Description
The Allen-Bradley 1756-DNB is a high-performance communication module designed for the ControlLogix platform, serving as a dedicated DeviceNet scanner. It enables seamless integration between ControlLogix processors and a wide array of DeviceNet-compatible field devices, including motor starters, drives, sensors, actuators, and distributed I/O systems.
Features
- Functions as a DeviceNet scanner for ControlLogix chassis environments.
- Supports communication with up to 64 DeviceNet nodes (addresses 00-63).
- Configurable communication rates: 125 Kbps, 250 Kbps, and 500 Kbps with automatic baud rate detection.
- Integrated network diagnostics and status monitoring via front-panel indicators.
- Backplane-powered operation with support for remote rack mounting via bridging modules.
- Supports Automatic Device Replacement (ADR) for simplified maintenance.
Applications
- Automotive Production: Weld cells, assembly sensors, and conveyor control.
- Oil & Gas: Telemetry, valve manifold control, and field instrumentation.
- Metals & Mining: High-vibration machinery, sorters, and heavy-duty processing gear.
- Water & Wastewater: Pump control, flow metering, and remote processing instruments.
- Warehouse & Fulfillment: AGV routing, sortation systems, and conveyor networks.
Technical Specifications
| Model |
1756-DNB |
| Series |
ControlLogix |
| Manufacturer |
Allen-Bradley |
| Backplane Current (5.1V DC) |
350 mA - 400 mA |
| Backplane Current (24V DC) |
210 mA |
| Max Thermal Dissipation |
19.8 BTU/hr (approx. 5.8 Watts) |
| Isolation Voltage |
30V |
| Max Network Distance (125 Kbps) |
500 meters |
| Max Network Distance (250 Kbps) |
250 meters |
| Max Network Distance (500 Kbps) |
100 meters |
Installation Guidelines
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ESD Protection: Always use a grounded wrist strap when handling the module to prevent electrostatic discharge damage.
-
Hot-Swapping: ControlLogix modules support RIUP (Removal and Insertion Under Power). However, you must disconnect the DeviceNet plug before removing the module to prevent electrical transients from affecting the network.
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Termination: The DeviceNet trunk line requires two 121-ohm termination resistors at the extreme ends of the network.
-
Grounding: The network shield must be grounded at a single point only, typically at the DeviceNet power supply, to prevent ground loops.
-
Configuration: Use RSNetWorx for DeviceNet to map I/O parameters and configure device settings.
FAQ
What is the primary function of the 1756-DNB?
The 1756-DNB acts as a bridge and scanner, allowing a ControlLogix controller to exchange data with distributed field devices over a DeviceNet network.
Can this module be used in a remote chassis?
Yes, the module can operate in a remote rack without a local CPU, provided there is a communication bridge (such as an EtherNet/IP or ControlNet module) in the same chassis to route data to the master controller.
How do I set the baud rate?
The module features Autobaud functionality to detect the network speed, or it can be manually configured via the front-panel buttons or through the RSLogix 5000 / Studio 5000 software environment.
