stepper motor description

8/7/2019 stepper motor description

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This project is actually an educational kit. One can study the full operation of unipolar typestepper motor using this board. As it is micro controller based it can be programmable also and

one can learn micro controller interfacing with LEDs, key board and stepper motor. Thus singleboard serves the purpose of learning stepper motor control as well as learning micro controller

programming.

General description and system block diagram:-

The complete board consists of transformer, control circuit, keypad and stepper motor as shownin snap. The given figure shows the block diagram of project.

System block diagram

The circuit has inbuilt 5 V power supply so when it is connected with transformer it will give thesupply to circuit and motor both. The 8 Key keypad is connected with circuit through which user

can give the command to control stepper motor. The control circuit includes micro controller89C51, indicating LEDs, and current driver chip ULN2003A. One can program the controller to

control the operation of stepper motor. He can give different commands through keypad like, runclockwise, run anticlockwise, increase/decrease RPM, increase/decrease revolutions, stop motor,

change the mode, etc. before we start with project it is must that we first understood theoperation of unipolar stepper motor.

Unipolar stepper motor:-

In the construction of unipolar stepper motor there are four coils. One end of each coil is tidetogether and it gives common terminal which is always connected with positive terminal of

supply. The other ends of each coil are given for interface. Specific color code may also begiven. Like in my motor orange is first coil (L1), brown is second (L2), yellow is third (L3),

black is fourth (L4) and red for common terminal.

By means of controlling a stepper motor operation we can

1. Increase or decrease the RPM (speed) of it2. Increase or decrease number of revolutions of it3. Change its direction means rotate it clockwise or anticlockwise


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To vary the RPM of motor we have to vary the PRF (Pulse Repetition Frequency). Number ofapplied pulses will vary number of rotations and last to change direction we have to change pulse

sequence.

So all these three things just depends on applied pulses. Now there are three different modes to

rotate this motor

1. Single coil excitation2. Double coil excitation3. Half step excitation

The table given below will give you the complete idea that how to give pulses in each mode

Pulses for stepper motor module

Note:- In half step excitation mode motor will rotate at half the specified given step resolution.

Means if step resolution is 1.8 degree then in this mode it will be 0.9 degree. Step resolutionmeans on receiving on 1 pulse motor will rotate that much degree. If step resolution is 1.8 degree

then it will take 200 pulses for motor to compete 1 revolution (360 degree).

Now let me give you the specification of the stepper motor that I have used.

Max rated voltage: - 5 V

Max rated current per coil: 0.5 AmpStep resolution: - 1.8 degree / pulse

Max RPM: - 20 in single/double coil excitation mode and 60 in half step modeTorque: 1.5 Kg/cm2

RPM calculation:-


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One can calculate the exact RPM at which motor will run. We know that motor needs 200 pulsesto complete 1 revolution. Means if 200 pulses applied in 1 second motor will complete 1

revolution in 1 second. Now 1 rev. in 1 sec means 60 rev. in 1 minute. That will give us 60 RPM.Now 200 pulses in 1 sec means the PRF is 200 Hz. And delay will be 5 millisecond (ms). Now

lets see it reverse.

* If delay is 10 ms then PRF will be 100 Hz.* So 100 pulses will be given in 1 sec

* Motor will complete 1 revolution in 2 second* So the RPM will be 30.

In same manner as you change delay the PRF will be changed and it will change RPM

Stepper motor control board circuit:-


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Stepper motor control board circuit

The circuit consists of very few components. The major components are 7805, 89C51 andULN2003A.

Connections:-

1. The transformer terminals are given to bridge rectifier to generate rectified DC.2. It is filtered and given to regulator IC 7805 to generate 5 V pure DC. LED indicates

supply is ON.3. All the push button micro switches J1 to J8 are connected with port P1 as shown to form

serial keyboard.4. 12 MHz crystal is connected to oscillator terminals of 89C51 with two biasing capacitors.5. All the LEDs are connected to port P0 as shown6. Port P2 drives stepper motor through current driver chip ULN2003A.7. The common terminal of motor is connected to Vcc and rest all four terminals are

connected to port P2 pins in sequence through ULN chip.

