btl dong ho so dung 7490

7/28/2019 BTL Dong ho so dung 7490

1/11

Bo co thc hnh mn k thut xung s Nhm sv: LTCH T2-K2

BI BO CO THC HNH XNG

MN : K THUT XUNG - S

TI : TM HIU V THIT K MCH NG H SDNG IC 74LS90 (HIN TH TRN LED 7 THANH).

GVHD : NGUYN NGC ANH

NHM SV : NGUYN MNH CNGNGY VN LNGNG XUN TRNGTRN VN TNG

ng h s s dng IC 7490 trang1


2/11


LI NI UNgy nay cng ngh khoa hc k thut rt pht trin,

khoa hc k thut c ng dng trong hu ht cc lnhvc ca cuc sng.c bit l cng ngh in t (k thutxung - s) v ang c ng dng nhiu vo trong cngnghip v i sng.trong cc nh my x nghip c cc mchm sn phm,mch thi gian,mch hin th,cc my chmcng s dng cng ngh k thut s. Trong i sng thmch ng h s l mt ng rt ph bin.

Sau mt thi gian hc tp v tm hiu ti liu v kthut xung - s, chng ti quyt nh chn ti:tm hiuv thit k mch ng h s dung IC 7490 lm bi tpln.Vi ti ny chng ti s dng cc IC s lmthnh mt mch ng h thi gian thc bao gm c gi,pht, giy.Bi tp bao gm c hnh nh v mch in minh

ho gip cc ban c d hiu hn v mch ng h s.Do thi gian c hn v kin thc cn hn ch m bi

tp cn thiu xt,chng ti rt mong nhn c cc kinng gp ca thy c gio v cc bn c. Chng ti xin chnthnh cm n!

Mi kin ng gp xin gi v cho chng ti theo ach :

Nhm SV: T2-K2Lp : LT C-H IN T 2_K2Trng : HCN H NI



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4/11


II/ S MCH IN MCH NG H S DNGIC 7490 :



5/11


1. IC 555 :

L IC to dao ng tn s 1Hz cp xung nhp cho IC 7490 m.

4 . 7 u

0

U 1 9L M 5 5 5

3

48

1 5

2

6

7O U TR

S

T

V

C

C

G

N

D

C

V

T R G

T H R

D S C H G

H

I

5 0 k

R 7

6 2 k

1 0 u

to ra tn s f=1Hz, cc linh kin cchn nh mch trn.

S khi 555



6/11


2. IC 7490 :

U 1

7 4 9 0

1 4

1

1 2

9

8

1 1

5

1

0

2

3

6

7

C L K A

C L K B

Q A

Q B

Q C

Q D

V

C

C

G

N

D

R 0 1

R 0 2

R 9 1

R 9 2

c im ca 7490- 7490 l b m thp phn gm 2 b m: 1 b m 2(dung FF A) va 1 b m

5 (3 b m B,C


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3. IC 7447 :

Vai tr IC7447 v cch kt ni:

y l IC dng chuyn tn hiu dng s nh phn ng vo sang m 7 on.

d thy IC ny hot ng tch cc mc thp. Do ta c bng chn thc sau:

BCD U VO TN HIU U RALED

A B C D a b c d e f g

0 0 0 0 0 0 0 0 0 0 1 00 0 0 1 1 0 0 1 1 1 1 10 0 1 0 0 0 1 0 0 1 0 20 0 1 1 0 0 0 0 1 1 0 30 1 0 0 1 0 0 1 1 1 1 40 1 0 1 0 0 1 0 0 1 0 50 1 1 0 1 1 0 0 0 0 0 60 1 1 1 0 0 0 1 1 1 1 71 0 0 0 0 0 0 0 0 0 0 8

1 0 0 1 0 0 0 1 1 0 0 9 IC hot ng ta kt ni chn 16 (Vcc) vi ngun 5 V, chn s 8 vi t. Ng

vo c 4 chn l 7,1,2,6 tng ng vi A,B,C,D trong mc ngha gim dn tA n D. Kt ni cc u ra ca IC 7490 vi cc u vo A,B,C,D ca IC 7447 IC chuyn i m BCD m c thnh s nh phn hin th led. Cc chn LT,BI/RBO, RBI khng cn kt ni.



