BK3150-0018 by Beckhoff

The BK3150-0018 is a PROFIBUS-to-I/O bus coupler manufactured by Beckhoff within the BK PROFIBUS Bus Couplers series. It functions as the head station of a terminal strand, converting PROFIBUS process data into the internal terminal bus format so that distributed digital or analog modules can be added directly on the DIN rail. In machines and plant cells, this unit aggregates sensor and actuator signals at the field level while maintaining deterministic communication with the central controller.

A single field cable terminates at a 9-pin D-sub plug on the front, and up to 64 terminals can be attached to the right side of the coupler. The module snaps onto a 35 mm mounting rail, and its fieldbus interface uses the RS-485 physical layer for communication. The housing measures 44 × 100 × 68 mm and is molded from polycarbonate and PA 6.6, providing mechanical stability without adding excessive width inside the control cabinet. An enclosure rating of IP20 limits installation to protected cabinets. The logic electronics operate from a 24 VDC supply. At startup, the unit draws 2.5 times its steady-state current before consumption settles at 320 mA. The same 24 VDC potential passes through the power contacts to supply the attached terminals while remaining within the contacts' voltage limit.

The internal circuitry withstands dielectric test voltages up to 500 V, providing electrical isolation between the fieldbus and I/O sections. PROFIBUS telegrams pass through the device at a maximum transmission rate of 12 Mbaud, supporting short cycle times even when the terminal strand is fully populated. The power contacts can conduct up to 10 A, allowing higher-current loads to share the field supply without separate supply wiring. Process images as large as 128 bytes are supported, enabling the simultaneous exchange of status, command, and diagnostic data for the attached terminals. The compact housing leaves room for adjacent control components while keeping the terminal connections accessible. Its modular arrangement also allows the I/O strand to combine digital and analog terminals according to the machine's signal requirements.