Allen-Bradley 1771-OBN Digital DC Output Module

The Allen-Bradley 1771-OBN, also cataloged as the 1771-OBN Digital DC Output Module, operates as a dedicated hardware component for high-density load switching within PLC 5 rack-based control systems.

Hardware Specifications

PLC 5 Backplane Integration and Firmware Compatibility

The 1771-OBN is engineered for deep integration within the PLC 5 I/O chassis architecture. Execution of output commands is managed through the module-specific backplane bus communication velocity, ensuring synchronization with the host processor scan cycle. Users must verify firmware flash compatibility between the PLC 5 CPU and the module backplane interface to ensure deterministic execution of logic transitions. I/O density scaling allows for the management of up to 32 independent output points, organized into four isolated sets. Conformal coating is applied to the PCB to maintain signal integrity and prevent oxidation in industrial environments.

Frequently Asked Questions

Q: Does the 1771-OBN support hot-swapping within the PLC 5 rack?

A: No. The module does not support hot-swapping. The chassis must be de-energized to prevent arcing at the backplane connector or unintended output activation during the removal or insertion process.

Q: How is the load current distributed across the output sets?

A: The module provides 8 outputs per set, with a maximum continuous current of 2 A per set and 0.5 A per individual output. Total module current must not exceed 8 A to prevent thermal overload of the output circuitry.

Field Installation Guidelines

1. Power down the I/O rack and verify the absence of voltage before installation to prevent electrical damage to the backplane pins.
2. Use the 1771-WH wiring arm for all field connections; ensure that wiring is routed away from high-voltage AC lines to prevent induced noise on the DC outputs.
3. Verify that the load voltage is within the 10-30 VDC operating range before connecting field devices to the outputs.
4. Ensure the output current load is balanced across the four sets to remain within the 8 A module limit.
5. Confirm that the module is securely latched into the rack guide rails to ensure proper engagement with the backplane connector.
6. Perform an I/O test after power-up using the PLC programming software to verify channel addressing and confirm output state transitions.