Overview
The Allen-Bradley 1771-OA /B is a Series B AC output module from the 1771 I/O product family, engineered for PLC-5 automation systems. Eight discrete output channels deliver 120V AC nominal output within a 92–138 VAC operating range at 47–63 Hz. This single-slot module installs directly into any 1771 I/O chassis and provides reliable AC voltage control for industrial loads including motor starters, solenoids, alarms, and indicator lamps.
Key Features
- 8 Discrete AC Output Channels – Each rated 1.5 A continuous, module maximum 6 A total
- 120V AC Nominal Output – Operating range 92–138 VAC, 47–63 Hz
- Onboard Fusing – 2A, 250V AGC fuse per output channel protects against overload and short circuits
- Status Indicators – Eight neon indicators display real-time output state; separate fuse-blown indicator for diagnostics
- Surge Current Capability – 4 A per channel for 8.3 ms, repeatable every 1 second
- Field Wiring Arm Compatible – Uses 1771-WA field wiring arm (included) for tool-free module swap
Technical Specifications
- Output Voltage Range: 92–138 VAC, 47–63 Hz nominal 120V
- Output Current Per Channel: 1.5 A continuous
- Module Maximum Current: 6 A total
- Backplane Current Draw: 210 mA @ 5 VDC
- Output Channels: 8 discrete
- Fuse Rating: 2 A, 250V AGC per output
- Surge Current: 4 A per channel @ 8.3 ms (repeatable every 1 second)
- On-State Voltage Drop: 2 V @ 100 mA
- Off-State Leakage: Maximum 5 mA per output @ 120 VAC
- Mounting: Single slot, 1771 I/O chassis
- Module Keying: Positions 4–6 and 12–14 (prevents incorrect slot installation)
- Wire Size: 14–22 AWG, max insulation 75°C, 1.2 mm thickness
- Status Indicators: 8 neon output indicators + fuse-blown indicator
- Field Wiring Arm: 1771-WA (included), optional fused version 1771-WHF
Typical Applications
The 1771-OA /B is ideal for controlling AC-powered industrial devices in process automation, manufacturing, and utility applications:
- Motor Starters & Contactors – Direct control of 3-phase and single-phase AC motors via magnetic contacts
- Solenoid-Operated Valves – Switching hydraulic and pneumatic solenoids for flow control
- Pilot Lights & Alarms – Energizing indicator lamps, sirens, and audible alarm devices
- Space Heaters & Heating Elements – Switching resistive heating loads
- AC-Powered Relays – Interlocking and signaling applications
Compatibility & Replacements
The 1771-OA /B is a legacy PLC-5/1771 I/O module with no direct modern replacements in current Rockwell Automation product lines. Successor platforms include CompactLogix and ControlLogix systems with integrated digital output capabilities. For existing PLC-5 systems, the 1771-OA /B remains the industry standard for AC output control. It can be paired with AC input modules (1771-IA, 1771-IA2, 1771-IAD) using proper RC snubber or resistor networks between output and common.
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