Allen-Bradley 1756-OB8EI ControlLogix 8-Point Electronically Fused Output Module

Product Overview

The Allen-Bradley 1756-OB8EI functions as a high-reliability digital output interface within the ControlLogix platform. This module provides eight independent, isolated output channels designed to switch DC loads. The "EI" designation indicates Electronic Fusing and Individually Isolated channels, offering superior protection and diagnostic capabilities compared to standard output cards. We supply this unit as 100% Brand New original factory stock, ensuring your mission-critical control loops benefit from advanced fault detection and circuit isolation.

Technical Specifications

Engineering Advantages

• Advanced Electronic Fusing: The 1756-OB8EI incorporates smart electronic fusing that detects overcurrent or short-circuit conditions on a per-channel basis. This hardware feature eliminates the need for physical glass fuses and provides an automatic reset capability once the fault clears, significantly reducing downtime.

• Point-to-Point Isolation: Each of the eight channels operates with total electrical isolation from the others (250V continuous). This prevents a single field-side fault or ground loop from propagating across the entire module, ensuring that a localized failure does not compromise the remaining seven control circuits.

• Real-Time Diagnostic Feedback: The module communicates "Fused-Out" and "Field Power Loss" status directly to the ControlLogix processor. Maintenance teams can view these diagnostics via Studio 5000 or an HMI, enabling rapid identification of the exact failed field device without manual testing.

• High-Current Drive Capability: Supporting up to 2.0A per point at 30°C, this module directly drives larger DC solenoid valves, motor starters, and signaling devices that typically require interposing relays when used with standard 0.5A output cards.

• Configurable States: Engineers can program the "Fault State" for each output (Hold Last State, On, or Off). This allows for a customized "Fail-Safe" strategy, ensuring the process enters a controlled, safe condition during a communication loss or controller fault.

FAQs

• Does the 1756-OB8EI require a specific Removable Terminal Block (RTB)?

  Yes. This module requires the 36-pin 1756-TBNH or 1756-TBSH RTB. Note that the terminal block is sold separately and must be wired according to the isolated channel layout.

• Can I use this module to switch AC loads?

  No. The 1756-OB8EI is strictly a DC sourcing module. Attempting to switch AC voltage will damage the internal power transistors and void the warranty. For AC applications, utilize a 1756-OA8 or 1756-OW16I.

• What happens when the electronic fuse trips?

  The module turns off the affected output and sends a diagnostic bit to the PLC. The "I/O" status LED on the front of the module will indicate a fault. Once you remove the short circuit, the fuse resets based on the module configuration in the software.

• How do I verify this is a 100% Brand New unit?

  Every 1756-OB8EI we ship arrives in its Original Factory Packaging with intact seals. As a brand-new unit, the gold backplane connectors will show no insertion marks, and the internal diagnostic logs will be clear, guaranteeing full service life.