Product Overview

The Allen Bradley 1790-0V16X CompactBlock LDX Digital Output Expansion Block is a 16-point DC sinking output expansion module used to increase the digital output capacity of a CompactBlock LDX distributed I/O assembly. It operates with a nominal 24 V DC field supply and provides additional switching channels for controlling compatible industrial devices.

Unlike the 1790-0B16X, which uses sourcing outputs, the 1790-0V16X uses sinking output circuitry. When an output is activated, the channel switches the connected load toward the DC common (GND), allowing current to flow from the positive field supply through the load and into the module output. This distinction is important when selecting compatible solenoid valves, relay interfaces, and other DC-operated equipment.

The module provides 16 individual output points arranged in two groups of eight. Each output supports up to 0.5 A, with a maximum current rating of 4 A per common. Its 37-pin D-shell connector provides the field wiring interface, while the expansion ribbon cable connects the module to a compatible CompactBlock LDX base block.

A typical application can be found in a conveyor handling system with multiple pneumatic actuators. The main CompactBlock LDX base block communicates with the PLC through DeviceNet, while the 1790-0V16X adds output channels for controlling diverter valves, pneumatic stops, and other machine functions. The PLC activates individual channels according to product position and sensor information.

The sinking output arrangement is particularly relevant when the connected devices are wired with their positive terminals connected to the field supply and their switched return connected to the module outputs. The common terminals must be wired according to the specified 24 V DC supply arrangement.

Another practical feature is the module’s photocoupler isolation between the field I/O circuits and internal logic circuits. This provides electrical separation between the output circuitry and the expansion logic, with a specified isolation voltage of 1250 V AC RMS.

The 1790-0V16X also supports relatively fast output switching, with a maximum delay of 0.5 ms from OFF to ON and 1.0 ms from ON to OFF. Sixteen green status indicators allow maintenance personnel to check individual output conditions during commissioning and troubleshooting.

For existing DeviceNet installations, the expansion architecture makes it possible to add output capacity without installing another independent network node. The base block remains responsible for network communication, while the 1790-0V16X handles additional field switching operations.

The module is suitable for distributed machine-control applications where 24 V DC sinking outputs are required and the existing CompactBlock LDX system needs additional output points.

Technical Specifications

Product Features

• 16 Sinking Output Points: Adds 16 DC sinking output channels to a compatible CompactBlock LDX assembly.
• 24 V DC Operation: Supports a nominal 24 V DC field supply with an operating range of 10–28.8 V DC.
• 0.5 A Per-Point Rating: Handles individual output loads up to 0.5 A.
• 4 A Per-Common Rating: Supports a maximum current of 4 A for each common connection.
• Eight-Point Grouping: Arranges the outputs into two groups of eight with separate common connections.
• 37-Pin D-Shell Connection: Provides the electrical interface for external field wiring.
• Ribbon Cable Expansion: Connects to a compatible CompactBlock LDX base block.
• Photocoupler Isolation: Provides 1250 V AC RMS isolation between field I/O and logic circuits.
• Individual Output Indicators: Uses 16 green LEDs to display output status.
• Fast Switching Response: Supports maximum OFF-to-ON and ON-to-OFF delays of 0.5 ms and 1.0 ms, respectively.
• Distributed Output Expansion: Adds local output capacity without requiring an independent DeviceNet connection.

Working Principle

The 1790-0V16X operates as a sinking digital output stage within a CompactBlock LDX distributed I/O assembly. It receives output commands through the expansion connection and switches the corresponding field circuits toward the DC common.

Its basic control arrangement is:

PLC Controller → DeviceNet → CompactBlock LDX Base Block → Expansion Ribbon Cable → 1790-0V16X → Field Devices

Output Command Processing

When the PLC activates an output address, the DeviceNet-connected base block receives the corresponding control data. The output information is transferred to the 1790-0V16X through the ribbon cable connection.

The expansion module then activates the selected output channel, allowing the connected field device to operate.

For example, when a PLC program activates an output assigned to a pneumatic diverter, the corresponding output channel switches toward DC common. Current flows through the connected solenoid valve, causing the valve to change state and operate the pneumatic cylinder.

Sinking Output Operation

The main characteristic of this module is its sinking output configuration.

In a typical 24 V DC circuit, the positive side of the field supply connects to the load. The other side of the load connects to the output channel. When the output is activated, the module provides the current return path toward GND.

The basic current path is:

+24 V DC → Field Load → 1790-0V16X Output → DC Common

This wiring arrangement differs from a sourcing output module, where the output supplies positive voltage to the load.

For this reason, the 1790-0V16X must be matched with field devices and wiring arrangements compatible with sinking outputs.

Independent Channel Switching

The module provides 16 output channels that can be controlled individually through the I/O data received from the base block.

In an automated assembly machine, separate channels may control pneumatic clamps, material stops, indicator circuits, and relay interfaces. The PLC can switch each device according to the production sequence without requiring a separate expansion module for every actuator.

