LI M UVi s pht trin khng ngng ca khoa hc k thut, con ngi pht minh ra nhiu cng c phc v cuc sng , t nhng vt dng hng ngy cho n nhng sn phm cng ngh cao. K thut s chc hn l mt cng c h tr ht sc quan trng trong thi i ngy nay. c th bit c nhng ng dng c th ca k thut s trong i sng , chng ta hy i tm hiu v chic ng h s mt vt dng hng ngy n gin nhng rt cn thit. ng h l mt thit b m hu nh bt c ai cng phi dng ti n. Mt chic ng h c, xem gi bng cch nhn vo kim ch vch chia thi gian s gy kh khn cho ngi s dng. Nhng i vi ng h s, thi gian c hin th r rng bng cc ch s s d dng s dng hn. Bi vy, sau y em xin thit k mt mch ng h s dng IC74LS90 , y l IC rt thng dng trong k thut s. Trong ti nycng cn nhiu thiu st rt mong s gp ca thy gio v cc bn ti c tt hn !!!

Sinh Vin Nguyn Hi Vit

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C S L THUYT1.H gii m Xy dng h gii m cho led 7 on anode chung.a a b c d e f g

D C B

* Bng chn l: Input D 0 0 0 0 0 0 0 0 1 1 1 1 1 C 0 0 0 0 1 1 1 1 0 0 0 0 1 B 0 0 1 1 0 0 1 1 0 0 1 1 0 A 0 1 0 1 0 1 0 1 0 1 0 1 0 a 0 1 0 0 1 0 1 0 0 0 X X X b 0 0 0 0 0 1 1 0 0 0 X X X c 0 0 1 0 0 0 0 0 0 0 X X X Output d 0 1 0 0 1 0 0 1 0 1 X X X e 0 1 0 1 1 1 0 1 0 1 X X X f 0 1 1 1 0 0 0 1 0 0 X X X g 1 1 0 0 0 0 0 1 0 0 X X X

Gii m led 7 on.

A

2

1 1 1

1 1 1

0 1 1

1 0 1

X X X

X X X

X X X

X X X

X X X

X X X

X X X

*Cc hin th tng ng ca LED 7 on vi ln lt cc u vo:

*S logic

* Phng trnh logic:a = DC BA + CA b = C BA + CB A = C ( B A) c = CB A d = C BA + C B A + CBA = C BA + C ( B A) e = CB + A f = BA + CB + DCA g = DC B + CBA

Trong bi ta s s dng IC7447 gii m cho LED 7 on3

2.H m 2.1Khi nim: H m ni tip: xung m ch a vo mt FF. H m song song: xung m c a vo tt c cc phn t m. thnh lp mt h m ta s dng JK- FF. Nu c n FF th thnh lp c h m c dung lng ti a l 2n . VD: 2FF thnh lp h m 4. 3FF thnh lp h dm 8. 4FF thnh lp h m 16. H m: m ni tip, m song song. * Xt h m ni tip 3bit:

2.2H m bt k: Gi: N l s trng thi ca 1 h m bt k n l s bit m. Ta c: 2 n 1 < N < 2 n VD: thnh lp h m 6 m ln. Ta c: 22 < 6 < 23 => s dng 3FF.

* Bng trng thi: S Q3Q2 Q1

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0 1 2 3 4 5

0 0 0 0 1 1 1

0 0 1 1 0 0 1

0 1 0 1 0 1 0Xo bit nh v 000

2.3 Ghp cc h m: Nu c hai h m N & M, ta c th ghp ni tip thnh h m c N*M thng thi. * Nguyn tc ghp: - t xung clock vo b m M. - Ly tn hiu t bit c trng s cao nht ca b m M lm xung clock cho b m N. VD: H m 10 ghp vi h m 6 thnh h m 60.MSB LSB

CK

A4 A3 A2 A1 m 10

CK

B3 B2 B1 m 6

Trong bi ta s s dng IC7490 thc hin cc h m.

