Allen-Bradley 1746-OB32 SLC 500 32-Point DC Output Module

1746-OB32 Allen-Bradley SLC 500 Digital Output Module

Product Introduction

The Allen-Bradley 1746-OB32 is a high-density, low-current digital DC output module designed for the SLC 500 controller platform. It provides 32 sourcing output channels organized into two groups of 16 points each. The operating voltage range spans 5 to 50V DC, with a nominal rating of 24V DC. Primarily, this module energizes discrete devices such as pilot lamps, buzzers, horns, solenoids, and small motors. Additionally, the 1746-OB32 can drive interposing relays to interface with AC-powered loads, offering flexibility in mixed-voltage systems. Its compact design, combined with LED status indicators and a removable terminal block, simplifies installation and diagnostics.

Technical Specifications

The 1746-OB32 delivers reliable output performance with clearly defined electrical parameters. Its backplane current consumption is 190 mA at 5V DC, with a total heat dissipation of 6.45W. The module's output circuit isolation is tested at 1500V AC for one minute, ensuring robust protection against electrical faults.

Key Output Characteristics:

• Number of Outputs: 32 (16 points per common)

• Voltage Range: 5 – 50V DC (nominal 24V DC)

• Current per Output: 0.5A (0-30°C); 0.25A (0-60°C)

• Current per Module: 8A maximum

• Current per Common: 2A maximum

• Off-State Leakage: 1 mA maximum

• Signal Delay: 0.1 ms (ON); 1.0 ms (OFF)

• On-State Voltage Drop: 1.2V maximum at 0.5A

• Surge Current: 1.0A for 1 ms, repeatable every 2 seconds

Performance and Protection Features

The 1746-OB32 offers fast signal response with maximum delays of only 0.1 ms for ON transitions and 1.0 ms for OFF transitions. This rapid switching capability is critical for applications requiring precise timing and high-speed actuation. The module also provides a surge current rating of 1.0A per point for 1 ms, accommodating momentary inrush currents from inductive loads.

Furthermore, the 1746-OB32 includes power dissipation of 0.172W per point. Although it lacks built-in electronic protection, its robust design and isolation rating provide reliable operation in typical industrial environments. The module is certified under C-UL and UL listings for Class I, Division 2, Groups A, B, C, D hazardous locations, and meets NEMA Standard ICS 2-230 noise immunity requirements.

Interposing Relay Applications

One notable feature of the 1746-OB32 is its ability to interface with AC-powered loads through interposing relays. In scenarios where output devices require AC voltage, a relay with a 24V DC coil can be connected to the module's output. The relay's Normally Open (N.O.) or Normally Closed (N.C.) contacts then switch the AC load.

Additionally, interposing provides isolation in older wired systems where electrical noise or poor grounding may be present. This external isolation protects the 1746-OB32 from damage and prevents unwanted behavior caused by undocumented modifications or repairs, enhancing system reliability.

Mechanical and Environmental Specifications

The Allen-Bradley 1746-OB32 is compatible with any available slot in a SLC 500 chassis, except slot 0, which is typically reserved for the processor. Its operating temperature range is 0 to 60°C, with a relative humidity of 5-95% noncondensing. The module can withstand operating shock of 30G and vibration of 2.5G at 10-200 Hz.

The module ships with a removable terminal block (RTB), an octal door label, and 32 dedicated LED indicators for real-time output status monitoring. A color-coded module bar displays the part number for easy identification. Compatible wiring systems include the 1746-N3 or the 1492 series, which ensure proper termination and adequate wire sizing.

Installation Guidelines

Proper installation of the 1746-OB32 ensures reliable performance and simplifies maintenance.

1. Chassis Selection: First, select an available slot in the SLC 500 chassis, avoiding slot 0. Ensure the backplane power supply can accommodate the 190 mA current draw.

2. Module Insertion: Next, insert the module into the chosen slot and secure it by tightening the retaining screws.

3. Wiring: Then, connect field devices to the removable terminal block, observing proper polarity for sourcing outputs. For inductive loads, consider using suppression diodes to reduce voltage spikes.

4. Interposing Configuration: If AC loads are required, connect the module output to a 24V DC relay coil and use the relay contacts to switch the AC circuit.

5. Testing: Finally, apply power and verify output status using the front-panel LED indicators. Use the octal door label for quick reference during troubleshooting.

Packaging List

Each shipment of the Allen-Bradley 1746-OB32 includes the following items:

• 1 x Digital DC Output Module

• 1 x Removable Terminal Block (RTB)

• 1 x Octal Door Label

• 1 x Installation Instructions manual

Frequently Asked Questions (FAQ)

1. What is the voltage range for the 1746-OB32 output module?
The Allen-Bradley 1746-OB32 operates from 5 to 50V DC, with a nominal rating of 24V DC. This wide range accommodates various DC loads.

2. How many outputs does the 1746-OB32 provide?
This module provides 32 sourcing outputs, organized into two groups with 16 points sharing a common connection.

3. Can the 1746-OB32 drive AC loads directly?
No, the 1746-OB32 is a DC output module. However, it can indirectly drive AC loads by using interposing relays with 24V DC coils.

4. What is the maximum current per output on the 1746-OB32?
The current per output is 0.5A at 0-30°C and derates to 0.25A at 60°C. The module also supports 1.0A surge current for 1 ms.

5. What shipping carriers do you use for the 1746-OB32 module?
We ship this product using trusted global carriers such as FedEx, UPS, and DHL to ensure safe and timely delivery.