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Microstep bipolar stepper motor control unit SMCU3 is used to control small and medium sized CNC machines (for wood and light metal alloys machining, engraving, coordinate drilling, gas cutting, water jet cutting, etc.).

SMCU3 is control unit for control of up to 4 stepper motors. Control unit contains of breakout board IO4 which have slots for inserting of up to 4 microstep drives MST-107 and one power supply board with motor brake PSB-1.

Front panel contains four stepper motor connectors, one connector for 5 limit switches and for analog output signal and centronics (IEEE1284) connector which is used for connection of control unit SMCU3 with PC via standard printer cable.

Control of a stepper motor is carried out over three lines, STEP, DIR and ENA (enable). This means that for a multi-axial control can be used already developed popular software such as: Mach2, Mach3, LinuxCNC (free), TurboCNC (free), KCam and similar.

For control unit SMCU3 power supply it is need to provide transformer with nominal power of 300-400 VA with two secondary outputs: 18-28VAC / 10-14A and 12-18VAC / 350mA. More data about power transformer can be found in power supply board with motor brake PSB-1 user manual.

pdfSMCU3 User's manual

Photo gallery


Description - function Pin number on the PC
side (connector DB25)
Line type on the
side of PC
Y axis STEP 4 Output -
Y axis DIR 5 Output -
Z axis STEP 6 Output -
Z axis DIR 7 Output -
A axis STEP 8 Output -
A axis DIR 9 Output -
ENA (enable) 17 Output -
Safety signal (charge pump) 14 Output OutputCan be optionally switched on and off
Spindle - Rele 1 1 Output Optionally analog output of 0-5 V or of 0-10 V
Coolant - Rele 2 16 Output -
Limit switch 1 (SW1) 10 Input -
Limit switch 2 (SW2) 11 Input -
Limit switch 3 (SW3) 12 Input -
Limit switch 4 (SW4) 13 Input -
E-Stop - Limit switch 5 (SW5) 15 Input -


Characteristics Description - Value
Type Control unit with microstep drives for bipolar stepper motor
PWM frequency 19kHz
Number of axis 1–4
Stepper motors current 7.5 A max (set up by using of one external resistor per axis)
Connection with PC Via parallel (LPT) port
Inputs 5 digital opto-insulated inputs for limit switch connection

- 2 relay outputs 220VAC / 5A max
- analog output 0–5 V or 0–10V optionally

Dimesions (wide x deep x high) -
NET weight -

NOTE: specifications are subject to change without notice


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