Allen-Bradley Compact I/O 1769-OB32 32-Point 24VDC Sourcing Discrete Output Module

Module Overview

The 1769-OB32 is a high-density solid-state output module designed for the Allen-Bradley CompactLogix and MicroLogix 1500 controller platforms. Delivering 32 points of 24V DC sourcing (positive logic) power in a compact form factor, this module is engineered for high-volume discrete control. It is frequently utilized to drive solenoid valves, actuators, and indicator lights in automated assembly lines and process control systems where space efficiency is a priority.

Detailed Engineering Specifications

The 1769-OB32 provides two independent groups of 16 points, allowing for segmented power distribution and enhanced circuit protection across the 32-point array.

• Number of Outputs: 32 (Arranged in 2 groups of 16)

• Voltage Category: 24V DC Source (Positive Logic)

• Operating Voltage Range: 20.4 to 26.4V DC

• Output Current per Point: 0.5A @ 60°C (Increases to 1.0A @ 30°C)

• Total Module Current: 4.0A @ 60°C (Max 8.0A @ 30°C)

• Surge Current: 2.0A for 10 ms (Repeatable every 2 seconds)

• Response Time (Typical): 0.1 ms (On) / 1.0 ms (Off)

• Backplane Current Draw: 300 mA at 5.1V DC

• Maximum Heat Dissipation: 4.5 Watts

• On-State Voltage Drop: 1.0V DC at 1.0A maximum

• Isolation Voltage: 75V DC continuous (Reinforced insulation)

• Slot Width: 1.5 modules (Note the slightly wider physical footprint)

• Physical Weight: Approximately 0.992 lbs (450 g)

Installation and Power Dynamics

When integrating the 1769-OB32, engineers must account for its specific Power Supply Distance Rating of 6. This means the module cannot be placed more than six slots away from the system power supply (such as a 1769-PA4 or 1769-PB4). Additionally, because this is a sourcing module, the load must be connected between the module output terminal and the negative DC common.

Thermal Management and Derating

A critical design factor for the 1769-OB32 is its thermal performance. At higher ambient temperatures (60°C), the current capacity per point is halved to 0.5A. If your application requires driving high-current DC loads in a warm enclosure, ensure the cabinet has adequate ventilation or reduce the simultaneous "On" count of the outputs to stay within the 4.0A module limit.

Technical FAQ

What type of terminal block does this module require?

The 1769-OB32 utilizes the 1769-RTBN18 removable terminal block. This allows for pre-wiring of the field signals and rapid module replacement without disconnecting individual wires, significantly reducing maintenance downtime.

Does this module support sinking loads?

No. The 1769-OB32 is a sourcing-only module. It switches the positive (+) 24V DC leg to the load. For sinking applications where the PLC must provide a path to ground, a different module like the 1769-OV32 would be required.

Can I mix different voltages between the two groups?

Yes. Since the two groups of 16 are isolated from each other, you can technically provide different 24V DC power sources to each group, provided they fall within the 20.4–26.4V DC operating range.