The document discusses driving a stepper motor using an 8051 microcontroller. It describes the objectives which are to learn about stepper motors, how to wire one, and interface it with an 8051. It explains that a ULN2003 chip is needed to provide sufficient current from the microcontroller pins to drive the motor. The document outlines how to determine the winding configuration, provides examples of full and half step sequences to rotate the motor clockwise and counterclockwise, and presents the algorithm to implement full stepping. It also discusses step angle and speed control.

1. DRIVING STEPPER MOTOR USING 8051

2. Objectives of the Lab
 The Applications of Stepper Motor
 Learning how to find the wiring combination of stepper motor
 Learning how to run stepper motor CW or CCW
 About ULN2003 chip
 Interfacing stepper motor with 8051

3. Deciding Pins or Ports to use
Use with
caution
If EA high
*Only 4 pins of
controller are
required. As this
is an output process
we may use any
port. We will use P2.

4. Applications of Stepper Motor
 Motors are majorly used for
driving mechanical assemblies
using electronic signals.
 Due to the working
mechanism of stepper motor, it
has many applications utilizing
position control, angle control,
precise movement and open
loop control.
 It is used in robotic limbs,
conveyer belts, hard disk
drives e.t.c.

5. Theory of Operation
 This is best explained using figures.

6. Wiring of Stepper Motor
 We can find stepper motor configuration
by first finding the common pins.
 See the entities where R is there, the pin
that is common will be ‘common’.
 Now, we give 12V to the common pins,
and give one by one ground on other pins.
12 13 14 15 16 23 24 25 26
R 2R OL OL OL R OL OL OL
34 35 36 45 46 56
OL OL OL R 2R R

7. Wiring of Stepper Motor (contd.)
 When we give ground on one-pin, the
stepper motor makes a step to either CW
or CCW.
 We need to give ground one-by-one to the
pins and adjust them in the sequence such
as when ground one-by-one is given to the
pins, the motor should move CW or CCW.
 Remember this combination and mark the
pins as ABCD.
 Now, we see that when we give ABCD
0111, 1011, 1101 & 1110, the motor
moves CW or CCW.

8. Stepper Motor combinations
A B C D
0 1 1 1
1 0 1 1
1 1 0 1
1 1 1 0
Alternate Combination
1 1 0 0
0 1 1 0
0 0 1 1
1 0 0 1
If motor is running in CW using above combination just reverse the combination to run in CCW.

9. Need of ULN2003A
 The ‘current’ requirement for stepper
motor can not be provided by µC pins.
 Thus a current amplifier is required.
 One problem arises, i.e. we need ‘0’ to
turn on the coil without current amplifier.
 But when we insert an amplifier, we need
to give ‘1’ to turn on coil.
 Thus the combination given on previous
slide will be reversed. i.e. ‘0’ to ‘1’ and ‘1’
to ‘0’.

10. ULN2003A configuration
Free-wheeling diodes

11. Step angle and speed of motor
 Step angle when in control can give
position and precision control in
applications.
 For a 360 degree, the steps that motor
takes are mentioned on the motor.
 e.g. If a stepper motor takes 200 steps for
360 degree, then 1 step will move
360/200=1.8 degrees. Thus to move let’s
say 30 degrees we need 30/1.8=16.67
steps.
 Speed of motor is controlled by the delay
given between the change of combination.

12. Phase(Coil) Current Waveforms
Less Torque than
full step drive
1 step angle=360/200
1/2 step angle=360/(2*200)

13. Full Step with ULN2003A
A B C D
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
Alternate Combination
0 0 1 1
1 0 0 1
1 1 0 0
0 1 1 0
If motor is running in CW using above combination just reverse the combination to run in CCW.

14. Half Step with ULN2003A
A B C D
0 0 0 1
1 0 0 1
1 0 0 0
1 1 0 0
0 1 0 0
0 1 1 0
0 0 1 0
0 0 1 1
If motor is running in CW using above combination just reverse the combination to run in CCW.

15. Algorithm for Full Step
Start
Send seq to
output
Store in A
Next Sequence
Call Delay
mov a,#66h;01100110b
mov p2,a
rr a
call delay

16. Proteus Devices needed in this Lab
1. AT89c51
2. ULN2003A
3. Stepper Motor

17. Lab Tasks
 Run Stepper Motor using 8051.