Output Current Management

Each output supports a maximum current of 0.5 A, while the maximum current per common is 4 A.

Both limits must be considered when planning the field wiring. For example, several solenoid valves may each operate within the individual channel rating, but their combined current must also remain within the permitted common rating.

The two groups of eight outputs have their own common connections, allowing the field circuits to be arranged according to the module’s wiring configuration.

Photocoupler Isolation

The module uses photocoupler isolation between the field I/O circuitry and the internal logic circuitry. The specified isolation voltage is 1250 V AC RMS.

This arrangement helps separate field-side electrical disturbances from the logic circuitry. However, the output channels themselves are non-isolated, so the specified common connections and field supply arrangement must be observed.

Expansion Assembly Communication

The 1790-0V16X does not communicate directly with the PLC as an independent DeviceNet node. Instead, it relies on a compatible CompactBlock LDX base block.

The base block receives network commands and transfers output information through the expansion ribbon cable. This allows the 16 additional output channels to become part of the existing distributed I/O assembly.

Role in the CompactBlock LDX Control Architecture

The Allen Bradley 1790-0V16X serves as a digital output expansion stage within the CompactBlock LDX architecture. Its function is to increase the number of available sinking output channels while using the base block for network communication.

A typical system arrangement follows this structure:

PLC Controller → DeviceNet Scanner → CompactBlock LDX Base Block → 1790-0V16X → DC Field Devices

In this arrangement, the base block acts as the communication interface between the controller and the expansion module. The 1790-0V16X handles the actual field output switching.

For example, a material-handling machine may use the expansion block to operate several pneumatic stops and sorting gates. The PLC receives product-position information from the input modules and activates the required outputs through the DeviceNet assembly.

Because the output channels use sinking circuitry, the field wiring must be arranged with the correct positive supply and common connections. This is particularly important when combining sourcing and sinking output devices within the same machine panel.

Industrial Applications

Installation and Maintenance

1. Verify the Module Model: Confirm that Allen Bradley 1790-0V16X is the required 16-point DC sinking output expansion block.
2. Check Base Block Compatibility: Ensure that the selected CompactBlock LDX base block supports the 1790-0V16X expansion module.
3. Inspect the Module: Examine the housing, 37-pin connector, expansion interface, and mounting points for physical damage.
4. Prepare the Mounting Location: Select a suitable DIN rail or panel mounting position with sufficient access for field wiring.
5. Isolate the Power Supply: Disconnect the relevant field and control power sources before installation or wiring work.
6. Mount the Expansion Block: Secure the module using the specified mounting arrangement and check its mechanical position.
7. Connect the Ribbon Cable: Connect the expansion interface to the compatible base block and verify that the cable is correctly seated.
8. Wire the Field Connector: Connect the external loads through the 37-pin D-shell interface according to the module’s terminal assignment.
9. Verify Sinking Output Polarity: Connect the common terminals and positive field supply according to the specified sinking output wiring arrangement.
10. Check Load Current: Ensure that each output remains below 0.5 A and that the current through each common connection does not exceed 4 A.
11. Test Individual Outputs: Restore power and activate each channel through the controller to verify switching behavior and the corresponding green status indicator.
12. Record the Wiring Configuration: Document the output assignments, common connections, connected loads, and field supply arrangements for future maintenance.

Compatible System Components

Recommended Related Models

Key Advantages

• Adds 16 sinking digital output points to a compatible CompactBlock LDX assembly.
• Supports nominal 24 V DC field operation.
• Handles up to 0.5 A per output and 4 A per common.
• Provides a 37-pin D-shell field wiring interface.
• Includes photocoupler isolation between field I/O and logic circuits.
• Uses individual green indicators for output status monitoring.
• Supports fast output switching for machine-control sequences.
• Extends existing distributed I/O capacity without requiring an independent DeviceNet connection.

Technical FAQs

What is the difference between the Allen Bradley 1790-0V16X and 1790-0B16X?

The main difference is the output switching configuration. The 1790-0V16X has 16 DC sinking outputs, while the 1790-0B16X has 16 DC sourcing outputs. The sinking version switches the load toward DC common, whereas the sourcing version supplies positive voltage to the load. The correct selection depends on the field device wiring and electrical interface.

How should the 1790-0V16X sinking outputs be wired?

For the specified sinking arrangement, the COM0 and COM2 connections are wired to the positive 24 V DC field supply, while COM1 and COM3 are connected to field power negative (GND). The load is connected between the positive supply and its corresponding output channel. Correct common-terminal wiring is essential for normal operation.

What is the maximum current supported by the output channels?

Each output supports up to 0.5 A, with a maximum of 4 A per common. Both ratings must be observed when connecting multiple loads. The total current of simultaneously energized devices should be calculated before assigning the output channels.

Can the 1790-0V16X connect directly to a DeviceNet network?

No. It is an expansion block rather than an independent DeviceNet communication module. It connects to a compatible CompactBlock LDX base block through the expansion ribbon cable. The base block provides the DeviceNet connection and transfers the output commands to the expansion module.