nema 17 stepper motor has one winding in each stator phase. A biphasic bipolar nema 17 stepper motor will have 4 leads. In bipolar stepper motors, we do not have a common lead like a single pole stepper motor. Therefore, there is no natural reversal of the direction of the current through the winding.
The bipolar nema 17 stepper motor is convenient to operate, but the operation is complex. In order to drive the bipolar stepper motor, we need a built-in H bridge circuit driver IC. Since the current needs to be reversed to reverse the polarity of the stator pole, this can only be done through the H bridge. There are two other reasons for using H bridge IC:
1. nema 17 stepper motor has quite high traction at present. SCM pin can only provide 15mA at most. The current required by the stepper is about 10 times that of this value. The external drive IC can handle such a high current.
2. Another reason for using the H bridge is that the stator coil is only an inductor. When the coil current changes direction, a spike will be generated. An ordinary microcontroller pin can’t stand such high spikes without damaging itself. Therefore, in order to protect the microcontroller pin, the H bridge is necessary. In most nema 17 stepper motor interface projects, the most commonly used H bridge IC is L293D.