Allen-Bradley 1746-OB32E SLC 500 Output Module 32-Point
Introduction:
The 1746-OB32E is a 32-point digital output module for SLC 500 systems. It features 24VDC outputs with electronic overload and short circuit protection.
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Product Overview
The Allen-Bradley 1746-OB32E is a digital DC output module. It belongs to the SLC 500 product family. This module features thirty-two (32) 24VDC, electronically protected output channels.
The outputs are arranged in two (2) groups. Each group has sixteen (16) points. Furthermore, the module may be installed in SLC 500 fixed or modular style hardware.
General Specifications
The 1746-OB32E offers high-density output capability with built-in protection.
Manufacturer: Rockwell Automation.
Brand: Allen-Bradley.
Series: SLC 500.
Part Number/Catalog No.: 1746-OB32E.
Module Type: Digital DC Output Module.
Number of Outputs: Thirty-two (32).
Points per Common: Sixteen (16) (2 groups).
Nominal Output Voltage: 24VDC.
Operating Voltage Range: 10-30 Volts DC.
Current Ratings
The 1746-OB32E delivers substantial current capacity with derating.
Continuous Current per Output: 0.5 Amps (0.25 Amps at elevated temperatures).
Continuous Current per Module: 8 Amps.
Backplane Current (5 Volts): 190 milliamps.
Backplane Current (24 Volts): 0 mA.
Thus, the module draws no power from the 24V backplane supply.
Signal Timing
The 1746-OB32E has defined switching characteristics.
Signal Delay, ON: 0.1 ms.
Signal Delay, OFF: 1.0 ms.
Step Response: 60 milliseconds in, 2.5 milliseconds out.
Therefore, the module responds quickly to control commands.
Electronic Protection
The 1746-OB32E includes integral electronic protection, distinguishing it from the standard 1746-OB32.
Protection Type: Electronic protection from overload conditions and short circuits.
Operation: Built-in protection works in accordance with thermal cut-out.
Response: Affected channel automatically limits current output within milliseconds after thermal cut-out is reached.
Channel Independence: Other channels not detecting fault conditions continue normal operation (individual detection capability).
Auto-Reset: Module auto-resets when overload is cleared.
Important Limitations:
Reverse polarity protection is not included.
Improper signal source wiring error protection is not included.
Electronic protection is not equivalent to an external electronic fuse.
For this reason, proper external protection may still be recommended for installation with this module.
Error Recovery Behavior
The 1746-OB32E has specific auto-reset behavior that must be considered.
After Overload Clear: The output module implements the previous command.
If Command is ON: The module will turn ON the connected load after error recovery.
This may be unsafe or ideal depending on the application. Therefore, this error recovery condition must be carefully considered during system design.
Terminal Block and Wiring
The 1746-OB32E simplifies field wiring with several features.
Terminal Blocks: Color-coded removable terminal blocks.
Wire Connection: Self-lifting pressure plates.
Wire Capacity: Receives two 14 AWG (2 mm²) wires per terminal.
Cable Routing: Route input power to the module with a separate path from the cable to the I/O device.
Hence, installation and maintenance are straightforward.
LED Indicators
The 1746-OB32E provides clear visual status indication.
LED Function: Show the status of each output point.
Illumination Conditions: Lights up when the correct signal to the output terminal is applied or when processor outputs are energized.
Consequently, operators can quickly identify which outputs are active.
Environmental Specifications
The 1746-OB32E withstands typical industrial conditions.
Operating Temperature: -13 to 140°F (-25 to 60°C).
Non-operating (Storage) Temperature: -40 to 185°F (-40 to 85°C).
Relative Humidity: 5 to 95% (non-condensing).
Operating Vibration: 2g at 10-500 Hz (2.5g at 57-2000 Hz).
Operating Shock: 30g.
Key Features
The 1746-OB32E offers several advantages for discrete output applications.
High Density (32 Outputs):
Provides 32 outputs in a single module. Therefore, it saves rack space compared to lower-density modules.
Electronically Protected Outputs:
Built-in short circuit and overload protection with auto-reset. Hence, external fusing may be reduced or eliminated.
Individual Channel Protection:
Each channel independently detects fault conditions. Consequently, a fault on one channel does not affect others.
Wide Voltage Range:
Operates from 10 to 30 VDC. Thus, it works with 12V and 24V DC systems.
Removable Terminal Blocks:
Color-coded terminal blocks simplify wiring and module replacement. For this reason, maintenance downtime is reduced.
Self-Lifting Pressure Plates:
Accept up to two 14 AWG wires per terminal. Hence, field wiring is secure and reliable.
Fast Switching Speed:
0.1 ms ON delay and 1.0 ms OFF delay. Therefore, it suits high-speed discrete applications.
LED Status Indicators:
32 LEDs show the on/off status of each output point. Consequently, troubleshooting is faster.
Comparison with 1746-OB32
The 1746-OB32E functions similarly to the 1746-OB32. However, it adds integral electronic protection for short circuits and overload conditions. Therefore, it provides enhanced robustness for demanding applications.
Typical Applications
The 1746-OB32E suits various discrete output control applications.
Solenoid valve control in industrial machinery.
Relay and contactor switching.
Pilot light and indicator driving.
High-density output applications requiring electronic protection.
SLC 500 fixed or modular hardware installations.
Installation Guidelines
Install the 1746-OB32E in any available slot of an SLC 500 chassis. First, ensure the chassis power supply can provide the required 190 mA at 5 VDC. The module draws 0 mA from the 24V backplane supply.
Connect field devices to the color-coded removable terminal blocks. Use self-lifting pressure plates to secure up to two 14 AWG wires per terminal. Route input power to the module with a separate path from the I/O device cable.
The module provides 32 outputs in two groups of 16. Each output is rated at 0.5A (derating may apply at elevated temperatures). The total module current is 8A maximum.
The electronic protection will limit current on a faulted channel. After the fault clears, the module auto-resets and implements the previous command. Therefore, if the command was ON, the output will turn back ON automatically.
What is in the Box
Please inspect all items upon delivery.
Allen-Bradley 1746-OB32E digital output module.
Color-coded removable terminal blocks.
Installation instruction manual.
Frequently Asked Questions (FAQ)
1. How many output points does the 1746-OB32E have?
The 1746-OB32E provides thirty-two (32) digital output points. These are arranged in two groups of sixteen (16) points per common.
2. What voltage range does this module support?
The 1746-OB32E operates from 10 to 30 Volts DC. The nominal output voltage is 24 VDC.
3. What type of protection does this module include?
The 1746-OB32E includes integral electronic protection for overload conditions and short circuits. However, reverse polarity protection is not included.
4. Does the module auto-reset after a fault is cleared?
Yes. The 1746-OB32E automatically resets when the overload is cleared. After error recovery, the module implements the previous command. Therefore, if the command was ON, the load will turn back ON.
5. How does the 1746-OB32E differ from the 1746-OB32?
The 1746-OB32E functions similarly to the 1746-OB32. However, it adds integral electronic protection for short circuit and overload current conditions. The standard 1746-OB32 does not include this protection.