Introduction to the Allen-Bradley 1746-OB32
When a SLC 500 system needs to drive dozens of discrete field devices from a single slot, the Allen-Bradley 1746-OB32 delivers the density and flexibility to get it done. This SLC 500 Digital DC Output Module packs Thirty-Two (32) 24VDC output channels into one module, arranged as Two (2) groups of Sixteen (16) points per common. It installs in any available slot of a 1746 chassis except slot 0, in either fixed or modular SLC 500 hardware.
Technical Specifications That Matter
The 1746-OB32 operates with a voltage range of 5-50 Volts DC and a nominal output of 24VDC. Each output point carries 0.5-0.25 amps, while the module handles 8 amps total and 2 amps per common. Backplane current draw is 190 milliamps at 5 Volts. Signal delay is fast: 0.1 ms ON and 1.0 ms OFF, with a step response of 60 milliseconds in and 2.5 milliseconds out.
Key Parameters at a Glance
| Specification | Value |
|---|---|
| Outputs | Thirty-Two (32) |
| Voltage Range | 5-50 Volts DC |
| Nominal Output | 24VDC |
| Current/Output | 0.5-0.25 amps |
| Current/Module | 8 amps |
| Points per Common | Sixteen (16) |
| Backplane Current (5V) | 190 mA |
| Signal Delay ON/OFF | 0.1 ms / 1.0 ms |
| Operating Temperature | 0-60°C |
| Shock/Vibration | 30G / 2.5G at 10-200Hz |
Comparison: 1746-OB32 vs. Similar Output Modules
- Channel count: 32 outputs vs. 16 outputs on lower-density SLC 500 DC modules
- Voltage range: 5-50VDC vs. narrower fixed-voltage modules
- Current per module: 8A total, 2A per common
- Signal delay: 0.1 ms ON / 1.0 ms OFF for fast switching
- Isolation: Output circuit isolation tested at 1500V AC for 1 minute
Applications and Use Cases
This module excels in high-current discrete output applications. It energizes pilot lamps, buzzers, horns, and sirens, and actuates solenoids, motors, and similar devices. When field devices require AC voltage, an interposing relay with a 24VDC coil can bridge the gap. In older wired systems with electrical noise, interposing also provides external isolation, protecting the module from grounding issues and undocumented modifications.
Installation and Setup
The 1746-OB32 ships with a Removable Terminal Block (RTB), an octal door label, 32 LED indicators (one per channel), and a color-coded module bar showing the part number. For proper termination, use Allen-Bradley 1746-N3 or 1492 wiring systems. These pre-assembled connectors ensure correct wire size and prevent improper wiring. Avoid oversized wires, which crowd the front panel and make troubleshooting difficult.
Maintenance and Reliability
With a 30G shock rating and 2.5G vibration tolerance at 10-200Hz, this module withstands demanding industrial environments. Operating temperature spans 0-60°C at 5-95% non-condensing humidity. Periodic inspection of terminal connections and LED indicators helps maintain reliable performance. The 1500V AC isolation test rating supports safe operation in Class I, Division 2, Groups A, B, C, D hazardous locations.
Compatibility and Integration
The 1746-OB32 integrates with SLC 500 fixed or modular hardware, occupying any slot except slot 0. It carries C-UL and UL Listed Industrial Control Equipment certification for hazardous locations and meets NEMA standard ICS 2-230 noise immunity. For wiring, pair it with 1746-N3 or 1492 systems.
Selection Guide
Before purchasing, verify your chassis slot availability, confirm field device voltage compatibility (5-50VDC), and check total current requirements against the 8A module limit. SpareTechPLC supplies industrial automation parts and can help confirm current lifecycle status and availability. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Frequently Asked Questions
Q: How many output channels does the 1746-OB32 provide?
A: It offers Thirty-Two (32) output channels, divided into Two (2) groups of Sixteen (16) points per common.
Q: What is the voltage range for this module?
A: The 1746-OB32 operates with a voltage range of 5-50 Volts DC and a nominal output of 24VDC.
Q: Can I use this module with AC field devices?
A: Yes, by implementing an interposing relay with a 24VDC coil. The relay contacts then switch the AC voltage.
Q: What wiring systems are compatible?
A: Allen-Bradley 1746-N3 or 1492 wiring systems are compatible for proper termination.
Q: What is the module’s current rating?
A: It handles 8 amps per module and 2 amps per common, with 0.5-0.25 amps per output point.
