170488434 Nghien Cứu Thiết Kế Mạch Đo Nhiệt Độ Dung LM35 Va Gửi Tin Hiệu Nhiệt Độ Len Internet

5/24/2018 170488434 Nghien C u Thi t K M ch o Nhi t Dung LM35 Va G i Tin Hi u Nhi t Len Inte...

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1

LI M U

Trong cc nghin cu khoa hc , trong cng nghip v i sng hng

ngy vic o nhit l iu rt cn thit. Tuy nhin, o c tr s chnhxc ca nhit li l vn khng n gin.Ngy nay vi s pht trin ca

cng ngh thng tin,cng ngh bn dn, s ra i ca cccm bin, vi iu

khin to iu kin thun li cho vic o nhit mt cch chinh xc hn ,

trn c s em xin trnh by ti: Nghin cu thit k mch o nhit

dng LM35 va gi tn hiu nhit ln internet

Ni dung bn n gm 3 chng:Chng 1: Tng quan v o nhit v cm bin o nhit

Chng 2: Thit k mch o nhit

Chng 3: Gi tn hiu o ln internet

Em xin chn thnh cm n Th.s Trn Th Phng Tho hng dn em

trong sut qu trnh xy dng v hon thnh bn n ny!

Do thi gian thc hin ngn v kin thc bn thn cn hn ch do vy n

khng trnh khi nhng thiu st.Em rt mong nhn c s ng gp ca

cc thy c.

Hi phng ngay 25 thang 11 nm 2012

Sinh vin

Nguyn Vn Hip



2

CHNG 1.

TNG QUAN V O NHIT V CM BIN

O NHIT

1.1.TNG QUAN V H THNG O LNG

1.1.1.Gii thiu

thc hin php o ca mt i lng no th tu thuc vo c

tnh ca i lng cn o,iu kin o,cng nh chnh xc theo yu cu

ca mt php o m ta c th thc hin o bng nhiu cch khc nhau trn csca cc h thng o lng khc nhau.

S khi ca mt h thng o lng tng qut

Hnh 1.1.S khi tng qut

-Khi chuyn i: lm nhim v nhn trc tip cc i lng vt l c

trng cho i tng cn o bin i cc i lng thnh cc i lng vt l

thng nht(dng in hay in p) thun li cho vic tnh ton.

-Mch o: c nhim v tnh ton bin i tn hiu nhn c t b

chuyn i sao cho ph hp vi yu cu th hin kt qu o ca b ch th.

-Khi ch th:lm nhim v bin i tn hiu in nhn c t mch

o th hin kt qu o.

H thng o lng s

H thng o lng s c p dng thc hin ti ny v c cc u

im:cc tn hiu tng t qua bin i thnh cc tn hiu s c cc xung r

rng trng thi 0,1 s gii hn c nhiu mc tn hiu gy sai s .Mt

khc ,h thng ny tng thch vi d liu ca my tnh,qua giao tip vi my

tnh ng dng rng ri trong k thut.

Chuyn Mcho Ch th



3

Hnh 1.2.S khi ca h thng o lng s

1.1.2.Nguyn l hot ng

i tng cn o l i lng vt l,da vo cc c tnh ca i tng

cn o m ta chn mt loi cm bin ph hp bin i thng s i lng

vt l cn o thnh i lng in ,a vo mch ch bin tn hiu(gm:b

cm bin,h thng khuch i,x l tn hiu).

B chuyn i tn hiu sang s ADC(Analog Digital Converter) lm

nhim v chuyn i tn hiu tng t sang tn hiu s v kt ni vi vi x l.

B vi x l c nhim v thc hin nhng php tnh v xut ra nhng

lnh trn c s trnh t nhng lnh chp hnh thc hin trc .

B dn knh tng t (multiplexers) v b chuyn ADC c dng

chung tt c cc knh . D liu nhp vo vi x l s c tn hiu chn ng

knh cn x l a vo b chuyn i ADC v c ng gi tr c trng

ca n qua tnh ton c kt qu ca i lng cn o.1.2.TNG QUAN V O NHIT

1.2.1.Khi nim chung

Trong nghin cu khoa hc, trong sn xut cng nh trong i sng sinh

hot hng ngy, lun lun cn xc nh nhit ca mi trng hay ca mt

vt no . V vy vic o nhit tr thnh mt vic lm v cng cn

thit. o nhit l mt trong nhng phng thc o lng khng in.

i lng

i lng iu khin chn

Hinth

Sdng

cmbin

ChbinTnhiu

Dnknhtngt

ADC

ChbinTnhiu

cmbin

Vi xl

Chngtrnh



4

Nhit cn o c th rt thp (mt vi Kelvin), cng c th rt cao (vi

ngn, vi chc ngn Kelvin). chnh xc ca nhit c khi cn ti mt

vi phn ngn , nhng c khi vi chc cng c th chp nhn c. Vic

o nhit c tin hnh nh cc dng c h tr chuyn bit nh cp nhit

in, nhit in tr, diode v transistor, IC cm bin nhit , cm bin thch

anh Ty theo khong nhit cn o v sai s cho php m ngi ta la

chn cc loi cm bin v phng php o cho ph hp.

1.2.2.Cc phng php o nhit

Ty theo nhit o c th dng cc phng php khc nhau. Thng

thng nhit o c chia thnh ba di: Nhit thp, nhit trung bnh,

nhit cao. nhit trung bnh v thp phng php o l phng php

tip xc ngha l cc cm bin c t trc tip ngay mi trng cn o.

i vi nhit cao o bng phng php khng tip xc, dng c t

ngoi mi trng o.

a)o nhit bng phng php tip xc

Phng php o nhit trong cng nghip thng l cc nhit k tip

xc. C hai loi l: nhit k nhit in tr v nhit k nhit ngu. Cu to ca

nhit k nhit in tr v cp nhit ngu cng nh cch lp ghp chng phi

m bo tnh cht trao i nhit tt gia chuyn i vi mi trng o. i

vi mi trng kh hoc nc, chuyn i c t theo hng ngc li vi

dng chy. Vi vt rn khi t nhit k st vo vt, nhit lng s truyn tvt sang chuyn i v s gy tn hao nhit, nht l vi vt dn nhit km. Do

vy din tch tip xc gia vt o v nhit k cng ln cng tt. Khi o nhit

ca cc cht ht (ct, t), cn phi cm su nhit k vo mi trng cn

o v thng dng nhit k nhit in tr c cp ni ra ngoi.



5

b)o nhit cao bng phng php tip xc

mi trng nhit cao t 1600oC tr ln, cc cp nhit ngu khng

chu c lu di, v vy o nhit cc mi trng ngi ta da trn

hin tng qu trnh qu t nng cp nhit :

)1()( /1

eTtf

(1.1)

Trong : - l lng tng nhit ca u nng trong thi gian t

T - hiu nhit ca mi trng o v cp nhit

- hng s thi gian ca cp nhit ngu

Da trn quan h ny c th xc nh c nhit ca i tng o

m khng cn nhit u lm vic ca cp nhit ngu phi t n nhit

y. Nhng nhit ngu vo mi trng cn o trong khong (0,4 0,6)s, ta s

c phn u ca c tnh qu trnh qu ca nhit ngu v theo tnh

c nhit ca mi trng. Nu nhit u cng tc ca cp nhit ngu

trong thi gian nhng vo mi trng cn o t nhit vo khong mt

na nhit mi trng th nhit tnh c c sai s khng qu hai ln sai

s ca nhit k nhit nhu o trc tip. Phng php ny dng o nhit

ca thp nu chy.

c)o nhit bng phng php khng tip xc

y l phng php da trn nh lut bc x ca vt en tuyt i, tcl vt hp th nng lng theo mi hng vi kh nng ln nht. Bc x nhit

ca mi vt th c trng bng mt ph

E ngha l s nng lng bc x

trong mt dn v thi gian vi mt n v din tch ca vt xy ra trn mt

n v ca di sng. Quan h gia mt ph bc x ca vt en tuyt i

vi nhit v di sng c biu din bng cng thc :

1)/(251

0 )1( TceCE (1.2)



6

Trong : C1, C2hng s, - di sng, T nhit tuyt i.

C1=37,03.10-17Jm2/s; C2=1,432.10

-2m..

d) Khong nhit o

- Khong nhit o bng phng php tip xc v dng cp nhit in

l t 2000C n 10000C, chnh xc c th t ti +/-1% -> 0.1%.

- Khong nhit o bng phng php tip xc v dng cp nhit in

(cp nhit ngu) l t 2700C n 25000C vi chnh xc c th t ti +/-

1% -> 0.1%.

- Khong nhit o bng phng php tip xc v dng cc cm bin tip

gip P-N (diode, transistor, IC) l t 2000C n 2000C,sai s n +/-0.1%.- Cc phng php o khng tip xc nh bc x,quang ph c

khong o t 10000C n vi chc ngn C vi sai s +/-1% -> 10%.

Thang o nhit gm: thang o Celcius(0C), thang o Kelvin (0K),

thang o Fahrenheit (0F), thang o Rankin (0R).

T(0C) = T(0K)273.15

T(0

F) = T(0

R) - 459.67T(0C) = [ T(0F)32 ]*5/9

T(0F) = T(0C)*9/5 +32

Bang1.1.S lin h gia cc thang o nhng nhit quan trng:

Kelvin( K) Celcius( C) Rankin( R) Fahrenheit( F)

0 -273.15 0 -459.67

273.15 0 491.67 32273.16 0.01 491.69 32.018

373.15 100 671.67 212

1.2.3.Qu trnh o nhit

Ta c th chia qu trnh o nhit ra lm ba khu chnh:

a)Khu chuyn i



7

Khu chuyn i nhit thng da vo nhng bin i mang tnh c

trng ca vt liu khi chu s tc ng ca nhit . C cc tnh cht c

trng sau y:

- S bin i in tr.

- Sc in ng sinh ra do s chnh lch nhit cc mi ni ca cc

kim loi khc nhau.

- S bin i th tch, p sut.

- S thay i cng bc x ca vt th khi b t nng.

i vi chuyn i nhit in, ngi ta thng da vo hai tnh cht u tin

ch to ra cc cp nhit in (Thermocouple), nhit in tr kim loi haybn dn, cc cm bin nhit di dng cc linh kin bn dn nh: diode,

transistor, cc IC chuyn dng.

b)Khu x l

Cc thng s v in sau khi c chuyn i t nhit s c x l trc

khi qua n phn ch th. Cc b phn khu x l gm c: phn hiu chnh,

khuch i, bin i ADC (Analog-Digital-Converter) Ngoi ra cn c thc cc mch in b sung nh: mch b sai s, mch phi hp tng tr

c)Khu ch th

Khu ch th trc y thng s dng cc c cu c in, kt qu

o c th hin bng gc quay hoc s di chuyn thng ca kim ch th.

Ngy nay, vi s pht trin ca cng ngh in t, sn xut nhiu loi IC

gii m, IC s chuyn dng trong bin i ADC, v vy cho php ta s dngkhu ch th s d dng nh dng LED 7 on hoc mn hnh tinh th lng

LCD. , kt qu o c th hin bng cc con s trong h thp phn.