Now by downloading different programs in to 89C51 we can control the operation of stepper

motor. Let us see all different kind of program.

Program 1:-It is advisable to begin with easy program. So in this program we shall see minimal functionality.

Only first two switches and first three LEDs will be used. When you press one switch the motorwill start rotating in clockwise direction and stops when completes one revolution. Pressing

second switch will do the same job but in anticlockwise direction. The speed will be 10 RPMfixed. Motor runs in single coil excitation mode. First LED indicates key press event. Second

blinks when motor rotates clockwise and third blinks when motor rotates anticlockwise.

Org 00h

mov r0,#01h ; initileze key countmov p1,#0ffh ; P1 as input port

lop: mov a,p1cjne a,#0ffh,jmp

ajmp lop ; loop until any key; is pressed

jmp: clr p0.0 ; indicates keypressloop: rrc a

jnc num ; get key no.inc r0

sjmp loopnum: acall dely ; key debounce delay

setb p0.0

cjne r0,#01h,nxt ; for 1st keyacall clkwise ; rotate motor


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sjmp over ; clock wisenxt: cjne r0,#02h,over ; for 2nd key

acall aclkwise ; rotate anticlock

over: mov p2,#00h ; restore initial

mov p1,#0ffh ; data andmov r0,#01hsjmp lop ; jump to loop again

clkwise:

mov r1,#32h ; load count 50dgo: clr p0.1

mov p2,#01h ;give 4 pulses in loopacall delay ; total 200 pulses

mov p2,#02h ; each coil energizedacall delay ; one by on in single

setb p0.1mov p2,#04h ; coil excitation

acall delay ; 30 ms delay in betwnmov p2,#08h ; means speed is

acall delay ; 10 RPMdjnz r1,go

retaclkwise:

mov r1,#32hgo1:clr p0.2

mov p2,#01hacall delay

mov p2,#08h ; revert the pulseacall delay ; sequence for

setb p0.2mov p2,#04h ; anticlockwise

acall delaymov p2,#02h

acall delaydjnz r1,go1

ret

delay:

mov r5,#1Eh ; load count 30lop2: mov r6,#FAh ; give 1 ms delay

lop1:nop ; so it gives fullnop ; 30 ms delay

djnz r6,lop1djnz r5,lop2

ret


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dely:mov r5,#0C8h ; load count 200

lop2: mov r6,#0FAh ; for 200ms delaylop1: nop

nop

djnz r6,lop1djnz r5,lop2ret

end

Program 2:-Here in this program we shall limit the motor to rotate only 7.2o in either direction when the keyis pressed. When first key is pressed motor rotates in clockwise direction and when second is

pressed anticlockwise direction. LED1 and LED2 indicate the clockwise and anticlockwiserotation.

Note: In industries this is also known as jogging (jog control). This is done to check in whichdirection motor will start running.

Org 00h



ajmp lop ; loop until any key is pressedjmp: clr p0.0 ; indicates keypress

loop: rrc ajnc num ; get key no.

inc r0sjmp loop

num: acall dely ; key debounce delaysetb p0.0

cjne r0,#01h,nxt ; for 1st key

acall clkwise ; rotate motorsjmp over ; clock wise

nxt: cjne r0,#02h,over ; for 2nd keyacall aclkwise ; rotate anticlock

over: mov p2,#00h ; restore initialmov p1,#0ffh ; data and

mov r0,#01hsjmp lop ; jump to loop again

clkwise:

clr p0.1mov p2,#01h ;give 4 pulses in loop

acall delay ; as 1.8o step resolution


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mov p2,#02h ; total 7.2o rotationacall delay ; in single coil

