i hc Quc Gia TP.HCM Trng i hc Cng Ngh Thng Tin ----- dng qua n
Q1 tng => lm in p chn E ca n tng , v ngc li ... n mn hc 1 : Thit
k xe d ng GVHD : Ths.Lm c KhiPage 10 Hnh 3 : IC n p LM7805 to ngun
5V. S vt l ca nhm : Hnh 4: s vt l khi ngun chuyn i 5V. Bao gm chn
cm ngun 9V,4 diode to mt mch chnh lu c chu k,IC LM7805 chuyn sang
ngun 5V,cc loi t lc,1 n Led bo hiu v in tr hn dng cho n Led. Lp mch
chnh lu : mch chnh lu c tc dng chuyn ngun xoay chiu sang 1 chiu.Do
,ta ko cn quan tm ti vic cc m v cc dng ca ngun khi lp vo chn cm.
Thng qua mch chnh lu ta thu c ngun 1 chiu nhp nh th t 1000F c tc
dng lm phng ngun 1 chiu,t ny c in dung cng ln th in p u ra cng bng
phng,thng thng c tr s khong vi trm n vi ngn F.Hai t cn li 2 u ca IC
LM7805 c tc dng lc nhiu cho IC ny.Theo datasheet,ta c : CIN
=0.33F,COUT = 0.1F v IOUT ti a chu c l 500mA.Do th trng khng c t
0.33F nn nhm gn lun t 0,1F,iu ny cng khng nh hng bao nhiu. Vi n bo
hiu,nhm s dng Led siu sng trng 2-3V..Nhm o c Led c p 2.8V. n mn hc
1 : Thit k xe d ng GVHD : Ths.Lm c KhiPage 11 Ta c dng qua Led thng
t 5-20mA. y,nhm mun n sng vi I=5mA,khi ta c cng thc tnh cho in tr
nh sau: R=(5-2.8)/0.005=440. Do th trng khng bn loi ny nn nhm dng
loi 330,ta c dng gn 6,6mA sng cho Led. 3.2.Khi vi iu khin : S vt l
ca nhm : Hnh 5 : s vt l khi vi iu khin. n mn hc 1 : Thit k xe d ng
GVHD : Ths.Lm c KhiPage 12 *Gii thch s : Vi iu khin Atmega8 c h tr
2 chn PWM(PB1 v PB2) c dng iu ch xung iu khin ng c.ng thi c b nh
flash,cng ngh np ISP (In System Programming) tc l np m khng cn tho
chip ra khi mch, gip vic lp trnh v test rt thun tin. Chn AREF v chn
AVCC dng cho b chuyn i ADC(nhm khng s dng).Trong : oAVCC l ngun cho
b ADC hot ng c mc trc tip ti ngun 5V. oAREF l in p tham chiu (in p
chun) ADC so snh,nu c dng lm in p tham chiu ni th cn chng nhiu nbng
cch ni thm ti t 104 ri ni t. Led c mc thm bo hiu mch c np thnh
cng,hoc dng test ng c trong qu trnh thc hin.Led c mc thm in tr 330
hn dng. Bus 5x2 dng np ISP vi cc v tr c mc ph hp vi chun cho mch np
USB AVR910,chuyn dng cho h AVR. Mch dao ng s dng thch anh 12Mhz,nh
vy khi dng Timer s c tn s f=12/12=1Mhz chu k T=1/1*106=10-6s=1s.Tin
cho vic tnh ton v lp trnh.Tuy nhin c hn ch l khng th truyn thng vi
my tnh qua cng COM(i hi thch anh 11.0592Mhz).Thch anh ny c ni t vi
t gm 22pF chng nhiu. Mch s dng SW to ngt,c ni ti chn INT1 v INT2 c
mc nh trn l hp l : oTrn m phng,thng thng cc chn INT ny ta mc nh
sau:
Hnh 6 : 1 v d v cch mc cng tc. oKhi n SW th VDK c ni ti t,lc VDK
c th c gi tr 0.Tuy nhin,lc nt nhn c th ra,chng ta thy rng ng vo ca
