Allen-Bradley 1769-OB8 CompactLogix 8-Point High-Current 24V DC Source Output Module

Technical Performance Summary

The 1769-OB8 is a high-capacity discrete output module designed for the Allen-Bradley CompactLogix and MicroLogix 1500 families. Unlike standard density modules, the 1769-OB8 is specifically engineered for "sourcing" configurations, where it provides 24V DC power to field-side loads. It is characterized by its ability to handle significantly higher current per point, making it ideal for driving heavy-duty inductive loads such as large solenoid valves, motor starters, and hydraulic actuators. The module features two isolated groups of four outputs, providing enhanced electrical protection and the flexibility to use different power sources for each group.

Critical Technical Specifications

• Manufacturer: Allen-Bradley / Rockwell Automation

• Product Series: Compact I/O

• Model Number: 1769-OB8

• Output Count: 8 High-Current Source Outputs

• Grouping: 2 Groups of 4 Channels each

• Voltage Category: 24V DC (Source)

• Operating Voltage Range: 20.4V to 26.4V DC

• Backplane Current Draw: 145 mA @ 5.1V DC

• Maximum Heat Dissipation: 2.20 Watts

• On-State Current (Min): 1.0 mA

• Surge Current: 4.0 Amps for 10ms (Repeatable every 2 seconds)

• Isolation Voltage: Tested at 1200V AC or 1697V DC for 1 second (Output-to-Bus and Group-to-Group)

• Slot Width: 1 (Single Slot)

• Module Location: DIN Rail or Panel Mount

• Power Supply Distance Rating: 8 Modules

• Compatible Power Supplies: 1769-PA2, 1769-PB2, 1769-PA4, 1769-PB4

• Physical Dimensions: 11.8 x 3.5 x 8.7 cm

Industrial Application and Reliability

The 1769-OB8 is optimized for rugged environments where standard PLC outputs might fail due to high inrush currents. Its robust surge rating allows it to withstand the momentary current spikes associated with switching large coils or DC motors. To ensure long-term reliability, the module incorporates optical and magnetic isolation to prevent field-side electrical noise or faults from damaging the controller's logic circuits. Its removable terminal block design facilitates rapid maintenance, allowing for module replacement without rewiring the field-side devices.

Frequently Asked Questions

What is the difference between "Source" and "Sink" outputs for the 1769-OB8?As a sourcing module, the 1769-OB8 connects the load to the positive (+24V) rail when activated. This is the standard configuration for North American safety and control circuits.

Can I use the 1769-OB8 to drive small relays?Yes, though its minimum on-state current is 1.0 mA. For extremely small loads that draw less than this, a "bleeder" resistor may be required to ensure the output circuit operates correctly.

Does this module require an external 24V DC power supply?Yes, while the logic power comes from the 1769 backplane, the current delivered to the field devices must be provided by an external DC power source connected to the module's VDC and COM terminals.