setb p0.1mov p2,#04h ; excitation

acall delay ; 30 ms delay in betwn

mov p2,#08h ; means speed isacall delay ; 10 RPMret

aclkwise:clr p0.1



setb p0.1mov p2,#04h ; anticlockwise


acall delayret

delay:

mov r5,#1Eh ; load count 30lop2: mov r6,#FAh ; give 1 ms delay

lop1:nop ; so it gives fullnop ; 30 ms delay


ret


lop2: mov r6,#0FAh ; for 200ms delaylop1:nop

nopdjnz r6,lop1

djnz r5,lop2retend

Program 3:-

This is also easy program. Now three keys are used and three LEDs are used. Please refer table.

The speed of motor is again fixed at 20 RPM. The mode is double coil excitation.


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Org 00h

mov r0,#01h ; initileze key count

mov p1,#0ffh ; P1 as input portlop: mov a,p1

cjne a,#0ffh,jmpajmp lop ; loop until any key is pressed

jmp: clr p0.0 ; indicates keypress


inc r0sjmp loop


cjne r0,#01h,nxt ; for 1st key rotate motoracall clkwise ; clock wise

sjmp overnxt: cjne r0,#02h,nxt2 ; for 2nd key

acall aclkwise ; rotate anticlocknxt2: cjne r0,#03h,over ; for 3rd key

mov p2,#00h ; stop motorover: mov r0,#01h

sjmp lop ; jump to loop again

clkwise:lop: clr p0.1

mov p2,#03h ; at a time two coilsacall delay ; energized in double

mov p2,#06h ; coil excitation modeacall delay

setb p0.1

mov p2,#0Chacall delaymov p2,#09h

acall delaymov p1, #0FFh ; continue loop

mov a,p1 ; until any key iscjne a,#0FFh,out ; not pressed

sjmp lop


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out: retaclkwise:

lop1: clr p0.1mov p2,#03h

acall delay

mov p2,#09h ; revert the pulseacall delay ; sequence forsetb p0.1

mov p2,#0Ch ; anticlockwiseacall delay


mov p1, #0FFhmov a,p1

cjne a,#0FFh,out1sjmp lop1

out1: ret

delay:mov r5,#0Fh ; load count 15

lop2: mov r6,#FAh ; give 1 ms delaylop1:nop ; so it gives full

nop ; 15 ms delaydjnz r6,lop1 ; to give speed

djnz r5,lop2 ; of 20 RPMret

dely:

mov r5,#0C8h ; load count 200lop2: mov r6,#0FAh ; for 200ms delay

lop1:nopnop


retend

Program 4:-This program is same as above but now the mode is changed to half step and RPM is now 30.

Org 00h



ajmp lop ; loop until any key is pressed


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jmp: clr p0.0 ; indicates keypressloop: rrc a

jnc num ; get key no.inc r0

sjmp loop


cjne r0,#01h,nxt ; for 1st keyacall clkwise ; rotate motor

sjmp over ; clock wisenxt: cjne r0,#02h,nxt2 ; for 2nd key

acall aclkwise ; rotate anticlocknxt2: cjne r0,#03h,over ; for 3rd key

mov p2,#00h ; stop motorover: mov r0,#01h

sjmp lop ; jump to loop again

clkwise:lop: clr p0.1

mov p2,#01h ; alternate pulsesacall delay ; given one from

mov p2,#03h ; single coil secondacall delay ; from double coil

mov p2,#02h ; in half step modacall delay


setb p0.1mov p2,#04h

acall delaymov p2,#0Ch



acall delaymov p1, #0FFh ; continue loopmov a,p1 ; until any key is

cjne a,#0FFh,out ; not pressedsjmp lop

out: retaclkwise:

lop1: clr p0.1mov p2,#01h

acall delay


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mov p2,#08h ; anticlockwiseacall delay

