 |
| 8051 Interfacing with stepper motor |
-------------------------------
; 4 PINS OF STEPPER MOTOR CONTROLLED BY 4 BITS OF 8051 P1.0 - P1.3
; IT IS INTERFACED USING DARLINGTON ARRAYS SUCH AS ULN2003 AS
; 8051 LACKS CURRENT TO RUN THE MOTOR. SO ULN2003 IS USED FOR ENERGIZING STATOR.
; PROGRAM BELOW SHOWS JUST ROTATING THE MOTOR STEP WISE
; BUT STEP WIDTH IS UNKNOWN
MOV A, #66H ; LOAD THE STEP SEQUENCE
BACK :
MOV P1, A ; LOAD SEQUENCE TO PORT
RR A ; CHANGE SEQUENCE ROTATE CLOCKWISE
ACALL DELAY : WAIT FOR IT
SJMP BACK ; NOW KEEP GOING
DELAY :
MOV R2, #100
H1 :
MOV R3, #255
H2 :
DJNZ R3, H2
DJNZ R2, H1
RET
END
; THIS OTHER PROGRAM CODE HOW IN SAME INTERFACING TO ROTATE A STEPPER MOTOR
; 64 DEGREES IN CLOCKWISE DIRECTION USING 4 STEP SEQUENCE
; IT TAKES SOME CALCULATIONS
; CONSIDER A MOTOR WITH STEP ANGLE 2 DEGREE
; SO STEPS PER REVOLUTION = 180
; NO OF ROTOR TEETH = 45
; MOVEMENT PER 4 STEP SEQUENCE IS 8 DEGREES
; FOR 64 DEGREE MOVEMENT WE NEED TO SEND 8 CONSECUTIVE 4 STEP SEQUENCE
; THAT IS IT WILL COVER 32 STEPS
ORG 0000H
MOV A, #66H
MOV R1, #32H ; 32 STEPS TO BE TAKEN
BACK :
RR A ; ROTATE CLOCKWISE
MOV P1, A ;
ACALL DELAY ;
DJNZ R1, BACK ;
END
-----------------
Now few question arises
q1) why did we took 66h as step value??
Ans))
A normal 4 step sequence is like below.
Step #
|
Winding A
|
Winding B
|
Winding C
|
Winding D
|
1
|
1
|
0
|
0
|
1
|
2
|
1
|
1
|
0
|
0
|
3
|
0
|
1
|
1
|
0
|
4
|
0
|
0
|
1
|
1
|
Going from step 1 to 4 we rotate motor clockwise
Going from step 4 to 1 we rotate motor counter clockwise
The stepper motor discussed here has total 6 leads. 4 leads
representing 4 windings and 2 commons for centre tapped leads. Here we have
used 2 phase 4 step sequence. It must also be noted we can start from any
step. Be it step 1,2,3 or 4. But we must
continue in proper order for proper rotation.
In programs on blog I have mostly begun from
step 3.
other step sequences are as below
Half Step 8 Step Sequence
Step #
|
Winding A
|
Winding B
|
Winding C
|
Winding D
|
1
|
1
|
0
|
0
|
1
|
2
|
1
|
0
|
0
|
0
|
3
|
1
|
1
|
0
|
0
|
4
|
0
|
1
|
0
|
0
|
5
|
0
|
1
|
1
|
0
|
6
|
0
|
0
|
1
|
0
|
7
|
0
|
0
|
1
|
1
|
8
|
0
|
0
|
0
|
1
|
Wave drive 4 step sequence
Step #
|
Winding A
|
Winding B
|
Winding C
|
Winding D
|
1
|
1
|
0
|
0
|
0
|
2
|
0
|
1
|
0
|
0
|
3
|
0
|
0
|
1
|
0
|
4
|
0
|
0
|
0
|
1
|
q2) how much movement is associated with a step angle??
Step angle
|
Steps per revolution
|
.72
|
500
|
1.8
|
200
|
2
|
180
|
2.5
|
144
|
5
|
72
|
7.5
|
48
|
15
|
24
|
------------------
Edit - 1: Changed the Line DJNZ R0 to R1 as it was a mistake in typing.