Solving High-Current Switching Challenges in Automation
Consider a packaging line where multiple solenoid valves must actuate simultaneously under a 24VDC control signal. The Allen-Bradley 1746-OB16, a SLC500 discrete DC output module, provides a reliable solution with sixteen outputs rated for continuous current up to 1.5 A per point at 30 °C (86 °F). This module ensures precise on/off control without voltage drop, even in demanding environments.
Technical Specifications Breakdown
Key parameters for the 1746-OB16 are listed below for quick reference:
| Feature | Specification |
|---|---|
| Manufacturer | Rockwell Automation |
| Module Type | Digital DC Output Module |
| Series | SLC500 |
| Part Number | 1746-OB16 |
| Brand | Allen-Bradley |
| Number of Outputs | Sixteen (16) |
| Output Voltage | 24VDC |
| Operating Voltage Range | 10-30VDC |
| Output Delay Time, OFF to ON | 1.0 ms |
| Output Delay Time, ON to OFF | 0.1 ms |
| OFF State Leakage Current | 1 mA |
| Backplane Current at 5.1 Volts | 0.135 A |
| Continuous Current per Point | 1.5 A @ 30 °C (86 °F), 1.0 A @ 55 °C (131 °F) |
| Continuous Current per Module, Max | 6.4 A @ 0...60 °C (32...140 °F) |
| Voltage Range | 10-50 Volts DC Source |
| Current/Output | 0.5 or 0.25 amps |
| Current/Module | 8 or 4 amps |
| Backplane Current (5 Volts) | 280 milliamps |
| Current/Module (30 Celsius) | 9 amps |
| Applications | High Current |
| Step Response | 60 milliseconds in, 2.5 milliseconds out |
| Heat Dissipation | 7.6 Watts |
Industry Applications
Manufacturing Assembly Lines
In automotive assembly, the module drives multiple DC actuators for clamping and positioning. Its 1.0 ms OFF-to-ON delay ensures rapid response, while the 0.1 ms ON-to-OFF delay minimizes coasting.
Material Handling Systems
Conveyor sortation systems benefit from the high-current capability (up to 9 A per module at 30 °C) to energize multiple brake solenoids simultaneously.
Process Control
For batch processing, the 16 outputs control indicator lights and small DC valves, with the 1 mA OFF-state leakage preventing false activation.
Installation & Setup Guidance
Mount the 1746-OB16 in any SLC500 chassis slot. Connect the 24VDC field power to the module's terminal block, observing polarity. Use the operating voltage range of 10-30VDC to ensure compatibility with your power supply. Wire each output to the load, respecting the continuous current per point limits: 1.5 A at 30 °C (86 °F) and 1.0 A at 55 °C (131 °F). For derating, refer to the max module current of 6.4 A across 0...60 °C (32...140 °F).
Maintenance & Reliability
Inspect the module quarterly for dust accumulation on the heatsink. Ensure ambient temperature stays within 0...60 °C (32...140 °F) to maintain full current rating. The heat dissipation of 7.6 Watts requires adequate airflow in the enclosure.
Compatibility & Integration
This module integrates with any SLC500 processor via the backplane. The backplane current draw is 0.135 A at 5.1 Volts (or 280 milliamps at 5 Volts). Use the 1746-N series terminal blocks for field wiring.
Selection Guide & Purchasing Advice
When selecting a replacement or new unit, verify the required number of outputs and current per point. For high-current applications like motor starters or large solenoids, the 1746-OB16's 1.5 A per point at 30 °C is ideal. SpareTechPLC stocks this module with fast shipping. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Troubleshooting & Common Issues
If an output fails to energize, check the field wiring and confirm the supply voltage is within 10-30VDC. Use a multimeter to measure the output voltage at the terminal. If the module overheats, reduce the load current per point or improve ventilation. The OFF-state leakage current of 1 mA may cause faint LED glow on sensitive loads; add a bleeder resistor if needed.
