Allen-Bradley 1756-OB16IS ControlLogix I/O Module

The Allen-Bradley 1756-OB16IS, also cataloged as the 1756-OB16IS ControlLogix I/O Module, operates as a discrete output execution component within ControlLogix distributed control architectures. It provides direct electrical switching for 16 individually isolated and 8 scheduled DC output channels across a 10–30 V DC operating range in ControlLogix backplane systems.

Hardware Specifications

EtherNet/IP Backplane Execution and I/O Density Scaling

The 1756-OB16IS integrates into ControlLogix backplane architecture where output state control is executed through scheduled task updates and module-level scan synchronization. Individually isolated output channels reduce cross-channel electrical coupling during high-frequency switching operations.

I/O density scaling is achieved through ControlLogix rack expansion, where distributed modules share deterministic backplane communication. Output scheduling supports mixed discrete timing execution, allowing separation between real-time and cyclic output updates within the controller task structure.

Frequently Asked Questions (FAQ)

Q: Are the outputs individually isolated at channel level?
A: Yes. The module provides 16 individually isolated outputs, reducing electrical interaction between switching channels during simultaneous actuation.

Q: What is the backplane power dependency during operation?
A: The module draws 350 mA from the 5.1 V backplane rail and a minimal 2.5 mA from the 24 V auxiliary rail depending on system configuration.

Q: Does output scheduling affect response latency?
A: Scheduled outputs are executed based on ControlLogix task scan intervals, introducing timing dependency on controller execution cycles.

Field Installation Guidelines

• Install module into a compatible ControlLogix chassis with proper backplane seating.

• Ensure 10–30 V DC field supply is stable before energizing output circuits.

• Maintain separation between isolated output wiring and high-noise power conductors.

• Verify channel load does not exceed 2 A pilot duty rating (DC-13SQ).

• Use shielded cabling for long-distance output wiring to reduce switching-induced interference.