1.3.CC LOI CM BIN O NHIT

1.3.1.Nhit in tr

Nhit in tr thng dng o nhit ca hi nc, kh than trong cc

ng ng, cc l phn ng ha hc, cc ni hi, khng kh trong phng



8

Nguyn l lm vic ca thit b ny l da vo s thay i in tr theo

nhit ca cc vt dn in, tc l in tr l mt hm theo nhit : R =

f(T). Cun dy in tr thng nm trong ng bo v, ty theo cng dng m

v ngoi c th lm bng thy tinh, kim loi hoc gm.

i vi hu ht cc vt liu dn in th gi tr in tr R ty thuc vo

nhit T theo mt hm tng qut sau:

R(T) = Ro.F(TTo) (1.3)

Vi : Ro :in tr nhit To

F : hm ph thuc vo c tnh ca vt liu

F = 1 khi T = To-i vi in tr kim loi :

R(T) = Ro( 1 + AT + BT2+ CT3) (1.4)

T : tnh bng 0C

To = 00C

-i vi nhit in tr bng oxyt bn dn :

R(T) = Ro.exp[ B(1/T1/To)] (1.5)T : nhit tuyt i (0K)

To = 273.150K

Nhng h s trong cng thc tnh in tr R thng c bit trc mt cch

chnh xc nh s o nhng nhit bit.

a)Nhit in tr kim loi

i vi nhit in tr kim loi th vic ch to n thch hp hn c l

s dng cc kim loi nguyn cht nh: platin, ng, niken. tng nhy

cm nn s dng cc kim loi c h s nhit in tr cng ln cng tt. Tuy

nhin ty thuc vo khong nhit cn kim tra m ta c th s dng nhit

in tr loi ny hay khc. C th: nhit in tr ch to t dy dn bng

ng thng lm vic trong khong nhit t -5001500C vi h s nhit

in tr =4,27.10-3; Nhit in tr t dy dn platin mnh lm vic trong



9

khong nhit -19006500C vi =3,968.10-3

C0

1

; Nhng khi lm vic

ngn hn, cng nh khi t in tr nhit trong chn khng hoc kh trung

tnh th nhit lm vic ln nht ca n c th cn cao hn.

Cu trc ca nhit in tr kim loi bao gm: dy dn mnh kp i

qun trn khung cch in to thnh phn t nhy cm, n c t trong

chic v c bit c cc cc a ra. Gi tr in tr nhit c ch to t

10100.

i vi nhit in tr kim loi th quan h gia in tr vi nhit c

dng sau:

R() = R0(1+.+.2+.

3+...) (1.6)

Trong : R0-in tr dy dn ng vi nhit ban u 00C.

R-in tr dy dn ng vi nhit .

-nhit [0C]

,,-cc h s nhit in tr = const.

C0

1

thy r hn na v bn cht ca nhit in tr kim loi, chng ta c

th xem qua in tr sut ca n c tnh theo cng thc :

.e.n

1 (1.7)

Trong : n--s in t t do trong mt n v th tch.

e -in tch ca in t t do.



10

- -tnh linh hot ca in t, c c trng bi tc ca n trong

trng c cng 1vn/cm.

Cc kim loi dng lm in tr nhit thng c in tr sut nh

10-510-6/cm, v c mt in t ln (khng ph thuc vo nhit ).

Khi nhit tng ph thuc vo s dao ng ca mng tinh th kim loi,

tc l n c xc nh bi tnh linh hot ca cc in t. Nh vy khi c s

thay i nhit th cng lm cho tnh linh hot ca cc in t thay i theo.

Tuy nhin tnh linh hot ca cc in t cn ph thuc vo mt tp chttrong kim loi. C th in tr sut ca kim loi nguyn cht c th xc nh

theo dng: = 0+ (), trong 0khng ph thuc vo nhit ; cn ()

l mt hm ph thuc khng c nh: ng vi nhit trong khong no

th n l tuyn tnh () = K., nhng ng vi nhit rt thp (00C) th

quan h l hm bc nm ca nhit . Trn hnh 1.3.a biu din mi quan

h gia in tr v nhit , hnh 1.3.b l dng c tnh vn-ampe ca nhitin tr kim loi.

nhy cm ca nhit in tr c xc nh theo biu thc:

R

d

dRS (1.5)

Trong : R -s thay i in tr khi c s thay i nhit . Vic

s dng nhit in tr kim loi o nhit cao rt tin cy, m bo

Hnh1.3. c tnh nhit (a) v c tnh vn_ampe

ca nhit in tr kim loi (b).

ng

platin

R

10

5

0 20 40 60 K

U

I

0

a) b)



11

chnh xc cao n 0,0010C v sai s o khng qu 0,5 n 1%; Tuy nhin khi

dng ti qua n c gi tr khng ln lm. Nu nh c dng in ln lun

chy qua nhit in tr, th s qu nhit ca n s ln hn rt nhiu so vi

mi trng xung quanh. Khi qu nhit xc lp s c xc nh bi

iukin truyn nhit trn b mt ca nhit in tr (tc chuyn ng ca

mi trng cn kim tra so vi nhit in tr, v t trng ca mi trng ).

Hin tng ny c s dng o tc thng lng (dng chy) ca cht

lng v kh, cng nh o t trng ca kh.... Bn cnh u im trn th bn

thn nhit in tr kim loi c nhng nhc im sau:

Th nht n l khu phi chu k c m t bng phng trnh vi phn

bc nht n gin

(TP+1)R(t) = K(t) (1.6)

Trong hng s thi gian T ca n c gi tr t vi giy n vi trm

giy. K chnh l nhy S.

Th hai rt c bn l kch thc ca nhit in tr kim loi ln nnhn chvic s dng n o nhit ni hp.

Mt s nhit in tr kim loi thng dng:

-Nhit in tr Platin: Nhit in tr Platin thng c ch to di

dng dy qun ng knh (0.05 -> 0.1)mm, o nhit t 2000C -> 10000C

vi chnh xc tng i cao,ngay c trong nhng iu kin mi trng d

oxy ha (= 3,9.10-3

/0

C).Tuy nhin, nhit xp x 10000C hoc cao hn, Platin thng km

bn v ch th nhit mt chnh xc.

-Nhit in tr Nickel:

C u im l nhy nhit rt cao (6,66.10-3/0C) t 00C n 1000C, in tr

sut l 1,617.10-8(cn ca Platin l 1,385.10-8). Nickel chng li s oxy ha,

thng c dng nhit nh hn 250

0

C.



12

-Nhit in tr ng:

c s dng v c tuyn rt tuyn tnh ca s thay i in tr theo nhit.

Tuy nhin v phn ng ha hc nn khng cho php s dng nhit ln

hn 1800C, v v in tr sut b nn khi dng, m bo c gi tr in tr

nht nh, chiu di dy phi ln gy nn mt s cng knh bt tin.

-Nhit in tr Tungstne:

C nhy nhit ca in tr ln hn ca Platin trong trng hp nhit

cao v n thng c s dng nhit cao hn Platin vi mt tuyn

tnh hn Platin.Tungstne c th c cu to di dng nhng si rt mnh

cho php thc hn in tr c gi tr cao, nh vy vi gi tr in tr chotrc, chiu di dy s gimthiu.

b)Nhit in tr bn dn (Thermistor)

Nhit in tr c ch to t vt liu bn dn c gi l termistor;

Chng c s dng rng ri trong cc h thng t ng kim tra v iu

khin. Termistor c ch to t hp kim ca ng - mng gan hoc c ban -

mng gan di dng thi, a trn hoc hnh cu. Loi ny hon ton tringc vi nhit in tr kim loi: khi nhit tng th in tr ca n li

gim theo quy lut:

R() = R0.e-

= R0(1- +2

2

2

- ...) (1.7)

Trong h s nhit in tr ca termistor thng c gi tr

= (0,03 0,06).

C0

1

in tr sut ca termistor c tnh theo cng thc:

= A.eB/

(1.8)

Trong : A -hng s ph thuc kch thc ca termistor



13

B -hng s ph thuc tp cht trong cht bn dn

Cng nh in tr nhit kim loi, termistor cng c hai c tnh: ctnh nhit l quan h gia in tr ca termistor vi nhit (hnh 1.2.a) v

c tnh vn - ampe l quan h gia in p t trn termistor vi dng in

chy qua n ng vi nhit no 0(hnh 1.2.b). Chng ta thy rng c

tnh vn - ampe ca termistor c gi tr cc i ca U ng vi I 1no , l do

khi tng dng ln hn I1th n s nung nng termistor v lm cho gi tr in

tr ca n gim xung. Cc loi termistor thng c ch to t vi chc n vi chc K. Termistor c in tr ln cho php t n v tr cn kim

tra kh xa so vi ni b tr h thng o lng. Chng c th lm vic trong

khong nhit t 600C n +1800C, v cho php o nhit vi chnh

xc 0,00050C. s dng termistor nhit ln hn, hoc nh hn khong

nhit lm vic bnh thng th ngi ta phi s dng n cc t hp cht

bn dn khc. So vi in tr nhit kim loi th termistor c kch thc v

trng lng nh hn, do cho php chng ta t n nhng ni cht hp

kim tra nhit ca i tng no .

U

03> 02> 01

01

02

03

0 I

R []

1200

1000

800

600

400

200

0 20 40 60 80 100 C

b)a)

Hnh 1.4.c tnh nhit (a) v c tnh vn ampe(b)



14

1.3.2.o nhit bng cp nhit in (Thermocouple)

Hnh 1.5.S cp nhit nguv s ni cp nhit ngu

B cm bin cp nhit ngu l mt mch c t hai hay nhiu thanh dn

in gm hai dy dn A v B. Ch ni gia hai thanh kim loi ny c hn

vi nhau. Nu nhit cc mi hn t v t0khc nhau th trong mch khp kn

c mt dng in chy qua. Chiu ca dng nhit in ny ph thuc vo

nhit tung ngca mi hn, ngha l t > t0 th dng in chy theo hngngc li. Nu h mt u th gia hai cc xut hin mt sc in ng

(s) nhit. Nh vy bng cch o s ta c th tm c nhit t ca i

tng o vi t0= const.

Cch u dng c o vo mch b bin i nhit in trn hnh 1.4b.

Mt s cp nhit in thng dng:

-Thermocouple Platin_Rhodium Platin:Nhit s dng : T = -500C -> 15000C

ng knh dy : 0,51mm

Sc in ng Seebeck : E = (-2,3 -> 16,7)mV

Loi 10% Platin : T = 00C -> 6000C , cp chnh xc l +/-2,5%

T = 6000C -> 16000C , cp chnh xc l +/-0,4%

Loi 13% Platin : T = 00

C -> 538

0

C , cp chnh xc l +/-1,4%



15

T = 5380C -> 15000C , cp chnh xc l +/-0,25%

Loi 30% Platin : T = 00C -> 17000C , cp chnh xc l +/-0,5%

-Thermocouple Wolfram-Rhenium:

ng knh dy : 0,40mm

Sc in ng Seebeck : E = (0 38,5)mV

Loi Wolfram_Rhenium 5% : T = 00C 27600C

Loi Wolfram_Rhenium 26% : T = 00C 19500C

Chuyn dng o nhit rt cao.

-Thermocouple Chromel_Alumel:

Nhit s dng : T = -2700C 12500C

ng knh dy : 3,25mm

Sc in ng Seebeck : E = (-5,35 50)mV

Cp chnh xc : T = 00C 4000C l : +/-3%

T = 4000C 12500C l +/-0,75%

-Thermocouple Chromel_Constantan:

Nhit s dng : T = -2700C 8700C

ng knh dy : 3,25mm


Cp chnh xc : T = 00C 4000C l +/-3%

T = 4000C 8700C l +/-0,75%

-Thermocouple Fer_Constantan :

Nhit s dng : T = -2100C 8000C

ng knh dy : 3,25mm

Sc in ng Seebeck : E = (-8 45)mV

Cp chnh xc : T = 00C 4000C l +/-3%

T = 4000C 12500C l +/-0,75%

-Thermocouple Cu_Constantan :



16

Nhit s dng : T = -2700C 3700C

ng knh dy : 1,63mm


Cp chnh xc : T = -1000C -400C l +/-2%

T = -400C 1000C l +/-8%

T = 1000C 3500C l +/-0,75%

1.3.3.o nhit bng ha k quang hc :

Ho k quang hc l tn gi chung ca cc dng c o nhit bng

cch ng dng cc tnh cht ca h thng thu knh quang hc thu ly cc

bc x ca vt th ri cn c theo bc x ca vt th xc nh nhit .

a)Nguyn l c bn

Nguyn l lm vic ca ha k quang hc l da trn cc hin tng

bc x ca cc vt th cc nhit cao, trong c lin quan n vai tr

ca vt en tuyt i. l mt thc th vt cht c kh nng hp thu hon

ton tt c cc bc x nhn c m khng phng x.

b)Mt s dng ca ha k quang hc thng dng

Hin nay, trong cng nghip, ngi ta dng rt nhiuloi ha k quang

hc nh ha k bc x, ha k vi sai, ha k o mu sc, ha k nhit ngu

Nu ha k tiu th ton b nng lng ca bc x ton phn ca vt

th, l ha k bc x ton phn.