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THIT K S MCHI. S khi

Khi to xungKhi to xung dng IC7400

Khi mMch m giy dng IC74LS90

Khi gii mMch gii m BCD dng IC74LS47

Khi hin thHin th giy qua led 7 on

Mch m pht dng IC74LS90

Mch gii m BCD dng IC74LS47

Hin th pht qua led 7 on

Mch m gi dng IC74LS90

Mch gii m BCD dng IC74LS47

Hin th gi qua led 7 on

* Nhim v cc khi: Khi to xung: to xung vung vi tn s 1Hz. Khi m: Gm cc IC7490 c ghp ni vi nhau to thnh cc h m ph hp. Khi gii m: Gm cc IC7447 gii m BCD a ra khi hin th. Khi hin th: Hin th tn hiu sau gii m qua LED 7 on

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II.Hot ng ca tng khi1.Khi to xung Ta dng IC7400(cng NAND) to ra xung u vo cho b m. Cu to Chn vo Chn ra 1,2 3 4,5 6 9,10 8 12,13 11 Chn 7 ni t, chn 14 ni ngun Mch to xung

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2. Khi m 2.1.IC 74LS90 2.1.1.Hnh dng

Bn chn thit lp: MR1, MR2, MS1, MS2. Khi t MR1 = MR2 = 1 ( mc cao) th b m c xo v 0 v cc u ra mc thp. MS1, MS2 l chn thit lp trng thi cao ca u ra: QA = QD = 1 , QB = QC = 0 . NC chn b trng. IC 7490 gm 2 b chia l chia 2 v chia 5: - B chia 2 do Input CKA iu khin u ra QA . - B chia 5 do Input CKB iu khin u ra QB , QC , QD . - u vo CKA, CKB tch cc sn m. - to thnh b m 10 ta ni u ra QA vo chn CKB to xung kch cho b m 5. QA , QB , QC , QD l cc u ra. 2.1.2 S logic v bng trng thi

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Hnh: Bng trng thi ca IC 7490.

Hnh: S d u ra QA , QB , QC , QD . 3. Khi gii m 3.1.IC 74LS47 3.1.1 Khi nim Mch gii l mch c chc nng ngc li vi mch m ho. Mc ch s dng ph bin nht ca mch gii m l lm sng t cc n hin th kt qu dng ch s. Do c nhiu loi n hin th v c nhiu loi m s khc nhau nn c nhiu mch gii m khc nhau. V d: gii m 4 ng sang 10 ng, gii m BCD sang thp phn

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IC74LS47 l loi IC gii m BCD sang led 7 on. Mch gii m BCD sang led 7 on l mch gii m phc tp v mch phi cho nhiu ng ra ln cao hoc xung thp (tu vo loi n led l anode chung hay cathode chung) lm cc n cn thit sng nn cc s hoc k t. IC 74LS47 l loi IC tc ng mc thp c ng ra cc thu h v kh nng nhn dng cao a vo trc tip cc n led 7 on loi anod chung. 3.1.2 Hnh dng v s chn:

Chn 1: BCD B Input. Chn 2: BCD C Input. Chn 3: Lamp Test. Chn 4: RB Output. Chn 5: RB Input. Chn 6: BCD D Input. Chn 7: BCD A Input. Chn 8: GND.

Chn 9: 7-Segment e Output. Chn 10: 7-Segment d Output. Chn 11: 7-Segment c Output. Chn 12: 7-Segment b Output. Chn 13: 7-Segment f Output. Chn 14: 7-Segment g Output. Chn 15: 7-Segment a Output. Chn 16: Vcc.

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3.1.3 S logic v Bng trng thi:

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* Nguyn l hot ng: IC 74LS47 l IC tc ng mc thp nn cc ng ra mc 1 l tt, mc 0 l sng, tng ng vi cc thanh a, b, c, d, e, f, g ca led 7 on loi anode chung, trng thi ng ra cng tng ng vi cc s thp phn (cc s t 10 n 15 khng c dng ti). Ng vo xo BI c khng hay ni ln mc 1 cho hot ng gii m bnh thng. Nu ni ln mc 0 th cc ng ra u tt bt chp trng thi ng ra. Ng vo RBI c khng hay ni ln mc 1 dng xo s 0 (s 0 tha pha sau s thp phn hay s 0 trc s c ngha). Khi RBI v cc ng vo D, C, B, A mc 0 nhng ng vo LT mc 1 th cc ng ra u tt v ng vo xo RBO xung mc thp. Khi ng vo BI/RBO ni ln mc 1 v LT mc 0 th ng ra u sng. Kt qu l khi m s nh phn 4 bit vo c gi tr thp phn t 0 n 15 n led hin th ln cc s nh hnh bn di. Ch l khi m s nh phn vo l 1111= 1510 th n led tt.