9/11


4. IC 7408 :

L IC c tch hp bi 4 cng AND nh hnh v.Dng AND logic tn hiu uvo.

III/ NGUYN L HOT NG:ng h s s dng IC 7490 trang9


10/11


B to xung kch c chc nng to xung vung a vo b m kch chob m hot ng. Mi khi c 1 xung a vo chn CLK ca b m th bm s thc hin m 1 ln. Vi mch ng h ta cn xung chun l 1 Hz ( dng

IC 555).Mch gm 3 khi :- Khi giy : Chc nng iu khin v hin th s giy ca ng h ( 0 -59).- Khi pht : iu khin v hin th s pht (0 59).- Khi gi : iu khin v hin th s gi (0 -23).Mi khi gm c 2 IC m 74LS90 , 2 IC gii m BCD 74LS47 , 2 led 7 onloi A chung.

1. Khi giy :Xung kch c a vo chn CKA (CP0) ca IC 74LS90 hng n v,nh vy c mi giy IC li tng 1 n v u ra

Bng cch ni u ra ca b m c s 2 vi u vo ca b m c s5 ,

tc l ni chn s 1 vi chn 12 , ta c b m c s 10. Xung kch sa vo chn s 14 (CPO) v u ra ca b m c s 10 l m BCDthong qua cc chn QA ,QB ,QC ,QD. IC m c ta s ccchn R01 ,R02 mc thp

thc hin b m c s 6 ta xut pht t b m 10 trn dng cchxa bt s m b m ch m t 0 5. Khi m n 5 v xung nhptip theo s nhy ln 6 tng ng vi QDQCQBQA l 0110 . Taly lun ura QCQB and voi nhau v a v 2 chn R01 v R02 nh th b m slp tc reset v 0. Nh vy b m c s 6 c thc hinB m 10 dng trong m hng n v. B m 6 m hng chc .Taghp chng li c b m 60. Vic ny c thc hin bng ccha chn Q3 ca b m 10 vo chn CP0 ca b m 6. R rang khi bm t 9 quay v 0 ( m BCD chuyn t 1001 sang 0000 ), chn Q3 scho 1 xung clock sn m v th n kch thch b m 6 tng thm 1 nv. ghp ni b m giy vi b m pht ,ta thy rng khi m n 59,chn QC ca b m 6 mc cao (0101) vy khi thm 1 xung nhp na th

b m quay v 0000. Vy chn Qc s quay v 0 v to ra xung clocksn m. Tn hiu ny c a v chn CP0 ca b m 10 ca khim pht

Vy mi khi m n giy 60 khi m pht s c kch thch tng 1n v.



11/11

Bo co thc hnh mn k thut xung s Nhm sv: LTCH T2-K22. Khi pht :

Nguyn l ca b m pht cng ging nh b m giy. Tuy nhin xungiu khiu ca hng n v ca khi pht c ly t chn QC ca IC74ls90 ca hng chc khi giy.

3. Khi gi :Nguyn l hot ng ca b m gi khc so vi 2 b m trn. Dy lb m 24 tc l m n 23 th s reset v 0Chn CP0 ca IC 7490 hng n v ca khi gi c ni vi chn QCca IC 7490 hng chc ca khi pht ly xung iu kin. B m gis nhy s khi b m pht nhy ti 60 . c th reset t 23 tr v 0, Ta

phi tin hnh reset c hai chn IC 7490 hng chc v hng n v.khikhi gi m ti 23 thi ta co trng thi cc chn u ra ca IC7490 hngchc v hang n v QDQCQBQA : QDQCQBQA l 0010 : 0011.nu thm mt

xung na th u ra QC ca hng n v l 1, vy ta and u ra QB ca IC7490 hng chc vi QC ca IC 7490 hng n v a v reset cho khim gi.


btl dong ho so dung 7490

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