LI NI UK thut in t ngnh cng nghip pht trin mnh m v ang c ng dng rng ri trong mi lnh vc nh cng ngh thng tin, cng nghip c s pht trin ln mnh nh vy l do ng dng k thut s vo k thut in t c c mt tc nhanh hn v cht lng cao hn. t nc ta tri qua 2 cuc chin tranh gian nan v vt v chnh v th ko theo s tt hu ca nn kinh t. Trong thi k mi ca nn kinh t cn yu km ang trn i ln pht trin mnh m trong mi lnh vc ni chung v ngnh in t - vin thng ni ring. Song lp tr khng ngng hc hi nhng thnh tu khoa hc k thut p ng c nhu cu pht trin ca ngnh in t - vin thng. L mt hc sinh trung hc chuyn nghip c o to 2 nm em nm c nhng k nng c bn ca k thut mch. Bi vy vic giao ti "Mch iu khin tn hiu n giao thng" gip em c c hi c m mang kin thc v lnh vc quan trng ny. ti ca em vi ni dung l: Phn I: Tm hiu nhng v nng c bn ca k thut mch. Phn II: Cc mch ng dng trong mch t ng iu khin tn hiu n giao thng.

PHN I: K THUT IN C BN CHNG I: CC LINH KIN IN T

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I. KHI NIM V MCH IN T V NHIM V.

* Cc mch in t c nhim v gia cng tn hiu theo theo nhng thut ton khc nhau chng c phn loi theo dng tn hiu c x l. - Tn hiu l s o (in p trong dng in) ca mt qu trnh, s thay i ca tn hiu theo thi gian to ra tin tc hu ch. - Trn quan im k thut ngi ta phn ra lm 2 loi tn hiu. + Tn hiu tng t. + Tn hiu s. - Tn hiu tng t l tn hiu bin thin lin tc theo thi gian v c th nhn mi gi tr trong khong bin thin ca n. - Tn hiu s l tn hiu c ri rc ho v thi gian v lng t ho v bin n c biu din bi nhng tp hp xung ti nhng im o ri rc. - Tn hiu c th c: khuch i, iu ch, tch sng, chnh lu, nh, o, truyn t, iu khin, bin dng, tnh ton (cng tr, nhn, chia) cc mch in t c nhim v thc hin cc thut ton ny.II. NHNG LINH KIN C BN TRONG K THUT MCH IN T.

1.II. in tr. - Ni mt cch khi qut in tr l mt linh kin v tuyn in c tc dng ngn tr dng in. n v c tnh bng hng m, K, M. C 2 loi in tr l in tr tnh v in tr ng. * in tr tnh: l loi in tr khng chnh c v c tr s nh sn. Trong in tr tnh li c 2 loi in tr: in tr than v in tr dy. * in tr than dng 1 lp than dn in hay cc hp cht hu c, c loi dng hn hp cacbon hay than ch vi cht cch in bc bn ngoi v c dng hnh tr. Loi in tr than c cng sut chu ti 1,4W vi W. Tr s ca in tr c th hin bng cc vch mu v c n nh t 0 9. 2

+ Trn in tr thng c 4 vch nm ngay cnh tri. Ba vch u dng xc nh tr s in tr v vch th t l tr s sai bit. * Cu to: R= X1, X2, X3, X4

* in tr dy: Thng dng mt dy kim loi c kch thc ln hoc nh ty theo gi tr in tr v c bc bng 1 lp cao snh hoc s cch in. Loi ny cng thng c hnh dng l hnh tr hoc hnh ch nht, chu cng sut ti v nhit ln t 1/4 W vi trm W. * in tr ng: Cn c gi l bin tr hay chit p, bin tr cng c 2 loi. bng than hay bng dy. - in tr than thng c hnh trn vi nm hoc hnh ch nht c cn ko. Loi ny khi thit k thng gn bn ngoi ngi s dng theo mun. Tr s thng in ngay trn v st ca bin tr thng vi trc ngn m. - Bin tr dy thng c dng trong lnh vc in t cng nghip do sc hiu dng ti v cng sut ln. * Hnh dng:

