Product Overview
The Allen-Bradley 1794-OB8 is a Flex I/O Digital DC Output Module from the 1794 series, designed for reliable discrete output control in demanding industrial environments. This module provides eight current-sourcing outputs with a nominal 24V DC on-state voltage, making it a versatile choice for controlling solenoids, valves, and indicator lamps. Rated for safe operation in both European and North American hazardous locations, the 1794-OB8 delivers robust performance where it matters most.
Part of the Rockwell Automation Flex I/O family, the 1794-OB8 mounts onto a terminal base unit, enabling quick insertion and removal under power without disturbing field wiring. This hot-swappable design minimizes downtime during maintenance or system expansion, ensuring your production line stays productive.
Technical Specifications
| Parameter |
Value |
| Manufacturer |
Rockwell Automation |
| Brand |
Allen-Bradley |
| Part Number |
1794-OB8 |
| Product Type |
Flex I/O Digital DC Output Module |
| Outputs |
8 Sourcing Current |
| On-state Voltage (nom.) |
24V DC |
| Output Current Rating |
4A |
| On-state Current (max.) |
500mA per Channel |
| On-state Voltage Drop (max.) |
0.5V DC |
| Off-state Leakage Current (max.) |
0.5mA |
| Isolation Voltage |
50V Continuous |
| Flexbus Current |
60mA @ 5V DC |
| Power Dissipation |
3.3W @ 31.2V DC max. |
| Thermal Dissipation |
11.2 BTU/hr. @ 31.2V DC max. |
| UPC |
10612598181299 |
The 1794-OB8 delivers up to 500mA per channel with a total output current rating of 4A, ensuring ample drive capability for a wide range of actuators. Its low on-state voltage drop of 0.5V DC maximizes efficiency, while the minimal off-state leakage current of 0.5mA prevents unintended operation. With an isolation voltage of 50V continuous, the module offers reliable electrical separation between channels.
Industry Applications
The Allen-Bradley 1794-OB8 excels in applications requiring dependable discrete output control. In automotive assembly lines, this module manages pneumatic valves and conveyor diverters, ensuring precise sequencing. In material handling systems, the 1794-OB8 controls motor contactors and warning beacons, improving safety and throughput. For process industries such as food and beverage, it operates solenoid valves for liquid filling, maintaining high hygiene standards.
Because the 1794-OB8 supports hot insertion and removal, it is ideal for facilities that cannot afford prolonged shutdowns. Its hazardous location rating also makes it suitable for chemical plants and oil refineries, where explosive atmospheres are a constant concern.
Installation Guide
Mount the 1794-OB8 onto a compatible terminal base unit—such as the 1794-TB3, 1794-TB3S, or 1794-TBKD—by snapping it into place on a DIN rail. Ensure power is applied only after secure installation. The module draws 60mA from the Flexbus at 5V DC and accepts an external power supply of 10–31.2V DC with a 5% AC ripple and 10–35mA current draw. Verify that the external power is within these limits before energizing the module.
Since the 1794-OB8 outputs are not fused at the factory, add external fusing to protect your field wiring and loads. The module's outputs are not isolated, so plan your wiring accordingly to avoid ground loops. Refer to the terminal base unit's wiring diagram for correct connection of field devices.
Maintenance & Reliability
The 1794-OB8 features 16 yellow LED status indicators—two per channel—that provide real-time visual feedback on output states and diagnostics. Regularly inspect these LEDs to detect channel faults early. The module operates reliably in temperatures from 0 to 55°C (32–131°F) and in noncondensing humidity from 5% to 95%, making it suitable for harsh environments.
For extended service life, keep the module free of dust and moisture. Periodically check the DIN rail mounting for secure fit and inspect wiring connections for signs of wear. The 1794-OB8 supports XT versions for extreme environments, which reduce panel and maintenance costs by withstanding vibration and temperature extremes.
Compatibility & Integration
The 1794-OB8 is part of the Flex I/O family, which interfaces seamlessly with Rockwell Automation controllers. It supports multiple communication protocols, including ControlNet, DeviceNet, EtherNet/IP, and Universal Remote I/O, allowing integration into both new and legacy systems. The module communicates with the field devices via the terminal base unit, which connects to the I/O bus.
Because the 1794-OB8 can be inserted or removed under power, system expansion or replacement does not require a full restart, saving valuable production time. This hot-swap capability is especially beneficial in continuous process operations.
Selection Guide & Purchasing Advice
When selecting the 1794-OB8 for your application, verify that your terminal base unit is compatible (1794-TB3, 1794-TB3S, or 1794-TBKD). Confirm that your controller supports one of the listed communication protocols. Check your external power supply meets the 10–31.2V DC requirement with the appropriate current rating.
For genuine, factory-tested Allen-Bradley 1794-OB8 modules, trust PLC Source PRO. Our extensive inventory of industrial automation spares ensures fast delivery and reliable performance for your control systems.