Chuong 13_DC Buoc - Ban Phim - DAC - Smith.N Studio

8/2/2019 Chuong 13_DC Buoc - Ban Phim - DAC - Smith.N Studio

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Ch-ng 13

Phi ghp vi th gii kiu II ng c b-c, bn phm v cc bDAC

13.1 Phi ghp vi mt ng c b-c.Phn ny bt u vi vic gii thiu tng quan v hot ng ca cc ng c

b-c. Sau chng ta m t cch phi ghp mt ng c b-c vi b vi iu khin8051. Cui cng ta s dng cc ch-ng trnh hp ng trnh din iu khin gc vh-ng quay ca ng c b-c.13.1.1 Cc ng c b-c.

ng c b-c l mt thit b s dng rng ri chuyn cc xung in thnhchuyn ng c hc. Trong cc ng dng chng hnnh- cc b iu khin a, ccmy in kim ma trn v cc my rbt th ng c b-c -c dng iu khinchuyn ng. Mi ng c b-c u c phn quay rto l nam chm vnh cu (cngcn -c gi l trc dn shaft) -c bao bc xung quanh l mt ng yn gi stato(xem hnh 131.1). Hu ht cc ng c b-c u c chung c 4 stato m cc cundy ca chng -c b tr theo cp i xng vi im gia chung (xem hnh 13.2),

Kiu ng c b-c ny nhn chung cn -c coi nhng c b-c 4 pha. im giacho php mt s thay i ca h-ng dng ca mt trong hai li khi mt cun dy-c ni t to ra s thay i cc ca stato. L-u rng, trc ca mt ng ctruyn thng th quay t do, cn trc ca ng c b-c th chuyn ng theo mt tng c nh lp li cho php ta chuyn dch n n mt v tr chnh xc. Chuynng c nh lp li ny c -c l nhkt qu ca l thuyn ttr-ng c sl cccc cng du th y nhau v cc cc khc du th ht nhau. H-ng quay -c xcnh bi t tr-ng ca stato. T tr-ng ca stato -c xc nh bi dng chyt quanli cun dy. khi h-ng ca dng thay i th cc t tr-ng cng thay i gy rachuyn ng ng-c li ca ng c (o chiu). ng c b-c -c ni y c 6

u dy: 4 u ca cun dy stato v hai u dy chung im gia ca cc cp dy.Khi chui xung ngun -c cp n mi cun dy stato th ng c s quay. C mts chui xung -c s dng rng ri vi cp chnh xc khc nhau. Bng 13.1trnh by chui 4 b-c thng th-ng.

Smith Nguyen Studio.


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Hnh 13.1: Cn chnh rto.Bng 13.1: Chui ngun nui 4 b-c thng th-ng.

S

B

SC

A

N

N

D

N

O

S

S

B

SC

A

N

N

D

N

O

S

Average

North

Average

South



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B-c Cundy A

Cundy B

Cundy C

Cundy D

1 1 0 0 1

2 1 1 0 0

3 0 1 1 0

4 0 0 1 1

Bng13.2: Cc gc b-c ca ng c b-c.

Gc b-c S b-c/ vng0.72 5001.8 2002.0 1802.5 1445.0 727.5 48

15 24

Bng13.2: Cc gc b-c ca ng c b-c.Hnh 13.2:B tr cc cun dy ca stato.

Hnh 13.3: Phi ghp 8051 vi mt ng c b-c.Cn phi nh rng mc d ta c th bt u vi cc chui bt k trong bng13.1. Nh-ng khi bt u th ta phi tip tc vi cc chui theo ng th t. V dta bt u b-c th ba l chui (0110) th ta phi tip tc vi chui ca b-c 4 risau 1, 2, 3 v.v...V d 13.1:

Hy m t kt ni 8051 vi ng c b-c ca hnh 13.3 v vit mt ch-ngtrnh quay n lin tc.Li gii:

Chiukimng

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Chiuquayb

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Hnh 13.2:



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Cc b-c d-i dy trnh by vic kt ni 8051 vi ng c b-c v lp trnhca n.