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ng dng in tr trong k thut mch. Cc in tr c nhng chc nng khc nhau. Nh to mch phn p cho Tranzitor mch phi hp tr khng mc d thun ty hay tr khng. * C 2 cch ghp in tr trong mch. + Mc ni tip Rtd = R1 + R2 + + Rn. + Mc song song Rtd = R1. R2 Rn Quan trng n cng sut. P = I2. R. 2.II. T in. + T in l linh kin ri vi chc nng tch v phng in c dng rt nhiu trong cc mch v thit b in t. T in c nhiu loi v kch c khc nhau v s dng vi ngun AC cng nh ngun NG C. * V nguyn l t in gm 2 bn cc kim loi c ngn cch bng 1 cht cch in c phm cht cao c gi l in mi ti s t in cng ln cht dung mi cng cao hoc bn cc cng ln. Khi phn loi t in ta thng da vo in mi nh t giy, t mica, t gm + Trong mch in t in thng k hiu l C, tr s o bng fara, micr fara, nanfara, picpara. 1F = 10-6F 1NF = 10-9F 1pF = 10-12F * Do chc nng ca t in ta c th chia t in thnh 4 loi: t in gii, t fanfaloum, t polystyreme v t xanh lc.

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A. T in gii. + -

q b (d)

(a)

(b)

(c)

+ T gi cn c gi l t ho c cu to bng 1 lp giy mng cch in trn c trng 1 lp nitrat bc. C in tch nh hn dng lm cc dng. Tt c c qun trn v b vo trong 1 v nhm cng vi 1 dung dch ta nh mt li du cch in.

Mt dy c bt kn bng 1 ming cao su hoc ba c lt v ch l ra 1 hoc 2 bo cc. (hnh a, b v c) cc tch c nh du ngang trn v bc cng vi tr s in dung v in p chu ti. Nhng t in ny thng c chc s t 1F vi chc ngn F vi in p t vi vn v trm vn. Cc t ho thng dng lc ngun, t bn lc gia cc tng mch vi nhau. Ngoi rra cn c 1 loi t ho dng cho in p AC. Cu to ca loi t ny cng ging nh cc t NG C. T loi ny cng c 1 hay nhiu cc tnh dng. i vi loi t mang nhiu cc tnh dng th tng cc tnh c mang nhng tr s in dung khc nhau. Cc m ca t thng l v t (hnh d) t ny thng gp trong cc TV s dng n in t. * D t in c s dng theo nhu cu no i na th cc tnh ca t lun lun c gn vi ng cc tnh ca ngun in.

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* T Tantalum.

T Tantalum l 1 t in c hnh dp c cu to bng 1 loi cht do tng hp, bn trong trng 1 lp bc mng vi din t nh hn lm cc tnh dng. T ny c nh du cc tnh r rt v c tr s in dung di 1 F. Cch p dng mu sc cho tr s t in cng tng t nh in tr. * ng dng: nhng t ho c tr s vi ngn F thng dng lm b lc ngun DC vi mc ch loi b cc nh tn hiu ca AC cn st li sau khi qua b nn dng. i khi cc t cn lm cc mch nhn i in p. + Khi 2 t ghp ni tip tr s in dung gim v ghp song song tr s in dung tng. Nhng t ho mang tr s nh hn thng lm cc t lin lc ghp cc tng vi nhau. + Khi t mc song song vi 1 in tr s to ra 1 mch cng hng tn s. 1 2 RC

F=

Vi cch p dng cng thc trn c 1 tn s cng hng trong 1 gii php tn rng ngi ta thay th t tnh bng t xoay. + Trong lnh cc m thanh ngi ta thng dung cc t v tr thit k cc mch iu chnh m sc v m lng vi nhng tn s khc nhau t n gin n phc tp.

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3.II. Cun dy. - Cun dy cn c gi l cun cm gm nhng lp dy ng c trang 1 lp cch in qun chng ln nhau trn 1 li. Li ca cun dy c th l: Giy, ferit st, khng kh tu theo mc tn s mch s dng m s dng cc li trn. - Tr s ca cun dy tnh bng Hery v mili Hery. 1 hery = 1000MH. - Thng thng trn cun dy t ghi tr s v nhng cun dy nh thng c minh ho bng mu sc. Tu theo vic s dng cc cun dy trong mch in m cun dy c hnh th khc nhau. - Vi tnh nng a dng ca cun dy t cng sut nh n cng sut ln vi dng chu phi cao, ta c th tch ton thit k cho ph hp. * ng dng: Bn c th dng hiu ng cm ng ca cun dy lp rp b lc phn tn. 4.II. Bin p. - Bin p cn gi l bin th c nhim v tng p hoc h p. B bin p thng c qun thm li st t v c ti thiu 2 cun dy qun chng ln nhau. Cun th nht c th l 1 loi 2 cun dng cho 2 in th ng vo vi hiu in th khc nhau gi l cun s cp. Cun th 2 c th l 1 hoc nhiu cun ni tip nhau hoc ri tng cun dng do nhiu mc in p u ra. - Tu vo vic s dng m bin p c nhiu kch c khc nhau, ti y in p v dng ti khc nhau ti vi ch miliampe hng trm ampe. - Trong ng dng tu vo cc kt cu mch m cc bin p c nhiu cng dng khc nhau nh bin p chiu dng ti nh (vi ch miliampe) cc mch dao ng (ngang, dc trong TV), mch dn tn hiu, bin p, xut m. i vi cc bin p c dng ti v in ln thng c dng trong cc bin p ngun nh h p hoc cao p.

