What is a stepper motor?

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15 Apr. 2020

A stepper motor (also called a stepper motor) is one that rotates in an intermittent manner, moving by a fixed angle at each step rather than continuously rotating its shaft.

The movement of the second hand on a clock, for example, which advances one second at a time, could be achieved by using a stepper motor that moves in 6°increments, once every second.

So, how does a stepper motor achieve this characteristic of rotating its shaft by a fixed angle at each step?

The secret lies in the use of electrical pulses. A pulse is an electrical signal produced by turning a power supply on and off, with each such switching counting as one pulse. A stepper motor uses these pulses to achieve precise mechanical control over the angle and speed of rotation.

Types of stepper motors [1] (classified by rotor structure)

stepper motors can be broadly grouped into the following three categories depending on the structure of their rotor.

Permanent magnet (PM) motor
The rotor contains a permanent magnet. A disadvantage of this structure is that it can not provide flexibility over the angle of rotation (step angle).
Variable reluctance (VR) motor
The rotor contains cores structured like the teeth of a gear. This allows for more flexibility in setting the step angle.
Hybrid (HB) motor
The rotor contains both permanent magnets and cores structured like the teeth of a gear. This type of motor is used in a wide variety of applications, combining the advantages of PM and VR motors. All of the stepper motors developed and manufactured by ASPINA are HB motors.

Operation principle of HB stepper motors

The rotor is designed with a cylindrical permanent magnet positioned between two cores, these being concentric to the motor shaft and offset by a half pitch from each other. The rotor rotates by a fixed step angle each time a pulse is input. As a two-phase HB stepper motor with a 1.8°step angle rotates by 1.8°for each pulse, it takes 360°/1.8°= 200 pulses to make one full rotation.

Types of stepper motors [2] (classified by current flow in coil)

stepper motors can also be grouped into the following two categories based on electric current flow in the coil.

Unipolar motor

Current in a unipolar motor always flow through the coil windings in the same direction. While this keeps the associated control circuit simple, it produces less torque than a bipolar motor.

Bipolar motor

Current in a bipolar motor can flow through the coil windings in either direction. While this requires a more complex control circuit than a unipolar motor, it produces more torque.

What is a stepper motor driver?

stepper motors are used in conjunction with a driver circuit. The driver controls the angle and speed of motor rotation based on the input of electrical pulses from the controller.

Programmable controller to Controller to(Pulses) Driver to(Current flow) stepper motor stepper motor unit(Driver stepper motor)

Two-phase HB stepper motor driver

Features of stepper motors

stepper motors differ from other motor types in the following ways.

Advantages
  • As the angle of rotation is determined by the number of pulses (digital input), control of position (angle of rotation) is simple
  • Can rotate at low speeds
  • Can use open-loop (non-feedback) position control
  • Excellent ability to remain locked in position when halted
Disadvantages
  • Requires a drive circuit
  • Loss of synchronization can occur due to factors such as unexpected changes in load
  • High level of vibration and noise

Applications for stepper motors

The excellent halting accuracy, high torque at medium and low speeds, and superior responsiveness of stepper motors means that they can be used in a wide range of drive applications that demand precise control.

  • Production machinery
  • Medical equipment
  • Analytical instruments
  • ATMs
  • Vending machines
  • Ticket vending machines
  • Copiers
  • Robots
  • Optical disk drives (Blu-ray and DVD drives, etc.)
  • Laser printers
  • Digital cameras
  • Air conditioning louvers
  • Amusement machines

Overcoming your problems with brushless DC motors

ASPINA supplies not only standalone stepper motors, but also system products that incorporate drive and control systems as well as mechanical design. These are backed by comprehensive support that extends from prototyping to commercial production and after-sales service.
ASPINA can offer solutions that are tailored to suit the functions and performance demanded by a diverse range of industries, applications, and customer products, as well as your particular production arrangements.

ASPINA supports not only customers who already know their requirements or specifications, but also those who are facing problems at early stages of development.
Do you struggle with the following concerns?

Motor selection
  • Don't have detailed specifications or design drawings yet, but need advice on motors?
  • Don't have anyone in-house with expertise in motors and can't identify what sort of motor will work best for your new product?
Motor and associated component development
  • Want to focus your resources on core technology, and outsource drive systems and motor development?
  • Want to save the time and effort of redesigning existing mechanical components when replacing your motor?
Unique requirement
  • Need a custom motor for your product, but been declined from your usual vendor?
  • Can't find a motor that gives you the control you require, and about to give up hope?

Seeking answers to these problems? Contact ASPINA, we’re here to help.

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