1. S dng mt m k o trkhng ca cc u dy. iu ny xc nh uchung (COM) no -c ni ti cun dy no?

2. Cc dy chung -c ni ti u d-ng ca ngun cp cho ng c. Trongnhiu ng c th + 5V l .

3. Bn u c cun dy stato -c iu khin bi 4 bt ca cng P1 trong 8051(P1.0 P1.3). Tuy nhin, v 8051 khng dng iu khin cc cun dyng c b-c nn ta phi s dng mt b iu khin chng hn nh-ULN2003 cp nng l-ng cho stato. Thay cho ULN2003 ta c th s dngcc bng bn dn lm cc b iu khin nh- ch ra trn hnh 13.4. Tuy nhinta rng, nu cc bng bn dn -c s dng nh- cc b iu khin chngta cng phi s dng cc i t ngn dng cm ng -c to ra khi tt cundy. Mt l do m ULN2003 -c -u chung hn cc bng bn dn nh- ccb iu khin l n c i t bn trong ngn cm ng in tng-c.

MOV A, # 66H ; Np chui xung b-c

BACK: MOV P1, A ; Xut chui xung n ng cRR A ; Quay theo chiu kim ng hACALL DELAY ; ChSJMP BACK ; Tip tc chy

DELAYMOV R2, # 100

H1: MOV R3, # 255H2: DJNZ R3, H2

DJNZ R2, H1RET

Hy thay i gi tr ca DELAY t tc quay. Ta c th s dng lnhn bt SETB v CLR thay cho lnh RRA to ra chui xung.13.1.2 Gc b-c (Step Angle).

Vy mi b-c c dch chuyn l bao nhiu? iu ny ph thuc vo cutrc bn trong ca ng c, c bit l s rng ca stato v r to. Gc b-c l quay nh nht ca mt b-c. Cc ng c khc nhau c cc gc b-c khc nhau.Bng 13.2 trnh by mt s gc b-c i vi cc ng c khc nhau. Bng 13.2 c sdng thut ng s b-c trong mt vng (Steps per revolution). y l tng s b-ccn quay ht mt vng 3600 (chng hn 180 b-c 20= 3600).

Cn phi ni rng d-ng nh- tri ng-c vi n t-ng ban u. Mt ng c

b-c khng cn nhiu u dy cho stato hn c cc b-c nh hn. Tt c ming c b-c -c ni y ch c 4 u dy cho cun dy stato v 2 u dychung cho nt gia. Mc d nhiu hng sn xut ch dnh mt u chung thay chohai th h cng vn phi c 4 u cun dy stato.13.1.3 Quan h s b-c trong giy v s vng quay trong pht RPM.

Quan h gia s vng quay trong pht RPM (revolutions per minute), s b-ctrong vng quay v s b-c trong vng giy l quan h thuc v trc gic v n -cbiu din nh- sau:



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60

quayvongtrongbuocSoRPMgiaytrongbuocSo

=

13.1.4 Chui xung bn b-c v s rng trn r to.Chui xung chuyn mch -c trnh by trong bng 13.1 -c gi l chui

chuyn mch 4 b-c bi v sau 4 b-c th hai cun dy ging nhau s -c btON. Vy dch chuyn ca 4 b-c ny s l bao nhiu? Sau mi khi thc hin 4

b-c ny th r to ch dch -c mt b-c rng. Do vy, trong ng c b-c vi 200b-c/ vng th r to ca n c 50 rng v 50 4 = 200 b-c cn quay ht mtvng. iu ny dn n mt kt lun l gc b-c ti thiu lun l hm ca s r ngtrn r to. Hay ni cch khc gc b-c cng nh th r to quay -c cng nhiurng. Hy xt v d 13.2.V d 13.2:

Hy tnh s ln ca chui 4 b-c trong bng 13.1 phi cp cho mt ng cb-c to ra mt dch chuyn 800 nu ng c gc b-c l 20.Li gii:

