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Stepper Motor Working Principle

By Admin on


Introduction

Stepper motors and RC servos are simple devices which can achieve precise position control without using feedback devices.  The purpose of this lab is to build a hardware/software system to properly sequence the windings of a stepper motor and use the motor to map an environment using a light sensor.


 Stepper motors are DC motors that move in discrete steps. 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.

With a computer controlled stepping you can achieve very precise positioning and/or speed control. For this reason, stepper motors are the motor of choice for many precision motion control applications. 

Stepper motors come in many different sizes and styles and electrical characteristics. This guide details what you need to know to pick the right motor for the job.

Wave Drive Sequence (full steps)

Step

A

B

C

D

1

ON




2


ON



3



ON


4




ON

5

ON





Two-Phase Drive Sequence (full steps)

Step

A

B

C

D

1

ON



ON

2

ON

ON



3


ON

ON


4



ON

ON

5

ON



ON


Half-Step Drive Sequence (half steps)

Step

A

B

C

D

1

ON




2

ON

ON



3


ON



4


ON

ON


5



ON


6



ON

ON

7




ON

8

ON



ON

9

ON




How it rotates



  1. The right electromagnet is energized and becomes a north pole (red) and the left electromagnet becomes a south pole (blue). This pulls the rotor around by one step so a blue tooth on the rotor snaps toward the right electromagnet and a red tooth snaps toward the left electromagnet.
  2. Now the bottom electromagnet becomes a north pole, the top magnet becomes a south pole, and the two horizontal magnets are switched off. Again, the teeth of the rotor are pulled around by one step.
  3. The vertical magnets are now switched off and the horizontal magnets are switched on again, but with the opposite polarity (pattern of magnetism) that they had before. The teeth of the rotor advance by one more step.
  4. Finally, the vertical magnets are switched on again, in the opposite polarity to before, and the horizontal magnets are switched off. The rotor mores around one more step. The whole cycle then repeats.





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