Allen-Bradley 1756-OB8 ControlLogix DC Output Module

Description

The 1756-OB8 is a high-integrity direct current (DC) digital source output module engineered for the Allen-Bradley ControlLogix 1756 chassis platform. This chassis-based I/O component functions as a solid-state electrical control switch, managing up to 8 independent field-side actuator channels. It delivers continuous, low-latency switching control across intensive industrial networks, including chemical processing, water treatment, automotive assembly, and power distribution systems. By routing logic-level system instructions into high-current sourcing circuits, this unit effectively drives external DC field loads—such as solenoids, relays, pilot lamps, and contactor coils—while shielding backplane microprocessors from electrical noise and voltage spikes.

Features

• 8-point digital DC sourcing output configuration.
• Organized into two isolated groups of 4 channels each, allowing for separate field power distribution loops.
• Compatible with 1756-TBNH and 1756-TBSH 20-pin Removable Terminal Blocks (RTB).
• Supports hot-swappable module replacement to minimize system downtime.
• Programmable fault and program mode states (Hold Last State, ON, or OFF).
• User-defined mechanical keying to prevent incorrect module insertion.

Applications

The 1756-OB8 is designed for demanding industrial environments requiring reliable DC load switching. Typical applications include:

• Automotive manufacturing and assembly lines.
• Municipal water and wastewater treatment facilities.
• Chemical and petrochemical processing plants.
• Power generation and distribution substations.
• General machine control and factory automation.

Technical Specifications

Installation Guidelines

• Ensure the ControlLogix chassis is powered down before inserting or removing the module.
• Use appropriate mechanical keying on the RTB to prevent incorrect module-to-wiring matches.
• Ensure field power supply is within the 10-30 VDC range and properly fused for the connected load.
• Maintain proper grounding practices for the chassis to minimize EMI/RFI interference.
• Verify that the RTB is securely latched to the module housing to ensure reliable electrical contact.
• Keep the module clear of high-heat sources and ensure adequate ventilation within the cabinet.

FAQ

Can I replace the 1756-OB8 while the system is running? Yes, this module supports Removal and Insertion Under Power (RIUP) when installed in a ControlLogix chassis, provided the hazardous area requirements are met.

What is the difference between the 1756-TBNH and 1756-TBSH terminals? The 1756-TBNH is a standard cage clamp terminal block, while the 1756-TBSH is a spring clamp terminal block. Both are compatible with the 1756-OB8.