BK4020 Beckhoff
Wake Industrial LLC is not an authorized distributor of this product.
The Beckhoff BK4020 is part of the BK EtherCAT Bus Couplers series and features support for 32 analog and 512 digital inputs or outputs. This coupler offers a supply voltage of 24 V DC, mounts on a 35 mm DIN rail, and has a protection rating of IP20. It is equipped with a 2 x D-sub, 9-pin bus interface and can connect up to 64 bus terminals, or 255 when using a K-bus extension.
Internal Product Review
The BK4020 is a Beckhoff EtherCAT bus coupler designed for distributed automation, with support for 64 bus terminals and 64 byte input / 64 byte output fieldbus data. With 24 V DC supply voltage and IP20 protection, this unit offers efficient cabinet integration and dependable industrial communication performance.
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Product Description:
The BK4020 bus coupler is built by Beckhoff and belongs to the BK EtherCAT Bus Couplers series. Acting as the interface between an EtherCAT ring and a string of Beckhoff K-bus terminals, it aggregates process data from local I/O modules and presents it to the controller in a single fieldbus node. Within industrial automation lines, the device enables decentralized installation of analog and digital sensors or actuators while maintaining deterministic, high-speed communication across long machine segments.
The coupler supports up to 512 inputs/outputs on the digital side, so a single station can handle extensive push-button, limit-switch, or relay clusters without an additional repeater. For analog measurement or control, the internal processor accepts 32 input or output channels, and all process variables are packed into a 64-byte input and 64-byte output image that is transferred during each EtherCAT cycle. Connection to the network is made through two 9-pin D-sub sockets, which allow a ring topology for redundancy. A backplane voltage of 24 V DC powers the terminal electronics, while separate power contacts can deliver up to 10 A to actuators driven by the attached modules.
Up to 1750 mA of K-bus supply current is available for the terminal stack, so as many as 64 standard bus terminals, or 255 when an extension is added, can be powered without auxiliary feeds. The coupler snaps onto a 35 mm DIN rail; once mounted, it occupies just 51 × 100 × 69 mm of panel space and maintains an IP20 rating for sheltered cabinet environments. EtherCAT optical repeaters are not required because the ring can extend to 12.8 km with segment spacing of 400 m when the specified LiYCY 3 × 2 × 0.22 mm² cable is used at a data rate of 500 kbaud. This physical layer selection balances deterministic timing with noise immunity in typical plant installations.
