Description
The Allen-Bradley 1791DS-IB16/A is a CompactBlock Guard I/O safety input module designed for DeviceNet Safety networks. It provides 16 single-channel safety-rated digital inputs (24V DC sinking) with integrated pulse test outputs for continuous circuit diagnostics. As part of the 1791DS series, this module enables distributed safety architectures by connecting safety devices (e.g., E-Stops, light curtains) directly to a safety controller (like GuardLogix or SmartGuard) over a single DeviceNet cable, reducing wiring complexity while meeting SIL 3 / PL e safety standards.
Application Scenarios
In an automotive body shop, the 1791DS-IB16/A is deployed to monitor safety gate switches and emergency stop buttons on robotic welding cells. The module is mounted locally on the machine frame, connecting field devices via short wiring runs. It communicates over the DeviceNet Safety network with a central GuardLogix 5570 controller. This setup eliminates the need for long, hardwired safety runs back to the main panel, reducing installation costs by 40% and providing real-time diagnostics for each safety point.
Parameter
| Parameter | Specification |
|---|---|
| Manufacturer | Rockwell Automation (Allen-Bradley) |
| Model | 1791DS-IB16 / 1791DS-IB16/A (Series A) |
| Product Family | CompactBlock Guard I/O (1791DS Series) |
| Function | DeviceNet Safety Digital Input Module |
| Number of Inputs | 16 (Single-Channel Safety, configurable as 8 dual-channel pairs) |
| Input Type | 24V DC Sinking (IEC 61131-2 Type 1/3) |
| Input Voltage | On-State: ≥11V DC, Off-State: ≤5V DC |
| Test Outputs | 16 Integrated Sourcing Pulse Test Outputs (for short-circuit detection) |
| Safety Standards | SIL 3 (IEC 61508), PL e / Category 4 (ISO 13849-1) |
| Network Protocol | DeviceNet with CIP Safety |
| Baud Rates | 125 kbps, 250 kbps, 500 kbps |
| Operating Voltage | 19.2 – 28.8V DC (24V DC nominal) |
| Power Consumption | ~85 mA @ 24V DC |
| Mounting | 35 mm DIN Rail (horizontal or vertical) |
| Enclosure Rating | IP20 (for cabinet mounting) |
| Operating Temperature | -20°C to +60°C (-4°F to 140°F) |
| Status Indicators | Per-point input LEDs, Network/Module Status LEDs |
| Connectors | Removable screw terminal blocks (I/O, Power, DeviceNet) |
Technical Principles and Innovative Values
The 1791DS-IB16/A is engineered to replace traditional hardwired safety relays with an intelligent, networked safety I/O system. Its core innovation lies in the CIP Safety protocol and advanced self-diagnostics.
- Innovation Point 1: CIP Safety Protocol over DeviceNet. Unlike standard I/O, this module uses the CIP Safety application layer, which adds time stamps, sequence counts, and CRC checks to every message. This ensures that corrupted or delayed data is detected, and the system can safely shut down, maintaining integrity even on a shared network with non-safety devices.
- Innovation Point 2: Integrated Pulse Test Outputs. Each of the 16 safety inputs is paired with a dedicated pulse test output. These outputs inject a low-current test signal into the field wiring to detect cross-channel shorts, wire-to-wire shorts, and shorts to power before a fault could lead to a dangerous failure. This allows the module to achieve SIL 3 reliability with single-channel wiring in many applications.
- Innovation Point 3: Distributed Safety Architecture. The module enables a decentralized I/O topology. Safety logic remains in the central safety controller (e.g., GuardLogix), but the I/O points are distributed to the machine edge. This drastically reduces the amount of safety wiring (replaced by a single DeviceNet trunk) and allows for faster troubleshooting via network diagnostics.
