Description
The Allen-Bradley 1746-OB8 is a high-performance digital DC output module designed for use within the SLC 500 programmable controller platform. This module provides eight sourcing output channels, engineered to drive 10V to 50V DC loads, including solenoids, relays, and various industrial actuators. By switching the positive potential of the DC supply, this sourcing module maintains compatibility with standard industrial control architectures requiring positive-side switching.
Features
- Eight (8) sourcing output channels grouped for streamlined wiring.
- Wide operating voltage range from 10V to 50V DC.
- Optical isolation rated at 1500V AC to protect the backplane and processor from transient electrical noise.
- Robust current handling with thermal derating support for high-temperature environments.
- Integrated status indicators for clear visual monitoring of individual output states.
Applications
This module is widely utilized in discrete manufacturing and process control environments where reliable DC load switching is required. It is ideal for interfacing with 24V DC control devices, such as pilot lights, contactors, and small DC motors, within an SLC 500 rack-based system.
Technical Specifications
| Brand |
Allen-Bradley |
| Series |
SLC 500 |
| Module Type |
Digital DC Output (Sourcing) |
| Number of Outputs |
8 (1 group of 8) |
| Voltage Range |
10-50V DC |
| Backplane Current (5V) |
135 mA |
| On-Signal Delay |
0.1 ms (resistive load) |
| Off-Signal Delay |
1.0 ms (resistive load) |
| Current per Point |
1.0A (30 degC) / 0.5A (60 degC) |
| Total Heat Dissipation |
6.9 Watts |
Installation Guidelines
- Ensure the SLC 500 power supply is disconnected before inserting or removing the module from the chassis.
- Mount the module in an appropriate SLC 500 chassis slot, ensuring the backplane connector is fully seated and the module is secured with the top and bottom retaining screws.
- Maintain proper ventilation within the control cabinet; note that current capacity is subject to thermal derating at temperatures above 30 degC.
- Use shielded cabling for I/O connections to minimize the impact of electromagnetic interference (EMI) in high-noise environments.
- Verify that the external power supply for the DC loads is within the specified 10-50V DC range to prevent damage to the output transistors.
FAQ
What is the primary function of the 1746-OB8 module?
The 1746-OB8 is a digital output module that provides eight sourcing DC outputs, allowing the SLC 500 PLC to control external 10V to 50V DC devices.
Does this module require external power?
Yes, the module requires an external DC power source to drive the connected loads, as it performs high-side switching of the provided DC voltage.
How does temperature affect the output current?
The module's current capacity is temperature-dependent. At 30 degC, it supports up to 1.0A per point, but this must be reduced to 0.5A per point when operating at the maximum ambient temperature of 60 degC.
