Product Overview

The Allen-Bradley 1756-OX8I is a high-performance ControlLogix discrete output module designed to interface between a programmable controller and a variety of field-side load devices. This module provides eight points of individually isolated relay contacts, offering maximum flexibility for systems requiring distinct voltage sources for each output. It features both Normally Open (N.O.) and Normally Closed (N.C.) contact configurations for every point, making it suitable for complex interlocking and signaling applications.

Built for versatility in industrial environments, the 1756-OX8I manages both AC and DC loads. While the module is natively isolated to prevent electrical noise and ground loop interference between channels, it can be bridged at the Removable Terminal Block (RTB) using jumpers (1756-JMPR) for applications requiring a common power supply. This modularity ensures the 1756-OX8I is an adaptable solution for driving contactors, solenoids, and indicators across diverse voltage ranges.

Technical Specifications

• Module Type: Isolated Relay Contact Output

• Operating Voltage Range: 10–240V AC / 5–125V DC

• Number of Outputs: 8 Points (Individually Isolated)

• Contact Arrangement: Form C (N.O. and N.C. contacts per point)

• Power Dissipation: 3.5 W (maximum)

• Contact Resistance: 100 mΩ (Initial at 6V DC, 1A)

• Switching Frequency: 0.3 Hz at rated load (1 operation every 3 seconds)

• Bounce Time: 1.2 ms (Mean)

• Physical Weight: 0.26 kg (0.57 lbs)

• Dimensions: 35 x 140 x 145 mm

• Mounting: Chassis-based (ControlLogix 1756 Chassis)

• Compatible RTB: 1756-TBCH or 1756-TBS6H

Operational Characteristics

The 1756-OX8I is engineered for long-term reliability in demanding cycles. It offers a mechanical life expectancy of 300,000 cycles for resistive loads and 100,000 cycles for inductive loads. By utilizing electromagnetic relays, the module provides a physical air gap when contacts are open, ensuring zero leakage current—a critical requirement for specific safety and signaling circuits where solid-state leakage might cause false triggering.

Maintenance and installation are streamlined through the use of a Removable Terminal Block (purchased separately). This design allows for the replacement of the module without disconnecting field wiring, significantly reducing Mean Time to Repair (MTTR). The module's rugged construction and USA-based manufacturing origin reflect the high standards required for critical PLC infrastructure.