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* ng dng: Do tnh cht a dng ca bin p, bn c th t qun 1 bin p i in 110VAC/220VAC v ngc li. v 1 bin p iu chnh v nguyn l khi ta a 1 in p AC u vo ta s c 1 in p thch hp u ra. 5.II. it: - it l 1 linh kin bn dn do 2 lp vt liu bn dn P - N ghp li thnh. Tip xc gia P - N c th l mt mt cng c th l 1 im tu theo yu cu chc nng hot ng ca dit. Do c tnh ca mch in dit c nhiu loi v hnh dng khc nhau. * Dit chnh lu: Cn gi l it nn in dng bin i dng in t AC thnh DC loi it ny c th c ch to t Silicon hoc geemanium hai loi ny c in p ngng khc nhau. Vi li Silicon l 0,6V cn geemanium l 0,2V. - Khi hot ng phn cc ngc in p tng n 1 gi tr no vng tip gip P - N s b nh thng v dng in ngc tng vt ln. ch ny cn phi m bo to nhit tt cho vng tip gip. Do khi s dng it no chn gi tr ngc tc ca mch nh hn so vi in p ngng.

vng tip gip P - N - Khi gi tr in p ngc v gi tr dng chnh lu cho php ca i t khng t yu cu. Ta c th chn nhiu it cng loi mc ni tip hoc song song. Trng hp khng gi tr in p ngc ta mc cc it ni

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tip nhau km theo cc in tr R sao cho dng qua chng ln hn vi ln so vi dng ngc qua it iu ho gi tr in tr ngc khc nhau gia cc it cng loi. iu ho tc phc hi in p trn cc it ta mc thm cc t song vi it gi tr in dung ca t ny ln hn vi ln so vi in dung ca it. Tuy nhin vi cch mc ny s tht thot nng lng v nh hng n h s chnh lu. Nu c tr dng chnh lu khng t ta mc cc it song song nhau v iu ho dng cho cc it bng in tr.

* Ch : khi lp it vo, mc nn cc tnh ca n c loi it c v k hiu ngoi v c loi khng c ta phi dng ng h o xc nh cc tnh. * ng dng: Vi mc ch chnh lu in p m cc loi it ny thng nn ngun AC thnh DC. T vi vn n vi trm vn. Ou t

* it n p: l 1 loi it dng n nh in p hay ni cch khc l n nh hiu s in th khng vt qu mc in p cho php. - Ty vo s dng trong mch in m it n p c nhiu loi khc nhau. phn bit trn v it ngoi k hiu it thng c thm 1 du chm v k n l gi tr in p cc i.

- Khi s dng it n p cn lu n cc thgn s sau: 9

+ in p n nh (VZ) l gi tr in p ca it khi dng qua n (IZOBUTAN) nm trong vng hot ng. + Dng n nh cho php ti thiu c xc nh bng gi tr dng qua it trc khi dng tng t ngt. + Dng n nh ti a cho php c xc nh theo cng thc tn x ca it hot ng an ton. Cng sut hot ng cho php ca it n p silicon c th t 100mW n 50W. * ng dng: n nh ngun dng in p 1 chiu dng it n p ta c th lp 1 mch nguyn l sau:

nng cao tnh n nh ca mch, ngi ta dng nhiu tng n p.

* it quang: (LED - LIGAT E aritting it). - y l loi it bn dn c kh nng bin i nng lng in thnh nng lng quang. Cu to ca it ny c dng c bit vi v bng kim loi hoc bng nha c ca s trong sut nng lng quang c th pht qua.