Mt ng c c gc b-c l 20 th phi c nhng c tnh sau: gc b-c 20, s

b-c/vng l 1800

, s rng ca r to l 45, dch chuyn sau mi chui 4 b-c l80. Vy dch chuyn 800 th cn 40 chui 4 b-c v 10 4 2 = 80.Nhn vo v d 13.2 th c ng-i s hi vy mun dch chuyn i 450 th lm

th no khi gc b-c l 20. Mun c phn gii nh hn th tt c mi ng cb-c u cho php chui chuyn mch 8 b-c, chui 8 b-c cng cn -c gichui na b-c (half stepping), v trong chui 8 b-c d-i y th mi b-c l mtna ca gc b-c bnh th-ng. V d, mt ng c c gc b-c l 20 c th s dnggc b-c 10 nu p dng chui bng 13.3.

Bng 13.3: Chui xung 8 b-c.

13.1.5 Tc ng c.Tc ng c -c o bng s b-c trong mt giy (b-c/giy) l mt hm

ca tc chuyn mch. trong v d 13.1 ta thy rng bng vic thay i thi gian tr ta c th t -c cc tc quay khc nhau.13.1.6 M mem gi.

D-i y l mt nh ngha v m men gi:M men gi l l-ng m men ngoi cn thit lm quay trc ng c tv

tr gi ca n vi iu kin trc ng c ang ng yn hoc ang quay vi tc

B-c Cun A Cun B Cun C Cun D

1 1 0 0 12 1 0 0 03 1 1 0 04 0 1 0 05 0 1 1 06 0 0 1 07 0 0 1 18 0 0 0 1

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RPM = 0. i l-ng ny -c o bng t l in p v dng cp n ng c. nv ca m men gi l kilgam centimet (hay ounce inch).13.1.7 Chui 4 b-c iu khin dng sng.

Ngoi cc chui 4 b-c v 8 b-c n trn y cn c mt chui khc -cgi l chui 4 b-c dng sng. N -c trnh by trong bng 13.4. 8 b-ctrong bng 13.3 l mt s kt hp n gin ca cc chui 4 b-c th-ng v chui 4

b-c iu khin dng sng -c cho bng 13.1 v 13.4.

B-c Cundy A

Cundy B

Cundy C

Cundy D

1 1 0 0 02 0 1 0 03 0 0 1 04 0 0 0 1

Hnh 13.4: S dng cc bng bn dn iu khin ng c b-c.

13.2 Phi ghp 8051 vi bn phm.Cc bn phm v LCD l nhng thit b vo/ra -c s dng rng ri nht ca8051 v cn phi thu hiu mt cch c bn v chng. phn ny tr-c ht ta giithiu cc kin thc c bn v bn phm vi c cu n phm v tch phm, sau giithiu v giao tip 8051 vi bn phm.13.2.1 Phi ghp bn phm vi 8051.

mc thp nht cc bn phm -c t chc d-i dng mt ma trn cc hngv cc ct. CPU truy cp c hng ln ct thng qua cc cng. Do vy, vi hai cng 8bt th c th ni ti mt bn phm 8 8 ti b vi x l. Khi mt phm -c n thmt hng v mt ct -c tip xc, ngoi ra khng c s tip xc no gia cc hng

v cc ct. Trong cc bn phm my tnh IBM PC c mt b vi iu khin (bao gmmt b vi x l, b nhRAM v EPROM v mt s cng tt c -c b tr trn mtchp) chu trch nhim phi ghp phn cng v phn mm ca bn phm. Trongnhng h thng nh- vy, n l chc nng ca cc ch-ng trnh -c l-u trongEPROM ca b vi iu khin qut lin tc cc phm, xc nh xem phm no -c kch hot v gi n n bo mch chnh. Trong phn ny nghin cu v c cu8051 qut v xc nh phm.13.2.2 Qut v xc nh phm.

Hnh 13.5 trnh by mt ma trn 4 4 -c ni ti hai cng. Cc hng -cni ti mt u ra v cc ct -c ni ti mt cng vo. Nu khng c phm no-c n th vic ng cng vo s hon ton l 1 cho tt c cc ct v tt c -c ni

ti d-ng ngun VCC. Nu tt c cc hng -c ni t v mt phm -c n th mttrong cc ct s c gi tr 0 v phm -c n to -ng xung t. Chc nng ca bvi iu khin l qut lin tc pht hin v xc nh phm -c n.

