PROJECT PAPER

Course no: EEE 4620

PROJECT: STEPPER MOTOR INTERFACING WITH SPECIFIC ANGLE

ENTERED THROUGH KEYPAD

Group No: 3

Student Id of the Group Member:

112419

112423

112426

112416

112414

112308

OBJECTIVE:

The objective of this project is to acquainted with the controlling of stepper motor via keypad. Whatever

we give input by keypad, stepper motor will rotate according to that given. We rotate the stepper motor

for some specific angle. Here in our project specific angle: 45o, 90o, 135o, 180o, 225o, 270o, 315o .

THEORY:

AT89S52:

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.

Stepper motor:

Stepper motor is a brushless DC motor which position can be changed in discrete step. There are 3 kinds

of stepper motor. They are:

i) Unipolar ii) Bipolar iii) Universal

In this project we use unipolar stepper (2 phase). There are four coils in the motor.it has one winding

center tape per phase. These common wire often ganged together which makes it 5 or 6 wires motor.

The common wire should be connected to the supply. In other 4 wires we give instruction bit to rotate

the stepper motor. These instruction bit is taken from microprocessor, send it to motor driver whose

output is connected to the stepper motor. When we give high to the microcontroller pin it becomes low

through ULN2803A driver. This low bit grounded the coil of stepper motor. Then the north pole of rotor

directed to the coil which is grounded.

ULN2803A:

ULN2803A is basically a motor control driver. Since the 8051 lacks sufficient current to drive the stepper

motor windings, a driver such as ULN2803 or ULN 2003 must be used to energize the stator. It is a 18 pin

IC. There are 8 input pin and corresponding 8 output pin. One ground and one common pin. The

common pin connected to all input pin through a diode. Common pin should be connected to VCC.

Instead of using ULN2803A we could have used transistors as drivers. But the problem is that if

transistors are used as drivers, external diodes must be used to take care of the inductive current

generated when the coil is turned off. In this regard using ULN2803A motor control driver is more

preferable since it has an internal diode to take care of back EMF.

Fig: Pin configuration of ULN2803A

Say if we give high to pin 1 and pin2 of ULN2803A then it gives low bit to coil X and Coil Y will be

grounded. Then the resultant magnetic force will be 450 between coil X and Y. In this way the rotor of

the stepper motor can be rotate. Now to rotate the motor the stride angle of the motor should be

known.

Fig: Rotation of the rotor due to instruction bit supplied it via ULN2803A

Keyboard:

To give input to stepper motor we use keypad. Keyboards are organized in a matrix of rows and

columns. The CPU accesses both rows and columns through ports. When a key is pressed, a row

and a column make a contact. Otherwise, there is no connection between rows and columns.

The rows are connected to an output port and the columns are connected to an input port. The

microcontroller scans the keyboard continuously to detect and identify the key pressed. To

detect a pressed key, the microcontroller grounds all rows by providing 0 to the output latch

then it reads the columns.

Fig: Keypad Configuration

If the data read from columns is D3 –D0 = 1111, no key has been pressed and the process continues till

key press is detected. If one of the column bits has a zero, this means that a key press has occurred.

After detecting a key press, microcontroller will go through the process of identifying the key. Starting

with the top row, the microcontroller grounds it by providing a low to row D0 only. It reads the columns,

if the data read is all 1s, no key in that row is activated and the process is moved to the next row. It

grounds the next row, reads the columns, and checks for any zero. This process continues until the row

is identified. After identification of the row in which the key has been pressed, it finds out which column

the pressed key belongs to.

Circuit Diagram:

Fig: Circuit Diagram

Program Algorithm:

No

Yes

No

Yes

yes No

Start

Set Counter

Set Memory

Location

Input=

Enter?

Save the input in

memory location

Increase Memory

Location

Decrease Counter

Convert ASCII input

to HEX

HEX

number

=specific

angle?

Set

Counter

Give instruction

bit to motor

Decrease

Counter

Counter

=0?

Stop

Assembly program:

ORG 00H MOV SP,#70H MOV PSW,#00H MOV R1,#60H ;save the ASCII value from keypad to memory location MOV R7,#4 ;number of input can be given from keypad to rotate in a specific angle ; program to take input from the keypad MOV P2,#0FFH K1: MOV P0,#0 MOV A,P2 ANL A,#00001111B CJNE A,#00001111B,K1 K2: ACALL DELAY MOV A,P2 ANL A,#00001111B CJNE A,#00001111B,OVER SJMP K2 OVER: ACALL DELAY MOV A,P2 ANL A,#00001111B CJNE A,#00001111B,OVER1 SJMP K2 OVER1:MOV P0,#11111110B MOV A,P2 ANL A,#00001111B CJNE A,#00001111B,ROW_0 MOV P0,#11111101B MOV A,P2 ANL A,#00001111B CJNE A,#00001111B,ROW_1 MOV P0,#11111011B MOV A,P2 ANL A,#00001111B CJNE A,#00001111B,ROW_2 MOV P0,#11110111B MOV A,P2 ANL A,#00001111B CJNE A,#00001111B,ROW_3 LJMP K2 ROW_0:MOV DPTR,#KCODE0 SJMP FIND ROW_1:MOV DPTR,#KCODE1 SJMP FIND ROW_2:MOV DPTR,#KCODE2 SJMP FIND ROW_3:MOV DPTR,#KCODE3 SJMP FIND

