Product Overview
The Allen-Bradley 1756-OB16I is a ControlLogix isolated DC output module from Rockwell Automation. It provides 16 individually isolated output points for precise control in demanding industrial environments. This module operates at 12-24 Volts DC in sink or source configuration, with an operating voltage range of 10-30 Volts DC. Its individual isolation allows each channel to be wired to different voltage sources, enhancing flexibility and protecting against fault propagation.
Technical Specifications Breakdown
Key parameters for the 1756-OB16I are listed below for quick reference:
| Feature | Specification |
|---|---|
| Module Type | Isolated DC Output Module |
| Outputs | 16-Point Individually Isolated |
| Voltage | 12-24 Volts DC Sink-Source |
| Operating Voltage Range | 10-30 Volts DC |
| Current per Point | 2 A @ 30 °C (86 °F) / 1 A @ 60 °C (140 °F) (linear derating) |
| Current per Module | 8 A @ 30 °C (86 °F) / 4 A @ 60 °C (140 °F) (linear derating) |
| Output Delay Time (OFF to ON) | 1 ms max |
| Output Delay Time (ON to OFF) | 2 ms max |
| Power Dissipation (Max) | 3.6 Watts at 60 Celsius |
| Backplane Current at 5 Volts | 350 milliamps |
| Backplane Current at 24 Volts | 3 milliamps |
| Isolation Voltage | 50 Volts Continuous |
| Removable Terminal Block(s) | 1756-TBCH, 1756-TBS6H |
Industry Applications
This module is ideal for applications requiring isolated discrete outputs, such as controlling relays, pilot lamps, indicators, solenoids, and buzzers in manufacturing lines or process control systems. The individual isolation per point allows mixing different voltage sources on the same module, reducing wiring complexity and improving system reliability. In high-inductive load scenarios, external surge protection is recommended to manage inrush currents.
Installation & Setup Guidance
Install the 1756-OB16I directly into any 1756 local or remote chassis. Use a compatible removable terminal block (1756-TBCH or 1756-TBS6H) for signal termination. Configure the module's safe state per point (Hold Last State, On, or Off) for Program and Fault conditions via the ControlLogix controller. Ensure external power is connected to a 12/24 VDC source. For non-isolated wiring, connect DC (+) and DC (-) to a common voltage source.
Maintenance & Reliability
Inspect the module periodically for dust accumulation and ensure adequate airflow for cooling. The module operates reliably within 0 to 60 °C ambient temperature. Linear derating applies for current per point and per module at higher temperatures. No internal fuses are provided; use external 5x20mm 4 A quick-acting fuses (SOC p/n MQ2-4A) for output protection.
Compatibility & Integration
The 1756-OB16I is part of the ControlLogix family and integrates with 1756 chassis and controllers. It supports multiple communication formats including output data, listen-only output data, rack optimization, listen-only rack optimization, and scheduled output data. The module features 16 LED indicators for channel status.
Selection Guide & Purchasing Advice
When selecting the 1756-OB16I, consider your voltage requirements (10-30 VDC) and current needs per point (up to 2 A at 30°C). For higher ambient temperatures, derate accordingly. This module is available at SpareTechPLC. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Troubleshooting & Common Issues
If an output channel fails to energize, check the corresponding LED indicator. If the LED is off, verify the external power supply and wiring. For intermittent operation, inspect the removable terminal block for secure connection. Ensure the module's safe state configuration matches the desired behavior during controller faults or program changes.
