1734-OB8S | Allen-Bradley POINT Guard I/O | 8-Point 24VDC Digital Safety Output Module

Module Overview

The 1734-OB8S is a high-reliability POINT Guard I/O module designed for safety-critical applications within the Allen-Bradley (Rockwell Automation) ecosystem. Functioning as a specialized 8-point digital safety output module, it provides the deterministic control required for emergency stops, light curtains, and safety gate interlocks. When integrated into a GuardLogix or SmartGuard controller system via EtherNet/IP or DeviceNet, the 1734-OB8S ensures that safety functions are executed with SIL 3, PLe, and Cat. 4 compliance. Its compact POINT I/O form factor allows for localized safety control, reducing complex wiring runs to the main control cabinet.

Detailed Engineering Specifications

The 1734-OB8S is engineered to provide fail-safe switching of 24V DC field loads while continuously performing internal diagnostics to detect short circuits or ground faults.

• Module Type: POINT Guard I/O Safety Output

• Safety Output Points: 8 Points (Sourcing)

• Nominal Supply Voltage: 24V DC

• Operating Voltage Range: 19.2 to 28.8V DC

• Maximum Output Current: 8.0A total per module (1.0A per point @ 40°C)

• Power Dissipation: 4.5 Watts

• Thermal Dissipation: 15.38 BTU/hour

• Safety Ratings: SIL 3 (IEC 61508), PLe (ISO 13849-1), Category 4

• Backplane Current Draw: 175 mA @ 5V DC

• Point-Level Diagnostics: Short-circuit detection, overload protection, and pulse testing

• Mounting Orientation: Horizontal or Vertical

• Physical Weight: 0.25 lbs (0.11 kg)

• Enclosure Rating: Open-style (IP20)

Advanced Safety and Diagnostic Features

The 1734-OB8S excels in identifying potential hardware failures before they lead to a dangerous state. Each output is capable of performing "Pulse Testing," which momentarily switches the output off and back on (too fast to affect the load) to verify that the switching circuitry is functional and that no external cross-circuit exists. In the event of a detected fault, the module transitions to a safe "Off" state and reports the specific error code back to the safety controller for rapid troubleshooting.

System Requirements and Installation

To utilize the 1734-OB8S, the module must be seated in a 1734-TB or 1734-TBS removable terminal base. It requires a 1734-AENTR (Ethernet) or 1734-PDN (DeviceNet) adapter that supports CIP Safety protocol. During configuration in Studio 5000 Logix Designer, the user must define the Safety Network Number (SNN) and ownership to ensure that the safety data is securely and uniquely identified across the network.

Technical FAQ

Can the 1734-OB8S be used in a standard (non-safety) POINT I/O rack?

While it can physically fit in the rack, the 1734-OB8S requires a Safety Controller (like a GuardLogix) and a safety-rated communication adapter to function. It cannot be controlled by a standard non-safety PLC.

What is the maximum current I can draw at high temperatures?

At 55°C (131°F), the total module current is typically derated. While the maximum per point is 1.0A at 40°C, always consult the 1734-OB8S derating curves if your enclosure ambient temperature exceeds 45°C to prevent thermal shutdown.

Does this module support bipolar output wiring?

The 1734-OB8S provides sourcing outputs. For applications requiring dual-channel (bipolar) switching where one side is sourced and the other is sunk, you would typically pair this with a safety input or use specialized wiring configurations as defined in the Guard I/O safety manual.