BK3110 by Beckhoff

The BK3110 is a PROFIBUS bus coupler produced by Beckhoff within the BK PROFIBUS Bus Couplers series. Acting as the gateway between a PROFIBUS network and modular Beckhoff I/O terminals, the unit converts fieldbus frames into the internal K-bus format so connected terminals can share power and data on a single rail. This coupler is intended for distributed control architectures that require deterministic collection of digital and analog signals. Its compact housing allows the fieldbus interface and local I/O system to be installed together on a standard DIN rail.

On the field side, the coupler communicates at a maximum rate of 12 Mbaud across an RS-485 physical layer and uses a single 9-pin D-sub plug for network attachment. It can exchange up to 32 bytes of process data per cycle, supporting as many as 256 inputs/outputs across the attached terminals. A capacity of 64 terminal nodes allows the channel count to be expanded without installing another coupler. The K-bus segment supplies 500 mA to downstream electronics, while the head module draws no more than 200 mA from the control-voltage rail. These separate current values help determine the available power for the coupler and its connected terminal electronics.

The control section operates from a 24 VDC supply and routes the same voltage to the power contacts, which can carry up to 10 A for connected loads. Beckhoff recommends a 10 A fuse, and the startup inrush can reach 2.5 times the continuous current. Dimensions of 50 x 100 x 68 mm support installation in compact control cabinets with standard DIN-rail mounting. The enclosure meets the IP20 protection class, providing protection against accidental finger contact but no protection against water ingress. Dielectric isolation of 500 V separates the logic circuit from the power contacts, helping prevent ground loops in machines that combine control and power circuits.