Interfacing 8051

8/13/2019 Interfacing 8051

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INTERFACING 8051

UNIT-8 INTERFACING 8051

STEPPER MOTOR INTERFACING:

Interfacing the Stepper motor to the 8051 is done to controlof angle and direction

of rotation

A stepper motor is a !idel" #sed de$ice that translates electrical p#lses intomechanical mo$ement

Applications

As disc dri$es In dot matri% printers

In ro&otics for position control

Tp!s o" st!pp!r #otor

'ermanent magnet

(aria&le Rel#ctance

'ermanent magnet Stepper motor consists of t!o parts

1 Rotor )shaft*+a permanent magnet

, Stator -s#rro#nds the rotor as sho!n in fig )a*

Fig )a*

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The most common steppers ha$e fo#r stator !indings that are paired !ith a

center+tapped common as sho!n in fig)&* This t"pe of stepper motor is

commonl" reffered to as a fo#r+phase or #nipolar stepper motor The center+tapallo!s a change of c#rrent direction in each of t!o coils !hen a !inding is

gro#nded res#lting in a polarit" change of the stator

Fig )&*

The stepper motor shaft mo$es in a fi%ed repeata&le increment !hich allo!s one

to mo$e it to a precise position

The stator poles are determined &" the c#rrent sent thro#gh the !ire coils

As the direction of the c#rrent is changed the polarit" is also changed ca#sing the

re$erse motion of the rotor

The stepper motor disc#ssed here has a total of leads2 3 leads representing the

fo#r stator !indings and , commons for the center+tapped leads

As the se4#ence of po!er is applied to each stator !indingthe rotor !ill rotate

There are se$eral !idel" #sed se4#ences !here each has a different degree of

precision

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INTERFACING 8051

Ta&le &elo! sho!s a ,+phase ) , !indings are energied at a time*3+step stepping

se4#ence

6e can start !ith an" of the se4#ences in the a&o$e ta&le once !e start !e m#st contin#e

in the proper order

For e%ample if !e start !ith st!p$%0110& !e m#st contin#e in the se4#ence of steps31,731,etc

Step angle is the minim#m degree of rotation associated !ith a single step

Step per re$ol#tion is the total n#m&er of steps needed to rotate one complete

rotation or 70 degrees) eg 180steps, degrees970*

(ario#s motors ha$e different step angles

Ta&le &elo! sho!s some step angles for $ario#s motors

Step angle Step per re$ol#tion:, 500

18 ,00

,0 180

,5 133

50 :,

:5 38

15 ,3

St!ps p!r s!con' an' rp# r!lation

0

re$ol#tion;stepsrpmondsec;steps

=



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INTERFACING 8051

T(! "o)r st!p s!*)!nc! an' n)#+!r o" t!!t( on rotor:

After completing e$er" "o)r st!ps the rotor mo$es onl" on! toot( pitc(

In a stepper motor !ith ,00 steps per re$ol#tion the rotor has 50 teeth since

3509,00 steps are needed to complete one re$ol#tion

The smaller the step angle the more teeth the rotor passes

E,a#pl!:

Gi$e the n#m&er of times the 3+step se4#ence m#st &e applied to a stepper motor to ma


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INTERFACING 8051

Unipolar !rs)s +ipolar st!pp!r #otor int!r"ac!:

There are three common t"pes of stepper motor interfacing2 #ni$ersal #nipolar

and &ipolar The" can &e identified &" the n#m&er of connections to the motor

A #ni$ersal stepper motor has 8 connections #nipolar stepper motor has connections And &ipolar stepper motor has 3 connectionsas sho!n in fig &elo!

The #ni$ersal stepper motor can &e config#red for all three modes !hile the

#nipolar can &e either #nipolar or &ipolar and the &ipolar cannot &e config#red for#ni$ersal nor #nipolar mode

Int!r "acin2 )nipolar st!pp!r #otor to 8051:

Controllin2 st!pp!r #otor ia optoisolator



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INTERFACING 8051

A&o$e fig#re sho!s an interface to a #ni$ersal stepper motor #sing optoisolator!hich are !idel" #sed to isolate the stepper motor=s &ac< E/F $oltage ie to

protect from damaging the digital;microcontroller s"stem

The fo#r leads of the stator !inding are controlled &" fo#r &its of the 8051

port)p10+p17*

Since the 8051 lac?N,007 to energise the stator

Instead of >?N,007 !e can also #se transistor as dri$ersas sho!n in fig#re

&elo!