mov p2,#09h

acall delaysetb p0.1mov p2,#04h

acall delaymov p2,#0Ch



acall delaymov p1, #0FFh

mov a,p1cjne a,#0FFh,out1

sjmp lop1out1: ret

delay:mov r5,#0Ah ; load count 10

lop2: mov r6,#FAh ; give 1 ms delaylop1: nop ; so it gives full

nop ; 10 ms delaydjnz r6,lop1 ; to give speed

djnz r5,lop2 ; of 30 RPMret



nopdjnz r6,lop1

djnz r5,lop2ret

end

Program 5:-

Now its time to start with harder programs. In this program all above facilities are there and two

more are included increasing and decreasing RPM. Five switches and four LEDs are used. Seethe table for key functions and LED indications.


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f equ 0fh ; direction flagOrg 00h

mov 30h, #3Ch ; make a table ofmov 31h, #1Eh ; four load values

mov 32h, #14h ; for variable delaymov 33h, #0Fh

mov r1, #30h ;initial location in r1mov r0,#01h ; initialize key count

mov p1,#0ffh ; P1 as input portlop: mov a,p1

cjne a,#0ffh,jmpajmp lop ; loop until any key

; is pressedjmp: clr p0.0 ; indicates keypress


inc r0

sjmp loopnum: acall dely ; key debounce delaysetb p0.0

cjne r0,#01h,nxt ; for 1st key

acall clkwise ; rotate motorsjmp over ; clock wise

nxt: cjne r0,#02h,nxt2 ; for 2nd keyacall aclkwise ; rotate anticlock

nxt2: cjne r0,#03h,nxt3 ; for 3rd keymov p2,#00h ; stop motor

nxt3: cjne r0,#04h,nxt4 ; for 4th keyacall incrpm ; increase RPM

jnb f, aclk ; and continue to rotateacall clkwise ; motor in same

sjmp over ; direction as it wasaclk: acall aclkwise ; running by

sjmp over ; checking flag fnxt3: cjne r0,#05h,over ; for 5th key


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acall decrpm ; decrease RPM andjnb f, aclkw ; again continue to

acall clkwise ; rotate motorsjmp over

aclks: acall aclkwise

sjmp over

over: mov r0,#01h

sjmp lop ; jump to loop againclkwise:

setb f ; for clkwise set directionallop: clr p0.1 ; flag

mov p2,#03h ; at a time two coilsacall delay ; energized in double

mov p2,#06h ; coil excitation modeacall delay

setb p0.1mov p2,#0Ch


acall delaymov p1, #0FFh ; continue loop

mov a,p1 ; until any key iscjne a,#0FFh,out ; not pressed

sjmp lopout: ret

aclkwise:clr f ; for aclkwise clear

lop1: clr p0.1 ; directional flagmov p2,#03h

acall delaymov p2,#09h ; revert the pulse

acall delay ; sequence forsetb p0.1

mov p2,#0Ch ; anticlockwiseacall delay


mov p1, #0FFhmov a,p1

cjne a,#0FFh,out1sjmp lop1

out1: ret

incrpm:

clr p0.3 ; indication


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cjne r1,#33h,incr ; if max limit isajmp noin ; reached no increase

incr: inc r1 ; increase otherwiseacall dely

setb p0.3

noin: ret ; led stays on for max limit

decrpm:

clr p0.3 ; indicationcjne r1,#30h,incr ; if min limit is

ajmp noin ; reached no decreaseincr: dec r1 ; decrease otherwise

acall delysetb p0.3

noin: ret ; led stays on for min limit

delay:mov 10h,@r1 ; load content of

lop2: mov r6,#FAh ; address in r1lop1:nop ; so it gives variable

nop ; delay every timedjnz 10h,lop1 ; to give variable

djnz r5,lop2 ; speed of motorret


lop2: mov r6,#0FAh ; for 200ms delaylop1:nop

nopdjnz r6,lop1

djnz r5,lop2ret

end

Program 6:-

Now I am adding one more functionality in the program. Now instead of continuously runningmotor, motor will run till desired no. of revolutions entered. Means motor will automatically

stops when it completes desired revolutions. One can increase or decrease revolutions in step ofone (1, 2, 3 ). I have used 6 keys and 5 LEDs.


