The project published here is a high-performance Unipolar stepper motor driver that offers PWM controlled high current output. An Arduino board and the project published here can be combined to create a good Unipolar stepper motor driver with micro-stepping, supply 36v DC and load current up to 4A. This board requires a sequence of 4 phase pulses which can be feed and generated using Arduino or any other microcontrollers.  IC incorporates various functions like built in over current detection, over heat output OFF, fault output (active low) when over current or over heat detected, and also has built in power on reset. LED D2 is the power indicator, LED D1 indicates a fault. PR1 trimmer potentiometer provided to set the current. Refer to datasheet of STK672-740 for pulse sequence and timing information. The projects supports 5 Wire, 6 Wire and 8 Wire Stepper Motors in unipolar mode.

The board works perfectly with motor supply up to 36V DC, however motor power supply is possible to go up to 50V DC, in this case remove LM317 regulator, and supply 5V from external power supply.


  • Motor Supply 36V DC ( Up to 50V DC Possible Read Note)
  • Logic Supply 5V DC ( On Board LM317 Regulator Provides 5V)
  • Motor Load Up to 4Amps
  • Required large size heat sink for IC
  • Built-in overcurrent detection function, overheat detection function ( output current OFF)
  • Fault signal ( active low) is output when over current or overheat is detected
  • Built-in power on reset function
  • Phase signal input driver activated with an active low and incorporates a simulation ON prevention function
  • Supports Schmitt input 2.5V high level input
  • Incorporating a current detection resistor, motor current can be set using trimmer pot
  • Enable pin can be used to cut output current while maintaining the excitation mode.
  • PCB Dimensions 30.32MM x 44.04MM