Stepper motor - How does it work?

Stepper motor is as the name implies, it's rotate distinct steps during its rotation and we can get precise excel rotation at every step. They have multiple coils that are organized in groups called "phases". By energizing each phase in sequence, the motor will rotate, one step at a time.

Stepper motors widely use in various applications, you can find in your printer, scanner and copier. Stepper motors are also used in automotive applications for electronic throttle control, stepper motors are also found in industrial equipment such as robotics, electronic component handlers, testers, dispensers, and other manufacturing equipment.

Structure of stepper motor :-

         

A stepper motor has some basic components. First, we have a soft iron stator. Each stator will be wrapped with multiple windings or phases that will be energized using a voltage source, initiating current flow through the winding to produce a polarity on each end or pole of the stator. The rotor is the actual rotating component on the motor. This can either be magnetized, as shown here, or non-magnetized depending on the type of motor you select.

Each motor defined by a step angle, like many motors comes as 90 degree angle rotation at single pulse, some others comes 1.8 degree at single pulse and many types.

Stepper motor can be control by microprocessor and get precision output. In the embedded applications a microcontroller can also control stepper motor and capable to provide high performance controlling. We can say stepper motor is a digital motor. A most important benefit to use the stepper motor is that we can use it without feedback loop. We only need to consider step pulse and get accurate motor position.

For a example motor is 1.8 degree step and we give 2000 pulse signal :-

One round = 360 degree

Pulse required for one round  =  360 / 1.8  =  200

2000 pulse  =  2000 / 200  =  10 round

Switching sequence

The stepper motor can be operated in three different stepping modes, namely, full-step, half-step, and microstep. Now we will discuss only full-step mode. To rotate the motor rotor, voltage is applied to each phase sequentially.

When we switch on Q1, current is applied to A and A' windings. Stator Winding becomes magnetize and one winding part become North Pole and second become south pole. This means that the rotor will only need to rotate 1.8° in the clockwise position. Suchlike "A" windings all of other windings work.

Normal DC motors don't have very much torque at low speeds. A Stepper motor has maximum torque at low speeds, so they are a good choice for applications requiring low speed with high precision.