The stator is the outer pairs of stationary electromagnet coils. The rotor is the inner arrangement that rotates along the axis of the shaft. This inner arrangement determines the three types of stepper motors:Īs the name implies, a permanent magnet serves as the rotor and the rotation is controlled by stator. The rotor in this type of motor uses a ferromagnetic material that induces an electromagnetic field in response to stator’s current flow. Since the previous two types of motors have their advantages it is natural to have the combined advantages of both types in the hybrid variation of the motor.Īnother key characteristic for stepper motors is number of power sources. If there is only one power source then the polarity of the stator is constant and the arrangement is unipolar. If polarity of the stator can be reversed by a secondary power source then the arrangement is bipolar. The key specifications of this stepper motor are tabulated below: The servo motor chosen for the test exercises is 28BYJ-48 (5V DC) which has the following pin connections: The model, 28BYJ-48, examined in this note is unipolar. The steps required by the motor to complete one full revolution (i.e. The motor requires 64 full revolutions to complete one full revolution of the external shaft (i.e. The key specification for the motor is the gear reduction ratio at 1:64 (In reality, this number could be slightly different depending on the quality of the counterfeit manufacturers but that is a story for another day). The steps required by the motor complete one full revolution on the external shaft: The step angle stated on the datasheet is: Accordingly, for the limited purposes of this starter demonstration exercise, let us assume that there are 64 discrete positions during one full revolution of the internal shaft. Since this particular stepper motor has many counterfeit versions where quality control is non-existent, the gear ratio in the above specifications may not hold true. The number of steps required by the motor to complete one full revolution will not be the same as theoretically estimated above for motors from some suppliers.
The following table summarizes the sequence to rotate the motor: Please review the reference below on Geared Stepper Motor for the related discussion in the corresponding Arduino forum. The practical arrangement is to use an interface board as shown below: The connection using an interface board and a dedicated power supply for the stepper motor is shown below: Owing to the power requirements the motor cannot be served directly by the Arduino board. Stepper ( steps, pin1, pin2, pin3, pin4 ) There is a standard library at the Arduino site for use with servo motors – Stepper. The constructor method to instantiate an entity object from the class definition for a stepper motor. Steps – number of steps for one revolution of the external shaft of the motor
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