Allen-Bradley 1746-OX8 Relay Output Module

Product Details

1746-OX8 Product Description

The Allen-Bradley 1746-OX8 is an 8-point relay output module engineered for the SLC 500 programmable controller platform — one of Rockwell Automation's most widely deployed control architectures in discrete manufacturing, process automation, and smart factory environments. As industrial sites transition toward data-transparent production lines, the 1746-OX8 serves as a critical field-level output node, bridging PLC logic execution with physical actuator control while remaining fully integrated within the broader industrial data chain.

In a connected factory, every output signal carries operational intelligence. The 1746-OX8 does not merely switch loads — it participates in a structured data flow that begins at the sensor layer, passes through the SLC 500 processor (such as the 1747-L553 or 1747-L543), and extends upward through communication backplanes to SCADA platforms, MES layers, and cloud-based analytics dashboards. Its relay contacts provide the physical actuation layer for solenoids, motor starters, indicator lamps, and control relays, while the SLC 500 backplane ensures real-time status feedback is continuously available to the control system.

Understanding the 1746-OX8 within a smart factory data architecture requires tracing the full signal path from field device to enterprise system. At the field level, sensors and proximity switches feed digital inputs into companion modules such as the 1746-IB16 (16-point DC input module), which captures machine state data and delivers it to the SLC 500 processor over the backplane. The processor evaluates ladder logic in real time and issues output commands to the 1746-OX8, which then actuates relays controlling downstream equipment — motor starters, pneumatic valves, warning beacons, and interlock circuits.

For sites requiring protocol translation and upward data visibility, the SLC 500 system connects to higher-level networks through communication modules such as the 1747-KE (DH-485 to RS-232 interface) or the 1761-NET-ENI Ethernet interface, enabling the SLC 500 to participate in EtherNet/IP-based plant networks. This allows SCADA platforms — including Rockwell's FactoryTalk View SE or third-party systems like Ignition by Inductive Automation — to poll real-time I/O status, including the relay output states managed by the 1746-OX8.

In multi-zone production environments, the 1746-OX8 is often deployed alongside 1746-NI4 analog input modules for temperature or pressure monitoring, and 1746-NO4I analog output modules for variable-speed drive setpoint control. Variable frequency drives (VFDs) such as the PowerFlex 40 or PowerFlex 525 receive run/stop commands from relay outputs, while their operational data — speed, current, fault codes — is fed back through the network to the SCADA layer for real-time visualization and alarm management.

Edge connectivity is further extended through industrial gateways such as the 1783-NATR NAT router or third-party Moxa and HMS Anybus gateways, which bridge legacy SLC 500 DH+ networks to modern EtherNet/IP or MQTT-based IIoT architectures. This enables remote diagnostics, OEE dashboards, and predictive maintenance workflows without requiring a full control system migration — preserving the investment in existing SLC 500 infrastructure while adding smart factory data transparency.

Industrial managed switches — such as the 1783-MS10T Stratix 2000 — provide the network backbone for deterministic EtherNet/IP communication between PLCs, HMI panels, and SCADA servers, ensuring low-latency data delivery critical for time-sensitive relay output coordination across multi-axis or multi-zone systems.

Protocol Fragmentation: Many legacy SLC 500 installations operate on DH+ or DH-485 networks that are isolated from modern EtherNet/IP plant backbones. The 1746-OX8, when paired with appropriate communication bridges, allows these systems to participate in unified plant data networks without requiring a full PLC migration. Protocol gateways translate between DH+ and EtherNet/IP, enabling SCADA systems to read and write I/O data — including relay output states — across previously siloed network segments.

Data Islands and Production Transparency: In facilities where relay output modules operate without upstream data visibility, production events — machine stops, alarm activations, interlock trips — go unrecorded at the SCADA level. Integrating the 1746-OX8 within a fully networked SLC 500 system ensures that every relay state change is logged, timestamped, and available for trend analysis, shift reporting, and OEE calculation. This transforms a simple output module into a data-generating node within the smart factory architecture.

Remote Monitoring and Alarm Tracking: With SCADA integration, operators can monitor relay output status remotely — identifying stuck relays, unexpected actuations, or interlock faults without physical presence on the production floor. Alarm management systems can be configured to trigger notifications when relay outputs deviate from expected patterns, enabling proactive maintenance and reducing unplanned downtime.

System Scalability: The 1746 series chassis architecture supports modular expansion, allowing additional output modules, analog I/O, and communication cards to be added as production requirements grow. The 1746-OX8 integrates seamlessly within this expandable framework, supporting phased smart factory upgrades without disrupting existing control logic.

Q1: Can the 1746-OX8 communicate directly over EtherNet/IP?The 1746-OX8 is a relay output module that communicates over the SLC 500 backplane — it does not have a standalone EtherNet/IP port. EtherNet/IP connectivity is achieved through the SLC 500 processor combined with an Ethernet interface module such as the 1761-NET-ENI or through an upstream gateway device. This allows the relay output states to be monitored and controlled via EtherNet/IP-connected SCADA and HMI systems.

Q2: What is the communication latency for relay output updates in an SLC 500 system?The SLC 500 backplane scan time is typically in the range of 1–10 ms depending on program size and chassis configuration. Relay output updates occur within the processor scan cycle, providing deterministic, low-latency response suitable for discrete control applications. Network latency for SCADA polling is additional and depends on the communication module and network topology in use.

Q3: Is the 1746-OX8 compatible with third-party SCADA platforms such as Ignition or WinCC?Yes. When the SLC 500 system is connected via an OPC-DA or OPC-UA gateway — or through an EtherNet/IP driver — third-party SCADA platforms including Ignition (Inductive Automation), Siemens WinCC, and GE iFIX can read and write relay output data from the 1746-OX8. This enables cross-platform SCADA integration without requiring Rockwell-exclusive software.

Q4: What warranty and quality assurance does NANKMOS provide for the 1746-OX8?NANKMOS provides a 12-month warranty on the Allen-Bradley 1746-OX8, covering functional defects under normal operating conditions. Each unit undergoes pre-shipment functional testing to verify relay contact integrity and backplane communication. Global express shipping is available, with stock maintained for fast dispatch to minimize production downtime for replacement and expansion projects.