What is a Stepper Motor and How it Works?

What is a Stepper Motor and How it Works?


Have you ever thought about how a
robotic arm moves with precision or how graphic printers create
accurate replications of images, or how consumable products are moved
precisely around a plant floor or any other type of motion
control positioning system? With this lesson and others to follow you will learn about motion control using
different types of motors available, primarily stepper and servo motors. Before we get into today’s
video, if you love our videos, be sure to click the like button below, and make sure to click subscribe and the bell to receive notifications
of new RealPars videos. This way you never miss another one! Selecting between a servo motor and a
stepper motor can be quite a challenge with the balancing of several design
factors in cost considerations, torque, speed, acceleration,
and drive circuitry all play an important role in selecting
the best motor for your application. In this lesson we will discuss what a
stepper motor is and how it works, so let’s first determine
what a stepper motor is and examine some unique
features of a stepper motor. Stepper motors have a permanent
magnetic rotating shaft called a rotor and stationary electromagnets surrounding
the rotor called the stator. Stepper motors have typically
50 to 100 electromagnet poles (pairs of north and south poles) generated either by a permanent
magnet or an electric current. Each permanent magnet pole offers a natural
stopping point for the motor shaft. The greater number of poles
allows for a stepper motor to position itself accurately and
precisely between each of the poles. This is a convenient feature
of the stepper motor in that the poles within a stepper motor allow it to be positioned accurately
without any positional feedback, In other words it works in
an open-loop control system. The open-loop control allows for a single
electrical pulse from a controller to move the motor shaft
from one pole to the other and stop aligned with the electromagnetic pole
without positional feedback to the controller. This is one of the benefits
of the stepper motor, but additional benefits of a stepper motor
will be discussed in a separate video. When we want to increase the resolution or
achieve the smallest rotational movement, the design of the stepper will contain
a larger number of magnetic poles. Basically, the incremental
step size of a stepper motor is fixed to a certain degree of rotation
based on the number of electromagnet poles. Therefore, moving to an accurate position is simply a matter of sending the
correct number of pulse commands. Stepper motors may have
up to 200 rotor teeth, or 200-400 full steps per
revolution of the motor shaft. To determine the resolution of
rotation we can perform a little math. If a stepper motor has 200 incremental steps and we know a full rotation is equal to a circle or 360-degrees then we can
divide 360-degrees by 200. This equates to 1.8-degrees of
a full step angle rotation. 400 steps divided into 360-degrees provides
0.9-degrees of full step angle rotation. Outputting one digital pulse from the controller
driver is equivalent to one step of rotation. Now let’s follow a simple movement
diagram of a stepper motor to determine how the stepper motor
works in one complete rotation. At position 1, the rotor is started
at the top electromagnet pole, which is currently energized with
current flowing through the wire. Now in order to move the
stepper rotor clockwise (CW) the top electromagnet pole is deactivated and the right electromagnet pole is activated
causing the rotor to move 90 degrees CW and align with the active
magnet as shown in position 2. Now as we continue to deactivate and activate
the electromagnet poles around the stator in positions 3 and 4 causing the rotor to
re-align with each new electromagnet pole we enable the rotor to rotate
90 degrees CW each time, this eventually completes a
full 360-degrees of rotation. Hint: Remember how like magnetic poles
repel and unlike poles attract. Depending on whether the power source current
is applied to electromagnetic pole coil wire we can cause LIKE and
UNLIKE magnetic attraction and reattraction forcing the
permanent magnet rotor to move. In the real-world stepper motors incorporate a
larger number of electromagnet poles on the stator and rotor to increase the resolution
as we have discussed earlier. With this increase in the
number electromagnet poles the operation is basically the same as the
example provided using 90-degree rotation but now the rotation would be more like
1.8-degrees of rotation as mentioned earlier. An example of a multi-pole stepper
motor is illustrated here. In position 1 the rotor is
aligned in the upper position with the top stator electromagnetic activated
indicating S for South polarization and in position 2 the top
electromagnet stator is de-energized and the electromagnet stator to the right
is energized the rotor moves clockwise and aligns with this electromagnet
indicating the new S polarization allowing for a precise
rotational movement of degrees. This changing of the electromagnetic polarization
continues creating 360-degree rotation. The faster the electromagnetic
polarization occurs the faster the speed. This concludes the video, what is
a Stepper Motor and how it Works. I hope you have learned what’s required to move
forward in creating your own motion control project. Make sure that you head
over to realpars.com. To find even more training material
for all of your PLC Programing needs. We offer many videos to assist you
in learning PLC Programing and landing that job in a high-paying, highly thought after field of
automation and controls engineering. Go to realpars.com and subscribe to our
highly effective training series now!

28 Replies to “What is a Stepper Motor and How it Works?”

  1. Thank you so much…
    Pls increase video upload frequency…
    We are waiting for ur much needed and helpful engineering videos..

  2. Muito bom os videos aqui visto,..Depois de  adquirir o curso eu consigo visualizar o mesmo no idioma de meu pais?"Portugues"

  3. Wow, great video. Have never heard of these motors before that I can remember, though it certainly don’t mean I didn’t unknowingly ever saw one and just didn’t know. I’m sure I have. Damn great detail animation in explanation for really precise movements.

  4. What a pulse generator does in stepper motor? Why when it is disconnected, it still works? If it is not needed, why has been designed?

  5. salut merci bc pour vos cours ils sont super mais svp est ce que vous pouvez mettre des exemples de programmation plus complexe merci bien

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