Allen-Bradley 1756-OX8I ControlLogix Digital Output Module

The Allen-Bradley 1756-OX8I, also cataloged as the 1756-OX8I Isolated Contact Module, operates as a dedicated hardware component for contact-closure signal generation within ControlLogix System networks.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks and Base Integration

The Allen-Bradley 1756-OX8I interfaces directly with the standard system backplane to synchronize physical contact outputs with processor operations driven via Profinet / EtherNet/IP deterministic networks. The module uses internal register logic to decode coil commands sent over the chassis backplane bus. Due to the high channel-to-channel physical isolation, switching signals are protected against electrical noise, maintaining timing deterministic bounds for high-voltage and low-voltage field circuits connected to the 8-channel array.

Frequently Asked Questions

Q: Does this contact output module support hot-swap insertion while the chassis backplane is energized?

A: Yes, this hardware supports Removal and Insertion Under Power (RIUP). Field technicians can extract or insert the module while backplane power is applied, provided all field-side electrical circuits are completely isolated to eliminate arcing risks.

Q: What is the benefit of the individual channel-to-channel isolation on this specific module?

A: Each of the 8 channels features complete electrical isolation. This configuration permits each contact to switch independent voltage potentials and phases across the 5-125 VDC and 125/240 VAC boundaries without causing cross-talk or backplane logic corruption.

Field Installation Guidelines

• Chassis Insertion: Guide the module straight into the slot guides of the 1756 chassis until the top and bottom locking tabs fully click into position. Verify alignment with the backplane connectors before applying mechanical force.
• Terminal Block Wiring: Terminate all N.O., N.C., and common return conductors using an approved Removable Terminal Block (RTB). Ensure screw terminals are tightened to specified torque ratings to avoid loose terminations on inductive loads.
• Conductor Routing and Segregation: Route all high-voltage AC or inductive DC field wires away from low-voltage digital signal and network communication media inside the cable ducts to mitigate inductive noise coupling.
• Surge Suppression: For highly inductive field circuits such as external solenoid valves or large magnetic starter coils, install appropriate external RC snubbers for AC loads or diodes for DC loads directly across the field device terminals.