Ho k quang in dng s so snh gia s pht sng ca dy tc ngn

n c ch to c bit vi sng ca vt nung nng v xc nh chnhxc dy tc v nhit .

Ha k quang in cho kt qu o khng ph thuc vo ngi quan st

v c th ni lin mch vi cc thit b khng ch nhit t ng.

c)Phm vi s dng

Phm vi s dng l nhit ca vt cn o khng di 800 0C. Tt c

cc loi ha k quang hc u c sai s khng vt qu 1%. Tuy nhin, bng



17

ch nhit trn cc ha k ch hon ton chnh xc vi vt en tuyt i (quy

c c bc x bng 1).V vy, vi gi tr tht ca nhit cc vt cn o ph

thuc vo mc en ca tng cht pht sng. Ho k quang in l dng c

o nhit gin tip nn c nhiu thun li, c th o t xa m khng cn

tip xc vi vt cn o.

1.3.4.o nhit dng diode v transistor

Nhng thnh phn c s dng, diode hay transistor Silicium c

mc nh diode (cc nn v cc thu ni chung) c cung cp theo chiu

thun dng in I khng i, in p V hai u cc ca chng, ty thuc

vo nhit , iu ny c th xem nh tn hiu in i ra t cm bin tythuc vo nhit .

Hnh 1.6.Cm bin o nhit dng diode v transistor

Cc thnh phn c s dng lm cm bin o nhit :

Hnh 1.6.a)diode

Hnh 1.6.b)Transistor mc thnh diode

Hnh 1.6.c)Hai Transistor ging nhau c mc nh diodeNgi ta li dng s thay i tuyn tnh ca mi ni p-n i vi nhit

ch to ra cc diode v transistor chuyn dng, lm cu cm bin nhit

trong o lng v khng ch nhit .

IV

a)

V

I

b)

V2V1

Vd

I1 I2c)



18

Hnh 1.7.S mch cm bin dng diode

Trong :

R1 : phn cc cho dng chy qua diode.

IC1 : dng khuch i o, h s khuch i bng 1, b tr

in p DC ca diode cm bin D.

IC2 : khuch i khng o, h s khuch i bng 5.

Nguyn l hot ng c dng tng t nh mch dng transistor

cm bin.

1.3.5.o nhit bng IC

a)Gii thiu:

K thut vi in t cho php ch to c nhng mch kt ni gm

nhng transistor ging nhau c s dng lm cm bin hon ho o nhit

da vo vic o s khc bit in p VBE di tc ng ca nhit .Cc

cm bin ny to ra cc dng in hc in p t l vi nhit tuyt i,vi

tuyn tnh cao; n c iu li l vn hnh n gin, tuy nhin phm vi hot

ng gii hn ch trong khong 500C n 1500C.

b)Nguyn l chung ca IC o nhit :

L mch tch hp nhn tn hiu nhit chuyn thnh tn hiu di

dng in p hoc tn hiu dng in. Da vo c tnh rt nhy ca cc bn

dn vi nhit , to ra in p hoc dng in t l thun vi nhit tuyt

i. o tn hiu in, ta bit c gi tr ca nhit cn o.



19

S tch cc ca nhit to ra in tch t do v cc l trng trong cht

bn dn bng s ph v cc phn t, bt cc electron thnh dng t do di

chuyn qua cc vng cu trc mng tinh th, to s xuthin cc l trng

nhit lm cho t l in t t do v cc l trng tng ln theo quy lut hm m

vi nhit . Kt qu ca hin tng ny l di mc in p thun, dng

thun ca mi ni p-n (trong diode hay transistor) s tng theo hm m theo

nhit .

V d kho st cm bin IC AD590. Cm bin ny to ra mt dng in thay

i tuyn tnh theo nhit tuyt i, n c dng o nhit trong trng

hp dng dy dn vi khong cch xa.

Hnh 1.8.S nguyn l IC AD590

Cc transistor Q3 v Q4 c cng in p VBEv c dng cc pht ging

nhau v bng:

IE3= IE4=IT/2

Dng in ny i qua Q4 cng chnh l dng in cc pht ca Q1 ,n

xc nh in p nn-pht l:

VBE1= (KT/q).log(IT/ 2Io)

Vi K : hng s Boltzmann

T : 0K



20

q: in tch

Io : dng in nghch (thng thng Io IT= (2/R).(KT/q).log8

S mch o nhit dng IC AD590:

Hnh 1.9.S nguyn l o nhit dng IC AD590

Dng in ITto nn hai u in tr R = 1Kmt in p c tr s

bng TmV(T l nhit tuyt i ca cm bin).

Ngun in p chun do IC AD580L c Eref= 2,5V v nh mch phn

p to ra in p c gi tr khong 273,15mV vi b khuch i c li G =

10, ng ra tn hiu Vo t l vi nhit ca cm bin (theo 0C):

Vo = 10(T273,15)mV = 10(T0C) (mV)

c tnh mt s IC o nhit thng dng:

-AD 590:

+

-(Vout)

10mV/ C Ng raG=10

AD580Eref=2,5V

10k

200

1k1k

0,1%

10k

IT

(VIN) ng vo

AD590

IT

R



21

Ng ra l dng in. nhy 1A/0K chnh xc : +4C Ngun cung cp : Vcc = 4V30V Phm vi s dng : -550C 1500C

-LX5700:

Ng ra l in p nhy : -10mV/0C chnh xc : 3,8K tuyn tnh :>= 1K Phm vi s dng : -550C 1500C Loi ny t s dng v chnh xc thp.

-LM135, LM235, LM335:

Ng ra l in p. nhy : 10mV/0C Dng lm vic : 400A 500A : khng thay i c

tnh.

LM135 c sai s cc i l 1,50C khi nhit ln hn1000C.

Phm vi s dng:LM335 : -100C 1250C

LM235 : -400C 1400C

LM135 : -550C 2000C

LM35 : -550C 1500C



22

1.3.6.Gii thiu m s loi ca cc hng khc nhau

Bng 1.2.My o nhit t xa T1315E

3000oC My o nhit t xa TI315E

M hng TI315E

Phm vi o 500 ~ +3000oC

chnh xc 2% / 2oC

hin th 1C / 1oF

T l khong cch / tit din o 120:1

Khi lng 600g

- S dng tia hng ngoi xc nh im o, o nhit nhng vt xa

bng phng php khng tip xc.Thit k nh gn, d s dng, d thao tc.

Phm vi o rng, o chnh xc. C ng ngm dng cho cc vt o xa.

- Mn hnh hin th LCD. Chc nng ci t gii hn, tnh ton v thng k

gi tr o. Chuyn i n v oC / oF.

Hinh1.10.My o nhit siu nh

Khong o: - C: -40o

C ~ + 200o

C.- F: -40o

F ~ +392o

F. chnh xc: - 1oC trong khong o t -20oC ~ +100oC (-4oF ~ +212oF); -

2oC trong khong o cn li.

chia: 0.1oC (0.1oF)

Pin: 1.5V



23

Bng 1.3.ng h o nhit

Khong

o

chia chnh xc

o

C

-50oC ~

1300oC

0.1o

C-50oC ~ 0oC: (0.5% + 1oC)

0oC ~ 199.9oC: (0.3% + 1oC)

1oC

-50oC ~ 300oC: (0.5% + 1oC)

301oC ~ 1000oC: (0.3% + 1oC)

1001oC ~ 1300oC: (0.5% + 1oC)

o

F

-58oF ~

1999oF

0.1o

F

-58oF ~ 199.9oF: (0.3% + 2oF)

1oF -58oF ~ 1999oF: (0.3% + 2oF)

Pin: 9V; Kch thc: 143 x 74 x 34mm.

Trng lng: 226g; Xut x: i Loan.



24

CHNG 2.

THITK MCH O NHIT

2.1.CC LINH KIN CHNH S DNG TRONG MCH

2.2.1.CM BIN O NHIT LM35

a.Gii thiu cm bin o nhit LM35

Trong bi ny chng ta s dng con LM35DZ

* c im:

- Di nhit bin i: 0 n 100

-Nhit ra thng thang o Celcius ngha l 25 C in p ra l 0.25V

- Tng ng 10mV/ C

- m bo chnh xc 0.5 C ti nhit 25 C.

- Lm vic vi ngun nui 4V n 30V

- Tr khng ra thp 0.1 ohm vi ti 1mA

- Kh nng t lm nng thp, 0.08 C trong khng kh.

Hnh 2.1. Cm bin nhit LM35DZ

Cch mc: n gin l ni chn +Vs vi ngun v chn GND vi t chn

OUTPUT ni vi chn Vin+ ca ADC0804



25

b.Di nhit v s thay i tr khng theo nhit ca LM35

Cc b bin i (Transducer) chuyn i cc i lng vt l v d nh

nhit , cng nh sng, lu tc v tc thnh cc tn hiu in ph

thuc vob bin i m u ra c th l tn hiu dng in p, dng, tr

khng hay dung khng. V d, nhit c bin i thnh v cc tn hiu

in s dng mt b bin i gi l Thermistor (b cm bin nhit), mt b

cm bin nhit p ng s thay i nhit bng cch thay i tr khng

nhng p ng ca n khng tuyn tnh.

Bng 2.1.Tr khng ca b cm bin nhit theo nhit

Nhit ( C) Tr khng ca cm bin (k)0 29.490

25 10.000

50 3.893

75 1.700

100 0.817

Bng 2.2.Hng dn chn lot cccm bin nhit h LM35

M sn phm Di nhit chnh xc u ra

LM35A -55 C to + 150 C + 1.0 C 10 mV/F

LM35 -55 C to + 150 C + 1.5 C 10 mV/F

LM35CA -40 C to + 110 C + 1.0 C 10 mV/F

LM35C -40 C to + 110 C + 1.5 C 10 mV/FLM35D 0 C to + 100 C + 2.0 C 10 mV/F

Lot cc b cm bin LM35 l b cm bin nhit mch tch hp chnh xc

cao m in p u ra ca n t l tuyn tnh vi nhit theo thang

Celsius. Chng cng khng yu cu cn chnh ngoi v vn chng c

cn chnh. Chng a rain p 10mV cho mi s thay i 10C. Bng2.2

hng dn ta chn cc cm bin h LM35.



26

c. Nguyn l o v chuyn i tng t/s ca ADC

Khi nhit mi trng thay i 1 lm cho tr khng ca cm bin

LM35 thay i dn n in p u vo Vinca ADC thay i. in p Vin

vo ADC s c so snh vi Ud ca ADC. Udc th thay i t 0V n

2(Vref/2).

Ban u Ud= 0, nu Vin > Udkhi Uds c cng thm mt gi tr l U .

UUU dd , trong :

mVV

U ref

10

256

)2/(2 (2.1)

ng thi gi tr b m tng thm 1. Qu trnh so snh c nh vy n khi

no Ud=Vinth dng. Khi gi tr ca b m chnh l gi tr thp phn.

Kh nng t lm nng ca LM35DZ trong khng kh l 0,1oC.

Cm bin LM35 c h s nhit l 10mV/oC, do sai s v nhit ca

LM35DZ s l 0,5oC. Khi in p u vo V ins c lm trn ln hoc

xung . Khi Vini vo so snh vi in p Udca ADC, ta nhn thy rng

mc in pca ADC l 10mV nn sai s m n gy ra l 0,5mV tng ng

vi gi tr nhit l 0,5oC.

Vy sai s tng cng ca h thng l 1.1oC.

Do vy nhit thc t ca ta s l : treal= to 1,1oC.

tng chnh xc ca php o ln ta c th dng mt cm bin khc c

chnh xc cao hn, c th gim in p a vo chn Vref/2 gim bc inp vi phn bc thang ca ADC, Tuy nhin, khi bc in p ca ADC v cm

bin khng ng nht th s gy kh khn cho qu trnh x l d liu a ra

khu hin th hoc c th gy ra sai s.Ty thuc vo php hin th m ngi

ta c th t gi tr in p cho chn Vref/2 sao cho hp l.