Hnh 13.5Hnh 13.5:Ni ghp bn phm ma trn ti cc cng.

13.2.3 Ni t cc hng v c cc ct. pht hin mt phm -c n th b vi iu khin ni t tt c cc hng

bng cch cp 0 to cht u ra, sau n c cc hng. Nu d -c c tcc

Chiukimng

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ct l D3 D0 = 1101 th khng c phm no -c n v qu trnh tip tc cho nkhi pht hin mt phm -c n. Tuy nhin, nu mt trong cc bt ct c s 0 thiu c ngha l vic n phm xy ra. V d, nu D3 D0 = 1101 c ngha lmt phm ct 1 -c n. Sau khi mt n phm -c pht hin, b vi iu khin schy qu trnh xc nh phm. Bt u vi hng trn cng, b vi iu khin ni tn bng cch ch cp mc thp ti chn D0, sau n c cc ct. Nu d liu c

-c l ton s 1 th khng c phm no ca hng ny -c n v qu trnh nychuyn sang hng k tip. N ni t hng k tip, c cc ct v kim tra xem c s0 no khng?Qa trnh ny tip tc cho n khi xc nh -c hng no c phm n.Sau khi xc nh -c hng c phm -c n th cng vic tip theo l tm ra phmn thuc ct no. iu ny tht l d dng v b vi iu khin bit ti thi im btk hng no v ct no -c truy cp. Hy xt v d 13.3.V d 13.3:

Thnh 13.5 hy xc nh hng v ct ca phm -c n cho cc tr-ng hpsau y:a) D3 D0 = 1110 cho hng v D3 D0 = 1011 cho ct.b) D3 D0 = 1101 cho hng v D3 D0 = 0111 cho ct.

Li gii:Thnhf 13.5 ct v hng c th -c s dng xc nh phm.

a) Hng thuc D0 v ct thuc D2, do vy phm s 2 -c n.b) Hng thuc D1 v ct thuc D3, do vy phm s7 -c n.

Ch-ng trnh 13.1 l ch-ng trnh hp ng ca 8051 pht hin v xc nhs kch hot phm. Trong ch-ng trnh ny P1 v P2 -c gi thit l cng ra vcng vo t-ng ng. Ch-ng trnh 13.1 i qua 4 giai on chnh sau y.1. Khng nh phm tr-c -c nh, cc s khng l u ra ti tt c cc hng

cng mt lc v cc ct -c c v -c kim tra chng no tt c mi ct ucao. Khi tt c cc ct -c pht hin l u cao th ch-ng trnh chmt thi

gian ngn tr-c khi n chuyn sang giai on k tip chmt phm -c n.2. bit c mt phm no -c n cc ct -c qut i qut li trong vng v tncho n khi c mt ct c s 0. Hy nh rng cc cht u ra -c ni ti cchng vn c cc s 0 ban u (-c cp giai on 1) lm cho chng -c nit. Sau khi pht hin n phm, n i 20ms chcho phm nh ra v sau qutli cc ct. iu ny phc v hai chc nng: a) n m bo rng vic pht hinn phm u tin khng b sai do nhiu v b) thi gian gi chm l 20ms ngnnga vic n cng mt phm nh- l nhiu ln n. Nu sau 20ms gi chm mphm vn -c n n chuyn sang giai on k tip pht hin phm n thuchng no, nu khng n quay trvng lp pht hin c mt phm n tht.

3. pht hin n phm thuc hng, n ni t mi hng ti mt thi im, c cc

ct mi ln. Nu n pht hin tt c mi ct u cao, iu ny c ngha l nphm khng thuc hng , do vy n ni t hng k tip v tip tc cho n khipht hin ra hng c phm n. Khi tm hng c phm n, n thit lp a ch btu cho bng trnh by gi cc m qut (hoc gi tr ASCII) cho hng vchuyn sang giai on k tip xc nh phm.

