Some differences between bipolar and unipolar stepper motor

A bipolar stepper motor for sale has one winding per stator phase. A two phase bipolar stepper motor will have 4 leads. In a bipolar stepper we don’t have a common lead like in a uni-polar stepper motor. Hence, there is no natural reversal of current direction through the winding.

A bipolar stepper motor has easy wiring arrangement but its operation is little complex. In order to drive a bipolar stepper, we need a driver IC with an internal H bridge circuit. This is because, in order to reverse the polarity of stator poles, the current needs to be reversed. This can only be done through a H bridge.

Bipolar Stepper Drives
Many companies have started assembling their own bipolar stepper drives. Care must be taken that you connect the stepper motor correctly to the drive. Also the drive must be able to supply sufficient current for you stepper. The micro-controller must only provide the step and direction signal to the drive. This method will occupy only two micro-controller pins and is very helpful in projects that require large number of micro-controller pins for other functions.
 

Unipolar Stepper v/s Bipolar Stepper
Both bipolar steppers and unipolar stepepr motor for sale are used widely in projects. However, they have their own advantages and disadvantages from the application point of view. The advantage of a uni-polar motor is that we do not have to use a complex H bridge circuitry to control the stepper motor. Only a simple driver like ULN2003A will do the task satisfactorily. But, there is one disadvantage of uni-polar motors. The torque generated by them is quite less. This is because the current is flowing only through the half the winding. Hence they are used in low torque applications. On the other hand, bipolar stepper motors are a little complex to wire as we have to use a current reversing H bridge driver IC like an L293D. But the advantage is that the current will flow through the full coil. The resulting torque generated by the motor is larger as compared to a uni-polar motor.