EL1804 by Beckhoff

The EL1804 is a digital input module produced by Beckhoff for the EL EtherCAT Terminals series. The terminal occupies a single slot in a distributed I/O station and converts discrete sensor signals into EtherCAT process data so that a PLC or IPC can react to limit switches, proximity sensors, or pushbuttons without long parallel wiring runs. Its localized control-level connections streamline signal collection in conveyor lines, packaging cells, and other automated equipment.

The terminal accepts a nominal supply of 24 VDC through its power contact and provides 4 input channels for connecting digital sensors. A hardware debounce stage fixed at 3 ms suppresses contact bounce before data is forwarded to the fieldbus. Compliance with the EN 61131-2 Type 1/3 signal standard allows direct connection of PNP sensors and mechanical contacts without additional interface relays. The housing provides 16 spring-cage connection points for feed-through wiring and sensor returns, keeping conductors orderly when three-wire sensors are used. The terminal fastens to a standard 35 mm DIN rail, supporting rapid enclosure assembly and effective EMC grounding. Four green status LEDs on the faceplate indicate channel activity and provide visual operating information. Solid, stranded, or ferruled conductors fit the clamps, while the three-wire connection technology routes sensor power, signal, and common through one terminal block.

An IP20 protection rating makes the terminal suitable for installation in cabinets where exposure to dust, water, and tools is controlled. The housing is only 12 mm wide, conserving rail space in densely populated I/O stations. The controller receives exactly 4 input bits from the device in the cyclic process image, which keeps address mapping straightforward. The installation position is variable because no internal components depend on gravity for cooling or operation. Power contacts pass through to the neighboring terminal, allowing the 0 V reference on the power contact to continue across the station while maintaining the sensor supply connection.