Allen-Bradley 1771-IND 16-point Digital Ac/Dc Input Module

Product Overview

The Allen-Bradley 1771-IND is a 16-point digital AC/DC input module for PLC-5 1771 I/O systems. It accepts both 16–30V AC and 9–30V DC signals, providing flexible dual-mode operation for interfacing a wide range of industrial switching devices with PLC-5 controllers.

Key Specifications

• Number of Inputs: 16 channels
• Voltage Category: 24V AC/DC
• AC Operating Range: 16–30V AC
• DC Operating Range: 9–30V DC
• Backplane Current: 250 mA
• Max AC Off-State Current: 1.5 mA
• Max DC Off-State Current: 0.6 mA
• Typical AC Signal Delay (On): 35 ± 10 ms
• Typical DC Signal Delay (On): 10 ms (Series B: 5 ms)
• Typical AC Signal Delay (Off): 45 ± 15 ms
• Typical DC Signal Delay (Off): 50 ms (Series B: 10 ms)
• Isolation: 1500V AC tested (Series B)
• Wiring Arm: 1771-WH
• Mounting: Rack mount
• Operating Temperature: 0–60 °C (32–140 °F)
• Weight: 2.05 lbs (930 g)

Features & Benefits

• Dual AC/DC Operation: Single module handles both AC and DC input signals, reducing inventory and simplifying design
• High-Speed DC Response: Series B offers 5 ms ON delay for fast DC signal detection
• Strong Electrical Isolation: 1500V AC isolation (Series B) protects controller from field-side transients
• Low Power Consumption: 3.8 mA per input (DC) minimizes power supply loading
• Wide Voltage Tolerance: 9–30V DC and 16–30V AC ranges accommodate typical industrial control voltages
• Standard 1771 Form Factor: Compatible with all 1771-series I/O chassis and wiring arms

Applications

• 24V DC sensor and switch interfacing
• 24V AC pilot device monitoring
• Machine control and safety circuit input
• Pushbutton and selector switch detection
• Limit switch and proximity sensor integration

Installation Guide

1. Module Configuration: The entire module must be configured for either AC or DC operation—do not mix AC and DC inputs on the same module.
2. Chassis Installation: Insert the 1771-IND into a compatible 1771 I/O chassis slot. Verify backplane current capacity (250 mA).
3. Wiring Arm Connection: Attach the 1771-WH wiring arm for screw-terminal field connections.
4. Field Wiring: Connect all 16 inputs to either AC (16–30V) or DC (9–30V) field devices. Maintain consistent voltage type across all channels.
5. Wire Separation: Route AC/DC input conductors separately from communication and low-level signal wiring to reduce electrical interference.
6. Torque Specification: Use a torque screwdriver set to 7–9 lb-in for secure, vibration-resistant terminal connections.

FAQ

Q: Can I mix AC and DC inputs on the 1771-IND?
A: No. The entire module must be configured for either AC or DC operation. All 16 inputs must use the same voltage type.

Q: What is the minimum activation voltage?
A: 16V AC or 9V DC is required to guarantee ON-state detection.

Q: What is the maximum wire length?
A: Up to 1000 feet (305 meters) with proper shielding and wire gauge. Verify voltage drop calculations for long runs.

Q: Is the 1771-IND suitable for outdoor use?
A: No. The module is rated for indoor/dry locations only. Install in NEMA-rated enclosures for environmental protection.

Selection Tips

• Verify all field devices use the same voltage type (AC or DC) before selecting this module
• Series B offers faster DC response (5 ms) and higher isolation (1500V) than earlier series
• Calculate total wire run length and verify signal integrity at the module terminals
• Use shielded cables for installations exceeding 100 feet to prevent noise pickup
• For new designs, consider CompactLogix 1769-IQ16 or ControlLogix 1756-IB16D modules