1. Interfacing circuit of Unipolar Stepper with 8051
Guided By:
Prepared By:
Pro. Rashmi K. Patel
Pro. Milind B. Trivedi
Brijesh Patel
Viresh Dadia
Fazal Ghanchi Vahora
Abhishek Gheewala
Jaimin Patel
C.K.PITHAWALLA COLLEGE OF ENGINEERING & TECHNOLOGY.-SURAT

2. Unipolar stepper Motor

3. A Stepper Motor is a brushless, synchronous DC Motor.
It has many applications in the field of robotics and mechatronics.
The total rotation of the motor is divided into steps. The angle of a single step is known as the stepper angle of the motor.
As usual stepper motors works on the principle of electromagnetic induction.
A unipolar motor contains centre tapped  windings. By using this arrangement a magnetic poles can be reversed without reversing the direction of current. Thus the commutation circuit can be made very simple.
Firstly one stator electromagnet is energised, this makes rotor teeth magnetically attracted to electromagnet’s teeth. When the rotor teeth gets align with first electromagnet, it gets misaligns with next electromagnet. So when the next electromagnet is turned on and the first one is turned off, the rotor rotates to align with the next one. This process is repeated to get the required rotation.

4. Driving Unipolar Stepper Motor with 8051
Unipolar stepper motors can be used in three modes
Wave Drive mode
Full Drive mode
Half Drive mode
Each drive have its own advantages and disadvantages, thus we should choose the required drive according to the application and power consumption.

5. Wave drive Mode
In this mode only one electromagnet is energized at a time.
Generated torque will be less when compared to full drive in which two electromagnets are energized at a time but power consumption is reduced.
It has same number of steps as in the full drive.
This drive is preferred when power consumption is more important than torque. It is rarely used.
Step A B C D 1 2 3 4

6. Full drive In this mode two electromagnets are energized at a time,
so the torque generated will be larger when compared to Wave Drive.
This drive is commonly used than others.
Power consumption will be higher than other modes.
Step A B C D 1 2 3 4

7. Half drive
In this mode alternatively one and two electromagnets are energized.
So it is a combination of Wave and Full drives.
This mode is commonly used to increase the angular resolution of the motor but the torque will be less, about 70% at its half step position.
We can see that the angular resolution doubles when using Half Drive.
Step A B C D 1 2 3 4 5 6 7 8

8. Interfacing Motor
To run and control of any motor with the use of microcontroller motor drivers are used.
A motor driver is an integrated circuit chip which is usually used to control motors in autonomous robots.
Motor driver ICs act as an interface between microprocessors in robots and the motors in the robot.
We used L293D driver IC to run the unipolar stepper motor.

9. Interfacing motor with driver ics

10. Interfacing stepper with 8051

11. Programming
#include <REG51.H> #define stepper P1 void delay() { unsigned char i,j,k; for(i=0;i<6;i++) for(j=0;j<255;j++) for(k=0;k<255;k++); }
void main() {
while (1)
stepper = 0x0C;
delay();
stepper = 0x06;
stepper = 0x03;
stepper = 0x09; }