BK9100 by Beckhoff

The BK9100 coupler is produced by Beckhoff within the BK Ethernet TCP/IP Bus Couplers series. It functions as a protocol bridge that links a stack of modular I/O terminals to an industrial Ethernet network in machine control systems. By hosting both the network interface and the K-bus backplane, the unit allows controllers to gather process signals from connected terminals and forward them to PLCs or motion processors. This arrangement supports distributed input and output stations in automated production equipment without requiring separate network interfaces for each terminal.

Network connectivity is provided through two RJ45 ports that support line and daisy-chain topologies. Each port automatically negotiates a communication rate of 10/100 Mbaud, enabling the coupler to transfer up to 512 bytes of process data in each direction. The internal K-bus supplies a maximum current of 1,750 mA to the attached terminals, while the logic electronics draw no more than 500 mA from the primary supply. The coupler provides dielectric strength of 500 V between the field and logic sections. It operates from a field supply of 24 VDC, which also feeds the power contacts. A fully populated terminal block can accommodate 128 analog inputs and outputs and 512 digital inputs and outputs, allowing mixed-signal devices to operate through a single network node.

Up to 64 terminals may be attached directly to the K-bus. Adjacent couplers can be connected in sequence so that as many as 20 stations share one network path. The total cable run must remain below 2 km, and the distance between two connected units must not exceed 100 m. Power throughput on the spring-clamp contacts is limited to 10 A, which establishes the maximum current available to terminal power contacts. The incoming feed should be protected by a fuse rated for the permitted contact current. Proper cable sizing and branch protection help control voltage drop and heating when sensors, actuators, and other field devices draw power through the terminal assembly.