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

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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

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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

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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.

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- -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)

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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

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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)

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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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