Its a motor which moves in discrete steps. After each step the motor holds itself in a position .
internally a stepper motor consists of a magnetized geared shaft that is surrounded by electro magnets controlling the current . magnets are controlled to move the shaft in steps.
there are 3 different types of design , based on the msagnetic gear created in the given shaft
* variable reluctance stepper
*permanent magnet stepper
steppers are controlled by applying current to the coils which in turn creates electromagnetism
there are 2 different coil wiring arrangments
BIPOLAR STEPPER MOTOR consiste of 2 sets of coils and has 4 wires i.e 2 wire per coil
the UNIPOLAR STEPPER MOTOR also consists of 2 coils but each coil has a center tap , therefore they have 6 conections but they have only 5 because the 2 centre taps are connected together
They have millions of applications the 3d printers and CNC machines make extensive use of stepper motor because they have to precisely position the print head or the cutting head , they are used in DVD and blue ray drive because they can precisely position the laser above the disc.
BIPOLAR STEPPER MOTOR
if we apply the current to the top coil we will notice that the rotor is attracted to that coil and locks itself into position if we then take the current off the coil and apply it to the other coil the rotor is attracted to that coil
here just reverse the polarity and then apply the current then the rotor is rotated in the counter clock wise
Apply the current to the first coil which attracts the rotor and then apply current to the 2nd coil the rotor is moved and its in half way . then remove the current off the first coil and apply current to the 2nd coil then the rotor is attracted towards the 2nd coil.
COUNTER CLOCK WISE
Here just reverse the polarity and then apply the current then the rotor moves in the opposite direction
we can do quater steps , 8 steps , 16 steps just by varing the amount of current .
UNIPOLAR STEPPER MOTOR
in unipolar stepper motor the both the center tap are connected together and is connected to positive signal.
When we apply negative voltage to the top coil the rotor will be attracted to that coil . And if we take the votage of the top coil the rotor is attracted to the negative coil .
FULLSTEP COUNTER CLOCKWISE
we simply apply the current to the other terminal of the coil then the rotor is rotated in counter clock wise