Product Overview

The Allen-Bradley 1791DS-IB8XOB8 is a high-integrity distributed I/O module engineered for safety-critical applications within a DeviceNet™ network. This Guard I/O™ module provides a compact, integrated solution for safety control, featuring 8 safety-rated digital inputs and 8 safety-rated solid-state outputs. Designed to facilitate SIL 3, PLe, and Category 4 safety architectures, it allows for the decentralized placement of safety I/O near field devices, significantly reducing wiring complexity while maintaining the highest levels of personnel and equipment protection.

Equipped with 4 additional pulse test outputs, the 1791DS-IB8XOB8 can actively monitor input circuits for short circuits or cross-loops, ensuring the validity of every safety signal. This "combination" module is ideal for managing emergency stops, light curtains, and safety gates in automated manufacturing cells where space is limited but diagnostic transparency is essential.

Safety Architecture and Intelligent Diagnostics

The 1791DS-IB8XOB8 utilizes a solid-state design to offer rapid response times and a longer operational life compared to traditional relay-based systems. It features extensive internal self-testing to detect hardware failures and ensures that the system enters a safe state if a fault is identified. The module communicates safety data using the CIP™ Safety protocol over DeviceNet, allowing safety and standard control data to coexist on the same physical wire without compromising the integrity of the safety function.

For simplified commissioning and maintenance, the module provides detailed diagnostic status indicators for every I/O point. These LEDs allow technicians to identify field-side issues—such as wire breaks or shorted outputs—directly at the module. Furthermore, the configuration lock feature ensures that once the safety parameters are validated, they cannot be altered without authorization, preserving the validated state of the safety loop.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1791DS-IB8XOB8

• Safety Inputs: 8 Points (Current Sinking)

• Safety Outputs: 8 Points (Solid-state Sourcing, 0.5A per point)

• Pulse Test Outputs: 4 Points

• Network Protocol: DeviceNet (CIP Safety)

• Input Voltage: 24V DC (Nominal)

• Voltage Range: 20.4–26.4V DC

• Safety Ratings: SIL CL3 (IEC 61508), PLe/Cat. 4 (ISO 13849-1)

• Enclosure Rating: IP20

• Operational Temperature: -10°C to +55°C (14°F to 131°F)

• Mounting: DIN Rail

• Dimensions: 8.0 x 19.6 x 7.7 cm

Installation and Environmental Durability

• Compact Footprint: The slim design maximizes cabinet space while providing high-density safety I/O.

• Robust Shock/Vibration: Tested to withstand 5G vibration (10-500Hz), making it suitable for mounting on heavy machinery or vibrating platforms.

• Removable Connectors: Features high-quality terminal blocks that facilitate quick module replacement without rewiring field devices.

• Software Integration: Fully compatible with RSNetWorx™ for DeviceNet and Studio 5000 Logix Designer® for streamlined configuration.