FIND: RRC A JNC MATCH INC DPTR SJMP FIND MATCH:CLR A MOVC A,@A+DPTR LJMP NXT1 NXT1: CJNE A,#01000100B,VALUIN ;if the given input is not ENTER (D button) then go to VALUIN label to store the input SJMP NXT ; if then jump to NXT label to convert the given input from ASCII to HEX VALUIN: MOV @R1,A ; store the given input to the memory location INC R1 ; increasing R1 to point next memory location DJNZ R7,NXT3 NXT3: LJMP K1 NXT: MOV R1,#60H ;to take input from keypad to rotate the motor until power supply is turn off MOV R7,#4 MOV A,61H ;take the 2nd input to A register ANL A,#00001111B ;make upper nibble zero SWAP A ;swap the value in A register MOV B,62H ;take the 3rd input to B register ANL B,#00001111B ;make upper nibble zero ORL A,B ; convert ASCII to HEX CMDEG: CJNE A,#01000101B,DIS ;check if the input is 45 DEG.if not then go to DIS label MOV R5,#72 ;number of loop to rotate motor 45 deg. HERE: ;give 8 step instructions to the motor through ULN2803A driver MOV A,#00001001B MOV P1,A ACALL DELAY MOV A,#00001000B MOV P1,A ACALL DELAY MOV A,#00001100B MOV P1,A ACALL DELAY MOV A,#00000100B MOV P1,A ACALL DELAY MOV A,#00000110B MOV P1,A ACALL DELAY MOV A,#00000010B MOV P1,A

ACALL DELAY MOV A,#00000011B MOV P1,A ACALL DELAY MOV A,#00000001B MOV P1,A ACALL DELAY LCALL DELAY DJNZ R5,HERE ; until the value of R5 is zero go to HERE label LJMP NXT3 ; then go to NXT3 to take input again from keypad DIS: CJNE A,#10000000B,DIS1 ;check if the input is 180 DEG.if not then go to DIS1 label ;number of loop to rotate motor 180 deg. MOV R6,#4 HERE1_1: MOV R5,#67 HERE1: ;give 8 step instructions to the motor through ULN2803A driver MOV A,#00001001B MOV P1,A ACALL DELAY MOV A,#00001000B MOV P1,A ACALL DELAY MOV A,#00001100B MOV P1,A ACALL DELAY MOV A,#00000100B MOV P1,A ACALL DELAY MOV A,#00000110B MOV P1,A ACALL DELAY MOV A,#00000010B MOV P1,A ACALL DELAY MOV A,#00000011B MOV P1,A ACALL DELAY MOV A,#00000001B MOV P1,A ACALL DELAY LCALL DELAY DJNZ R5,HERE1 ;until the value of R5 is zero go to HERE1 label DJNZ R6,HERE1_1 ;until the value of R6 is zero go to HERE1_1 label LJMP NXT3 ; go to NXT3 label to take again input from keypad DIS1: CJNE A,#10010000B,DIS2 ; check if the input is 90 DEG.if not then go to DIS2 label ; number of loop to rotate motor 90 deg. MOV R6,#2 HERE2_1: MOV R5,#67

HERE2: ; give 8 step instructions to the motor through ULN2803A driver MOV A,#00001001B MOV P1,A ACALL DELAY MOV A,#00001000B MOV P1,A ACALL DELAY MOV A,#00001100B MOV P1,A ACALL DELAY MOV A,#00000100B MOV P1,A ACALL DELAY MOV A,#00000110B MOV P1,A ACALL DELAY MOV A,#00000010B MOV P1,A ACALL DELAY MOV A,#00000011B MOV P1,A ACALL DELAY MOV A,#00000001B MOV P1,A ACALL DELAY LCALL DELAY DJNZ R5,HERE2 ;until the value of R5 is zero go to HERE2 label DJNZ R6,HERE2_1 ;until the value of R6 is zero go to HERE2_1 label LJMP NXT3 ; go to NXT3 label to take again input from keypad DIS2: CJNE A,#00010101B,DIS3 ;check if the input is 315 DEG.if not then go to DIS3 label ;number of loop to rotate motor 315 deg. MOV R6,#7 HERE3_1: MOV R5,#67 HERE3: ; give 8 step instructions to the motor through ULN2803A driver MOV A,#00001001B MOV P1,A ACALL DELAY MOV A,#00001000B MOV P1,A ACALL DELAY MOV A,#00001100B MOV P1,A ACALL DELAY MOV A,#00000100B MOV P1,A ACALL DELAY MOV A,#00000110B