27

Hnh 2.1.S ghp ni LM35

2.2.GII THIU V H VI IU KHIN PIC

2.2.1.Tng quan v h vi iu khin PIC

PIC l vit tt ca Programable Intelligent Computer, c th tm dch

l my tnh thngminh kh trnh do hng Genenral Instrument t tn chovi iu khin u tin ca h:

PIC1650 c thit k dng lm cc thit b ngoi vi cho vi iu khin

CP1600. Vi iukhin nysau c nghin cu pht trin thm v t

hnh thnh nn dng vi iukhin PIC ngy nay.

Hin nay trn th trng c rt nhiu h vi iu khin nh 8051,

Motorola 68HC, AVR,ARM,... Ngoi h 8051 c hng dn mt cch cnbn mi trng i hc,bn thnngi vit chn h vi iu khin PIC

m rng vn kin thc v pht trin cc ngdng trn cng c ny v cc

nguyn nhn sau:

H vi iu khin ny c th tm mua d dng ti th trng Vit Nam.

Gi thnh khng qu t.

C y cc tnh nng ca mt vi iu khin khi hot ng c lp.



28

L mt s b sung rt tt v kin thc cng nh v ng dng cho h vi

iu khinmang tnh truyn thng: h vi iu khin 8051.

S lng ngi s dng h vi iu khin PIC. Hin nay ti Vit Nam

cng nh trn th gii, h vi iu khin ny c s dng kh rng ri. iu

ny to nhiu thun li trongqu trnh tm hiu v pht trin cc ng dng

nh: s lng ti liu, s lng cc ng dngm c pht trin thnh

cng, d dng trao i, hc tp, d dng tm c s ch dn khi gp kh

khn,

S h tr ca nh sn xut v trnh bin dch, cc cng c lp trnh, np

chng trnht n gin n phc tp,Cc tnh nng a dng ca vi iu khin PIC, v cc tnh nng ny khng

ngng cpht trin.

2.2.2.Kin trc PIC

Cu trc phn cng ca mt vi iu khin c thit k theo hai dng kin

trc: kin trcVon Neuman v kin trc Havard.

Hnh 2.2.Kin trc Havard v kin trc Von-Neuman

T chc phn cng ca PIC c thit k theo kin trc Havard. im

khc bit gia kintrc Havard v kin trc Von-Neuman l cu trc b nh

d liu v b nh chng trnh.



29

i vi kin trc Von-Neuman, b nh d liu v b nh chng trnh

nm chung trong mtb nh, do ta c th t chc, cn i mt cch linh

hot b nh chng trnh v b nh d liu. Tuy nhin iu ny ch c

ngha khi tc x l ca CPU phi rt cao, v vi cu trc , trong cng

mt thi im CPU ch c th tng tc vi b nh d liu hoc b nh

chng trnh. Nh vy c th ni kin trc Von-Neuman khng thch hp vi

cu trc camt vi iu khin.

i vi kin trc Havard, b nh d liu v b nh chng trnh tch

ra thnh hai b nhring bit. Do trong cng mt thi im CPU c th

tng tc vi c hai b nh, nh vytc x l ca vi iu khin c cithin ng k.

Mt im cn ch na l tp lnh trong kin trc Havard c th c ti u

ty theo yu cu kin trc ca vi iu khin m khng ph thuc vo cu trc

d liu. V d, i vi vi iu khin dng 16F, di lnh lun l 14 bit

(trong khi d liu c t chc thnh tngbyte, cn i vi kin trc Von-

Neuman, di lnh lun l bi s ca 1 byte (do d liuc t chc thnhtng byte). c im ny c minh ha c th trong hnh 2.2.

2.2.3.RISC v CISC

Nh trnh by trn, kin trc Havard l khi nim mi hn so vi

kin trc Von-Neuman. Khi nim ny c hnh thnh nhm ci tin tc

thc thi ca mt vi iu khin.

Qua vic tch ri b nh chng trnh v b nh d liu, bus chngtrnh v bus d liu,CPU c th cng mt lc truy xut c b nh chng

trnh v b nh d liu, gip tng tc x l ca vi iu khin ln gp i.

ng thi cu trc lnh khng cn ph thuc vo cu trc d liu na m c

th linh ng iu chnh ty theo kh nng v tc ca tng vi iukhin.

V tip tc ci tin tc thc thi lnh, tp lnh ca h vi iu khin PIC

c thit k sao cho chiu di m lnh lun c nh (v d i vi h



30

16Fxxxx chiu di m lnhlun l 14 bit) v cho php thc thi lnh trong mt

chu k ca xung clock ( ngoi tr mt strng hp c bit nh lnh nhy,

lnh gi chng trnh con cn hai chu k xung ng h).

iu ny c ngha tp lnh ca vi iu khin thuc cu trc Havard s

t lnh hn, ngn hn,n gin hn p ng yu cu m ha lnh bng

mt s lng bit nht nh.

Vi iu khin c t chc theo kin trc Havard cn c gi l vi

iu khin RISC(Reduced Instruction Set Computer) hay vi iu khin c tp

lnh rt gn. Vi iu khin c thit k theo kin trc Von-Neuman cn

c gi l vi iu khin CISC (ComplexInstruction Set Computer) hay viiu khin c tp lnh phc tp v m lnh ca n khngphi l mt s c

nh m lun l bi s ca 8 bit (1 byte).

2.2.4.Pipelining

y chnh l c ch x l lnh ca cc vi iu khin PIC. Mt chu k

lnh ca vi iu khins bao gm 4 xung clock. V d ta s dng oscillator c

tn s 4 MHZ, th xung lnh s ctn s 1 MHz (chu k lnh s l 1 us). Gis ta c mt on chng trnh nh sau:

1. MOVLW 55h

2. MOVWF PORTB

3. CALL SUB_1

4. BSF PORTA,BIT3

5. instruction @ address SUB_1 y ta ch bn n qui trnh vi iu khin x l on chng trnh

trn thng quatng chu k lnh. Qu trnh trn s c thc thi nh sau:



31

Hnh 2.3.C ch pipelining

TCY0: c lnh 1

TCY1: thc thi lnh 1, c lnh 2

TCY2: thc thi lnh 2, c lnh 3

TCY3: thc thi lnh 3, c lnh 4.

TCY4: v lnh 4 khng phi l lnh s c thc thi theo qui trnh thc thi

ca chngtrnh (lnh tip theo c thc thi phi l lnh u tin ti label

SUB_1) nn chu k thc thilnh ny ch c dng c lnh u tin tilabel SUB_1. Nh vy c th xem lnh 3cn 2 chu k xung clock thc thi.

TCY5: thc thi lnh u tin ca SUB_1 v c lnh tip theo ca

SUB_1.

Qu trnh ny c thc hin tng t cho cc lnh tip theo ca

chng trnh.

Thng thng, thc thi mt lnh, ta cn mt chu k lnh gi lnh, v mt chu kxung clock na gii m v thc thi lnh. Vi c ch

pipelining c trnh by trn, mi lnh xem nh ch c thc thi trong

mt chu k lnh. i vi cc lnh m qu trnh thc thi n lm thay i gi tr

thanh ghi PC (Program Counter) cn hai chu k lnh thc thi v phithc

hin vic gi lnh a ch thanh ghi PC ch ti. Sau khi xc nh ng v

tr lnhtrong thanh ghi PC, mi lnh ch cn mt chu k lnh thc thi xong.



32

2.2.5.Cc dng PIC v cch la chon PIC

Cc k hiu ca vi iu khin PIC:

PIC12xxxx: di lnh 12 bit



C: PIC c b nh EPROM (ch c 16C84 l EEPROM)

F: PIC c b nh flash

LF: PIC c b nh flash hot ng in p thp

LV: tng t nh LF, y l k hiu c

Bn cnh mt s vi iu khin c k hiu xxFxxx l EEPROM, nuc thm ch A cui l flash (v d PIC16F877 l EEPROM, cn

PIC16F877A l flash).

Ngoi ra cn c thm mt dng vi iu khin PIC mi l dsPIC.

Vit Nam ph bin nht l cc h vi iu khin PIC do hng

Microchip sn xut.

Cch la chn mt vi iu khin PIC ph hp:Trc ht cn ch n s chn ca viiu khin cn thit cho ng

dng. C nhiuvi iu khin PIC vi s lng chn khc nhau, thm ch c vi

iu khin ch c 8 chn,ngoi ra cn c cc vi iu khin 28, 40, 44, chn.

Cn chn vi iu khin PIC c b nh flash c th np xa chng trnh

c

nhiu ln hn.Tip theo cn ch n cc khi chc nng c tch hp sn trong vi

iu khin,cc chun giao tip bn trong.

Sau cng cn ch n b nh chng trnh m vi iu khin cho

php.Ngoi ra mi thng tin v cch la chn vi iu khin PIC c th c

tm thy trongcun sch Select PIC guide do nh sn xut Microchip cung

cp.



33

Ngn ng lp trnh cho PIC rt a dng. Ngn ng lp trnh cp thp c

MPLAB (c cungcp min ph bi nh sn xut Microchip), cc ngn ng

lp trnh cp cao hn bao gm C,Basic, Pascal, Ngoi ra cn c mt s

ngn ng lp trnh c pht trin dnh ring cho PIC nh PICBasic,

MikroBasic,

y cng l mt dng sn phm rt a dng dnh cho vi iu khin PIC.

C th s dng ccmch np c cung cp bi nh sn xut l hng

Microchip nh: PICSTART plus, MPLAB ICD 2, MPLAB PM 3, PRO

MATE II. C th dng cc sn phm ny np cho vi iukhin khc thng

qua chng trnh MPLAB. Dng sn phm chnh thng ny c u th l npc cho tt c cc vi iu khinPIC, tuy nhin gi thnh rt cao v thng

gp rtnhiu kh khn trong qu trnh mua sn phm.

Ngoi ra do tnh nng cho php nhiu ch np khc nhau, cn c rt

nhiu mch np cthit k dnh cho vi iu khin PIC. C th s lc mt

s mch np cho PIC nh sau:

JDM programmer: mch np ny dng chng trnh np Icprog chophp np cc viiu khin PIC c h tr tnh nng np chng trnh in p

thp ICSP (In Circuit SerialProgramming). Hu ht cc mch np u h tr

tnh nng np chng trnh ny.WARP-13A v MCP-USB: hai mch np ny

ging vi mch np PICSTART PLUSdo nh sn xut Microchip cung cp,

tng thch vi trnh bin dch MPLAB, ngha l ta c th trc tip dng

chng trnh MPLAB np cho vi iu khin PIC m khng cn s dng mtchng trnh np khc, chng hn nh ICprog.

P16PRO40: mch np ny do Nigel thit k v cng kh ni ting. ng cn

thit kc chng trnh np, tuy nhin ta cng c th s dng chng trnh

np Icprog.

Mch np Universal ca Williem: y khng phi l mch np chuyn dng

dnh cho PIC nh P16PRO40.



34

Cc mch np k trn c u im rt ln l n gin, r tin, hon ton

c th t lp rpmt cch d dng, v mi thng tin v s mch np, cch

thit k, thi cng, kim tra v chng trnh np u d dng tm c v

download min ph thng qua mng Internet. Tuynhin cc mch np trn c

nhc im l hn ch v s vi iu khin c h tr, bn cnh mi mch

np cn c s dng vi mt chng trnh np thch hp.

2.3.VI IU KHIN PIC 18F4680

2.3.1.Gii thiu v PIC18F4680:

y l vi iu khin thuc h PIC18Fxxx vi tp lnh gm 35 lnh c

di 16 bit. Mi lnh u c thc thi trong mt chu k xung clock. Tc hot ng ti a cho php l 40 MHz vi mt chu k lnh l 200ns. B nh

chng trnh 48K byte , b nh d liu SRAM 3328 byte v b nh d liu

EEPROM vi dung lng 1024 byte. S PORT I/O l 5 vi 44 pin I/O.

Hnh 2.4.S cu trc chung ca Pic18f4680



35

S lc v Vi iu khin PIC 18F4680:

48 K Flash ROM.

3328 Bytes RAM.

1024 Bytes EEPROM.

5 ports (A, B, C, D, E) vo ra vi tn hiu iu khin c lp.

2 b nh thi 8 bits (Timer 0 v Timer 2).

