Overview
The Allen-Bradley 1771-0A is a proven 120V AC output module engineered for PLC-5 automation platforms. The 1771-0A /B variant provides eight discrete AC outputs with individual fusing and front-panel status indicators for real-time diagnostics. This module is a workhorse component in legacy Allen-Bradley control systems and integrates seamlessly with any compatible 1771 I/O chassis.
Key Features
- Eight discrete 120V AC outputs: Each channel independently rated at 1.5A continuous current, supporting diverse AC-driven loads
- Individual channel fusing: Each output line is individually protected with easily replaceable fuses accessible via front panel
- Non-isolated outputs: Direct connection to 120V AC supply; simplifies wiring for many applications
- Status indicators: Front-panel LEDs indicate the logic state of each output for immediate field diagnostics
- Field wiring arm (1771-WA): Removable pivot-style connector allows hot installation/removal without disturbing field wiring
- Compact single-slot design: Fits any standard 1771 I/O chassis; keyed backplane prevents cross-slot installation
Technical Specifications
- Module Type: AC Discrete Output
- Output Voltage Rating: 92–138 VAC at 47–63 Hz
- Nominal Output Voltage: 120V AC
- Channels: 8 outputs
- Current per Channel: 1.5A continuous
- Maximum Module Current: 6A
- Backplane Current Draw: 210 mA at 5VDC
- Fusing: Individual fuses per output (accessible front-side)
- Isolation: Outputs not isolated from common return
- Compatibility: 1771-A1B and later I/O chassis
- Wiring Arm: 1771-WA included
- Chassis Slot Height: Single slot (standard 1771 card slot)
Typical Applications
- AC solenoid valve control in packaging and process automation
- Indicator lamp and alarm horn circuits
- Motor starter output control for NEMA duty loads
- Pneumatic/hydraulic actuator pilot signal circuits
- Cooling fan and pump relay outputs in temperature control systems
Compatibility & Replacements
The 1771-0A /B is a direct drop-in replacement within the 1771 I/O family and is compatible with all PLC-5 processors and 1771-A1B through A4B I/O chassis or later. Related output modules include the isolated 1771-OD (6 outputs, isolated), 1771-OAN (four 120V AC outputs), and the 1771-OAD Series C (fused isolated variant). For systems transitioning from PLC-5 to CompactLogix or ControlLogix, modern equivalents include the 1756 digital output modules, though direct field installation would require chassis replacement. Used units of this vintage are widely available as surplus stock and work well in maintenance situations where original component sourcing is preferred for legacy system continuity.
