High-Density Distributed I/O for DeviceNet Networks

The Allen-Bradley 1790D-T8BV8B is a high-performance CompactBlock LDX base module designed to provide a cost-effective and space-saving solution for distributed I/O applications. As part of the Rockwell Automation family, this module integrates seamlessly into DeviceNet networks, allowing engineers to expand their control systems without the need for large, centralized racks. The 1790D-T8BV8B features a combined configuration of 8 digital inputs and 8 digital outputs, making it an ideal choice for localized control of sensors and actuators in material handling, packaging, and assembly line environments.

Detailed Technical Specifications

The 1790D-T8BV8B module offers robust electrical characteristics to ensure reliable operation in demanding industrial settings:

• Manufacturer: Allen-Bradley / Rockwell Automation
• Product Line: CompactBlock LDX
• Part Number: 1790D-T8BV8B
• Network Communication: DeviceNet
• I/O Count: 8 Inputs / 8 Outputs
• Input Type: Sinking or Sourcing (Non-isolated)
• Output Type: Sourcing (Non-isolated)
• Nominal Voltage: 24V DC
• Voltage Range: 10V DC to 28.8V DC
• Input Impedance: 4.8 kΩ (Nominal)
• Output Current Rating: 0.5 A max per output (4.0 A max per common)
• Isolation Voltage: 1250V AC RMS (I/O to logic)
• Power Dissipation: 1.2 W max @ 28.8V DC
• Wiring Terminal: M3.0 screw terminals (7 lb-in torque)

Versatile Input and Output Configuration

The 1790D-T8BV8B provides exceptional flexibility through its universal input design. The 8 input points support both sinking and sourcing configurations, allowing the module to interface with a wide variety of field sensors. With an on-state voltage range of 9.6V to 28.8V DC, the inputs remain highly immune to electrical noise while ensuring fast signal detection.

On the output side, the module features 8 sourcing outputs. Each output channel can deliver up to 0.5 Amperes of current, which is sufficient for driving solenoids, small relays, and indicator lights. The total current capacity of 4.0 Amperes across the common rail ensures that the module can handle multiple simultaneous loads without overheating. Furthermore, the output signal delay is impressively low, with an “Off to On” time of just 0.5 ms, facilitating rapid response in time-critical processes.

Advanced Isolation and Diagnostic Features

Reliability is a core feature of the CompactBlock LDX series. The 1790D-T8BV8B utilizes photocoupler isolation to separate the I/O circuits from the internal logic and DeviceNet communication lines. With an isolation rating of 1250V AC RMS, the module protects the network and the controller from high-voltage transients and ground loops often found in industrial environments.

For rapid troubleshooting, the module includes 16 green status LED indicators—one for every input and output point. These LEDs allow maintenance personnel to verify signal activity at a glance. Additionally, the DeviceNet interface provides comprehensive diagnostic data to the master controller, reporting network status and power health in real-time.

Installation and Wiring Efficiency

The compact footprint of the 1790D-T8BV8B makes it perfect for mounting in small junction boxes or directly on machine frames. It utilizes a standard M3.0 screw terminal block for secure wiring. The module draws its logic power directly from the DeviceNet network (11–28.8V DC range), which simplifies the wiring architecture by reducing the number of required power supplies.

Whether you are implementing a new DeviceNet architecture or maintaining a legacy system, the 1790D-T8BV8B offers the durability and precision required for modern industrial automation. Its lightweight design (0.31 lbs) and high vibration resistance ensure it remains a staple for distributed I/O strategies.