Allen-Bradley 1771-OWNA Digital Output Module | PLC-5 Series

Allen-Bradley 1771-OWNA: Industrial Data Link for PLC-5 Digital Output Control

The Allen-Bradley 1771-OWNA is a relay-type digital output module engineered for the PLC-5 programmable controller platform. Designed to operate within the 1771 I/O chassis, this module serves as a critical node in the industrial data link between the PLC-5 processor and field-level actuators, solenoids, motor starters, and control relays. In smart factory environments where deterministic output switching, signal integrity, and system uptime are non-negotiable, the 1771-OWNA delivers the reliability that automation engineers depend on.

At its core, the 1771-OWNA translates digital commands from the PLC-5 processor — transmitted via the 1771 backplane — into isolated relay contact closures that drive field devices. This output switching function sits at the heart of the automation data flow: from SCADA supervisory commands, through the PLC-5 logic engine, across the 1771 backplane, and finally to the physical output terminals that energize or de-energize field equipment. Every millisecond of switching latency and every cycle of contact reliability matters in high-throughput production lines.

Network Communication Table

Connected Automation Data Flow

In a typical PLC-5 controlled production cell, the 1771-OWNA operates as the final output stage in a layered automation architecture. The data flow begins at the SCADA layer — where systems such as Rockwell’s FactoryTalk View SE or Wonderware InTouch aggregate real-time process data — and cascades down through the PLC-5 processor. The processor executes ladder logic and relay output instructions, writing output image table data across the 1771 backplane to the 1771-OWNA module.

Upstream, the PLC-5 processor communicates with the plant network via Data Highway Plus (DH+), enabling peer-to-peer messaging with other PLC-5 or SLC 500 controllers on the same network segment. For facilities integrating legacy PLC-5 systems with modern EtherNet/IP infrastructure, a 1761-NET-ENI or 1756-ENBT EtherNet/IP bridge module provides the protocol gateway between DH+ and TCP/IP networks, allowing SCADA and MES systems to poll real-time output status from the 1771-OWNA without disrupting the control loop.

On the remote I/O side, the 1771-ASB remote I/O adapter extends the 1771 I/O chassis to distributed locations on the plant floor, enabling the 1771-OWNA to be deployed in remote enclosures hundreds of meters from the PLC-5 rack. This architecture is common in large-scale process plants, automotive assembly lines, and material handling systems where centralized control must reach distributed field devices.

For HMI integration, PanelView Plus 6 and PanelView 800 terminals connect to the PLC-5 via DH+ or EtherNet/IP, providing operators with real-time output status visualization. Alarm conditions — such as output coil failures or field device faults — are surfaced through the HMI and simultaneously logged in the SCADA historian for post-event analysis and predictive maintenance workflows.

In drive control applications, the 1771-OWNA relay outputs are frequently used to issue run/stop commands to PowerFlex 40 or PowerFlex 700 variable frequency drives, with the drive’s digital input terminals wired directly to the relay contacts. This hardwired interlock ensures fail-safe operation even in the event of network communication interruptions. Feedback signals from the drives — such as fault status or speed-at-setpoint — are returned to the PLC-5 via 1771-IFM or 1771-IA2 digital input modules in the same 1771 chassis, completing the closed-loop control circuit.

For sensor integration, proximity switches, photoelectric sensors, and limit switches feed their signals into 1771-IA or 1771-IB digital input modules. The PLC-5 processes these inputs in real time and issues corresponding output commands to the 1771-OWNA, enabling precise sequencing of conveyors, actuators, and safety interlocks. In safety-critical zones, the output relay contacts of the 1771-OWNA are wired in series with safety relay modules to enforce machine guarding and emergency stop logic.

Edge computing nodes — such as the Cisco IE 4000 industrial Ethernet switch or Moxa EDS series managed switches — provide the network backbone that connects PLC-5 systems, HMI terminals, and SCADA servers within the plant LAN. These switches support IGMP snooping and QoS prioritization, ensuring that real-time I/O data from the 1771-OWNA’s status feedback reaches the SCADA layer with minimal latency.

Solving Data Isolation in Industrial Sites

One of the most persistent challenges in legacy PLC-5 environments is protocol fragmentation. Older 1771-based systems often operate on DH+ or Remote I/O networks that are isolated from modern EtherNet/IP plant networks, creating data silos that prevent real-time visibility into output states, cycle counts, and fault conditions. The 1771-OWNA, when paired with appropriate gateway modules such as the 1756-DHRIO ControlLogix DH+/RIO bridge, enables seamless data exchange between legacy 1771 I/O systems and modern Logix-based control architectures — without requiring a full system replacement.

For facilities pursuing production line transparency, integrating the 1771-OWNA’s output status data into MES and ERP systems via OPC-DA or OPC-UA servers allows production managers to monitor output utilization rates, detect abnormal switching patterns, and correlate output events with quality defects or downtime incidents. This data-driven approach transforms the 1771-OWNA from a simple relay output module into a source of actionable operational intelligence.

Remote diagnostics represent another critical capability enabled by proper network integration. Through FactoryTalk Diagnostics or third-party SCADA platforms, maintenance engineers can remotely monitor the forced output status, output image table values, and I/O fault flags associated with the 1771-OWNA — reducing mean time to repair (MTTR) and enabling predictive maintenance scheduling without requiring physical access to the control panel.

System expandability is a key advantage of the 1771 platform. Additional 1771-OWNA modules can be added to existing 1771 I/O chassis slots without modifying the PLC-5 program structure, provided chassis capacity and power supply ratings are respected. For applications requiring higher output density or mixed AC/DC output types, the 1771 family offers complementary modules such as the 1771-OW16 and 1771-OBD that can coexist in the same chassis, sharing the same backplane communication infrastructure.

Industrial Connectivity FAQ

Q1: What communication protocols does the Allen-Bradley 1771-OWNA support?
The 1771-OWNA communicates via the 1771 backplane bus, which is natively compatible with PLC-5 processors operating on Data Highway Plus (DH+), Remote I/O (RIO), and DH-485 networks. For integration with EtherNet/IP or ControlNet networks, gateway modules such as the 1756-DHRIO or 1761-NET-ENI are required to bridge the protocol gap.

Q2: How is output status monitored in real time from a SCADA system?
The PLC-5 processor continuously updates the output image table based on the 1771-OWNA’s relay states. SCADA systems connected via DH+ or EtherNet/IP gateways can poll these image table values at configurable scan rates, providing real-time output status visibility. FactoryTalk View SE and Wonderware InTouch both support native DH+ and EtherNet/IP data sources for this purpose.

Q3: Is the 1771-OWNA tested before shipment, and what warranty is provided?
Yes. Every 1771-OWNA unit is functionally tested prior to shipment, including relay contact continuity verification, backplane communication checks, and output switching cycle tests. All units are covered by a 12-month warranty from the date of shipment, covering manufacturing defects and functional failures under normal operating conditions.

Q4: Can the 1771-OWNA be added to an existing PLC-5 system without reprogramming?
In most cases, yes. Adding a 1771-OWNA to an available slot in an existing 1771 I/O chassis requires only a chassis slot address assignment and corresponding I/O configuration update in the PLC-5 program. No changes to the existing ladder logic are required unless new output control rungs are being added. Always verify chassis power supply capacity before adding new I/O modules.

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