Overview
The Allen-Bradley 1771-OBD is a 16-point DC digital output module engineered for the PLC-5 1771 I/O platform. This module provides sourcing-type (positive logic) outputs and operates within a 10–60V DC supply range, with a nominal output of 48V DC. It is designed for direct control of DC-powered loads including solenoids, relay coils, contactors, indicator lamps, and pilot devices in industrial automation and motion control systems.
Key Features
- 16 Non-Isolated Output Points – Individually controlled, directly addressable via PLC-5 processor
- 10–60V DC Supply Range – Nominal 48V DC output with field-voltage flexibility
- Sourcing Output Type – Positive logic output for driving standard DC loads
- Fast Response Time – Less than 1 ms output switching for time-critical applications
- Integrated Status Indicators – Green module-active LED and 16 red output status LEDs for field diagnostics
- Compact 1771 Chassis Form Factor – Mounts directly in 1771-A1B through 1771-A4B I/O chassis (excludes 1771-A4)
Technical Specifications
- Output Points: 16 nonisolated
- Output Voltage Range: 10–60V DC (nominal 48V DC)
- Current Rating: 2 A per output (resistive), max 8 A per module total, 0.2 A per pilot duty
- Inrush Current: 4 A per output (10 ms, repeatable every 2 s); 25 A per output (10 ms surge, repeatable every 2 s)
- Leakage Current: 2.5 mA maximum (rated voltage)
- On-State Voltage Drop: 1.5V DC maximum (at rated current)
- Off-State Leakage: 0.5 mA maximum
- Response Time: 0.1 ms turn-on, 0.2 ms turn-off
- Power Dissipation: 15.6 W maximum; 53.3 BTU/hr maximum thermal output
- Backplane Current Draw: Approx. 210–400 mA at 5V DC
- Operating Temperature: 0°C to +60°C (32°F to 140°F)
- Storage Temperature: −40°C to +85°C (−40°F to +185°F)
- Isolation Voltage: 1500V RMS between output group and logic backplane
- Operating Shock: 30 G (3-pulse, 11 ms)
- ESD Immunity: 4 kV contact discharge; 8 kV air discharge
- Certifications: UL, CSA, CE
- Series/Type: 1771 I/O, Series C DC Output Module
Typical Applications
The 1771-OBD is ideal for:
- Motor control and solenoid valve actuation in process automation
- Manufacturing line indicator lamps and alarm devices
- Conveyor system motor starter control
- HVAC and pump system contactor switching
- Lighting and status display control in factory floor systems
- Pilot duty applications in safety-critical and logic control circuits
Compatibility & Replacements
The Allen-Bradley 1771-OBD is compatible with PLC-5 systems exclusively. It mounts in 1771-A1B through 1771-A4B I/O chassis (do not use with 1771-A4 chassis). The module requires a field-wiring arm such as the 1771-WH, 1771-WHF, or 1771-WHFB (sold separately) for terminal connections. In two-slot addressing mode, the 16-point output module must occupy an odd-numbered slot on the backplane. Compatible companion input modules include the 1771-IB, 1771-IC, 1771-IBD, and 1771-ICD series. When pairing with input modules, use the same DC power source to maintain ground potential. No direct modern replacements exist in current CompactLogix or ControlLogix platforms; legacy PLC-5 systems rely on this module for continued operation.
