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Description
Technical Specifications
- Product Model: 1771-A2B
- Manufacturer: Allen-Bradley (Rockwell Automation)
- Product Type: Universal I/O Chassis / Backplane Assembly
- Number of Slots: 8 slots
- Backplane Power Rating: 16 A @ 5 V DC (total capacity)
- Compatible Systems: PLC-5 Series (e.g., PLC-5/10, 5/15, 5/25, 5/40, 5/60, 5/80)
- Compatible Modules: All 1771 Series A and B I/O modules (digital, analog, special function)
- Power Supply Requirement: Requires external 1771-P4R, P4S, P6S, or P7 power supply module
- Mounting Method: Panel mount (back-panel) or rack mount
- Enclosure Type: Open style (requires external cabinet for protection)
- Operating Temperature: 0 °C to 60 °C (32 °F to 140 °F)
- Dimensions: 12.4″ W × 14.0″ H × 7.6″ D (315 × 356 × 193 mm)
- Weight: ~10.3 lbs (4.67 kg)
- Shock/Vibration Resistance: 30g non-operating shock; 2g @ 10–500 Hz operating vibration
Main Features and Advantages
High-Capacity Parallel Backplane
The backplane bus architecture provides low-impedance power distribution and deterministic data transfer, essential for critical process control loops.
Universal Module Compatibility
Supports both legacy Series A and newer Series B 1771 modules, protecting long-term investments in existing automation systems.
Ruggedized Mechanical Design
Constructed from heavy-gauge steel with precise card-edge alignment guides to withstand industrial shock and vibration.
Serviceability and Redundancy
Removable wiring arms allow module swaps without rewiring. Supports redundant 1771-P4R power supplies for high availability.
Application Field
The 1771-A2B is deployed in large-scale industrial plants such as water treatment facilities, mining operations, and chemical processing sites. In these environments, it houses the PLC-5 processor along with analog and discrete I/O modules to control processes like chemical dosing, filtration, and motor operations. Its robust construction ensures reliable performance even in electrically noisy and mechanically stressful conditions.
Related Products
- 1771-P4R: Redundant AC power supply module designed to plug directly into the 1771-A2B chassis.
- 1771-ASB: Remote I/O adapter module used to connect the chassis to a remote PLC-5 network.
- 1771-WH: Removable field wiring arm that attaches to the bottom of the chassis for easy maintenance.
- 1785-L40E: Example PLC-5/40 Ethernet processor that would occupy Slot 0 of the chassis.
- 1771-IAD: 16-point 24V DC input module commonly installed in the I/O slots.
- 1771-OAD: 12-point 120V AC output module commonly installed in the I/O slots.
Installation and Maintenance
Before installation, ensure the enclosure is properly grounded. Calculate the total current draw of all modules to verify the 16 A backplane limit is not exceeded. When installing or removing any module or wiring arm, you must remove power from the chassis backplane to prevent equipment damage or unexpected operation. For maintenance, use the status LEDs on each module for diagnostics. If replacing a module, pivot the wiring arm upward to disconnect it, swap the module, and then pivot the arm back into place.
