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The Allen-Bradley 1756-CN2R/B is a Series B ControlNet communication bridge module engineered for the ControlLogix platform. This module provides deterministic, high-speed data exchange between controllers, I/O, and field devices, featuring dual-channel redundancy to maintain network integrity during physical cable faults. As a critical component for ControlLogix architectures, it ensures reliable communication in demanding industrial environments.
Features
- Redundant Communication: Supports dual-channel coaxial connections, allowing for automatic failover if a primary cable segment experiences a fault, ensuring continuous operation.
- Deterministic Throughput: Maintains a steady 5 Mbps data rate, essential for time-critical control applications.
- High Capacity: Manages up to 131 total connections, including 128 dedicated Logix connections, across a maximum of 99 network nodes.
- Integrated USB Port: Includes a local USB port for configuration and diagnostics at 12 Mbps speed.
- Series B Hardware: Updated internal circuitry and firmware to improve reliability and performance within the ControlLogix backplane.
Applications
This module is widely utilized in large-scale automation systems requiring high-speed, deterministic data routing. It is suitable for distributed control systems, remote I/O management, and complex machine integration where network downtime must be minimized through redundant media paths.
Technical Specifications
| Model | 1756-CN2R/B |
| Series | Series B |
| Communication Rate | 5 Mbps (ControlNet) / 12 Mbps (USB) |
| Backplane Current (5.1V) | 1300 mA |
| Power Dissipation | 6.7 Watts |
| Thermal Dissipation | 22.9 BTU/hr |
| Operating Temp | 0 to 60 deg C |
| Slot Width | Single-slot |
Installation Guidelines
- Power Off: Ensure the ControlLogix chassis is powered down before inserting or removing the module to prevent electrical damage.
- ESD Precautions: Use an anti-static wrist strap or grounded work surface when handling the module to protect internal circuitry from electrostatic discharge.
- Seating: Ensure the module is properly aligned with the chassis guide rails and fully seated in the backplane connector before securing with the top/bottom latching screws.
- Cabling: Use only 1786-RG6 quad-shield coaxial cable for ControlNet connections. Ensure BNC connectors are securely tightened to prevent signal degradation or impedance mismatches.
- Environment: Install within an enclosure suitable for the application environment; ensure adequate airflow around the chassis to maintain operating temperatures below 60 deg C.
FAQ
Does the 1756-CN2R/B support redundant power supplies? Yes, the module is compatible with various ControlLogix redundant power supply systems including the 1756-PA75R and 1756-PB75R.
Can I use this in any ControlLogix chassis? It is compatible with standard ControlLogix chassis such as the 1756-A4, A7, A10, A13, and A17 series.
What happens if one ControlNet cable is disconnected? The module features seamless media failover; if one channel fails, the communication traffic is automatically routed through the secondary channel without interrupting the processor's connection to the network.
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