Overview
The Allen-Bradley 1771-ASB /B is a remote I/O adapter module for the PLC-5 family, enabling communication between PLC processors and distributed I/O modules over extended distances. This adapter allows remote sensing and actuation without the cost and complexity of point-to-point wiring, making it ideal for large-scale automation installations where I/O devices are physically separated from the central controller.
Key Features
- Extended Transmission Range: Transmits data up to 10,000 cable-feet at 57.6K baud, with faster backplane scanning and data transmission up to 2500 cable-feet at 230.4K baud
- Multiple Baud Rate Support: Communication rates of 57.6 kbps, 115 kbps, and 230 kbps for flexible system integration
- Flexible I/O Addressing: Supports 1/2-slot, 1-slot, and 2-slot addressing methods with any mix of I/O (4, 6, 8, 16, or 32 points)
- Enhanced Diagnostics: Active, Adapter Fault, and I/O Rack Fault indicator lights for troubleshooting
- Series B Compatibility: Can emulate series B adapters, providing system response similar to the 1771-ASB series B, compatible with 1771-S4A and -S4B scanners
- Optimized Scan Time: Scans all slots in the chassis or all but the last four slots, allowing improved scan time and I/O image space savings
Technical Specifications
- Communication Speeds: 57.6 kbps, 115 kbps, 230 kbps
- Maximum Cable Distance: 10,000 feet at 57.6K baud; 5,000 feet at 115.2K baud; 2,500 feet at 230.4K baud
- Backplane Current: 1.0 Amp at 5 Volts DC
- Maximum Power Dissipation: 5.2W
- Weight: 1.9 pounds
- Dimensions: 3.5 x 6.5 x 2.0 inches (89 x 165 x 51 mm)
- Communication Protocol: Remote I/O (RIO) serial link
- I/O Capacity: Supports up to 32 remote racks
- Addressing Modes: 1/2-slot, 1-slot, 2-slot
- Mounting: Must be installed in leftmost slot of Universal I/O Chassis
- Compatible Chassis: 1771-A1B, 1771-A2B, 1771-A3B, 1771-A4B
- Termination: 82 Ohm or 150 Ohm terminating resistor (daisy-chain topology)
- Certifications: UL Listed, CSA Certified, Class I Division 2 Groups A–D, CE Compliant
Typical Applications
- Factory Automation: Multi-station manufacturing lines with distributed motor starters, solenoids, and sensors
- Distributed Control Systems (DCS): Large facilities (refineries, chemical plants, water treatment) where I/O is spread over extended areas
- Remote Sensing & Actuation: Temperature, pressure, and flow monitoring across geographically dispersed equipment
- Legacy PLC-5 Integration: Retrofit and expansion of existing PLC-5 networks requiring remote I/O gateway functionality
Compatibility & Replacements
The 1771-ASB /B is part of the Allen-Bradley 1771 series family and functions as a universal remote I/O adapter for PLC-5 systems. It is compatible with all Allen-Bradley Universal I/O Chassis models (1771-A1B through 1771-A4B) and works with Remote I/O scanners in the PLC-5 processor module. The Series B version (/B) maintains backward compatibility with earlier 1771-ASB designs while supporting modern Remote I/O (RIO) networking. For systems requiring different communication protocols or I/O counts, consider other Allen-Bradley adapter modules such as the 1771-ASC (ControlNet adapter) or 1771-OD (Output module alternatives).