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INTERFACING 8051

If the transistors are #sed as dri$ers !e m#st also #se diodes to ta?N,007 has aninternal diode to ta


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INTERFACING 8051

Fig)a*

Fig#re &elo! sho!s the s!itch config#ration for t#rning the motor in onedirection

6hen s!itches 1 and 3 are closed the c#rrent is allo!ed to pass thro#gh the

motor cloc

6hen s!itches , and 7 are closed the c#rrent is allo!ed to pass thro#gh the

motor co#ntercloc

Fig#re &elo! sho!s the in$alid config#ration C#rrent flo!s directl" to gro#nd

creating a short circ#it



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The same effect )in$alid state*occ#rs !hen s!itches 1 and 7 are closed ors!itches ,and 3 closed

P)ls! 7i't( #o')lation%P4M&

The speed of the motor depends on three factors2

1* load ,* $oltage and 7*c#rrent

For a gi$en fi%ed load !e can maintain a stead" speed &" #sing a method called

p#lse !idth mod#lation)'6/*

" changing )mod#lating* the !idth of the p#lse applied to the @C motor !e can

increase or decrease the amo#nt of po!er pro$ided to the motor ther&" increasing

or decreasing the motor speedie !ider the p#lse higher the speed

Fig#re &elo! sho!s the '6/ comparisions

3C #otor control 7it( optoisolator:

Fig#res &elo! sho!s the connections to a simple @Cmotor #sing a &ipolar and a

/SFET transistor

The 8051 is protected from E/I created &" motor &r#shes &" #sing an optoisolator and a

separate po!er s#ppl"

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INTERFACING 8051

Separate po!er s#pplies to the motor and logic !ill red#ce the posi&ilit" of damage to the

control circ#itr" And also allo!s the #se of high+$oltage motors

The deco#pling capacitor across the motor helps to red#ce the E/I created &" the motor

The ener diode is #sed to red#ce gate $oltage &elo! the rated ma%im#m$al#e

1*!rite a program to monitor the stat#s of the s!itch and perform the follo!ing )a* if S691 the @C motor mo$es co#ntercloc

)&* if S690 the @C motor mo$es cloc

Sol#tion2

rg 0000h/AIN2 C?R '10

C?R '11 C?R '1,

SET',:

/NITIR2 SET '10

N ',: C?C.6ISE

C?R '11

SET '1,

S/' /NITR

C?C.6ISE2 SET '11 C?R '1,

S/' /NITR

EN@



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INTERFACING 8051

,*!rite a program to monitor the stat#s of the s!itch and perform the follo!ing

)a* if p,:91 the @C motor mo$es !ith ,5 d#t" c"cle p#lse )&* if p,:90 the @C motor mo$es !ith 50 d#t" c"cle p#lse

Sol#tion2 rg 0000h/ain2

C?R '10

SET ',:

/NITR2

N ',: FIFT'ERCENT Hif p,:91 follo! the ne%t instr#ction if p,:90 go to la&el fift"percent

SET '10

/( R5,5

ACA?? @E?A C?R '10

/( R5:5 ACA?? @E?A

S/' /NITR

FIFT'ERCENT2

SET '10

/( R550

ACA?? @E?A C?R '10

/( R550

ACA?? @E?A

S/' /NITR

@E?A2

/( R, FF

?12 /( R7 FF ?,2 @NJ R7 ?,

@NJ R, ?1

RET EN@

3AC INTERFACE

@igital to analog con$erters)@AC* is a de$ice !idel" #sed to con$ert digital p#lses toanalog signals

The first criterion for K#dging a @ACis its resol#tion !hich is a f#nction of then#m&er of &inar" inp#ts

R!sol)tion2 This is the n#m&er of possi&le o#tp#t le$els the @AC is designed to

reprod#ce This is #s#all" stated as the n#m&er of&itsit #ses !hich is the &aset!o logarithmof the n#m&er of le$els For instance a 1 &it @AC is designed to

reprod#ce , ),1* le$els !hile an 8 &it @AC is designed for ,5 ), 8* le$els

http://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Logarithmhttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Logarithm


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INTERFACING 8051

An 8+&it @AC s#ch as @AC 0808 pro$ides ,5 discrete $oltages )or c#rrent*

le$els of o#tp#t similarl" 1,+&it @AC pro$ides 30D discrete $oltage le$els

The digital inp#t are con$erted to c)rr!ntIo#t L &" connecting a r!sistor to the

Io#t pin !e con$ert the res#lt to olta2!

i! Io)tR9o)t

The total c#rrent pro$ided &" the Io#t pin is a f#nction of the &inar" n#m&er atthe @o+@:

