Overview
The Allen-Bradley 1746-OB16 is a digital DC output module engineered for the SLC 500 PLC series. This 16-output discrete control module delivers industry-standard switching performance for field device actuation, solenoid valves, motor contactors, indicator lights, and other 24V DC loads. The module mounts in any available slot of the 1746 modular I/O chassis (except the leftmost slot reserved for the processor or communication module), making it a flexible addition to existing SLC 500 control systems.
Key Features
- 16 DC Output Channels: All 16 outputs grouped together as a single common group for simplified wiring and control
- Electronic Overload Protection: Built-in thermal current limiting protects against short circuits; channels with overload automatically limit current within milliseconds while healthy channels continue operating
- Single Slot Module: Compact form factor fits any free slot in SLC 500 chassis for rapid integration
- Load-Dependent Signal Delay: 0.1 ms ON state delay, 1 ms OFF state delay ensures predictable output timing
- Removable Terminal Block: Simplifies field wiring changes and maintenance
Technical Specifications
- Output Voltage (Nominal): 24V DC
- Operating Voltage Range: 10–50V DC
- Number of Outputs: 16 discrete points, single group
- Continuous Output Current per Point: 0.5 A @ 30°C (86°F); 0.25 A @ 60°C (140°F)
- Maximum Module Current: 8.0 A @ 30°C; 4.0 A @ 60°C
- Backplane Current Draw: 0.28 A @ 5V DC; 0 A @ 24V DC
- ON State Voltage Loss: 1.2V @ 0.5 A per point
- OFF State Leakage Current: 1 mA maximum per point
- Minimum Load per Output: 1 mA
- Signal Delay: 0.1 ms ON; 1 ms OFF (load-dependent)
- Heat Dissipation: 0.388 W per point; 7.6 W total module
- Series Designation: Series D
- Module Type: Single-slot I/O module
- Certifications: UL Listed; Class I, Division 2
Typical Applications
The 1746-OB16 output module is used across a wide range of discrete control applications, including:
- Solenoid valve actuation and hydraulic/pneumatic control
- Motor starter and contactor energization
- Status indicator and alarm lamp control
- Process automation and material handling systems
- HVAC system control and status signaling
- Assembly line and manufacturing equipment control
- Pump and fan motor control circuits
Compatibility & Replacements
Compatible With
- SLC 500 fixed and modular processor controllers (all series)
- 1746 modular I/O chassis (any available slot except leftmost)
- MicroLogix 1100/1500 series (via SLC 500 extension adapter)
- RSLogix 500 programming software
- Discrete 24V DC field devices rated for electronic switching
Replaces / Drop-In Replacement For
- 1746-OB16 Series A, B, and C (with minor firmware/timing variations; verify ladder logic in Studio 5000 before field deployment)
- Earlier generation SLC 500 sourcing output modules requiring 16-point discrete control
Works With
- RSLogix 500 programming environment (native SLC 500 support)
- Rockwell Automation CompactLogix/ControlLogix (via legacy bridge modules or network gateways)
- EtherNet/IP gateways for remote I/O supervision (with appropriate network module in chassis)
- Standard 24V DC industrial power supplies and control terminals
