Allen-Bradley 1786-RPFM/A ControlNet Fiber Repeater Module

Allen-Bradley 1786-RPFM/A ControlNet Fiber Repeater Module

Configured for medium-distance network extension and electrical noise isolation in ControlNet deterministic networks, the Allen-Bradley 1786-RPFM/A (1786-RPFM ControlNet Fiber Repeater Module) provides direct physical/electrical execution. It converts standard electrical coaxial signals into 820 nm optical pulses, preventing ground loops and electromagnetic interference across multi-building and distributed control architectures.

Hardware Specifications

Backplane Bus Communication Velocity and Deterministic Control

The 1786-RPFM/A operates as a physical layer repeater designed to maintain EtherNet/IP and ControlNet deterministic networks without introducing non-deterministic signal latency. In high-density PLC I/O architectures, the module manages frame synchronization across the physical medium, ensuring real-time backplane bus communication velocity across extended segments. The hardware preserves scheduled I/O traffic timing profiles and system firmware flash compatibility, allowing seamless integration into existing Allen-Bradley PLC-5, SLC 500, and ControlLogix networks without altering network schedule parameters or media access control (MAC) frame structures.

Frequently Asked Questions

Q: Can the 1786-RPFM/A be replaced while the rest of the ControlNet segment remains active?

A: Yes. The module supports hot-swapping under power without interrupting communication on adjacent operational nodes, provided the physical ring or trunk topology permits redundant path routing.

Q: What is the impact on signal latency when inserting a 1786-RPFM/A fiber repeater into a network loop?

A: The physical propagation delay added by the optical conversion hardware is negligible and fits within the standard ControlNet Network Access Time (NUT) configuration parameters.

Q: How is power provided to the 1786-RPFM/A module during standalone operation?

A: The module draws its required 24 VDC operating power directly through the standard ControlNet tap connection connected to the module housing.

Field Installation Guidelines

1. Mount the module securely on a grounded standard 35 mm DIN rail within an IP54 or NEMA 12 rated enclosure to protect against environmental contamination.
2. Ensure the optical fiber cable ends are clean and terminated with high-quality ST connectors. Maintain a minimum bend radius of 30 mm for multi-mode fiber runs to avoid micro-bending signal attenuation.
3. Verify that the optical power budget does not exceed 13.3 dB across the full length of the 3000 m fiber link using an optical power meter set to 820 nm prior to final commissioning.
4. Connect the earth ground terminal of the mounting assembly to the main cabinet ground busbar using a short, low-impedance braided copper strap.