*)IrefIo#t,5

1@

1,8

1@

3

,@

7,

7@

1

3@

8

5@

3

@

,

:@+++++++=

The Iref c#rrent is generall" set to ,mA

calc#late (o#t for the follo!ing &inar" inp#t

1*10011001&,* 11001000& ass#me resistance95.ohms

Sol#tion2

1*

1D1m,*)m,Io#t,5

157

,5

1

1,8

0

3

0

7,

1

1

1

8

0

3

0

,

1==+++++++=

$D:55


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INTERFACING 8051

Inp#t $al#es for @AC for $ario#s angles is calc#lated and sho!n as in ta&le &elo! for

step angle 70 degree

Angle sin 9o)t5%5sin &

3AC inp)t al)!s

%1;81;8 sin &

'!ci#al

Inp#t $al#es in(!,

0 0 5 1,8 80

70 5 :5 1D, C0

0 8 D77 ,78 EE

D0 10 10 ,55 FF

1,0 8 D77 ,78 EE

150 5 :5 1D, C0

180 0 5 1,8 80

,10 +5 ,5 3 30

,30 +8 : 1: 11

,:0 +10 0 0 0

700 +8 : 1: 11

770 +5 ,5 3 3070 0 5 1,8 80

C 'rogram to generate a sine !a$e of step angle70 degree

incl#dereg51hO

Sfr dacdata9'1H(oid main) *

P

>nsigned char !a$e$al#eQ1,9P1,81D,,78,55,781D,1,831:01:3H

>nsigned char %H

6hile)1*P

For )%90H %1,H %MM*

@acdata 9 !a$e$al#eQ%H

C 'rogram to generate a triangle !a$e


3AC inp)t al)!s 1;81;8 sin


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INTERFACING 8051

incl#dereg51hO

(oid main) *

>nsigned char co#ntH

P

6hile)1*

P For )co#nt90H co#nt90%ffH co#ntMM*

'09co#ntH

P

For)co#nt90%ffH co#ntO0Hco#nt++* '09co#ntH

C 'rogram to generate s4#are !a$e incl#dereg51hO

(oid main) *>nsigned char co#ntH

P

6hile)1*

P

'090%00H For)%90H %1,50H %MM*

P

'090%ffH

For)%90H %1,50H %MM*

8051 conn!ction to 3AC8082



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INTERFACING 8051

Fig#re sho!s the generation of c#rrent reference setting Iref9,mA L&" #sing the

standard 5$ po!er s#ppl" L 1< or 15< ohm resistors

Con$ert this c#rrent to $oltage and monitor the o#tp#t on scope

Ideall" !e connect the o#tp#t pin Io#t to a resistor

#t this resistor affect the o#tp#t $oltage For this reason Iref c#rrent o#tp#t is isolat!'&" connecting it to an op+amp s#ch

as :31 !ith Rf95


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INTERFACING 8051

>E?6OAR3 INTERFACING:

.e"&oard L?C@s are the most !idel" #sed inp#t;o#tp#t de$ices of the 8051

.e"&oards are organied in a matri% of ro!s and col#mns

The 8051 C'> accesses &oth ro!s and col#mns thro#gh , 8+&it ports an 88

matri% of


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6hen a


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EUA/'?E2

From Fig identif" the ro! and col#mn of the pressed


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Fig &2Flo!chart for detection and identification of


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.C3 INTERFACING:

In recent "ears the ?C@ is finding !idespread #se replacing ?E@s )se$en segment* d#eto the follo!ing reasons2

1 The declining prices of ?C@s

, The a&ilit" to displa" n#m&ers characters and graphics7 Ease of programming for characters and graphics

The ?C@ descri&ed in this chapter has 13 pins The f#nction of each pin is gi$en in ta&le&elo!

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9CCB 9SS 9EE: %pin 1B;$&

(CC (SS pro$ide M5( and gro#nd respecti$el"

(EE is #sed for controlling lcd contrast

RS- R!2ist!r s!l!ct %pin D&:

If RS0Bthe instr#ction command code register is selected !hich

Allo!s the #ser to send a command s#ch as clear displa" c#rser at home etc

ta&le 1 &elo! lists the instr#ction command codes

If RS1B the data register is selected !hich Allo!s the #ser to send data to &e

displa"ed on the ?C@

To displa" letters and n#m&ers !e send ASCII codes for the letters A+J a+

and n#m&ers 0+D to 8+&it data pins )@0+@:* !hile ma


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fig d sho!s ?C@ timing to !rite)B+? for E pin*

Ta+l! 1 : .C3 co##an' co'!s2

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Interfacing 8051

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