- Khi LED c phn cc thun in t t lp bn dn M chuyn sang lp bn dn P. Ti hp vi l dn ngang vng hin ca tip gip P - M v lp 10

tc ra nh sng. Tu theo vt liu ch to m it quang c nhng mu sc khc nhau. * ng dng: it pht quang khng ch dng lm b ch th cho cc thit b in t m cn s dng rng ri trong cc lnh vc kim tra o lng khc. - Do c tuyn V - ampe ca it quang kh dc nn khi s dng cn bit gi tr in p hot ng v dng cc i ca n. 6.II. Dinisto hai chiu (DIAC). - y cng l 1 dng bn dn bn lp nhng c kh nng dn in 2 chiu. - in p m ca Diac u ging nhau c 2 chiu thun v nghch v in p ny thng nm trong khong 200V - 400V. - Diac c th chu dng ti qua n t 3A 30A. kch m Diac, ngi ta dng 1 xung in c bin khong 5A. * ng dng: Ngi ta dng diac to cc mch xung iu khin ng m cc mch khc. 7.II. Thyristo. Thyristo cn gi l SCR khc vi Tinisto l c thm 1 cc lp bn dn P ca bn dn 4 lp. Cc ny gi l cc iu khin. Nu khng c in cc iu khin chc nng tng t nh Dinisto.

Ghi G ngt: RAK = RKA = - Khi c in kch vo cc G th CR dn. - Chnh lu cong sut ln. UA >> UG UK

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Ni A vi G th KR ging nh 1 it phn cc thun. * ng dng: Do SCR ch dn in khi c 1 in p dng kch vo cc khin. n linh kin ny s dng rt nhiu trong mch bo v, iu khin, Ig, IAKmax, UAKmax 8.II. Triac. Triac l linh kin in t c nguyn l lm vic nh 2 Thyristor ni song song ngc v cu to.

S dng mch cng sut ln, Ig, I1-2max, U1-2max. iu kin lm vic: MT1 MT2 UMT1 >> UG UMT2 hoc UMT1 UG UB > UC

UC > UB > UE

Trong hu ht cc ch hot ng 1 cng dng in ln chy qua gia 2 cc E v C ca (T) c iu khin bi 1 dng phn p nh cc B. Dng phn p ny c th iu ch c v v th tn hiu xut c khuch i ln ln. - Tu vo nhu cu trong mch in m cc (T) c nhiu hnh dng cng nh chu nhiu dng ti khc nhau.

* ng dng.

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Do tnh o o dng ca chng cc (T) thng dng hu ht trong cc mch in t t khuch i cao tn, tng tn, m tn n cc mch dao ng. * Trarsirtor c 3 cch lp xp c bn. * Cc B chung: IC = IE. IE = IC + IB IB = (1 - )IE.

Thng p dng trong cc mch cp ngun do c tnh dng n nh khng gy mch ni tip tn s cao v kh nng khuch i tt. * Cc E chung.

- Vi cch mc cc E chung mch to thin p bng phng php nh dng. - C cc im l ni tr cc B c th thay i ch lm vic trong nhin mch c khuyt im km n nh theo nhit. V vy khi lm vic nhit cao ngi ta thng lp thm in tr ti chn E ca (T). - Vi cc E duy th tn hiu ra c khuch i v ng pha vi tn hiu vo. * Cc C chung.

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- Mch C chung rt t khi s dng do tnh cht o pha ca n. Do tnh cht o pha nn trc y thng s dng trong cc mch chuyn h SECAM v NTSC. * Cc mch in chnh lu dng in.

Mch chnh lu 1/2 chu k

Bin

* C chu k 2 it

- nu L3 (+) L2 (-) th D1 thun D2 ngt v ngc li. * C chu k 4 i t.

D1 D2

D2 D3

- Gi s mc ban u.

T2 T115

- D2 v D4 dn th dng in i nh sau: ia vo D2 sau qua t v sa tr ti tr v m t sau qua D 4 tr v ngun. - D1 v D3. Th D3 n qua t C v qua Rt xung t qua D1 v ngun. * Mch nhn i.

D1 C1 D2 C2

Nu A (+) v B (-) th D1 dn C1 np cn D2 ngt. A (-) v B (+) th D2 dn C1 np cn D1 ngt. * Cc mch dao ng. * Mch dao ng a hi.

Led1 RC1 C1 Rb1 Rb2 C2

Led2 RC2

T1* Mch dao ng hnh sin.

T2

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C5 R1 C1 C5 C2 R2 R3

* Mch dng transistor.

V V2 R7

V V1 R8 R6

C1 R1

C2 R2

Q2

* Mch t dao ng ghp bin p. S :M

M