Product Overview
When ControlNet network reliability is critical, the Allen-Bradley 1756-CNBR delivers redundant media capability for your ControlLogix system. This ControlNet Bridge Module features two ControlNet ports, enabling connection to both simplex and redundant networks. As part of the ControlLogix family, the 1756-CNBR interfaces the controller with high-speed ControlNet networks, supporting scheduled and unscheduled data transfer.
The 1756-CNBR operates at a communication rate of 5 Mbps and supports 40-48 Logix communication connections, with a maximum of 64 connections. It handles up to 99 nodes, making it suitable for distributed I/O architectures and large-scale control systems.
Technical Specifications
| Parameter |
Value |
| Manufacturer |
Rockwell Automation |
| Brand |
Allen-Bradley |
| Series |
ControlLogix |
| Module Type |
ControlNet communication module |
| No. of Ports |
Two (2) ControlNet ports |
| ControlNet Rate of Communication |
5 Mbps |
| Logix Communication Connections |
40-48 |
| Max Connections Supported |
64 |
| Max Number of Nodes |
99 |
| Backplane Current (5.1 VDC) |
970 milliamps |
| Backplane Current (24 VDC) |
1.7 milliamps |
| Isolation Voltage |
30 Volts Continuous |
| Power Dissipation (Max) |
5.5 Watts |
| Enclosure |
Open Type |
| Communication Cable |
1786-RG6 quad shield RG6 coaxial cable |
| Dimensions |
5.51 x 4.41 x 5.71 inches |
| Operating Temperature |
32-140 Fahrenheit (0-60 Celsius) |
| Slot Width |
1 |
| Weight |
0.64 lbs (0.293 kg) |
Key Features & Benefits
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Redundant Media Support: Two ControlNet ports allow connection to redundant trunk cables, preventing communication loss if a tap or trunkline is disconnected.
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High Throughput: 5 Mbps communication rate ensures fast data exchange for time-critical control applications.
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Scalable Connectivity: Supports up to 64 connections and 99 nodes, accommodating medium to large distributed I/O systems.
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Backplane Powered: Draws 970 mA at 5.1 VDC and 1.7 mA at 24 VDC, simplifying installation without external power.
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Compact Design: Single-slot module fits in standard ControlLogix chassis, saving rack space.
Industry Applications
The Allen-Bradley 1756-CNBR excels in applications where ControlNet redundancy is essential. Typical use cases include:
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Manufacturing Lines: Coordinating multiple PLCs and remote I/O racks on a redundant ControlNet backbone to minimize downtime.
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Process Control: Bridging ControlLogix controllers with field devices in continuous processing plants, ensuring reliable communication.
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Material Handling: Connecting conveyors, sorters, and robotic cells in a distributed architecture with redundant media for high availability.
Installation & Setup Guidance
Install the 1756-CNBR into any available slot of a compatible ControlLogix chassis (1756-A4, 1756-A7, 1756-A10, 1756-A13, 1756-A17). The module requires only one slot. Use 1786-RG6 quad shield RG6 coaxial cable for trunk connections. Before connecting, verify the tap drop cable label to ensure correct tap polarity; reversed connections cause status errors and require troubleshooting. For redundant networks, connect both ControlNet ports to separate trunk cables.
Compatibility & Integration
The 1756-CNBR integrates seamlessly with ControlLogix processors and supports both standard and redundant power supplies. Compatible standard power supplies include 1756-PA72/C, 1756-PA75/B, 1756-PB72/C, 1756-PB75/B, 1756-PC75/B, and 1756-PH75/B. For redundant power, use 1756-PA75R, 1756-PB75R, or 1756-PSCA2. The module also provides one Network Access Port (NAP) with an RJ-45 8-pin shielded connector for local programming.
Selection Guide & Purchasing Advice
Before purchasing, confirm your system requires redundant ControlNet media. If a single ControlNet port suffices, consider the 1756-CNB. Verify chassis compatibility and available slot space. For guaranteed genuine Allen-Bradley 1756-CNBR modules with reliable support, choose PLC Source PRO as your supplier.