BK3100 by Beckhoff

The BK3100 is a bus coupler produced by Beckhoff for the BK Bus Couplers series. It connects a PROFIBUS fieldbus line to modular K-bus I/O terminals, providing the point where network frames are converted into backplane signals for local input and output modules. In machine control systems, the unit allows a PLC to collect sensor data and set actuator states through one gateway instead of relying on separate proprietary interfaces. Its modular design supports centralized communication with distributed terminals mounted together on a DIN rail.

The coupler handles up to 512 digital inputs and outputs and an additional 128 analog inputs and outputs for measurement and control signals. The PROFIBUS connection supports transmission rates up to 12 Mbaud, enabling frequent data updates across the attached terminal set. The K-bus can supply up to 1750 mA to the terminal electronics and supports configurations containing as many as 64 terminals. Network wiring uses one shielded 9-pin D-sub plug, which provides a secure, strain-relieved connection inside a control cabinet. The maximum process image is 128 bytes in DP-only operation or 64 bytes when DP and FMS services are combined, allowing the controller's memory area to be allocated according to the selected communication mode.

The control side operates from a 24 VDC power supply that also feeds the power contacts used by downstream terminals. These contacts can carry application currents up to 10 A, allowing connected I/O modules to power devices such as relays and solenoids without separate supply wiring for each terminal. The enclosure has an IP20 protection rating, making it suitable for installation inside a protected electrical cabinet. Galvanic isolation between the field side and the logic side withstands 500 V, reducing the transfer of electrical interference between the network and local electronics. The plastic housing measures 100 mm in height, 50 mm in width, and 68 mm in depth. Its compact dimensions allow the coupler to share a standard DIN-rail row with other automation components while preserving access to the fieldbus connector, power contacts, and attached terminals.