Description
The 1756-OB8EI is a high-integrity digital DC sourcing output module designed for the Allen-Bradley ControlLogix 1756 chassis platform. This module provides eight independent, galvanically isolated output channels, each equipped with integrated electronic fusing to protect against short-circuit conditions and overcurrent events. It is engineered for demanding industrial environments, including power distribution, automotive manufacturing, and water treatment, where reliable, low-latency control of field devices such as solenoids, relays, and valves is required.
Features
- Eight isolated DC sourcing output channels.
- Electronic fusing per channel for rapid short-circuit protection.
- Point-level diagnostics with +/- 1 ms timestamp accuracy.
- Supports 10 to 30 VDC operating voltage range.
- Compatible with 1756-TBCH and 1756-TBS6H Removable Terminal Blocks (RTB).
- Designed for single-slot installation in any ControlLogix chassis.
Applications
This module is suitable for critical control applications requiring channel-to-channel isolation to prevent common-tie interference. It is commonly used to drive external field loads such as pilot lamps, buzzers, and hydraulic valves while maintaining isolation between independent DC power loops.
Technical Specifications
| Model |
1756-OB8EI |
| Outputs |
8 Points (Isolated/Fused) |
| Voltage Range |
10 to 30 VDC |
| Current per Point |
2 Amps @ 60 deg C |
| Short-Trip Threshold |
> 4.5 Amps |
| Isolation |
250 V continuous (Channel-to-channel/Backplane) |
| Backplane Power |
1.30 Watts |
| Operating Temp |
0 to 60 deg C |
Installation Guidelines
- Ensure the ControlLogix chassis is powered down before inserting or removing the module.
- Use a compatible 1756-TBCH or 1756-TBS6H Removable Terminal Block for field wiring.
- Maintain proper grounding practices for the chassis to ensure effective EMI protection.
- Ensure adequate ventilation within the enclosure; observe derating requirements for current based on ambient temperature.
- Handle with care to prevent electrostatic discharge (ESD) damage to the module backplane connectors.
FAQ
Q: Does the 1756-OB8EI require an external power supply?
A: Yes, the module requires an external 24 VDC power source to drive the field loads connected to the output channels.
Q: What is the purpose of the electronic fusing?
A: The electronic fusing provides rapid, resettable protection for each channel, tripping in under 500 microseconds during an active short-circuit to prevent damage to the module and field wiring.
