Allen-Bradley 1756-DNB ControlLogix DeviceNet Scanner Module

The Allen-Bradley 1756-DNB is a specialized communication bridge and scanner module designed for the ControlLogix platform. It enables seamless integration between a ControlLogix controller and a DeviceNet network, facilitating real-time data exchange with distributed field devices such as drives, sensors, motor starters, and operator interfaces.

Features

• Serves as a high-performance DeviceNet scanner for ControlLogix chassis environments.
• Supports up to 64 DeviceNet nodes with configurable addressing from 00 to 63.
• Provides selectable communication baud rates of 125 Kbps, 250 Kbps, and 500 Kbps.
• Integrated diagnostic capabilities for network health and status monitoring.
• Backplane-powered design for streamlined installation within standard ControlLogix racks.
• Supports Automatic Device Replacement (ADR) for simplified maintenance.

Applications

• Automotive Manufacturing: Managing weld cells, assembly sensors, and conveyor logic.
• Oil and Gas: Interfacing with field instruments, valve manifolds, and remote telemetry units.
• Metals and Mining: Connecting heavy machinery, sorters, and high-vibration equipment.
• Water and Wastewater: Integrating flow meters, pumps, and process control instrumentation.
• Warehouse Logistics: Enabling sortation systems and AGV routing control.

Technical Specifications

Installation Guidelines

• Ensure the ControlLogix chassis power supply has sufficient capacity to support the module's current draw (typically 350 mA at 5.1V DC).
• Always disconnect the DeviceNet cable before attempting to hot-swap the module to prevent electrical transients from affecting the network.
• The DeviceNet trunk line requires two 121-ohm termination resistors at the extreme ends of the network.
• Maintain single-point grounding for the network shield, preferably at the DeviceNet power supply location.
• Verify firmware compatibility, particularly when transitioning between older series modules and newer Series E hardware.

FAQ

What is the primary function of the 1756-DNB?

The 1756-DNB acts as a bridge and scanner, allowing a ControlLogix processor to read inputs from and write outputs to remote DeviceNet-compliant field devices.

Is this module compatible with remote chassis configurations?

Yes, the 1756-DNB can be installed in a remote rack without a local CPU, provided a bridge module (such as EtherNet/IP or ControlNet) is present to facilitate communication with a master controller in a separate chassis.

How is the baud rate configured?

The module supports Autobaud detection, or you can manually configure the network speed and node address via the front-panel interface or through RSNetWorx for DeviceNet software.