EL1859 by Beckhoff

The EL1859 is a digital combination terminal from Beckhoff in the EL EtherCAT Terminals series. It combines eight inputs and eight outputs on a 12 mm slice, letting controllers read sensors and drive actuators from one node. Installed inside a machine control cabinet, the EL1859 forwards process data over EtherCAT and simplifies wiring in industrial automation lines that rely on distributed I/O.

The terminal uses 1-Wire connection technology on each input and accepts a nominal field level of 24 VDC, so standard control-voltage proximity switches can be connected without level shifters. Within the EtherCAT system, the device draws an E-bus supply current of 130 mA, while each input draws only 3 mA from the upstream sensor. This low input current accommodates sourcing electronics with limited drive capability. The inputs are debounced by an internal 3 ms filter, reducing false transitions from mechanical contacts. Output drivers can source up to 0.5 A per channel, allowing the module to switch small solenoids or indicator lamps directly. For fast, deterministic response, the process image transfers the corresponding input and output bits during each cycle, while reverse-voltage and short-circuit protection guard the power paths.

The power distribution rail feeds the outputs through a power contact that draws 15 mA in addition to the actual load current. This arrangement helps keep communication stable during inrush events. A turn-on reaction time of 60 µs and a turn-off reaction time of 300 µs allow the terminal to toggle outputs quickly enough for most discrete motion sensors. The housing has an IP20 rating, so the terminal must be mounted inside an enclosure that protects it from moisture and small foreign objects. It locks onto a 35 mm DIN rail for secure installation in a control panel. The compact housing helps conserve rail space while placing both signal directions in one terminal. Its integrated protective circuits reduce the risk of damage caused by incorrect polarity or excessive output current.