Single-channel stepper positioning for ET 200S
The Siemens 6ES7138-4DC00-0AB0 is a SIMATIC DP electronic module for the ET 200S distributed I/O system, purpose-built for single-channel stepper motor positioning. It outputs differential signals for pulses (PULSE, notPULSE) and direction (DIR, notDIR) to RS-422, running at 204 kHz step frequency. The module occupies a 15 mm wide slot on the ET 200S terminal rail and draws 1.5 W typical power loss. It accepts 24 V DC nominal load voltage and includes two multifunction digital inputs configurable as reference-cam inputs (REF) or pulse-disable / external-stop inputs (DI).
Input specs and cable limits
Digital inputs are rated for signal "1" from +11 to +30 V, with a typical current draw of 9 mA at signal "1". Signal "0" spans -30 to +5 V (-15% / +20%), with a maximum permissible quiescent current of 2 mA. Input transition times are 300 µs max in both directions, supporting a repeat frequency up to 1 kHz. Cable length limits depend on shielding: unshielded runs up to 600 m, shielded up to 1 000 m. For the stepper feedback or encoder lines, the spec calls for twisted and shielded pairs at a maximum of 100 m.
Panel integration and diagnostics
Reverse polarity protection is built in on the load voltage input. The module draws up to 10 mA from the backplane bus and typically 40 mA from the 24 V load voltage line (no load).