1791-16AC | Allen-Bradley Block I/O Module, 120VAC, 16 Inputs & 16 Outputs

The 1791-16AC is a block I/O module designed for use in Remote I/O architectures within industrial automation systems. It integrates 16 discrete 120VAC input channels and 16 discrete 120VAC output channels, making it suitable for systems that require both types of signals. The module includes built-in signal conditioning, a communication interface, and its own power supply, which simplifies installation and integration. It can communicate with a PLC or other master device using the Remote I/O protocol in a daisy-chain configuration. This allows for centralized monitoring and control of distributed field devices like sensors and actuators.

The module features an isolation voltage of 500VAC between the power supply and Remote I/O circuitry. Additionally, it has 1250VAC isolation between I/O groups and between I/O and logic circuits. This level of isolation protects the system from electrical surges and cross-talk, enhancing system robustness. Isolation also allows for safe integration of various devices with different electrical potentials. These protective measures are crucial in industrial settings with high-power equipment.

The 1791-16AC is compatible with standard binary input devices like pushbuttons, selector switches, limit switches, and float switches. On the output side, it can drive pilot lamps, relays, horns, solenoids, and other 120VAC actuated equipment. This wide compatibility makes it ideal for traditional automation environments. The AC voltage rating ensures the module can be directly interfaced with industrial-grade devices. This eliminates the need for additional interface relays in many use cases.

For input signals, the 1791-16AC has an Off-to-On delay of 1.0 ms and an On-to-Off delay of 26 ms. For output signals, the Off-to-On delay is 1.0 ms and the On-to-Off delay varies—8.3 ms at 60 Hz and 10.0 ms at 50 Hz. These delays help filter out signal noise and prevent false triggering due to transient fluctuations. The module is designed to work reliably with standard industrial signal timing. Accurate response times are crucial in automation systems to maintain synchronized and predictable control.

The 1791-16AC has been used extensively in legacy Remote I/O systems, but it is considered an older model and is likely no longer in active production. Rockwell Automation recommends reviewing lifecycle status via their Product Compatibility and Download Center (PCDC). While it may still be available through surplus or aftermarket suppliers, users should consider migrating to modern alternatives such as FLEX or POINT I/O systems for enhanced functionality and support. It's advisable to check for last-time buy or migration documents from Allen-Bradley.