2 b nh thi 16 bits (Timer 1 v Timer 3) c th hot ng trong ch

tit kim nng lng (SLEEP MODE) vingun xung Clock ngoi.

- 2 b CCP( Capture / Compare/ PWM).

- 1 b bin i AD 10 bits, 10 ng vo.- 2 b so snh tng t (Compartor).- 1 b nh thi gim st (WatchDog Timer).- Mt cng song song 16 bits vi cc tn hiu iu khin.- Mt cng ni tip.- tit kim nng lng.- Np chng 15 ngun ngt.- C ch trnh bng cng ni tip ICSP.- 35 tp lnh c di 16 bits.- Tn s hot ng ti a 40MHz



36

Hnh 2.5.Hnh dng v s chn Pic18f4680



37

Hnh 2.6.S khi ca Pic18f4680



38

Mt s im c bit ca CPU:

a)Dao ng:

Pic18F4680 c kh nng s dng mt trong 4 loi oscillator, l:

- LP: (low power crystal).

- XT: thch anh bnh thng

- HS: (high-speed crystal).

- RC: (resistor/capacitor)

Trong cc ch LP,XT v HS chng ta s dng thch anh dao ng ni vo

cc chn OSC1 v OSC2 to dao ng.

Bng 2.3.l chn t trong dao ng thch anh

Hnh 2.7.S to dao ng

Vic la chn t trong dao ng thch anh da vo bng sau:

Lu : T c gi tr ln s tng tnh n

nh ca dao ng nhng cng lm tng

thi gian khi ng.

Ch dao ng RC c s dng

nh mt gii php tit kim trong cc ng

dng khng cn s chnh xc v thi gian.

Hnh 2.8.Ch dao ng RC



39

b)Cch tnh chu k my:

V d ta s dng thch anh 10Mhz. Khi :

Tn s dao ng ca thch anh l Fosc = 10Mhz

=> Chu k dao ng ca thch anh l Tosc = 1/Tosc= 1/10*106 (s)

Chu k my:

T_instruction = 4*Tosc = 4/10*106(s) = 0.4 s = 400 ns

2.3.2.Cc cht Reset

C nhiu ch reset vi iu khin, bao gm:

- Power-on Reset POR (Reset khi cp ngun hot ng cho vi iu khin).

- Reset trong qu trnh hot ng.- T ch sleep.

- WDT reset (reset do khi WDT to ra trong qu trnh hot ng).

- WDT wake up t ch sleep.

- Brown-out reset (BOR).

- Power-on reset (POR): y l xung reset do vi iu khin to ra khi pht

hin ngun cung cp VDD. Khi hot ng ch bnh thng, vi iu khincn c m bo cc thng s v dng in, in p hot ng bnh

thng. Nhng nu cc tham s ny khng c m bo, xung reset do POR

to ra s a vi iu khin v trng thi reset v ch tip tc hot ng khi no

cc tham s trn c m bo.

Power-up Timer (PWRT): y l b nh thi hot ng da vo mch

RC bn trong vi iu khin. Khi PWRT c kch hot, vi iu khin s ca v trng thi reset.

PWRT s to ra mt khong thigian delay (khong 72 ms) VDD

tng n gi tr thchhp.

Oscillator Start-up Timer (OST): OST cung cp mt khong thi gian

delay bng 1024 chu k xung ca oscillator sau khi PWRT ngng tc ng (vi

iu khin iu kin hot ng) m bo s n nh ca xung do



40

oscillator pht ra. Tc ng ca OST cn xy ra i vi POR reset v khi vi

iu khin c nh thc t ch sleep. OST ch tc ng i vi cc lai

oscillator l XT, HS v LP.

Brown-out reset (BOR): Nu VDD h xung thp hn gi tr VBOR

(khong 4V) v ko di trong khong thi gian ln hn TBOR (khong 100

us), BOR c kch hot v vi iu khin c a v trng thi BOR reset.

Nu in p cung cp cho vi iu khin h xung thp hn VBOR trong

khong thi gian ngn hn TBOR, viiu khin s khng c reset. Khi in

p cung cp cho vi iu khin hot ng, PWRT c kch hot to ra

mt khong thi gian delay (khong 72ms). Nu trong khong thi gian nyin p cung cp cho vi iu khin li tip tc h xung di mc in p

VBOR, BOR reset s li c kch hot khi vi iu khin in p hot

ng. Mt im cn ch l khi BOR reset c cho php, PWRT cng s

hot ng bt chp trng thi ca bit PWRT.

Hinh 2.9.S cc ch reset ca PIC 18F4680



41

Tm li vi iu khin hot ng c t khi cp ngun cn tri qua cc

bc sau:

- POR tc ng.

- PWRT (nu c cho php hot ng) to ra khong thi gian delay

TPWRT n nh ngun cung cp.

- OST (nu c cho php) to ra khong thi gian delay bng 1024 chu k

xung ca oscillator n nh tn s ca oscillator.

n thi im ny vi iu khin mi bt u hot ng bnh thng. Thanh ghi

iu khin v ch th trng thi ngun cung cp cho vi iu khin l thanh ghi PCON

a)MCLR

PIC18F4680 c mt b lc nhiu phn MCLR. B lc nhiu ny s

pht hin v b qua cc tn hiu nhiu.

Ng vo MCLR trn chn 4 ca PIC18F4680 .Khi a chn ny xung

thp th cc thanh ghi bn trong VK s c ti nhng gi tr thch hp

khi ng li h thng.

(Lu : reset do WDT khng lmchn MCLR cung mc thp).b) Interrupts

PIC18F4680 c nhiu ngun ngt khc nhau. y l mt s ngt tiu biu:

- Ngt ngoi xy ra trn chn INT.- Ngt do Timer0.- Ngt do Timer1.-

Ngt do Timer2.- Ngt do Timer3.- Ngt do thay i trng thi trn cc chn PortB.- Ngt so snh in th.- Ngt do Port song song.- Ngt USART.- Ngt nhn d liu.



42

- Ngt truyn d liu .- Ngt chuyn i ADC.- Ngt mn hnh LCD.- Ngt hon tt ghi EEPROM.- Ngt module CCP.- Ngt Module SSP.

Cc thanh ghi chc nng ngt: INTCON,PIE1,PIR1,PIE2,PIR2 (cc thanh

ghi ny s c nghin cu cc phn sau).

2.3.3.T chc b nh

Cu trc b nh ca vi iu khin PIC18F4680 bao gm b nh chngtrnh (Program Memory) v b nh d liu (Data Memory).

a)B nh chng trnh

B nh chng trnh ca vi iu

khin PIC18F4680 l b nh flash,

dung lng b nh 48K byte v c

phn thnh nhiu trang (t page0 npage 3) . Nh vy b nh chng trnh

c kh nng cha c 48*1024 =

49154 lnh (v mt lnh sau khi m ha

s c dung lng 1 word (14 bit).

Khi vi iu khin c reset, b m

chng trnh s ch n a ch 0000h(Reset vector). Khi c ngt xy ra, b

m chng trnh s ch n a ch

0004h (Interrupt vector). B nh

chng trnh khng bao gmb nh

stack v khng c a ch ha bi b

m chng trnh. Hnh 2.10.B nh chng trnh Pic18f4680



43

b) B nh d liu

B nh d liu ca PIC l b nh EEPROM c chia ra lm nhiu bank.

i vi PIC18F4680 b nh d liu c chia ra lm16 bank. Mi bank c

dung lng 256 byte, bao gm cc thanh ghi c chc nng c bit SFR

(Special Function Register) nm cc vng a ch thp v cc thanh ghi mc

ch chung GPR (General Purpose Register) nm vng a ch cn li trong

bank. Cc thanh ghi SFR thng xuyn c s dng (v d nh thanh ghi

STATUS) s c t tt c cc bank ca b nh d liu gip thun tin

trong qu trnh truy xut v lm gim bt lnh ca chng trnh. S c th

ca b nh d liu PIC18F4680nh sau:

Hnh 2.11.B nh d liu Pic18f4680



44

c)Thanh ghi chc nng c bit SFR

y l cc thanh ghi c s dng bi CPU hoc c dng thit lp v

iu khin cc khi chc nng c tch hp bn trong vi iu khin. C th

phn thanh ghi SFR lm hai lai: thanh ghi SFR lin quan n cc chc nng

bn trong (CPU) v thanh ghi SRF dng thit lp v iu khin cc khi

chc nng bn ngoi (v d nh ADC, PWM ).

Thanh ghi STATUS (03h, 83h, 103h, 183h):thanh ghi cha kt qu thc

hin php ton ca khi ALU, trng thi reset v cc bit chn bank cn truy

xut trong b nh d liu.

Bng 2.4.Thanh ghi STATUS (03h, 83h, 103h, 183h):

Thanh ghi OPTION_REG (81h, 181h): thanh ghi ny cho php c v ghi,

cho php iu khin chc nng pull-up ca cc chn trong PORTB, xc lp

cc tham s v xung tc ng, cnh tc ng ca ngt ngoi vi v b m

Timer0.Bng 2.5.Thanh ghi OPTION_REG (81h, 181h)

Thanh ghi INTCON (0Bh, 8Bh,10Bh, 18Bh):thanh ghi cho php c v

ghi, cha cc bit iu khin v cc bit c hiu khi timer0 b trn, ngt ngoi vi

RB0/INT v ngt interrputon- change ti cc chn ca PORTB.Bng 2.6.Thanh ghi INTCON (0Bh, 8Bh,10Bh, 18Bh)

Thanh ghi PIE1 (8Ch): cha cc bit iu khin chi tit cc ngt ca cc

khi chc nng ngoi vi.



45

Bng 2.7.Thanh ghi PIE1 (8Ch)

Thanh ghi PIR1 (0Ch) cha c ngt ca cc khi chc nng ngoi vi, cc

ngt ny c cho php bi cc bit iu khin cha trong thanh ghi PIE1.

Bng 2.8.Thanh ghi PIR1 (0Ch)

Thanh ghi PIE2 (8Dh): cha cc bit iu khin cc ngt ca cc khi chc

nng CCP2, SSP bus, ngt ca b so snh v ngt ghi vo b nh EEPROM.

Bng 2.9.Thanh ghi PIE2 (8Dh)

Thanh ghi PIR2 (0Dh): cha cc c ngt ca cc khi chc nng ngoi vi,

cc ngt ny c cho php bi cc bit iu khin cha trong thanh ghi PIE2.

Bng 2.10.Thanh ghi PIR2 (0Dh)

Thanh ghi PCON (8Eh): cha cc c hiu cho bit trng thi cc ch

reset ca vi iu khin.

Bng 2.11.Thanh ghi PCON (8Eh)

d)Thanh ghi mc ch GPR

Cc thanh ghi ny c th c truy xut trc tip hoc gin tip thng

qua thanh ghi FSG (File Select Register). y l cc thanh ghi d liu thng

thng, ngi s dng c th ty theo mc ch chng trnh m c th dng



46

cc thanh ghi ny cha cc bin s, hng s, kt qu hoc cc tham s phc

v cho chng trnh.

e)Stack

Stack khng nm trong b nh chng trnh hay b nh d liu m l mt

vng nh c bit khng cho php c hay ghi.

Khi lnh CALL c thc hin hay khi mt ngt xy ra lm chng trnh

b r nhnh, gi tr ca b m chng trnh PC t ng c vi iu khin ct

vo trong stack. Khi mt trong cc lnh RETURN, RETLW hat RETFIE c

thc thi, gi tr PC s t ng c ly ra t trong stack, vi iu khin s thc

hin tip chng trnh theo ng qui trnh nh trc.B nh Stack trong vi iu khin PIC h 18F4680 c kh nng cha c

8 a ch v hot ng theo c ch xoay vng. Ngha l gi tr ct vo b nh

Stack ln th 9 s ghi

ln gi tr ct vo Stack ln u tin v gi tr ct vo b nh Stack ln th 10

s ghi ln gi tr ct vo Stack ln th 2.

Cn ch l khng c c hiu no cho bit trng thi stack, do ta khngbit c khi no stack trn. Bn cnh tp lnh ca vi iu khin dng PIC

cng khng c lnh POP hay PUSH, cc thao tc vi b nh stack s hon

ton c iu khin bi CPU.

