Product Overview

The Allen-Bradley 1756-OB16IS is a specialized digital output module designed for the ControlLogix® platform, providing 16 channels of individually isolated 10-30V DC sourcing or sinking outputs. Unlike standard high-density modules, the 1756-OB16IS features point-to-point electrical isolation, allowing each channel to operate on a different voltage potential or circuit branch. This architecture is essential for complex industrial systems where cross-channel interference must be eliminated and where mixed power sources are utilized within a single chassis.

Engineered for high-precision timing, this module supports 8 "Scheduled Outputs," which allow the controller to synchronize output transitions with Coordinated System Time (CST) to within 16.7 microseconds. This makes the 1756-OB16IS an ideal solution for high-speed packaging, motion synchronization, and time-critical process events where millisecond accuracy is mandatory.

Advanced Load Management and Synchronization

The 1756-OB16IS is optimized for driving heavy-duty DC loads while maintaining rigorous safety standards.

• Point-to-Point Isolation: Provides 250V continuous isolation between individual outputs and between outputs and the backplane, ensuring field-side faults remain localized.

• High Current Capacity: Supports a 2A contact rating per point, with a total module current capacity of up to 8A at 30°C.

• Surge Protection: Capable of handling repeatable 4A surge currents for up to 10ms, facilitating the startup of inductive loads like large DC solenoids and motor starters.

• Deterministic Scheduling: The 8 scheduled outputs ensure that logic execution and physical output firing are decoupled from the RPI (Requested Packet Interval) for sub-millisecond precision.

• Customizable Fault States: Users can pre-configure each point to "Hold Last State," "On," or "Off" (default) in the event of a communication failure with the controller.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1756-OB16IS

• Output Type: DC Sinking/Sourcing (Isolated)

• Number of Outputs: 16 (8 Scheduled)

• Operating Voltage Range: 10V to 30V DC

• Backplane Current: 350mA @ 5.1V DC; 2.5mA @ 24V DC

• Response Time: OFF to ON: 1ms (max); ON to OFF: 2ms (max)

• Maximum Power Dissipation: 3.6W @ 60°C

• Isolation Voltage: 250V (Continuous); Basic Insulation Type

• Operating Temperature: 0°C to 60°C (32°F to 140°F)

• Vibration/Shock: 2g @ 10-500Hz; 30g Operational Shock

• Dimensions: 3.5 x 14.2 x 14.5 cm

• Weight: 0.2 kg (0.44 lbs)

Industrial Reliability and Safety

The 1756-OB16IS is built to sustain performance in demanding environments, featuring North American T4A and IEC T4 temperature code compliance. The module is routine-tested at 1350V AC to ensure insulation integrity and is designed for the high-vibration conditions common in automotive and heavy manufacturing plants.

For field wiring, this module requires a Removable Terminal Block (RTB), such as the 1756-TBCH (36-pin Cage Clamp) or 1756-TBS6H (Spring Clamp), to be ordered separately. The RTB allows for module replacement without disconnecting individual field wires, significantly reducing MTTR (Mean Time To Repair).