4B and later universal chassis models). Requires 1771-WH field wiring arm for terminal connections.