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In the first program we have limit the number of applied pulses to 200. Now again we shall load

the number every time that will change number of applied pulses. There is no maximum limit but

sure there is minimum limit that is 1 revolution.

Org 00hmov 30h, #3Ch ; make a table of

mov 31h, #1Eh ; four load valuesmov 32h, #14h ; for variable delay

mov 33h, #0Fhmov r1, #30h ; initial location in r1

mov 2fh,#32h ; initial load valuemov 2eh,#01h ; for no. of rev.

mov r0,#01h ; initialize key countmov p1,#0ffh ; P1 as input port


ajmp lop ; loop until any key is pressed

jmp: clr p0.0 ; indicates keypress


inc r0sjmp loop


cjne r0,#01h,nxtacall clkwise

sjmp overnxt: cjne r0,#02h,nxt2

acall aclkwisesjmp over

nxt2: cjne r0,#03h,nxt3


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acall incrpmsjmp over

nxt3: cjne r0,#04h,nxt4acall decrpm

sjmp over

nxt4: cjne r0,#05h,nxt5acall increvsjmp over

nxt5:cjne r0,#06h,overacall decrev

over: mov p2,#00h

mov p1,#0ffhmov r0,#01h

sjmp lopclkwise:

mov r1,2Fh ; load variable countgo: clr p0.1

mov p2,#01h ; single coilacall delay ; excitation

mov p2,#02hacall delay ; variable delay


acall delaymov p2,#08h;

acall delaydjnz r1,go

retaclkwise:

mov r1,2Fhgo1:clr p0.2





acall delaydjnz r1,go1

retincrpm:

clr p0.3 ; indicationcjne r1,#33h,incr ; if max limit is


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ajmp noin ; reached no increaseincr: inc r1 ; increase otherwise

acall delysetb p0.3

noin: ret ; led stays on for max limit

decrpm:clr p0.3 ; indication

cjne r1,#30h,decr ; if min limit isajmp noin ; reached no decrease

decr: dec r1 ; decrease otherwiseacall dely

setb p0.3noin: ret ; led stays on for min limit

increv:clr p0.4 ; indication

inc 2Eh ; increment multiplying factormov a,#32h

mov b,2Ehmul ab ; multiply it by load value

mov 2Fh,a ; stores the new load valueacall dely

setb p0.4ret

decrev:clr p0.4

mov r4,2Ehcjne r4,#01h,decn ; check for min

ajmp out2 ; limit of multiplyingdecn: dec 2Eh ; factor. If not reached

mov a,#32h ; decrease itmov b,2Eh

mul ab ; multiply it with loadmov 2Fh,a ; value and store the

acall dely ; new load valuesetb p0.4

out2: ret

delay:

mov 10h,@r1 ; load the countlop2: mov r6,#FAh ; from table

lop1: nopnop

djnz 10h,lop1djnz r5,lop2

ret


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nop

djnz r6,lop1djnz r5,lop2ret

end

Program 7:-This program adds two more things to above program. It changes the mode of operation of

stepper motor also it adds jog control. It changes three different modes on pressing one key. Alleight keys and eight LEDs are now used.

When J7 key is pressed first time the mode will change from single coil to double coil. When

pressed second time mode will change from double coil to half step. And on pressing third timeagain the same mode will repeat. When J8 key is pressed the motor will rotate in previously

selected direction. Means if motor was running in clockwise direction then the jog will be insame direction.

Program 8:-

In above program motor doesnt rotate continuously. In this program motor rotates continuously

and one can change the RPM and operating mode while running. 6 keys and 8 LEDs are used.


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by

Ashutosh M Bhattwww.multyremotes.com

stepper motor description

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