The number of groups is chosen by the designer of the stepper motor. The circular arrangement of electromagnets is divided into groups, each group called a phase, and there is an equal number of electromagnets per group. In that way, the motor can be turned by a precise angle.
Each of those rotations is called a "step", with an integer number of steps making a full rotation. This means that when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one. When the gear's teeth are aligned to the first electromagnet, they are slightly offset from the next electromagnet. To make the motor shaft turn, first, one electromagnet is given power, which magnetically attracts the gear's teeth.
The electromagnets are energized by an external driver circuit or a micro controller. Stepper motors effectively have multiple "toothed" electromagnets arranged as a stator around a central rotor, a gear-shaped piece of iron. Each pulse rotates the shaft through a fixed angle.
The stepper motor is known for its property of converting a train of input pulses (typically square waves) into a precisely defined increment in the shaft’s rotational position. Switched reluctance motors are very large stepping motors with a reduced pole count, and generally are closed-loop commutated.īrushed DC motors rotate continuously when DC voltage is applied to their terminals.
The motor's position can be commanded to move and hold at one of these steps without any position sensor for feedback (an open-loop controller), as long as the motor is correctly sized to the application in respect to torque and speed. When the top electromagnet (1) is again enabled, the rotor will have rotated by one tooth position since there are 25 teeth, it will take 100 steps to make a full rotation in this example.Ī stepper motor, also known as step motor or stepping motor, is a brushless DC electric motor that divides a full rotation into a number of equal steps. This results in a rotation of 3.6° in this example.įrame 3: The bottom electromagnet (3) is energized another 3.6° rotation occurs.įrame 4: The left electromagnet (4) is energized, rotating again by 3.6°. With the teeth aligned to electromagnet 1, they will be slightly offset from right electromagnet (2).įrame 2: The top electromagnet (1) is turned off, and the right electromagnet (2) is energized, pulling the teeth into alignment with it. Animation of a simplified stepper motor (unipolar)įrame 1: The top electromagnet (1) is turned on, attracting the nearest teeth of the gear-shaped iron rotor.