Purchase now: Allen-Bradley 1756-OB8 ControlLogix High-Current Output Module
Atlantechdrives provides you the 1756-OB8, a specialized 8-point sourcing DC output module designed for heavy-duty industrial applications. Unlike standard high-density modules, the 1756-OB8 is built to deliver higher current per point, making it the preferred choice for driving large contactors, heavy-duty solenoids, and other DC loads that exceed the capacity of standard 0.5A modules.
- Outputs: 8 Points (Sourcing DC)
- Voltage Range: 10-31.2V DC
- Current Rating: 2.0A per point (Max 8A per module @ 60°C)
- Surge Current: 4A for 10ms
- Isolation: Group-to-backplane isolation
Engineered for Heavy Loads: The 1756-OB8 Advantage
The 1756-OB8 is the «heavy lifter» of the ControlLogix discrete output family. While most modules are limited to 0.5A per point, the 1756-OB8 can provide a continuous 2.0A at 60°C for each of its 8 points (as long as the total module current does not exceed 8A). This capability eliminates the need for interposing relays in many applications, simplifying your control cabinet design and reducing points of failure. The module features robust output transistors capable of handling significant inrush currents, which is typical when energizing large inductive loads. Front-panel LEDs provide a clear «On/Off» status for each point, facilitating quick field diagnostics.
Installation Advice: Wiring for High Current
When wiring the 1756-OB8, the gauge of your field wire is critical. Because this module can deliver 2.0A per point, we recommend using at least 14-16 AWG wire to prevent significant voltage drops over long distances. Use the 1756-TBNH or 1756-TBSH Removable Terminal Block. Ensure that your 24V DC power supply is adequately sized; if all 8 points are driving 1A loads, your power supply must be able to handle an 8A instantaneous draw without dropping below the 10V DC minimum operating threshold. Always install flyback diodes on the solenoids to protect the 1756-OB8 from inductive voltage spikes.
Maintenance and Thermal Management
Because the 1756-OB8 handles higher current, thermal management is its most important maintenance factor. Ensure that the ControlLogix chassis has adequate vertical spacing for ventilation. Periodically check the RTB (Removable Terminal Block) for any signs of heat stress or loose screws, as high current through a loose connection will quickly cause oxidation and failure. In the Studio 5000 software, use the module’s diagnostic information to monitor for any «Field Side Power Loss,» which could indicate a blown fuse or a power supply failure in the field circuit.
FAQs
Q: Can I use the 1756-OB8 to drive a small DC motor?
A: Yes, provided the motor’s continuous running current is under 2.0A and the startup surge does not exceed the module’s rating.
Q: Does the 1756-OB8 require a 36-pin terminal block?
A: No, the 1756-OB8 uses the standard 20-pin terminal blocks (1756-TBNH or 1756-TBSH).
Do you need more references from this brand? Explore our full catalog of Allen-Bradley here.
This compact 8-point DC output module is a reliable choice for small-scale control within a 1756-A4 compact chassis.
