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Motors

Stepper Motor

Stepper motor one of the most accurate electric motors it can precisely control the position to suit engineering applications that need position control Stepper motor used in 3D printers, lathes, computer numerical control (CNC) milling machine and embedded Systems. This motor is a kind of Brushless DC Motor so no brushes this motor can provide applications with high torque But distinguishes this motor from other motors is the ability to control the torque for each position called by step position control is easy to control using any type of electronic controller.

Stepper Motor Components

To understand the installation of Stepper motors and how they work, let us disassemble one. This type of motor is found in industry fields.

  • Bearings – Ring to less friction for the axle.
  • Windings – Converts electricity to a magnetic field that rotates the axle.
  • Axle – Transfers the motion rotation of the motor to the applications.
  • Contacts – Brings power from the power source to Windings.
  • Poles – Increase motor accuracy.
  • Magnets – magnetic field for the windings to stable motion ( attract and repel).

Work theory

The Stepper motor is different from a Brushless DC Motor in step size is smaller. the direction of current flow control polarity for each winding. ِAC current changes the polarity, that giving each winding a push and pull. The mini controller (Driver) is used to guide the magnetic poles correctly.

The stepper motor can contain many coils which means more precision and control, The following picture shows how the Stepper Motor is connected with driver:


Stepper Motor Specifications

The choice of stepper motor is different from the choice of other motors such as brushless DC motor but a bit like a servo motor. In our stepper motor, we focus on torque and number of rpm. Generally, these are the characteristics that should be considered when choosing a stepper motor:

  1. Rated voltage: Your driver must be able to provide the required voltage for the engine to rotate properly and to give the correct torque and RPM. It is possible to find stepper motors running on only 5 volts.
  2. Number of phases or coils: One of the most important differences between stepper motors is the number of coils used to drive the rotor.
  3. Speed variation ratio (SVR): This ratio refers to the rotation of the outer rotor one rev to the number of internal revelations The reason for this difference is the presence of a gearbox that increases the torque value.
  4. Stride Angle: Number of steps to complete one full rotation.
  5. Torque: Motor torque varies depending on the gearbox ratio and motor voltage.

Let’s select a stepper motor, for example, taking the model 2028BYJ-48 download Datasheet and you will notice a lot of details, the most important of which is the following table:

PropertyValue
Rated voltage5 V-DC
Number of phase4
Speed variation ratio (SVR)1/64 or 1:64
Stride Angle5.625°/64
In-traction Torque>34.3 mN.m (120Hz)
Noise (in dB)<35 dB (120Hz, No load, 10 cm)

Stepper Motor Driver

In fact, we cannot connect the stepper motor directly to an electronic controller such as the Arduino. An electronic circuit should be used to control the reflected pulses called by Driver. There are two types of driving circuits:

  • full-half step.
  • Micro Step.

Some of the types of drivers we can use to control the stepper motor:


Advantages and Disadvantages

Advantages:

  • High position accuracy. 
  • High holding torque.
  • You can control everything in this motor.
  • Long operating life.
  • The angle of rotation is proportional to the input pulses.
  • Excellent response to start, stop and reverse.
  • It is possible to achieve a very low rotational speed in conjunction with the load directly associated with the shaft.

Disdvantages:

  • Heavy weight.
  • It requires good knowledge in its own mini controller (Driver).
  • Expensive.
  • It can not be used at high speeds (RPM).
  • Consume current when not moving.
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