4. xc nh phm n, n quay cc bt ct, mi ln mt bt vo cnh v kim traxem n c gi tr thp khng? Khi tm ra s 0, n ko m ASCII dnh cho phm ra tbng trnh by. Nu khng tm -c s 0 th n tng con tr ch n



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phn t k tip ca bng trnh by. Hnh 13.6 trnh by l-u qu trnh tm phmn ny.

Ni t mi hng

c mi ct

Chnh phm

Ni t hng ktip

Ni t mi hng

Bt u

Miphm

h

c mi ct

Cphm

n

c mi ct

Cphm

n

Cphmh

hngny

Tm phm no-c n

Tm phm no

-c n

Trv

C

KhngKhng

C

Khng

C

Khng C



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Hnh 13.6: L-u tm phm n ca ch-ng trnh 13.1.Trong khi vic pht hin n l chun cho tt c mi bn phm th qu trnh xc

nh phm no -c n li khng ging nhau. Ph-ng pht s dng bng trnh by-c -a ra trong ch-ng trnh 13.1 c th -c sa i lm vic vi bt k matrn kch th-c 8 8 no. Hnh 13.6 l l-u thut ton ca ch-ng trnh 13.1 qut v xc nh phm n.

C nhng chp IC chng hn nh- MM74C924 ca hng NationalSemiconductor kt hp vic qut v gii m bn phm tt c vo mt chp. Cc chpnh- vy s s kt hp cc b m v cc cng l gc (khng phi b vi iu khin) thc thi cc khi nim -c trnh by trong ch-ng trnh 13.1 d-i y.

Ch-ng trnh 13.1:; Ch-ng trnh con bn phm Keyboard ny gi m ASCII; Cha phm -c n n chn P0.1; Cc chn P1.0P1.3 -c ni ti cc hng cn P2.0P2.3 ti cc ct.

13.3 Phi ghp mt DAC vi 8051.Phn ny s trnh by cch phi ghp mt b bin i s t-ng t DAC vi

8051. Sau minh ho to mt sng hnh sin trn my hin sng s dng b DAC.13.3.1 B bin i s t-ng t DAC.

B bin i t-ng t DAC l mmt thit b -c s dng rng ri chuyni cc xung s ho v cc tn hiu t-ng t. Trong phn ny ta gii thiu c s phighp mt b DAC vi 8051.

Xem li cc kin thc in t s ta thy c hai cch to ra b DAC: Ph-ngpht trng s nh phn v ph-ng trnh thang R/2R. Nhiu b DAC da trn ccmch t hp, bao gm MC1408 (DAC808) -c s dng trong phn ny u sdng ph-ng php hnh thang R/2R v n c th t chnh xc cao hn. Tiu

chun nh gi mt b DAC u tin l phn gii hm ca s u vo nh phn.Cc phn gii chng l 8, 10 v 12 bt. S cc u vo bt d liu quyt nh phn gii ca b DAC, v s mc u ra t-ng t bng 2n vi n l u vo bt d liu.Do vy, mt b DAC 8 bt nh- DAC808 chng hn c 256 mc u ra in p (dngin) ri rc. T-ng t nh- vy, mt b DAC 12 bt cho 4096 mc in p ri rc.cng c cc b DAC 16 bt nh-ng chng rt t.13.3.2 B bin i DAC MC1408 (hay DAC808).

Trong b ADC808 cc u vo s -c chuyn i thnh dng (Iout) v vicni mt in tr ti chn Iout ta chuyn kt qu thnh in p. dng tng -c cpbi chn Iout l mt hm s nh phn cc u vo D0 D7 ca DAC808 v thamchiu Iref nh- sau:

)256

0D

128

1D

64

2D

32

3D

16

4D

8

5D

4

6D

2

7D(II refout +++++++=

Trong D0 l bt thp nht LSB v D7 l bt cao nht MSB i vi cc uvo



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Chuong 13_DC Buoc - Ban Phim - DAC - Smith.N Studio