Allen-Bradley PLC-5 | 1771-OBN | 32-Point DC Sourcing Output Module

Product Description

The 1771-OBN is a high-density digital output solution designed for the legacy Allen-Bradley PLC-5 chassis architecture. This module provides 32 sourcing outputs, organized into four isolated groups of eight channels each. Engineered for reliability in demanding industrial environments, the 1771-OBN features conformal coating to protect internal circuitry from moisture and contaminants. It is primarily used to drive high-current DC loads such as solenoids, motor starters, and indicators directly from the PLC backplane, supporting both BCD and Natural Binary data formats for flexible system integration.

Detailed Technical Specifications

• Module Function: Digital DC Sourcing Output

• Catalog Number: 1771-OBN

• I/O Density: 32 Outputs (4 sets of 8 points)

• Voltage Category: 10V to 60V DC Sourcing

• Operating Voltage Range: 10V to 30V DC

• Backplane Current Load: 330 mA at 5V DC

• Maximum Output Current: 0.5 Amps per channel (continuous)

• Group Current Limit: 2.0 Amps per set of 8 outputs

• Total Module Capacity: 8.0 Amps maximum

• Signal Propagation Delay: 50 ms (Off-to-On / On-to-Off)

• On-State Voltage Drop: 1.5V DC at 0.5A

• Off-State Leakage Current: 1.0 mA maximum

• Wiring Arm Requirement: 1771-WH

• Circuit Protection: Conformal Coated (Standard)

• Mounting Style: 1771 Universal I/O Chassis (Rack Mount)

• Product Weight: 0.94 kg (2.06 lbs)

Module Comparison and Installation FAQ

How does the 1771-OBN differ from the 1771-OB16?While both are DC output modules, the 1771-OBN doubles the point density with 32 outputs compared to the 16 outputs on the 1771-OB16. This allows for significant space savings within the 1771 rack, though it requires more careful management of current limits per group to ensure thermal stability.

What is the purpose of the conformal coating on this specific module?The "N" designation often indicates enhanced protection. The conformal coating provides a thin polymeric film over the circuit board, which shields the 1771-OBN from environmental stressors like salt spray, humidity, and chemical vapors, which is critical for longevity in wastewater or chemical processing plants.

Does this module require an external power supply?Yes. While the logic side of the 1771-OBN is powered by the 1771 backplane, the field-side DC power for the 32 outputs must be supplied externally through the 1771-WH wiring arm to maintain isolation between the PLC processor and the field devices.