MOV P1,A ACALL DELAY MOV A,#00000010B MOV P1,A ACALL DELAY MOV A,#00000011B MOV P1,A ACALL DELAY MOV A,#00000001B MOV P1,A ACALL DELAY LCALL DELAY DJNZ R5,HERE3 ;until the value of R5 is zero go to HERE3 label DJNZ R6,HERE3_1 ;until the value R6 is zero go to HERE3_1 label LJMP NXT3 ; go to NXT3 label to take again input from keypad DIS3: CJNE A,#01110000B,DIS4 ;check if the input is 270 DEG.if not then go to DIS4 label ;number of loop to rotate motor 270 deg. MOV R6,#6 HERE4_1: MOV R5,#67 HERE4: ; give 8 step instructions to the motor through ULN2803A driver MOV A,#00001001B MOV P1,A ACALL DELAY MOV A,#00001000B MOV P1,A ACALL DELAY MOV A,#00001100B MOV P1,A ACALL DELAY MOV A,#00000100B MOV P1,A ACALL DELAY MOV A,#00000110B MOV P1,A ACALL DELAY MOV A,#00000010B MOV P1,A ACALL DELAY MOV A,#00000011B MOV P1,A ACALL DELAY MOV A,#00000001B MOV P1,A ACALL DELAY LCALL DELAY DJNZ R5,HERE4 ;until the value of R5 is zero go to HERE4 label DJNZ R6,HERE4_1 ;until the value R6 is zero go to HERE4_1 label

LJMP NXT3 ; go to NXT3 label to take again input from keypad DIS4: CJNE A,#00100101B,DIS5 ;check if the input is 225 DEG.if not then go to DIS5 label ;number of loop to rotate motor 225 deg. MOV R6,#5 HERE5_1: MOV R5,#67 HERE5: ; give 8 step instructions to the motor through ULN2803A driver MOV A,#00001001B MOV P1,A ACALL DELAY MOV A,#00001000B MOV P1,A ACALL DELAY MOV A,#00001100B MOV P1,A ACALL DELAY MOV A,#00000100B MOV P1,A ACALL DELAY MOV A,#00000110B MOV P1,A ACALL DELAY MOV A,#00000010B MOV P1,A ACALL DELAY MOV A,#00000011B MOV P1,A ACALL DELAY MOV A,#00000001B MOV P1,A ACALL DELAY LCALL DELAY DJNZ R5,HERE5 ;until the value of R5 is zero go to HERE5 label DJNZ R6,HERE5_1 ;until the value R6 is zero go to HERE5_1 label LJMP NXT3 ; go to NXT3 label to take again input from keypad NXT3: LJMP K1 DIS5: CJNE A,#00110101B,NXT4 ;check if the input is 135 DEG.if not then go to DIS5 label ;number of loop to rotate motor 135 deg. MOV R6,#3 HERE6_1: MOV R5,#67 HERE6: ;give 8 step instructions to the motor through ULN2803A driver MOV A,#00001001B MOV P1,A ACALL DELAY MOV A,#00001000B MOV P1,A

ACALL DELAY MOV A,#00001100B MOV P1,A ACALL DELAY MOV A,#00000100B MOV P1,A ACALL DELAY MOV A,#00000110B MOV P1,A ACALL DELAY MOV A,#00000010B MOV P1,A ACALL DELAY MOV A,#00000011B MOV P1,A ACALL DELAY MOV A,#00000001B MOV P1,A ACALL DELAY LCALL DELAY DJNZ R5,HERE6 ;until the value of R5 is zero go to HERE6 label DJNZ R6,HERE6_1 ;until the value R6 is zero go to HERE6_1 label LJMP NXT3 ;go to NXT3 label to take again input from keypad ;delay sub routine DELAY: MOV R3, #10 AGAIN_2: MOV R4, #50 AGAIN: DJNZ R4, AGAIN DJNZ R3, AGAIN_2 RET ORG 300H KCODE0: DB '1','2','3','A' KCODE1: DB '4','5','6','B' KCODE2: DB '7','8','9','C' KCODE3: DB '*','0','#','D' END

Problem Faced (Hardware/Software):

During performing the software and hardware parts of the project we have to face a lot of problems

especially in hardware part. In software part to find the value of the counter to rotate the stepper motor

precisely is the most difficult parts. To find the common wire in the stepper motor we faced some

problem. The relative resistance between common wire to any wire would be half of the relative

resistance between any wire. In hardware parts we have to build the circuit in both breadboard and in

PCB or Vero broad. In Vero board there are lot of wires. So it is difficult to recheck every connection.

Due to loose connection sometimes the stepper motor will not rotate. In Vero board when we construct

our circuit we check all the time whether it is shorted or not. If not then removing the solder we again

solder it. After that we have to check if the IC is getting any supply or not.

Remarks:

Before starting the project learn the operation of stepper motor, stride angle of the motor which is

going to be used, keypad and its connection. Before writing the assembly code make the algorithm of

the code. In the hardware part during soldering the IC base, don’t keep the IC in the IC base because it

may damage the IC. In keypad column and row should be connected properly otherwise it gives some

garbage value. By improving the project in further you can rotate solar panel with the rotation of sun, in

medical case it can be used as scanners, samplers, digital dental photography machine etc. In security

purpose it can be used in close circuit camera to rotate it. It can also be used in statues with a waving

hand.