Product Description:

The EL2521/PL3 is a Beckhoff output terminal in the EL EtherCAT Terminals series that converts internal position values into high-speed pulse streams for external motion devices. By mounting this module on the EtherCAT I/O rail, the system can add hardware-timed pulse generation without a separate controller card, using the EtherCAT E-bus as its only power and data source. A distributed-clock time stamp is also available, allowing sub-microsecond alignment between the terminal’s edge timing and the global EtherCAT cycle so axis coordination remains deterministic.

The terminal employs Pulse Train Output technology and can toggle its differential drivers up to 50 kHz, a rate suitable for mid-range stepper and servo drives. Internal electronics draw approximately 280 mA from the E-bus, so no extra 24 V feed is required. Output lines follow the RS422 differential standard, giving balanced signaling that resists noise on long machine cables. Position data is handled with a resolution of 15 Bit, which sets the granularity between consecutive pulses and directly affects mechanical step accuracy. This arrangement supports precise pulse generation while keeping synchronization tightly linked to the EtherCAT cycle.

The step accumulator increases or decreases in increments of 10 mHz, meaning velocity commands can be tuned in ten-millihertz steps around the configured base frequency. The terminal provides 1 channel with complementary A and B pairs, while two auxiliary inputs, +T and +Z, return feedback such as limit sensors to the 16-bit process image. The housing meets the IP20 protection class and is intended for enclosed control cabinets, and the signal conductors must present at least 120 Ω impedance to satisfy the combined RS422 and optocoupler load requirement. Output drivers can source or sink up to 50 mA, allowing the channel to interface directly with high-speed optically isolated receivers without extra line buffers.