2.3.4.Cc cng xut nhp ca Pic18f4680

Cng xut nhp (I/O port) chnh l phng tin m vi iu khin dng

tng tc vi th gii bn ngoi. Bn cnh , do vi iu khin c tch hpsn bn trong cc c tnh giao tip ngoi vi nn bn cnh chc nng l cng

xut nhp thng thng, mt s chn xut nhp cn c thm cc chc nng

khc th hin s tc ng ca cc c tnh ngoi vi nu trn i vi th gii

bn ngoi.

Vi iu khin PIC18F4585 c 5 cng xut nhp, bao gm PORTA,

PORTB, PORTC, PORTD v PORTE.



47

a) port a

PORTA (RPA) bao gm 8 I/O pin. y l cc chn hai chiu

(bidirectional pin), ngha l c th xut v nhp c. Chcnng I/O ny c

iu khin bi thanh ghi TRISA (a ch 85h). Mun xc lp chc nng ca

mt chn trong PORTA l input, ta set bit iu khin tng ng vi chn

trong thanh ghi TRISA v ngc li, mun xc lp chc nng ca mt chn

trong PORTA l output, ta clear bit iu khin tng ng vi chn trong

thanh ghi TRISA. Thao tc ny hon ton tng t i vi cc PORT v cc

thanh ghi iu khin tng ng TRIS (i vi PORTA l TRISA, i vi

PORTB l TRISB, i vi PORTC l TRISC, i vi PORTD l TRISD vivi PORTE l TRISE). Bn cnh PORTA cn l ng ra ca b ADC, b so

snh, ng vo analog ng vo xung clock ca Timer0 v ng vo ca b giao

tip MSSP (Master Synchronous Serial Port).

Cc thanh ghi SFR lin quan n PORTA bao gm:

- PORTA (a ch 05h) : cha gi tr cc pin trong PORTA.

- TRISA (a ch 85h) : iu khin xut nhp.- CMCON (a ch 9Ch) : thanh ghi iu khin b so snh.

- CVRCON (a ch 9Dh) : thanh ghi iu khin b so snh in p.

- ADCON1 (a ch 9Fh) : thanh ghi iu khin b ADC.



48

Bng 2.12.Tm tt cc thanh ghi lin quan n Port A

b) port b

PORTB (RPB) gm 8 pin I/O. Thanh ghi iu khin xut nhp tng ng

l TRISB. Bn cnh mt s chn ca PORTB cn c s dng trong qu

trnh np chng trnh cho vi iu khin vi cc ch np khc nhau.

PORTB cn lin quan n ngt ngoi vi v b Timer0. PORTB cn c tchhp chc nng in tr ko ln c iu khin bi chng trnh.

Cc thanh ghi SFR lin quan n PORTB bao gm:

- PORTB (a ch 06h,106h) : cha gi tr cc pin trong PORTB

- TRISB (a ch 86h,186h) : iu khin xut nhp

- OPTION_REG (a ch 81h,181h) : iu khin ngt ngoi vi v b

Timer0.



49

Bng 2.13.Tm tt cc thanh ghi lin quan n Port B

c)port c

PORTC (RPC) gm 8 pin I/O. Thanh ghi iu khin xut nhp tng ng

l TRISC. Bn cnh PORTC cn cha cc chn chc nng ca b so snh,

b Timer1, b PWM v cc chun giao tip ni tip I2C, SPI, SSP, USART.

Cc thanh ghi iu khin lin quan n PORTC:- PORTC (a ch 07h) : cha gi tr cc pin trong PORTC

- TRISC (a ch 87h) : iu khin xut nhp.

Bng 2.14.Tm tt cc thanh ghi lin quan n Port C



50

d)port d:

PORTD (RPD) gm 8 chn I/O, thanh ghi iu khin xut nhp tng ng l

TRISD. PORTD cn l cng xut d liu ca chun giao tip PSP (Parallel

Slave Port).

Cc thanh ghi lin quan n PORTD bao gm:

- Thanh ghi PORTD : cha gi tr cc pin trong PORTD.

- Thanh ghi TRISD : iu khin xut nhp.

Bng 2.15.Cc thanh ghi lin quan n Port D

e)port e:

PORTE (RPE) gm 4 chn I/O. Thanh ghi iu khin xut nhp tng ng

l TRISE. Cc chn ca PORTE c ng vo analog. Bn cnh PORTE cn

l cc chn iu khin ca chun giao tip PSP.

Cc thanh ghi lin quan n PORTE bao gm:

- PORTE : cha gi tr cc chn trong PORTE.

- TRISE : iu khin xut nhp v xc lp cc thng s cho chun giao tip

PSP.

- ADCON1 : thanh ghi iu khin khi ADC.



51

Bng 2.16.Cc thanh ghi lin quan n Port E

2.3.5.Cc timer

a) Timer 0y l mt trong ba b m hoc b nh thi ca vi iu khin

PIC18F4585. Timer0 l b m 16 bit hoc 8 bit c kt ni vi b chia tn

s (prescaler) 16 bit. Cu trc ca Timer0 cho php ta la chn xung clock tc

ng v cnh tch cc ca xung clock. Ngt Timer0 s xut hin khi Timer0 b

trn.



52

2.12: S khi ca timer 0Mun Timer0 hot ng ch Timer ta clear bit TOSC

(OPTION_REG), khi gi tr thanh ghi TMR0 s tng theo tng chu k

xung ng h (tn s vo Timer0 bng tn s oscillator). Khi gi tr thanh

ghi TMR0 t FFh tr v 00h, ngt Timer0 s xut hin. Thanh ghi TMR0 cho

php ghi v xa c gip ta n nh thi im ngt Timer0 xut hin mt

cch linh ng. Mun Timer0 hot ng ch counter ta set bit TOSC(OPTION_REG). Khi xung tc ng ln b m c ly t chn

RA4/TOCK1. Bit TOSE (OPTION_REG) cho php la chn cnh tc

ng vo bt m. Cnh tc ng s l cnh ln nu TOSE=0 v cnh tc

ng s l cnh xung nu TOSE=1. Khi thanh ghi TMR0 b trn, bit TMR0IF

(INTCON) s c set. y chnh l c ngt ca Timer0. C ngt ny

phi c xa bng chng trnh trc khi b m bt u thc hin li qutrnh m. Ngt Timer0 khng th nh thc vi iu khin t ch sleep.

Cc lnh tc ng ln gi tr thanh ghi TMR0 s xa ch hot ng ca

prescaler.

Khi i tng tc ng l Timer0, tc ng ln gi tr thanh ghi TMR0 s

xa prescaler



53

nhng khng lm thay i i tng tc ng ca prescaler. Khi i tng tc

ng l WDT, lnh CLRWDT s xa prescaler, ng thi prescaler s ngng

tc v h tr cho WDT.

Cc thanh ghi iu khin lin quan n Timer0 bao gm:

- TMR0 (a ch 01h, 101h) : cha gi tr m ca Timer0.

- INTCON (a ch 0Bh, 8Bh, 10Bh, 18Bh): cho php ngt hot ng (GIE

v PEIE).

- OPTION_REG (a ch 81h, 181h): iu khin prescaler.

b)Timer 1

Timer1 l b nh thi 16 bit, gi tr ca Timer1 s c lu trong haithanh ghi (TMR1H:TMR1L). C ngt ca Timer1 l bit TMR1IF (PIR1).

Bit iu khin ca Timer1 s l TMR1IE (PIE). Tng t nh Timer0,

Timer1 cng c hai ch hot ng: ch nh thi (timer) vi xung kch

l xung clock ca oscillator (tn s ca timer bng tn s caoscillator) v

ch m (counter) vi xung kch l xung phn nh cc s kin cn m ly

t bn ngoi thng qua chn RC0/T1OSO/T1CKI (cnh tc ng l cnh ln).Vic la chn xung tc ng (tng ng vi vic la chn ch hot ng l

timer hay counter) c iu khin bi bit TMR1CS (T1CON). Sau y l

s khi ca Timer1:



54

2.13. 1

Cc thanh ghi lin quan n Timer1 bao gm:

- INTCON (a ch 0Bh, 8Bh, 10Bh, 18Bh): cho php ngt hot ng (GIE

v PEIE).

- PIR1 (a ch 0Ch): cha c ngt Timer1 (TMR1IF).

- PIE1( a ch 8Ch): cho php ngt Timer1 (TMR1IE).

- TMR1L (a ch 0Eh): cha gi tr 8 bit thp ca b m Timer1.

- TMR1H (a ch 0Eh): cha gi tr 8 bit cao ca b m Timer1.

- T1CON (a ch 10h): xc lp cc thng s cho Timer1.

d)Timer 2

Timer2 l b nh thi 8 bit v c h tr bi hai b chia tn s prescaler

v postscaler. Thanh ghi cha gi tr m ca Timer2 l TMR2. Bit cho php

ngt Timer2 tc ng l TMR2ON (T2CON). C ngt ca Timer2 l bit

TMR2IF (PIR1). Xung ng vo (tn s bng tn s oscillator) c a

qua b chia tn s prescaler 4 bit (vi cc t s chia tn s l 1:1, 1:4 hoc 1:16

v c iu khin bi cc bit T2CKPS1:T2CKPS0 (T2CON)).



55

2.14.S khi ca Timer 2

Ngoi ra ng ra ca Timer2 cn c kt ni vi khi SSP, do

Timer2 cn ng vai tr to ra xung clock ng b cho khi giao tip SSP.

Cc thanh ghi lin quan n Timer2 bao gm:

- INTCON (a ch 0Bh, 8Bh, 10Bh, 18Bh): cho php ton b cc ngt

(GIE v PEIE).

- PIR1 (a ch 0Ch): cha c ngt Timer2 (TMR2IF).

- PIE1 (a ch 8Ch): cha bit iu khin Timer2 (TMR2IE).

- TMR2 (a ch 11h): cha gi tr m ca Timer2.

- T2CON (a ch 12h): xc lp cc thng s cho Timer2.

- PR2 (a ch 92h): thanh ghi h tr cho Timer2.

Timer0 v Timer2 l b m 8 bit (gi tr m ti a l FFh), trong khi

Timer1 l b m 16 bit (gi tr m ti a l FFFFh). Timer0, Timer1 v

Timer2 u c hai ch hot ng l timer v counter. Xung clock c tn s

bng tn s ca oscillator. Xung tc ng ln Timer0 c h tr bi

prescaler v c th c thit lp nhiuch khc nhau (tn s tc ng,

cnh tc ng) trong khi cc thng s ca xung tc ng ln Timer1 l c

nh. Timer2 c h tr bi hai b chia tn s prescaler v postcaler c lp,

tuy nhin cnh tc ng vn c c nh l cnh ln. Timer1 c quan h vi

khi CCP, trong khi Timer2 c kt ni vi khi SSP.



56

e) Timer 3

Timer1 l b nh thi 16 bit, gi tr ca Timer1 s c lu trong hai thanh

ghi (TMR3H:TMR3L). C ngt ca Timer1 l bit TMR3IF (PIR1). Bit

iu khin ca Timer3 s l TMR3IE (PIE). Tng t nh Timer0,

Timer1, Timer2, Timer3 cng c hai ch hot ng: ch nh thi

(timer) vi xung kch l xung clock ca oscillator (tn s ca timer bng tn

s ca oscillator) v ch m (counter) vi xung kch l xung phn nh cc

s kin cn m ly t bn ngoi thng qua chn RC0/T1OSO/T1CKI (cnh

tc ng l cnh ln). Vic la chn xung tc ng (tng ng vi vic la

chn ch hot ng l timer hay counter) c iu khin bi bit TMR1CS(T3CON).

2.15. S khica Timer 2

f) ADC

ADC (Analog to Digital Converter) l b chuyn i tn hiu gia hai dng

tng t v s. PIC18F4680 c 11 ng vo analog (RA0,RA1,RA2,RA3,RA5;



57

RE2:RE0 v RB0,RB1,RB7). Hiu in th chun VREF c th c la chn

l VDD, VSS hay hiu in th chun c xc lp trn hai chn RA2 v RA3

2.16.S khi ADC

Kt qu chuyn i t tn tiu tng t sang tn hiu s l 10 bit s

tng ng v c lu trong hai thanh ghi ADRESH:ADRESL.Cc thanh ghi lin quan n b chuyn i ADC bao gm:

- INTCON (a ch 0Bh, 8Bh, 10Bh, 18Bh): cho php cc ngt (cc bit

GIE, PEIE).

