SMI2 - Two-channel stepper motor interface unit with SSI encoder input

The SMI2 is a motion control interface module which is capable of controlling two stepper motor drives by STEP/DIR signals, receiving an SSI encoder. With encoder a closed-loop stepper motor control can be realized, with which significantly better accuracy and reliability characteristics can be reached than those of the open-loop solution. In addition, the module provides each of the channels with one digital input and one digital output. Both the input and the output are of 24 V and are galvanically isolated.

The stepper motor handling by SMI2 differs from the typical position-controlled stepper motor solutions, because the SMI2's command input is the rotational speed of the stepper motor. The SMI2 was designed to realize such a CNC control method where the CNC motion controller sends speed command value to the stepper motor drivers and receives the position from the encoders of the stepper motors, which means the position loop is closed in the CNC controller.

Features

• EtherCAT LVDS connection
• Two-channel design
• Control of stepper motor driver via STEP/DIR signals
• SSI encoder interface
• Galvanically isolated digital I/O (one input and one output / channel)
• Software update through EtherCAT (FoE)
• Parameterization via CoE protocol
• SM and DC synchronized operation modes
• Mechanically it can be snapped on the DIN-35 rail

Specification

• EtherCAT connection: LVDS
• Encoder supply voltage: 5 V
• Encoder interface: SSI (RS422), fixed 400 kHz
• Stepper motor driving: STEP/DIR, max. 200 kHz, open collector
• Overall dimensions: 108 x 56 x 30 mm