Overview
The Allen-Bradley 1771-OA /B is a digital AC output module engineered for legacy PLC-5 automation systems. This eight-channel discrete output module provides reliable switching of 120 VAC industrial loads and integrates seamlessly into 1771 backplane chassis configurations. Series B models are built with non-isolated outputs, onboard per-channel fusing, and integral field wiring connectivity.
Key Features
- Eight discrete AC output channels rated for 120 VAC nominal operation (92–138 VAC range)
- Per-channel current capacity: 1.5 A continuous; maximum module current: 6 A
- Onboard fusing for each output with accessible front fuse compartment
- Eight orange status indicators for real-time field-side output diagnostics
- Compatible with 1771-WA field wiring arm for toolless service access
- Keyed backplane connectors (positions 4–6, 12–14) prevent misinstallation
- Operates at 47–63 Hz; 210 mA backplane draw at 5 VDC
- Single I/O chassis slot occupancy for compact modular design
Technical Specifications
- Output Voltage: 120 VAC nominal (92–138 VAC operating range)
- Output Channels: 8 discrete outputs
- Per-Channel Current Rating: 1.5 A continuous
- Maximum Module Current: 6 A
- Frequency: 47–63 Hz
- Backplane Power Draw: 210 mA at 5 VDC
- Fusing: Individually fused per channel
- Status Indicators: 8 orange LEDs (field side)
- Mounting: Single slot in 1771 I/O chassis
- Wiring Arm: 1771-WA field wiring arm (included)
- Series: B
- Isolation: Non-isolated outputs
Typical Applications
- Solenoid and relay coil switching in industrial automation
- Indicator lamp and pilot light control
- Motor starter and contactor excitation (size 2 and compatible sizes)
- Alarm horn and audible warning actuation
- AC load control in PLC-5–based machinery and process lines
Compatibility & Replacements
The 1771-OA /B is directly compatible with all 1771-series I/O chassis and PLC-5 processors. This module is one of the industry-standard non-isolated AC output options in the 1771 family. Related modules in the Allen-Bradley 1771 product line include the 1771-OAD (16-channel isolated), 1771-OAN, 1771-OM, 1771-OMD, and isolated variants (1771-OD series). When connecting 1771-OA outputs to 120 VAC input modules such as 1771-IA or 1771-IA2, users must add a 2.5 kΩ, 10 W external resistor between the output terminal and common (L2) to ensure reliable signal coupling. The 1771-OA /B remains in active use for retrofit and OEM support in legacy systems. Current-condition units offer cost-effective solutions for system upgrades and replacement of failed I/O chassis components.