- PIR1 (a ch 0Ch): cha c ngt AD (bit ADIF).

- PIE1 (a ch 8Ch): cha bit iu khin AD (ADIE).



58

- ADRESH (a ch 1Eh) v ADRESL (a ch 9Eh): cc thanh ghi cha kt

qu chuyn i AD.

- ADCON0 (a ch 1Fh) v ADCON1 (a ch 9Fh): xc lp cc thng s

cho b chuyn i AD.

- PORTA (a ch 05h) v TRISA (a ch 85h): lin quan n cc ng vo

analog PORTA.

- PORTE (a ch 09h) v TRISE (a ch 89h): lin quan n cc ng vo

analog PORTE.

g)Giao tip ni tip

USART (Universal Synchronous Asynchronous Receiver Transmitter) lmt trong hai chun giao tip ni tip.USART cn c gi l giao din giao

tip ni tip SCI

(Serial Communication Interface). C th s dng giao din ny cho cc giao

tip vi cc

thit b ngoi vi, vi cc vi iu khin khc hay vi my tnh. Cc dng ca

giao din USART ngoi vi bao gm:- Bt ng b (Asynchronous).

- ng b_ Master mode.

- ng b_ Slave mode.

PIC16F4680 c tch hp sn b to tc baud BRG (Baud Rate

Genetator) 8 bit hoc 16bit dng cho giao din USART. BRG thc cht l

mt b m c th c s dng cho c hai dng ng b v bt ng b vc iu khin bi thanh ghi PSBRG. dng bt ng b, BRG cn c

iu khin bi bit BRGH ( TXSTA). dng ng b tc ng ca bit

BRGH c b qua. Tc baud do BRG to ra c tnh theo cng thc

sau:



59

Bng 2.15.Tc baud do BRG

Trong X l gi tr ca thanh ghi RSBRG ( X l s nguyn v 0



60

RC6/TX/CK v RC7/RX/DT).

- Thanh ghi TXREG (a ch 19h): thanh ghi cha d liu cn truyn.

- Thanh ghi TXSTA (a ch 98h): xc lp cc thng s cho giao din.

- Thanh ghi SPBRG (a ch 99h): quyt nh tc baud.

* USART ng b: Giao din USART ng b c kch hot bng cch

set bit SYNC. Cng giao tip ni tip vn l hai chn RC7/RX/DT,

RC6/TX/CK v c cho php bng cch set bit SPEN. USART cho php hai

ch truyn nhn d liu l Master mode v Slave mode. Master mode c

kch hot bng cch set bit CSRC (TXSTA), Slave mode c kch hot

bng cch clear bit CSRC. im khc bit duy nht gia hai ch ny lMaster mode s ly xung clock ng b t b tao xung baud BRG cn Slave

mode ly xung clock ng b t bn ngoi qua chn RC6/TX/CK. iu ny

cho php Slave mode hot ng ngay c khi vi iu khin ang ch sleep.

Cc thanh ghi lin quan n qu trnh truyn d liu bng giao din

USART ng b Master mode:

- Thanh ghi INTCON (a ch 0Bh, 8Bh, 10Bh, 18Bh): cho php tt c ccngt.

- Thanh ghi PIR1 (a ch 0Ch): cha c hiu TXIF.

- Thanh ghi PIE1 (a ch 8Ch): cha bit cho php ngt truyn TXIE.

- Thanh ghi RCSTA (a ch 18h): cha bit cho php cng truyn d liu

(hai pin RC6/TX/CK v RC7/RX/DT).

- Thanh ghi TXREG (a ch 19h): thanh ghi cha d liu cn truyn.- Thanh ghi TXSTA (a ch 98h): xc lp cc thng s cho giao din.

- Thanh ghi SPBRG (a ch 99h): quyt nh tc baud.



61

2.4.6.S ghp ni mch o nhit

Mch o nhit LM35 hin th trn LCD 16x22.3.7code mch o nhit d, hin th trn LCD.//================================================= ====// Ten chuong trinh : Mach do nhiet do// Mo ta phan cung : Dung PIC16F4680 thach anh 20MHz// : LCD giao tiep voi PORTD// : Dau ra LM35 dua vao chan AN0

// // Chu thich : hoac cac chu thich khac// : dung che do Power On Reset// : chuong trinh viet cho PIC Tutorial#include #include #device *=16 adc=10#FUSES NOWDT, HS, NOPUT, NOPROTECT, NODEBUG,

NOBROWNOUT,

NOLVP, NOCPD, NOWRT

LCD

D7

D6

D5

D4

D3

D2

D1

D0

E RW

RS

VEE

VCC

VSS

AKVCC

21

22

23

24

25

26

27

28

29

30

20

19

18

17

17

15

14

13

12

11

10

RD2/PSP2/C2 IN +

RD3/PSP3/C2 IN -

RB7/KBI3/PGD

40

RD3/PSP3/C2 IN -

RD3/PSP3/C2 IN -

RD3/PSP3/C2 IN -

RD3/PSP3/C2 IN -

C2/CLK0/RA6

OSC1/CLK1/RA7

VSS

VDD MCLR/VPP/RE3

RAO/ANO/CVBEF

39

38

37

36

35

34

33

32

31

10

9

8

7

6

5

4

3

2

1

18F4680

VCC

1

3

Vout2

VDD

VSS

14

13

12

11

10

9 8 7 6 5 4 3 2 115

16



62

#use delay(clock=20000000)#use rs232(baud=115200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=9)#include // Thu vien ham cho LCDint8 low,high,key,mode,min,max,mode1,i;

int1 do_F;void convert_bcd(int8 x);void bao_dong();void test();// void main(){ float value;on_off =1;min =15; //nhiet do min defaultmax =35; //nhiet do max defaultdo_F =0 ;i = 50 ;mode =0 ;mode1 = 0 ;trisa = 0xFF;trisb = 0x01;trisd = 0x00;

LCD_init();Printf(LCD_putchar, dc 1201);

LCD_putcmd(0xC0);Printf(LCD_putchar,Khoi tao...);

// Khoi tao cho ngat ngoaienable_interrupts (INT_EXT);ext_int_edge(H_TO_L);enable_interrupts (GLOBAL);

// Khoi tao che do cho bo ADCsetup_adc_ports(AN0);setup_adc(ADC_CLOCK_INTERNAL);

delay_us(10);// Lay mau nhiet do lan dau tien

value=(float)read_adc();value = (value 558.5)/2.048; // For 5V supply// value = (value 754.8)/2.048; // For 3.7V Supply// value = (value 698.2)/2.048; // For 4V supplyconvert_bcd((int8)value); // Tach so tram, chuc, donvi de hien thi len

LED 7delay_ms(1000);

LCD_putcmd(0xC0);



63

Printf(LCD_putchar,Khoi tao xong);while(1){if (i==50)

{ value = read_adc();

value=(value558.5)/2.048;if (do_F==1) value=1.8*value+32;convert_bcd((int8)value);

printf(\n\rNhiet do phong: %u,value);// Gui gia tri len may tinhLCD_putcmd(0xC0);

printf(LCD_putchar,Temp = );

LCD_putchar(high); LCD_putchar(low);if (do_F==0) printf(LCD_putchar,C);else printf(LCD_putchar,F);i=0;

}i++;if(((int8)value > 40) || ((int8)value < 15)) on_off=1;else{

on_off = 0;LCD_Putcmd(0xCF);LCD_putchar();

blink=0;}if (on_off==1){if (blink==0) {

LCD_Putcmd(0xCF);LCD_putchar( !);blink=1;delay_ms(250);}

else {LCD_Putcmd(0xCF);LCD_putchar();blink=0;delay_ms(250);}}

}}//end main

#INT_EXT

void test(){

if (do_F == 1) do_F=0;else do_F=1;



64

}void convert_bcd(int8 x){low=x%10; //chia lay phan du, so hang don vi

high=x/10; //tach hang tram va hang chuclow = low + 0x30;high = high + 0x30;

}void bao_dong(){int8 i;if (blink == 0) blink = 1;else blink=0;

for(i=0;i



65

CHNG 3.

GI TN HIU O LN INTERNET

3.1.TNG QUAN V MNG INTERNET

3.1.1.Gii thiu

Internet l mt h thng thng tin ton cu c th c truy nhp cng

cng gm cc mng my tnh c lin kt vi nhau. H thng ny truyn

thng tin theo kiu ni chuyn gi d liu (packet switching) da trn mt

giao thc lin mng c chun ha (giao thc IP). H thng ny bao gm

hng ngn mng my tnh nh hn ca cc doanh nghip, ca cc vin nghin

cu v cc trng i hc, ca ngi dng c nhn, v cc chnh ph trn

ton cu. Chng cung cp mt khi lng thng tin v dch v khng l trn

Internet.Mng Internet mang li rt nhiu tin ch hu dng cho ngi s

dng, mt trong cc tin ch ph thng ca Internet l h thng th in t

(email), tr chuyn trc tuyn (chat), my truy tm d liu (search engine),

cc dch v thng mi v chuyn ngn, v cc dch v v y t gio dc nh

l cha bnh t xa hoc tchc cc lp hc o.

Ngun thng tin khng l km theo cc dch v tng ng chnh l h

thng cc trang Web lin kt vi nhau v cc ti liu khc trong WWW

(World Wide Web). Tri vi mt s cch s dng thng ngy, Internet v

WWW khng ng ngha. Internet l mt tp hp cc mng my tnh kt ni

vi nhau bng dy ng, cp quang, v.v..; cn WWW, hay Web, l mt tp

hp cc ti liu lin kt vi nhau bng cc siu lin kt (hyperlink) v cc a

ch URL, v n c th c truy nhp bng cch s dng Internet. Trong

ting Anh, s nhm ln ca a s dn chng v hai t ny thng c chm

bim bng nhng t nh "the intarweb".



66

3.1.2.Hot ng ca mng Internet

Internet da trn m hnh khch ch (client server), trong d liu

c trao i thng qua cc trang web. Trong m hnh client server, mi

my tnh c xc nh bi mt a ch Internet protocol (IP) v c my tnh

client, server cng chp nhn mt giao thc chung giao tip vi nhau.

a)Cc giao thc(Internet protocols)

-Cc giao thc l tp cc lut m cc my tnh phi tun theo khi giao

tip trn Internet.

-Tranmission Control Protocol (TCP): thit lp kt ni gia hai my

tnh truyn ti d liu, chia d liu thnh nhng gi nh v m bo vic truyn

nhn d liu. TCP l giao thc hng kt ni (connection-oriented protocol).

-User Datagram Protocol (UDP): thit lp kt ni nhanh nhng khng

chc chn gia cc my tnh truyn ti d liu, cung cp t dch v khc

phc li.

-Internet Protocol (IP): iu chnh ng i ca nhng gi d liung truyn nhn trn Internet. TCP l giao thc phi kt ni (connectionless

protocol).

-HTTP: cho php trao i thng tin trn Internet.

-FTP: cho php truyn nhn file trn Internet.

-SMTP: cho php gi th in t trn Internet.

-POP3: cho php nhn th in t trn Internet.b)a Ch IP(IP adress)

Internet l mt mng kt ni rng ln gia cc my tnh. xc nh

mt my tnh trn mng ny, ngi ta dng mt con s gi l a ch IP. a

ch IP gm mt tp 4 s nh hn 255 v c ngn cch bi cc du .. V

d: 41.212.196.197.



67

c)M hnh khchch (Clientserver model)

Trong m hnh khch - ch, my khch (client computer) yu cu thng

tin t mt my ch (server). My ch chp nhn yu cu v gi thng tin v

cho my khch. Vic trao i thng tin ny c din ra thng qua nhng

trang web.

d) H thng tn min (Domain name system)

Mi my tnh trn mng Internet c xc nh bng a ch IP, nhng

con s ny rt kh nh. khc phc nhc im ny, ngi ta dng h

thng tn min t tn cho my tnh. V d: tn min www.yahoo.com

ng vi a ch IP 216.109.127.28. request web page Min (domain) ngvi mt tp cc my tnh trn Internet. Phn m rng ca tn min (domain

name extension) c dng xc nh quc gia hay t chc.