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4. Khi hin th: Hin th dng led 7 on loi anode chung do u ra ca IC 7447 c mc tch cc l mc 0 ( mc thp). loi anode chung ( anode ca n c ni ln +5V, on no sng ta ni u cathode ca on xung mc thp thng qua in tr hn dng.

Chn 3, 8 l Vcc_c ni li vi nhau.

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III.Thit k mch1 S nguyn l

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2 Nguyn l hot ng Xung kch c to ra t mch to xung v xung ny c a ti chn CKA ca IC 74LS90 m giy. Ng ra ca IC7490 cc chn QA , QB , QC , QD c a n ng vo ca IC gii m 74LS47. i vi hai IC m giy (IC1 v IC2): Ta ni chn Qa vo chn CKB ca IC1 thnh b m 10,xung CLK t b to xung c cp cho IC1 qua u vi CKA, IC1 ny m gi tr ca 9 xung ( led hin th s 9), sau khi m ht gi tr ca 9 xung th cp cho IC 2 mt xung m. Khi , IC1 m v 0 v IC2 m ln 1, ta s c s 10. Sau IC1 tip tc m t 0 n 9 v tip tc cp xung cho IC2 tng ln 2, 3, Khi IC1 m m 9 v IC2 m n 5 chuyn sang 6 th khi 2 bit C ,B ca IC2 s mc 1 v ta s cho 2 u ra ny vo 2 chn MR1,MR2 ca 2 IC 7490 reset c hai IC tr v 0. ng thi u ra Qc ca IC2 ny c ni vi chn CKA ca IC m pht.Khi Qc ang trng thi 1 khi m s 5 s reset v 0,nh vy xung ny s kch vo u vo CKA ca IC3 m 1 n v tng ng vi 1 pht. i vi IC m pht (IC3 v IC4): Khi IC3 nhn c xung t n li m ging nh IC1 m giy , tng t IC4 ging IC 2.Nh vy 2 IC 3 v 4 s m n gi tr 59. V ly xung t IC m giy nn khi mch m giy m n 59 th mch m pht mi nhn c mt xung. Khi c IC m giy v m pht u m n gi tr 59 th tt c 4 IC cng c reset v 0, ng thi IC4 m pht cp cho IC5 l IC m gi mt xung. i vi IC m gi (IC5 v IC6): Khi IC5 nhn c mt xung th n cng bt u m ln. Khi IC5 m n 9 th cp xung cho IC6 m, khi hai IC m gi m n 23 v ti thi im sang 24 l lc c hai IC c reset. V s nh phn tng ng ca 2 l DCBA = 0010, ca 4 l DCBA = 0100 nn ng ra B ca IC m gi ( m hng chc) v ng ra C ca IC m gi (m hng n v) c a vo 2 chn MR1,MR2 ca 2 IC m gi thc hin reset v 0.Nh vy khi mch ang trng thi 23:59:59, nu nhn thm 1 xung CLK t b to xung th ta c trng thi tip theo s l 00:00:00.

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KT LUNQua bi thc tp trn, em hiu c cch thit k b m gi pht giy cho ng h s dng IC7490.Ngoi ra, t bi thc tp trn, em cn rt ra c cch ghp ni 1 b m bt k t cc IC7490. Em xin chn thnh cm n thy . hng dn em hon thnh tt bi thc tp ny.

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Trng i Hc Bch Khoa H Ni Khoa in T Vin Thng====o0o====

TRUNG TM THC HNH IN T

BO CO THC TP NNG CAOMch ng h sGio vin hng dn: Sinh vin thc hin: Nguyn Hi Vit SHSV: 20073450 Nhm: D42-045 Lp: in t 11-K52

H NI 10/2010

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