BK3500 by Beckhoff

The BK3500 EtherCAT bus coupler is produced by Beckhoff within the BK EtherCAT Bus Couplers series. This unit connects a field EtherCAT segment to a block of modular I/O terminals, allowing PLCs or industrial PCs to command discrete and analog points through the K-bus backplane. By translating high-speed optical-fiber communication into the local terminal format, the coupler serves as the gateway between the network and machine-level sensors, actuators, and process variables.

Communication on the EtherCAT side uses a single optical fiber in a 2 HP Simplex housing, and link traffic is sustained at a line rate of 1.5 Mbaud. Internally, the device distributes signals to the K-bus, where up to 64 bus terminals can be attached. The coupler can process 512 digital inputs and outputs and an additional 64 analog channels without overrun. The power contacts provide up to 24 VDC for the sensor supply. The power-feed conductors and replaceable protection fuse support a maximum current of 10 A, matching the load limits of typical terminal blocks. A starting-current factor of 2.5 times the steady-state draw helps protect upstream power supplies during cold starts.

During normal operation, the electronics consume 500 mA from the supply rail, while the integrated K-bus regulator can provide 1750 mA to the attached terminals so their logic sections remain powered. Communication with the controller occurs in deterministic frames containing 128 bytes of process data, in accordance with the limits of the EtherCAT mapping tables. Electrical isolation between the field side and the I/O stack provides 500 V of dielectric strength. The coupler has an IP20 protection rating and is intended for cabinet installation. It must be mounted in a clean, dry enclosure that prevents exposure to moisture, conductive debris, and excessive airborne contamination.