Overview
The Allen-Bradley 1771-OAD is an AC discrete output module designed for PLC-5 programmable logic controllers. It provides 16 individually controlled output points supporting AC loads across a wide operating voltage range (10–138VAC, 47–63 Hz). This module is well-suited for controlling solenoids, relays, indicator lights, and general AC-powered industrial equipment. The 1771-OAD uses zero-crossing switching technology to minimize electrical stress on connected devices and extend component life.
Key Features
- 16 discrete AC output channels with individual control
- Voltage range: 10–138VAC at 47–63 Hz
- Output current: 2A maximum per point; 8A maximum module load (pilot duty)
- Zero-crossing switching technology to reduce load stress
- Individual status LED indicators for each output channel
- Fuse-blown indicator for diagnostics
- Backplane current draw: 295 mA @ 5VDC
- Field-wiring arm interface (1771-WH standard; optional fused arm 1771-WHF available)
- Compatible with most 1771 I/O chassis (1771-A1B through -A4B and later; 1771-AM1, -AM2)
Technical Specifications
| Output Voltage Range | 10–138VAC |
| Frequency | 47–63 Hz |
| Output Channels | 16 (discrete, non-isolated common) |
| Output Current Per Point | 2A maximum |
| Module Load Rating | 8A maximum (pilot duty) |
| Minimum Load Current | 5 mA |
| OFF State Leakage | 3.0 mA @ 138VAC maximum |
| Backplane Current | 295 mA @ 5VDC (0.7A per some sources) |
| Power Dissipation | 13W maximum; 1.5W minimum |
| Switching Technology | Zero-crossing |
| Mounting Style | Rack-mount in 1771 I/O chassis |
| Field Wiring Arm | 1771-WH (standard); 1771-WHF (fused option) |
| Status Indicators | Per-channel LED; Active indicator; Fuse-blown indicator |
| Certifications | UL/CSA listed |
| Compatibility | PLC-5 systems; 1771-A1B through -A4B and later chassis; 1771-AM1, -AM2 |
| Series Variants | Series A, B, C, D available (check compatibility and date codes) |
Typical Applications
- AC load switching in factory automation and machinery control
- Motor starter and solenoid valve control
- Pilot light and indicator device switching
- Industrial heating and cooling equipment control
- General-purpose AC power distribution within PLC-5 systems
Compatibility & Replacements
The 1771-OAD is a legacy PLC-5 I/O module, discontinued by the manufacturer but widely available through industrial surplus and refurbishment channels. It is compatible with 1771 I/O chassis supporting AC output modules (specifically 1771-A1B through -A4B and later revisions, plus 1771-AM1 and -AM2 chassis). Not compatible with early 1771-A1, 1771-A2, or 1771-A4 chassis. Series variants (A, B, C, D) exist; verify your specific series requirement with your system documentation. Direct modern equivalents in the Rockwell Automation portfolio include CompactLogix or ControlLogix-based systems with digital output modules, but those require chassis and controller migration. The 1771-OAD remains a cost-effective replacement for existing PLC-5 installations.
