Sunday, 22 February 2015

Basics of stepper motor

Basics of stepper motor
A stepper motor is a widely used device that converts electrical pulses to equivalent mechanical movement with high accuracy.
A stepper motor is widely used in disk drivers ,dot matrix printers , robotics and many other automatic applications.
Stepper motor has a permanent magnet rotor that is also called shaft. The most common stepper motor has four stator winding and they are paired with a center-tapped common.
These types of motors are generally called “four phase stepper motor”.  Centre tap needs to change the direction of current flow in each two coils when a winding is grounded. This change in direction in current in stator coil changes the polarity of electromagnetic stator. It helps to control the direction of movement of shaft. 

A conventional motor runs freely, but in stepper motor the shaft moves in a fixed repeatable increment which allows one to move it to a precise position. This repeatable fixed movement is possible by using basic electromagnetic theory. same polarity repel and opposite poles attract. This direction of the rotation is dictated by the stator poles. 

Resolution of a stepper motor- resolution of a stepper motor describes how perfectly the motor can move it’s shaft at a predefined angle. For demonstration purpose we show four stator winding. But practically a good stepper motor has much more number of field winding. Increase in number of field winding increases the resolution of a stepper motor. for example , if a stepper motor having resolution of 5 degree, that means motor shaft moves 5 degree for each pulse. For one full rotati
on of 360 degree 72 pulses needed.
Types of stepper motor
Variable reluctance stepper motor (It has a wound rotor and a stator made of ferromagnetic material. Direction of motor rotation is independent of stator current. Reluctance of the magnetic circuit formed by the stator and rotor varies with the angular position of the rotor. So it is called variable reluctance stepper motor)
Permanent magnet stepper motor(it’s stator is wounded and the rotor is permanent magnet. It has a cylindrical rotor. The direction of the rotor depends on the direction of the stator current)
Hybrid stepper motor ( it has wound stator and permanent magnet rotor. It is best suitable for small step angles like 1.8 degree)
Controlling movement of stepper motor- to control movement of stepper motor microcontroller is mainly used.

 We will use arduino to control the stepper motor in next projects.
Thank you for reading.
Post written by Abhijit Maity