Trng HCN H Ni
Khoa in T
N 2 Ti : Thit k mch m chn l hin th bng Led 7 thanh Khi v tr A th
m s chn Khi v tr B th m s lI. S khi ca h thng B m Gii m Hin th
Khi to xung
- Mch to xung ng h l mch to xung vung bng mch nh thi gian IC555-
Mch m l b m dng IC 74LS192- Mch gii m t m BCD sang led 7 thanh dung
IC 74LS47- Hin th l Led 7 thanh . II. Mch to xung ng h Yu cu vi mch
to xung ng h l to c xung vung vi chu k giy. Dui y l mch to xung dng
IC555.
n 2 Lp :LTC H T2 K3
1
SVTH: Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni
Khoa in T (u
Hai b so p c u vo c nh du + (u vo ca thun) v du
vo ca o). Khi V+ > V- u ra b so p c mc logic cao v khi V +
< V-_th ngc li. Ba in tr 5K c mc ni tip thnh mch phn p a in p
chun ti li vo ca b so p. in p V - = Vcc a ti li vo ca o(-) ca Upper
comp, cn in p V+ = Vcc c a ti ca thun (+) ca Lower comp. - S chn ca
IC555 trong thc t nh sau:
- S mch to xung
- u ra ca mch to xung dng IC555 l mt xung vung vi tn s l 2
n 2 Lp :LTC H T2 K3
SVTH: Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni f=
Khoa in T
Thi gian np ca t l : Tm=ln2*(R1+R2)*C Thi gian phng ca t l:
Ts=ln2*R2*C Tu yu cu ca xung ra m ta chn gi tr thch hp. III. B m 1.
Tm hiu v IC 74LS192 IC 74LS192 l IC thuc h 74xx,IC ny c chc nng m
thp phn khng ng b.Con TTL ny cng kh quen thuc n l con m m nh phn
chia 10 m ha ra BCD. C mi 1 xung vo th n m tin ln 1 v c m ha ra 4
chn u ra. _ S chn ca IC:
-Vcc: Ngun cp 5V. 3
n 2 Lp :LTC H T2 K3
SVTH: Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni -P0-3: u vo d liu. -Q0-3: D liu u ra. -CPU: Tn hiu
xung vo m thun. -CPD:Tn hiu xung vo m ngc
Khoa in T
-MR:Tn hiu Reset khng ng b (tch cc mc + ). - : u vo ti song song
khng ng b. - : u ra m thun.(sau mt chu k m th xung ny chuyn t cao
xung thp) - : u ra m ngc..(sau mt chu k m th xung ny chuyn t cao
xung thp) _ S logic ca IC74LS192:
_Bng la chn ch : MR H PL X CPU X CPD X Ch Reset (khng ng b)
4
n 2 Lp :LTC H T2 K3
SVTH: Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni L L L L L H H H X H H X H H
Khoa in T Preset (khng ng b) Khng i tng thi m thun m ngc
_Bng chn l m ha ra BCD Khi sn xut ra con ny nh sn xut cung cp
cho chng ta bng m ha ca con ny do m mnh khng th to ra bng m ny c.
Sau y l bng m ca n.
m 0 1 2 3 4 5 6 7 8 9 Q0 L H L H L H L H L H
u ra Q1 Q2 L L L L H L H L L H L H H H H H L L L L
Q3 L L L L L L L L H H
IV . B gii m hin th qua Led 7 on1.Mch chuyn m Trong cc h thng in
t dng mch s,d liu(lnh,s liu) c truyn i hay x l dng t (word) nh phn
gm cc bit 0 v 1.Mt t n bit c th biu din cho 2n phn t tin khc nhau
vi gi tr thp phn t : 0=>2n -1.T nh phn n bits gi l m ca cc phn t
tin tc. - IC74LS47 : y l IC dng iu khin hin th Led 7 on theo m BCD.
Bn trong IC l cc cng NAND,cc b m ng vo,v 7 cng n 2 Lp :LTC H T2 K3
5 SVTH: Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni
Khoa in T
chuyn i AND_OR. 7 cng NAND kt hp vi mt b li to ra m BCD cho vic
gii m 7 cng chuyn i AND_OR. - S chn ca IC74LS47:
_ Bng m h thng gia ng vo v ng ra:
2.Led 7 thanh
n 2 Lp :LTC H T2 K3
6
SVTH: Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni
Khoa in T
Led 7 thanh(LED7SEG) c 2 loi: Anot chung v Katot chung.Trong
thit k s dng loi Anot chung .Nu dng loi Katot chung th cn dng loi
IC gii m c u ra tch cc mc dng (+) nh IC 74ls147.Trn s chn: gm 10
chn chia ra 2 hng chn nh hnh sau:
Chn s 3 ni VCCChn s 5 (poin) v chn s 8(Anode) khng c s dng trong
thit kCc chn 1(e), 2(d), 4(c), 6(b), 7(a), 9(f), 10(g) c ni vi cc
chn tng ng ca IC 74ls47. V . Thit k mch m s chn l hin th s c 2 ch s
1.Nguyn l -Ta c cc s t 0 n 9 nh sau: S 0 1 2 3 4 5 6 7 8 9 D 0 0 0
0 0 0 0 0 1 1 C 0 0 0 0 1 1 1 1 0 0 B 0 0 1 1 0 0 1 1 0 0 A 0 1 0 1
0 1 0 1 0 1
T ta thy: u vo A mc thp th mch lun hin th s chn. Khi uvo A mc
cao th hin th s l. V vy c c mch m chn l n 2 Lp :LTC H T2 K3 7 SVTH:
Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni
Khoa in T
ta dng cng tc nhn 3 chn .Chn 1 ni vi ngun vo.chn 2 l u ra ni vo
u vo A ca IC74LS47,chn 3 ni vi mass. Ban u cng tc thng ni 1-2.u vo
A mc cao => mch m l. Khi nhn nt cng tc ni 2-3 => u vo A mc
thp => mch m chn. hin th s hng chc ta ch cn ni chn 12 ca
IC74LS192 th nht ti chn 5 ca IC74LS192 th 2. V sau mi chu k m t 0 n
9 th tn hiu chn 12 s chuyn t cao xung thp ,nh vy ch s hng chc s tng
ln 1. 2 . S nguyn l mch
n 2 Lp :LTC H T2 K3
8
SVTH: Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni
Khoa in T
n 2 Lp :LTC H T2 K3
9 SVTH: Nguyn Vn Ton Nguyn Vn Ton
Trng HCN H Ni 3.S mch in
Khoa in T
VI. Phng n thay th Ngy nay vi s pht trin ca vi iu khin th vic m
chn l s tr ln n gin hn.Ch cn vi chng trnh iu khin np vo IC ta c th
thc hin m ti bt k s no m chng ta mong mun.
n 2 Lp :LTC H T2 K3
10
SVTH: Nguyn Vn Ton Nguyn Vn Ton
