BK1120 by Beckhoff

The BK1120 is a modular bus coupler built by Beckhoff for the BK EtherCAT Bus Couplers series. Serving as the interface between decentralized I/O terminals and a higher-level controller, the unit forwards process data over the EtherCAT fieldbus so PLCs can read sensor states or actuate outputs without local wiring complexity in industrial automation. Installed on DIN rail segments, the coupler forms the head of a terminal strand and supplies internal K-bus power while passing through the system voltage.

It communicates via the EtherCAT protocol at a line speed of 100 Mbaud, and two RJ45 sockets enable an in-line topology without external hubs. The integrated process image supports 1024 input and 1024 output fieldbus bytes, which establishes the cyclic data frame size that can be exchanged with the controller during each scan. Inside the coupler, distributed clocks can address up to 8192 digital I/O points through the attached terminal chain. A K-bus supply current of 1750 mA powers those terminals, and up to 64 K-bus modules can be inserted consecutively on the 35 mm mounting rail before a second coupler is required. The device itself draws no more than 500 mA from the system voltage, supporting the use of compact power supplies.

Analog channels are also supported, and the design maps up to 256 analog I/O points into the same process image without additional gateways. Both the logic electronics and power contacts share a supply of 24 VDC, simplifying power source selection. High-current loads on the terminal row can be supplied through the copper power contacts at up to 10 A, so separate feed modules are unnecessary for moderate actuator banks. The housing meets the IP20 protection class, so the coupler is intended for protected control cabinets rather than exposed field locations.