BK5120 by Beckhoff

The BK5120 is an EtherCAT bus coupler produced by Beckhoff and supplied as part of the BK EtherCAT Bus Couplers series. It links a plant's EtherCAT backbone to modular K-bus I/O terminals, so decentralized sensors and actuators can be scanned from a central PLC with minimal field wiring. By collecting terminal data locally and transmitting it over the real-time network, the unit streamlines installation in machine cells and process lines where space and wiring density are critical design factors.

Up to 64 K-bus terminals can be attached. The combined analog channel capacity reaches 60 inputs and outputs, while the digital channel capacity reaches 960 inputs and outputs. Field supply and network signals enter through a single 1 × 5-pole open-style connector. The housing measures 50 × 100 × 68 mm, allowing placement in shallow control cabinets. Internal electronics draw no more than 500 mA from the 24 V DC logic rail, and they can supply 1750 mA through the K-bus to power terminal electronics. For actuator loads, separate power contacts conduct up to 10 A at 24 V DC. A backup fuse protects the downstream wiring connected to these contacts. The device also exchanges 16 receive PDOs and 16 transmit PDOs with CANopen gateways, enabling mixed-protocol installations across a facility.

The coupler accepts its logic supply from a 24 V DC source and secures conductors with a cage-clamp spring-loaded wiring system that does not require torque settings. Permissible ambient moisture reaches 95% relative humidity, allowing operation in humid industrial spaces when condensation is prevented. The IP20 housing protects against accidental contact with internal components but does not provide protection from water. The unit must therefore be installed in a dry control cabinet or another suitable enclosure. Its compact format supports dense DIN-rail layouts, while the EtherCAT connection provides deterministic communication between the controller and attached K-bus terminals.