Overview
The Allen-Bradley 1771-OW is a selectable relay contact output module for PLC-5 industrial control systems. This module provides eight relay output channels arranged in four groups of two channels each, with each group sharing an individual common terminal. The 1771-OW enables precise digital output control for motor starters, solenoids, indicator lights, and other field devices in manufacturing and process automation applications.
Key Features
- Eight Selectable Outputs: Configured in four groups of two channels, each independently addressable in PLC logic.
- Configurable Contact Form: Each output is selectable as normally-open (N.O.) or normally-closed (N.C.), allowing flexible control strategies.
- Wide Voltage Range: Supports AC operation at 24–138VAC RMS and DC operation at 24–125VDC (up to 235V DC with proper circuitry).
- Dry Contact Isolation: Complete electrical isolation between module logic and output relay circuitry eliminates leakage current to connected equipment.
- Robust Relay Design: All eight channels can actuate simultaneously, with typical operate/release time of 5 milliseconds.
- Field-Replaceable Jumpers: Factory-preset to normally-open; users can reconfigure each pair individually without removing the module from the chassis.
Technical Specifications
- Output Channels: 8 (4 groups × 2 channels per group)
- Contact Form: Selectable normally-open or normally-closed per output pair
- AC Operating Voltage: 24–138VAC RMS
- DC Operating Voltage: 24–125VDC (up to 235VDC)
- Rated Current Per Output: 1.0 ampere
- Maximum Continuous Current (Per Module): 0.25A @ 120VAC/VDC or 1.0A @ 30VAC/VDC (30W maximum)
- Backplane Current Draw: 700 milliamperes maximum
- Minimum Load: 10 mA @ 24VDC/VAC
- Operate/Release Time: 5 milliseconds
- Contact Bounce: 1 millisecond
- Switching Frequency: 10 Hz
- Power Dissipation: 3.3–3.7 watts
- Thermal Dissipation: 11.3–12.7 BTU/hr
- Field Wiring Arm: 1717-WD (requires separate purchase)
- I/O Keying: Plastic keying bands between pins 6–8 and pins 16–18
Typical Applications
The 1771-OW serves critical switching functions in:
- Motor starter and drive enable/disable circuits
- Solenoid valve and hydraulic load control
- Indicator light and beacon logic
- Process pump and compressor on/off sequencing
- Machine guard and safety interlock circuits
- Equipment standby and shutdown safety chains
Compatibility & Replacements
The 1771-OW is compatible with all 1771-series I/O chassis for PLC-5 processors. Related output modules include the 1771-OWN (32 selectable outputs), 1771-OW16 (8 normally-open + 8 selectable), and 1771-OX (4 selectable outputs). The module installs in any 1771 chassis slot except the leftmost (processor) position. For field wiring, pair this module with the 1717-WD wiring arm. Used units of this module are widely available through industrial surplus and automation distributors for cost-effective system upgrades and repairs.