3.1.3.Kt ni Internet

kt ni vi Internet cnc mt s yu cu v phn cng v phn mm sau:

-Phncng:my tnh, kt nithng qua ngdy inthoi hoc kt

nicp, modem.-Phn mm: kt ni internet, h iu hnh, giao thc TCP/IP, trnh

duytweb.

Cc yu cu thit yu khi kt ni vi Internet: kt ni vi Internet

thng qua mt nh cung cp Internet (Internet Service Provider), modem,

trnh duytv achURL

-TCP/IP c dng lm giao thc chun khi giao tip trn Internet vn c lp vi nn ca h thng (platform independent) v khng c t chc

no c quyn s hu giao thc ny..

3.2. GII THIUIC ENC28J60

3.2.1.Gii thiu chung v IC ENC28J60

Trn th gii c rt nhiu hng cung cp vi mch h tr sn sng cho

cc giao tip theo giao thc TCP/IP, nh cc hng ln:Realtek, Conexant,



68

MicroChip,... Tuy nhin, xt trn quan im ca ngi thit k th cc chp

c nh gi cao l chp p ng c nhu cu thc t (khng thiu v cng

khng qu d tha tnh nng), c s h tr ti a t hng v cc th vin

lp trnh, d dng giao tip vi cc vi x l, mch thit k n gin, t i

hi cc linh kin ngoi. T nhng tiu ch , cng vi s ra i dng chp

h tr hon ton giao thc ethernet, vic la chn ENC28J60 ca

MicroChip l la chn rt ph hp, c v tnh nng k thut v gic .

Ngoi ra, hng h tr y ti liu v cc th vin lp trnh, rt thn

thin khi ghp ni vi cc h vi x l c trn th trng.

ENC28J60 l mt b iu khin Ethenet c lp vi SPI.Vi mch

ENC28J60 c s dng nh mt giao din Enthernet cho bt k thit b

ngoi vi no.

ENC28J60 p ng tt ccc kthut theo chun IEEE802.3. N cung

cp mt Model DMA ni b cho php truyn dliu nhanh v c sdng

trong cc giao thc mng.

Hnh 3.1.S chn ENC28J60



69

3.2.2. Cutrc v chc nng

-Giao tip vi cc thit b ngoi vi theo chun SPI vi tc ln ti

10Mbps.

-Giao thc chun IEEE802.3.

-B lc c bit t ng nh gi, chp nhn hoc t chi MagicPackit,

unicast, muliticast.

-C b nh m Sram ln ti 8kb, c th qun l d liu ng tinh cy v

linh hot.

3.2.3. Chc nng cc chn ca ENC28J60:

-VDD, VDDOSC, VDDPLL, VDDRX, VDDTX : cc chn ny dng cp ngunnui cho IC, ni vi +3,3V, .

-VSS, VSSOSC, VSSPLL, VSSRX, VSSTX : cc chn ny c ni Mass.

-/RESET: chn Reset v mc thp thit lp li ch cho chip.

-OSC1,OSC2: 2 chn nhn b giao ng bn ngoi, ECC28J60 hot ng

vi thach anh 25Mhz.

-CLOUT: tao ra xung clock khong 6,25MHz.

-LedA, LedB: c chc nng h tr t ng pht hin v Reset.



70

3.2.4.Cc khi c bn bn trong ENC28J60:

Hnh 3.2.Cc khi c bn bn trong ENC28J60

Bao gm 7 khi c bn sau:

1. Mt giao din SPI dng giao tip vi vi iu khin.2. Khi gim st v iu khin ENC28J60.3. B nh m Sram cho vic truy v nhn gi tin.4. Khi gim st vic truy cp vo b nh m.5. Khi Bus d liu gi m lnh thng qua SPI.



71

6. Module Mac theo chun IEEE802.3.7. Module PHY m ha v gii m tn hiu in.

3.2.5.B th vin TCP/IP STACK

a)S lc v TCP/IP Stack ca Microchip

B th vin TCP /IP Stack ca Microchip cung cp mt nn tng cho cc

ng dng Ethernet do x l hu ht cc yu cu tng tc gia cc tng vt l

v tng ng dng .N bao gm cc ng dng ph bin ca tng ng dng,

bao gm HTTP2 phc v cc trang web, SMTP gi e-mail, SNMP cung

cp tnh trng, kim sot, Telnet, TFTP,-to Serial Ethernet, v nhiu hn

na.Ngoi ra, b th vin TCP/IP stack ny c dung lng tng i nh v

hiu sut trin khai cao ca TCP v UDP tng giao vn, cng nh cc

module h tr khc nh IP, ICMP, DHCP,ARP,vDNS.

B th vin TCP / IP Stack ca Microchip. Ti u ho cho tt c cc

PIC18, PIC24, dsPIC v gia nh vi iu khin PIC32.Cc ngn xp c

chia thnh nhiu lp, mi lp truy cp dch v t mt hoc nhiu lp trc tip

di n..B th vin TCP / IP Stackbao gm cc tnh nng chnh:

-Ti u ho cho tt c cc PIC18, PIC24, dsPIC v PIC32 gia nh.H tr

giao thc: ARP, IP, ICMP, UDP, TCP, DHCP, SNMP, HTTP, FTP, TFTP

-Socket h tr cho TCP v UDP

-Secure Sockets Layer (SSL)

-NetBIOS v dch v tn

-DNS - Domain Name System-Ethernet Device

Discovery

-H tr cho MPLAB C18, C30, C32 v trnh bin dch



72

Hnh 3.3.S b th vin TCP/IP stack

B th vin TCP/IP stack c vit bng ca ngn ng lp trnh

'C.Ton b code c dung lngkhong 28-34 KB, ty thuc vo mc ch c

s dng, B th vin li nhiu khng gian trn ngi dng c th iu

chnh cho ph hp vi ng dng ca mnh.

b)M hnh tham chiu TCP/IP stack

Ging nh m hnh tham chiu TCP / IP, TCP / IP Stack cng cchia thnh nhiu lp(Hnh 2).Mi lp c 1 chc nng ring, trong khi cc

dch v v cc API(Giao din lp trnh ng dng) c nh nghathng qua

cc tiu , bao gm cc tp tin.Khng ging m hnh TCP / IP, cc lp trong

TCP / IPStack trc tip truy cp vo mt hoc nhiu lp m khng ph thc

vo lpdi n.Mt b sung ln ca TCP / IPStack l thc hin vic b

sung hai modules mi: "StackTask" v "ARPTask".StackTask qun lhotng ca Stack v tt c cc module ca n, trong khi ARPTask qun l cc

dch v ca cc a chNgh quyt Protocol (ARP) lp.Nh cp trc

, TCP / IP Stack l mt b chng trnh;mt s lp ca n phi c kh

nng thc hin mt s hot ng khng ng b. c th p ng c iu

nyi hi phi c tnh tng i c lp khi s dng dch v.



73

Hnh 3.4.So snh m hnh TCP/IP v mo hnh TCP/IP Stack

c)Cu hnh

TCP/IP Stack l b chng trnh c vit bng ngn ng C. bt,

tt hoc thit lp mt tham s no ngi s dng ch cn thay i mt

hoc nhiu tham s trong cc nh ngha .Hu ht cc tham s ny c

nh ngha trong tp tin header,"StackTsk.h".Mt s nh ngha c quy

nh ti cc tp tin khc c hin th vi tn tp tin tng ng. Mt khitp

tin ny c sa i, ngi s dng phi xy dng li cc ng dng cho ph

hp vi d n ca mnh.Cc nh ngha clit k trong Bng sau



74

Bng 3.1.Cc nh ngha

nh ngha Gi tr S dng Chc nng

CLOCK_FREQ

(compiler.h)

Oscillator

Frequency(Hz)

Tick.c

Xc nh h

thng dao ngtn s

TICKS_PER_SECONDS 10-255 Tick.c tnh ton mt

ln th hai

TICK_PRESCALE_VALUE

2, 4, 8, 16,

32,

64, 128, 256

Tick.c

xc nh gi

tr nh du vo

truy cp

MPFS_USE_PGRM N/AMP FileSystem

(MPFS.c)

S dng b nhchng trinh d

lu tr MPFS

MPFS_USE_EEPROM N/A MPFS.cS dng eeprom

d lu tr MPFS

MPFS_RESERVE_BLOCK 0-255 MPFS.cS byte MPFS

duo9c5 lu tr

EEPROM_CONTROL

External Data

EEPROM

Control Code

MPFS.ca ch lu vo

eeprom

STACK_USE_ICMP N/AStackTsk.

c

Yu cu s dng

ICMP

STACK_USE_SLIP N/A SLIP.cYu cu s dng

SLIPSTACK_USE_IP_GLEANIN

GN/A

StackTsk.

c

Yu cu s dng

IP

STACK_USE_DHCP N/A

DHCP.c,

StackTsk.

c

Yu cu s dng

dhcp

STACK_USE_FTP_SERVER N/A FTP.cYu cu s dng

FTP



75

STACK_USE_TCP N/A

TCP.c,

StackTsk.

c

Yu cu s dng

TCP

STACK_USE_UDP N/AUDP.c,StackTsk.

c

Yu cu s dng

TCP

STACK_CLIENT_MODE N/AARP.c,

TCP.cKch hot client

TCP_NO_WAIT_FOR_ACK N/A TCP.cTCP s i ACK

trc khi truyn

MY_DEFAULT_IP_ADDR_BYTE

MY_DEFAULT_MASK_BY

TE?

MY_DEFAULT_GATE_BYT

E?

MY_DEFAULT_MAC_BYT

E?

0-255

User

Applicatio

n

Xc nh mc

nh IP, MAC,

gateway v

subnet mask gi

tr.

MY_IP_BYTE?

MY_MASK_BYTE?

MY_GATE_BYTE?MY_MAC_BYTE?

0-255

MAC.c,

ARP.c,

DHCP.c,

UserApplicatio

n

IP, MAC,

gateway v

subnet mt n gi

tr nh lu / nh

ngha bi ng

dng.Nu DHCP

c kch hot,

nhng hn nh

cc gi tr hin ti

my ch DHCP

giao cu hnh.

MAX_SOCKETS 1-253 TCP.c xc nh tng

s sockets h tr



76

(gii hn bi b

nh RAM c

sn).

kim tra thigian thc hin

m bo rng

sockets l

chn TCP ng

dng.

MAX_UDP_SOCKETS 201-1500TCP.c,

MAC.c

Xc nh kch

thc b m.

MAX_TX_BUFFER_COUNT 1-255 MAC.c

Xc nh tng s

truyn qua b

m. con s ny

c hn ch bi

kch thc b

m ca Mac

MAX_HTTP_CONNECTION

S1-255 HTTP.c

Xc nh s

lng ti da

HTTM c kt

ni

MPFS_WRITE_PAGE_SIZE

(MPFS.h)1-255 MPFS.c

Xc nh kch

thc c th ghi

trn MPFS

FTP_USER_NAME_LEN

(FTP.h)1-31 FTP.c

Xc nh di

ti a ca FTP

MAX_HTTP_ARGS

(HTTP.c)1-31 HTTP.c

Xc nh s ti da

ca HTML

MAX_HTML_CMD_LEN

(HTTP.c)1-128 HTTP.c

Xc nh di

ti a ca HTML



77

d)S dng TCP/IP Stack

B th vin TCP/IP Stack ch y cc Modem h tr nh :HTTP,

IP, FTP, DHCP. Ty vo mc ch s dng m ngi lp trnh c th thay i

cho ph hp vi d n camnh, nhng mt s tp tin nht nhphi c trong

d n ph hp vi bin dch. Cc Module v tp tin c trnh by

trong bng sau:

Bng 3.2.Cc module

170488434 Nghien Cứu Thiết Kế Mạch Đo Nhiệt Độ Dung LM35 Va Gửi Tin Hiệu Nhiệt Độ Len Internet

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