VDK chng c ni ti mt linh kin no c,vy l in p chn ca VDK s tri ni
khng xc nh.Nu khng may mn,in p tri ni ny ri vo vng logic 0,ri li
nhy sang vng logic 1th r rng chng ta khng th xc nh c nt bm c c bm
hay khng?!!! n mn hc 1 : Thit k xe d ng GVHD : Ths.Lm c KhiPage 13
oV vy, m bo,nu khi khng bm nt SW,VDK phi c in p tham kho l 5V(chip
Atmega chu c ngun 4,5V-5,5V v 20mA),sau khi bm nt th in p s gim
xung 0V:
Hnh 7 : cch mc cng tc trnh b in p tri ni. oTuy nhin,nu n nt
bm,th s gy ra ngn mch,v R=0, I= .Do ta cn phi a thm vo mt in tr gia
t ,nt bm v ngun.Vn t ra l in tr s c t u,v gi tr ca n l bao nhiu?Khi
ta c 2 cch mc sau : Hnh 8: 2 cch mc cng tc trnh ngn mch. -Ta c
I=U/R,nu mc tr R=10k,ta c:I=5V/10k=0.5mA. -Thit k ny m bo cho hot
ng ca VDK c an ton.Ta c th thay R=1k thu cI=5mA vn ph hp. -Cch mc
1,n nt th chn VDK c ni ti t. -Cch mc 2,khng c hin tng tri ni in
p.
oKhinthSW,schintngrung,khongthigianrung
VDKkhcthnhnbitntbmangtrngthinhay khng,mbokhinntmVDKlunnhnbitc,ta
nisongsongvintnmttha(tphncc).Khivan nt,inpcnpchot,
khongthigianrung,lcVDK khngnhnctrngthinSWthtxinptotrng thi nh n
nt.Tuy nhin,dng loi t c gi tr bao nhiu cho va ?!!! n mn hc 1 : Thit
k xe d ng GVHD : Ths.Lm c KhiPage 14 -Khi t np in,ta c :
Vc(t)=VDC(1-e-t/T). t: thi gian t np (s),T=RC l hng s thi gian(s),
y khng c mc R nn ta chxt gi tr C. VccngtingnvVDC1/et/T
>>0et/T>> T>>0C>>0. T c gi tr cng nh th np
cng nhanh. -Khi t x in,ta c :Vc(t)=VDC*e-t/T. VccngtingnvVDC1/et/T
>>1et/T>>1 t/T>>0T>>C>>. T c gi tr
cng ln th x cng nhiu. -Tcgitrcnglnthnpcngluvxcng nhiu.
-Tcgitrcngnhthnpcngnhanhvx cng t. -Da vo cch tnh trn,v ta thy khong
thi gian nhn ntSWxyrartngnnntacnloitnpnhanh,do
chnloitctrsnh,thactrst1F-10000F.Do,tachntha1F(cthchncao hn,chng hn
nh 10F). 3.3.Khi ng c : S vt l : Hnh 9 : S vt l khi ng c . n mn hc
1 : Thit k xe d ng GVHD : Ths.Lm c KhiPage 15 *Gii thch s vt l : IC
L298Nbn trong tch hp hai mch cu H,mi mch cu H gm 4 cng AND v 2
Tranzito. S khi bn trong ca n nh sau(Hnh 10) : +Mi mch cu H c iu
khin bi 2 tn hiu Input v 1 tn hiu Enable .V d vi mch cu H iu khin
Out1 v Out2 cho ng c 1(bnh tri ) c iu khin bi 3 tn hiu In1,In2,EnA
(In1,In2,EnA c xut t vi iu khin,EnA=5V). Ta c mi quan hgia cc tn
hiu ny nh sau : In1In2EnAOut1Out2 0010 VDC0 VDC 0110 VDC12 VDC
10112 VDC0 VDC 11112 VDC12 VDC Xx0TreoTreo Khi c chnh p gia Out1 v
Out2 th ng c quay.NuIn1In2=01 th tin ti,v In1In2=10 th li. Tng t
cho mch cu H th 2 chu iu khin bi In3,In4 xut tn hiu Out3,Ou4 iu
khin ng c 2(bnh phi). n mn hc 1 : Thit k xe d ng GVHD : Ths.Lm c
KhiPage 16 Cung cp ngun Vcc=5V cho IC hot ng,v cp ngun Vs=12V cho
