Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756-OB8 |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | ControlLogix Digital DC Output Module |
| Series | ControlLogix 1756 |
| Output Channels | 8 (current sourcing) |
| Output Voltage Range | 10–30V DC |
| Output Current | 2A per point |
| Terminal Block | 20-pin removable terminal block (RTB) |
| Communication Format | Output Data, Listen-Only Output Data, Scheduled Output Data |
| Diagnostic Features | Open wire, field power loss, fuse blown, no load, output verify fault |
| Country of Origin | Malaysia |
| Lifecycle Status | Active |
| Standard Warranty | 1 year |
| Certifications | CE, UL Listed Hazardous, ATEX, IECEx, CCC, RCM |
Main Features and Advantages
The 1756-OB8 delivers a combination of current capacity and diagnostic capability that makes it a practical choice for demanding discrete output applications. The 2A per-point rating distinguishes the 1756-OB8 from lower-current ControlLogix output modules, allowing it to directly drive solenoids, contactor coils, and small motor starters that would otherwise require external amplification or interposing relays. This reduces panel component count and wiring complexity, contributing to more compact and maintainable control cabinets .
The diagnostic architecture of the 1756-OB8 provides visibility into field circuit integrity that basic output modules lack. The module can detect open wire conditions, field power loss, blown fuses, and no-load states, reporting these faults back to the controller through the module-defined data type . This diagnostic data enables maintenance personnel to identify failed field devices or wiring problems without performing manual circuit checks, reducing mean time to repair and improving overall equipment effectiveness. For applications where output verification is critical, the 1756-OB8 supports an output verify fault diagnostic that confirms whether an output commanded to a given state has actually achieved that state.
The 1756-OB8 supports multiple communication formats within the ControlLogix environment. In addition to standard output data communication, the module can be configured for Listen-Only Output Data or Scheduled Output Data formats. The Scheduled Output Data format enables the use of Coordinated System Time (CST) timestamping, allowing output state changes to be synchronized across multiple modules in the chassis for applications requiring precise coordination of discrete outputs . Configuration parameters for fault mode and program mode behavior are also accessible, allowing users to define how the 1756-OB8 responds to communication loss or controller mode changes.
Application Field
The 1756-OB8 is deployed across discrete manufacturing and process control applications where reliable, high-current DC output control is required. In material handling and conveyor systems, the module drives motor starters, divert gates, and brake releases, with the 2A per-point capacity enabling direct control of many conveyor actuator coils without intermediate relays. The diagnostic feedback provided by the 1756-OB8 is particularly valuable here, as a failed diverter solenoid or open coil can be identified immediately rather than discovered when a package is misrouted.
In packaging machinery, the 1756-OB8 controls pneumatic valve manifolds, ejector solenoids, and indicator lamps. The module’s sourcing output configuration matches the common return topology of many packaging machine control circuits, simplifying wiring and panel layout. For process industry applications, the 1756-OB8 is used to actuate pilot valves, relay coils, and audible/visual alarms, with the fault diagnostics assisting in maintaining reliable operation of safety-related annunciation circuits.
Water and wastewater treatment facilities employ the 1756-OB8 for pump control, valve actuation, and chemical feed system enable signals. The module’s active lifecycle status and Rockwell Automation’s long-term supply commitment make the 1756-OB8 a suitable choice for new builds and spares inventory in infrastructure projects where equipment must remain serviceable for decades. The multiple hazardous area certifications carried by the module also make it applicable to installations in classified environments where standard commercial-grade I/O would be unacceptable .