1794-OB16 Allen Bradley Flex I/O 16 Channel Sourcing DC Module

1794-OB16 24V DC Sourcing Output Architecture

The 1794-OB16 is a high-density, 16-channel discrete DC sourcing output module designed for the Allen-Bradley Flex I/O Series by Rockwell Automation. Built for driving 24V DC field actuators, this module provides current-sourcing outputs operating across a supply voltage envelope of 19.2 to 31.2V DC (nominal 24V DC, including 5% AC ripple). Each output delivers up to 500 mA, supporting an overall aggregate load current of 8.0 A across all 16 channels. The solid-state output circuitry features high-speed propagation times of ≤0.5 ms for OFF-to-ON and ≤1.0 ms for ON-to-OFF transitions. It mounts to terminal base units including 1794-TB2, 1794-TB3, 1794-TB3S, 1794-TB3K, and 1794-TB3SK using Keyswitch Position 2, drawing 80 mA from the 5V DC Flexbus backplane while providing 850V DC isolation between field power and logic buses for 1 second.

Technical Specifications Summary

Target Equipment & Field Application Scenarios

The 24V DC current-sourcing capability of the 1794-OB16 makes it standard hardware across automated manufacturing lines and machinery enclosures:

• Direct control of 24V DC pneumatic directional solenoid valves on packaging equipment
• Driving 24V DC interposition relays and contactor coils inside distributed motor control cabinets
• Actuating 24V industrial LED stack lights, panel indicators, and audible alarm buzzers
• Interfacing discrete output triggers to variable frequency drives (VFD) digital input terminals
• Controlling high-speed sorting gates, diverters, and part ejectors on conveyor systems

Diagnostic Visuals & Circuit Protection Capabilities

Field diagnostics and integrated protective mechanisms simplify system monitoring and field maintenance:

• Field-Side LED Indicators: Sixteen yellow status LEDs aligned on the front housing provide clear visual indication when output driver gates are activated.
• Inrush Surge Suppression: Integrated transistor protection handles transient surge currents up to 2.0 A for 50 ms, accommodating inductive coil inrush without tripping outputs.
• Optocoupler Backplane Protection: Optoisolators safeguard internal Flexbus logic circuits against field-side electrical noise and voltage transients up to 850V DC.

Packaging, Express Shipping & Warranty Terms

• Product Condition: 100% Brand New, Original Factory Sealed Stock
• Warranty Period: Covered by a Complete 12 Months Replacement Warranty
• Dispatch Handling: Orders ship within 24 to 48 hours following confirmation
• Worldwide Express Delivery: Fast international transit via FedEx, UPS, or DHL

Global PLC Spare HUB's Insight

The 1794-OB16 is one of the most widely deployed DC output modules in the Flex I/O ecosystem due to its high density and low power footprint. However, because this module lacks internal electronic short-circuit protection, an accidental short on a 24V field wire directly connected to an output pin will permanently damage the internal output transistor. To prevent hardware damage during commissioning or wire degradation, we strongly recommend installing external SAN-O MQ4-800 mA fast-acting fuses on individual output channels or utilizing a fused terminal base assembly. Furthermore, when switching inductive coils, fitting suppression diodes across field load terminals absorbs back-EMF spikes and prevents premature transistor fatigue.

Frequently Asked Questions (FAQ)

Q: What causes an output channel on this module to fail permanently in a closed (always ON) position?

A: Overcurrent shorts or high inductive voltage spikes exceeding the transistor's thermal limits typically break down the solid-state output junction, causing it to short internally and stay ON; installing SAN-O MQ4-800 mA fuses prevents this failure mode.

Q: Can field loads requiring 12V DC power be driven reliably using this output card?

A: Yes; the module supports an ON-state voltage range from 10V DC up to 31.2V DC, allowing it to switch 12V DC control loads provided the auxiliary power supply matches the load voltage requirement.

Q: How many of these discrete output modules can be installed under a single Flex I/O adapter node?

A: Up to eight modules can be mounted sequentially on a single Flex I/O backplane cluster, provided the total 5V DC Flexbus current draw of all cards does not exceed the adapter's power supply rating.

Q: Why does a 24V LED indicator connected to an inactive channel stay faintly illuminated?

A: The 0.5 mA off-state leakage current inherent to solid-state output transistors can pass enough residual energy to faintly light high-efficiency LED indicators; placing a parallel resistor across the load bleeds off this voltage.

Q: Selection Guide: How do I choose between specifying the 1794-OB16 sourcing card and the 1794-OV16 sinking output card?

A: Select the 1794-OB16 when field actuators require current-sourcing logic (+24V DC switched to the load). Select the 1794-OV16 when field equipment utilizes current-sinking logic (DC Common switched to the load).

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