ng c hot ng. Mi mch cu H bao gm 1 ng ngun Vs(tht ra l ng chung cho
2 mch cu),mt chn current sensing(cm bin dng) phn cui ca mch cu(ta c
2 chn SENA v SENB cho 2 mch cu),chn ny khng c ni t m b trng ngi dng
ni 1 in tr gi l sensing resistor,mc ch n nh dng,n l in tr cng sut c
gi tr c nh,thng t 0,5-2ohm,2W(theo datasheet),khi b chuyn mch trong
L298N dn,n trng thi bo ha mnh,dng qua gn nh l maximum,do kh nng ht
dng rt ln d st ngun nu khng c in tr ny. T C1 l t lc nhiu cho
L298N,thng l t 0.1uF,t C2 v C4 l t lc ngun ,gip ngun cp 12V c
phng,n nh hn. Khi o chiu ng c hay ngng ng c,lc ny ng c ging nh 1 ci
my pht in nh.N pht sinh dng in ngc c th c gi tr rt ln,v l thuyt
L298N chu c 4A,nhng nu l 2A th IC rt nng,nu dng pht sinh t ngng ny
chy ngc v IC th rt d gy hng IC.Chnh v vy mt mch diode cu i theo bo
v chip.my con diode ny dng ngn dng ngc khi ng c o chiu hay ngng
khng cho dng ny quay ngc tr li lm chy IC . Nhm dng diode 1N5399,2A.
3.4.Khi cm bin : ng i ca xe c v bng vch en nm trn nn trng. nhn ra c
ng i,nhm s dng cc cp led thu pht hng ngoi t gn nhau.Led pht hng
ngoi khng pht ra nh sng m pht ra cng ,led thu c in tr ph thuc vo c
nhn c cng hng ngoi phn x li t ng i hay khng. Hnh 11 : s phn x nh
sng ca led pht trn nn trng v en. n mn hc 1 : Thit k xe d ng GVHD :
Ths.Lm c KhiPage 17 S ca 1 cp thu pht hng ngoi (Hnh 12): L1 l n pht
hng ngoi c di in p ??(cha test li) R1 Led thu c mc ngc.Vic tnh ton
R2 y sao cho chnh lch ca Vs khi c v khng c nh sng l ln nht.(Vs l in
p ri trn R2). -Gi s in tr ca Led thu khi c nh sng l Rmin,v khi khng
c nh sng l Rmax. -Tng ng c in p khi c nh sng l
Vs=I*R2=Vcc*R2/(R2+Rmin) V khi khng c nh sng l Vs=Vcc*R2/(R2+Rmax)
= chnh lch in p : Delta= |Vcc*R2/(R2+Rmax) - Vcc*R2/(R2+Rmin)| Kho
st hmy(R2)= |Vcc*R2/(R2+Rmax) - Vcc*R2/(R2+Rmin)|.Tm R2 sao cho hm
y(R2) t cc i. Tnh ton n thun ta c cng thc R2=sqrt(Rmin*Rmax). Vi
Led thu,theo tnh ton thc nghim ca cc nhmnghin cu trc lm th khi khng
c nh sng,in tr ca led thu c 100k; khi c nh sng th gim xung cn 1k
R2=sqrt(1*100)=10k Vi s trn,theo l thuyt : +Khi khng c nh sng(gp
vch en) : Vs=5*10/(10+100)=0.45V +Khi c nh sng(vch trng) :
Vs=5*10/(10+1)=4.54V Tuy nhin,trong qu trnh chy thc nghim,ty khong
cch gia led thu v led pht,v khong cch gia cm bin v mt ng m cho gi
tr n mn hc 1 : Thit k xe d ng GVHD : Ths.Lm c KhiPage 18 Vs khc
nhau khi c nh sng.Vi kt qu thc nghim ca nhm,khi c nh sng nhm o c Vs
xp x 1,6V,v khi khng c nh sng l xp x 0V. in p 1,6V l rt thp,khng th
a vo vi iu khin hot ng c,do cn phi c khch i.in p Vs c so snh vi in
p Vref c tinh chnh theo cch mc sau(Hnh 13) :
Vref Vs Vref c tinh chnh in p 1V C ch hot ng ca mch so snh :
-Khi c nh sng : Vs=1,6V>Vref => Output =5V -Khi khng c nh sng
: Vs=0V Output=0V Nhm s dng 8 cp led thu-pht.Do cn ti 8 b so
snh.Nhm s dng 2 IC LM324.Mi IC LM324 cha 4 b so snh.Vi s chn nh sau
(Hnh 14) : IC LM324 vi ngun nui 5V th ch cho Output cao nht 3.7V,do
in p ri trn cc van chuyn mch,cc in tr bn trong n.Nhm o c xp x
3,6V.Tuy nhin,in p ny vi iu khin hiu c l n mn hc 1 : Thit k xe d ng
GVHD : Ths.Lm c KhiPage 19 mc logic 1.Qua c th kim tra cc trng thi
ca cm bin iu khin ng c i ng hng. Ngoi ra,nhm cn s dng 8 n led bo
hiu cho 8 cp led thu-pht d dng nhn bit c trng thi cm bin gp vch en
hay vch trng. Nhm s dng n 1,4V-1,8V.Nhm o c 1,8V,v mun dng 15mA .Do
ta c : R=(5-1,8)/0.015=213 ,xp x 220 Khi gp vch en,Output(ca b so
snh)=0 c s chnh p n Led sng. Khi gp vch trng,Output=3,6V s chnh p
rt thp n Led tt . S nguyn l : gm 2 mch Hnh 15 : mch d ng gm cc cp
led thu pht. n mn hc 1 : Thit k xe d ng GVHD : Ths.Lm c KhiPage 20
Hnh 16 : mch so snh ,khch i. Trn mch ny,4 n bn tri dng n bo hiu,4 n
bn phi dng n vng bo hiu (n vng c V=2V T=(5-2)/220=13,6mA). Xt t tri
qua,n bo hiu c nh s t 1-8.Cc trng hp cm bin d ng (bt vch en): Phm
vi n 4-5 : i thng. Phm vi n 1-5 : lch tri quo tri. Phm vi n 4-8:lch
phi quo phi. n mn hc 1 : Thit k xe d ng GVHD : Ths.Lm c KhiPage 21
*Lu gii thut(Hnh 17) : 4.Ti liu tham kho : 1.Bi ging vi x l vi iu
khin-Thy Nguyn Minh Sn. 2.Mt s trang web tham kho : -www.hocavr.com
-www.dientuvietnam.net -www.dieukhien.net -www.micromouse.tk 5.Ph
lc: 5.1.Hnh nh cc khi v sn phm hon chnh : *Khi ngun v khi vi x l
cng nm trn mt board(Hnh 18) KHI TO GII THIU D NG LCH YESNO Cua tri
Or Cua phi i thng n mn hc 1 : Thit k xe d ng GVHD : Ths.Lm c
KhiPage 22 *Khi ng c (Hnh 19): n mn hc 1 : Thit k xe d ng GVHD :
Ths.Lm c KhiPage 23 *Khi cm bin gm 2 phn : +B d ng (Hnh 20): *B
khch i tn hiu t b d ng(Hnh 21): n mn hc 1 : Thit k xe d ng GVHD :
Ths.Lm c KhiPage 24 *Sn phm hon chnh (Hnh 22): *ng ua (Hnh 23): n
mn hc 1 : Thit k xe d ng GVHD : Ths.Lm c KhiPage 25 *Hnh nh xe i d
ng(Hnh 24) : 5.2. Danh sch thit b : Tn thit bS lng ng c hp s2 Bnh
xe ng c2 Bnh xe dn hng1 Pin 9V(sc c)3 Led pht8 Led thu8 Led thng10
T in cc loi : t s 22pF,t gm 0.1F,t ha 0.1F, 100F,1000F, 1F vi in tr
cc loi : 220,330,10k,100kVi Atmega81 n mn hc 1 : Thit k xe d ng
GVHD : Ths.Lm c KhiPage 26 LM78051 L298N1 LM3241 Diode 1N53998 Thch
anh 12Mhz1 Tn nhit loi nh1 Jump cc loivi Lcvi Cp ni : 6,8,10vi Dy
ng1 cun 5.3.CcDatasheet 1. Atmega8 2. LM7805 3. LM324 4. L298N
