Mach Phan Tich Pho Am Thanh

n thit k mch tng t ph tn m thanh Mc Lc M U

Thit k mch phn tch

Tran g 2 3 3

Chng 1: Tng quan 1.1. Gii thiu tng quan v mch phn tch ph

m thanh 1. 2. Phn tch h thng mch phn phn tch ph 3 m thanh 1. 2.1 Kh nng p ng yu cu ca h thng 1.2.2 S khi v nguyn tc hot ng hin th dng qut : Chng 2: C s l thuyt 2.1. Mch lc tn s 2. 1.1. Gii thiu v cc loi mch lc tn s 2.1.2. Mch lc thng thp 2.1.3. Mch lc thng cao 2.1.4. Mch lc thng di 2.1.5. Mch lc chn di 2.1.6 Chi tit v mch lc di thng 2.2 Mch iu khin LED 2.2.1 Mch iu khin LED bng linh kin ri 2.2.1 Mch iu khin LED dng IC LM 3915 Chng 3: Thit k v ch to mch phn tch ph m thanh 3.1. S khi 3.2. Thit k s nguyn l v phn tch tnh 4 4

1.3. S khi mch phn tch ph m tn dng 5 6 6 6 6 7 8 9 9 11 11 13 17 17 19

ton 3.21. Thit k v tnh ton mch lc 19 3.2.2 Thit k chuyn mch in t: 24 3.2.3. Khi mch dao ng, m v gii m, mch 26 thc v iu khin LED3.2.4 Thit k khi mch ma trn LED hin th.

31 1

n thit k mch tng t ph tn m thanh 3.3 Thit k mch in Kt lun

Thit k mch phn tch 32 36

2

n thit k mch tng t ph tn m thanh

Thit k mch phn tch

Li ni uCng ngh in t hin nay c nhng bc pht trin rt nhanh. N lun gn lin vi s pht trin ca cc cng ngh khc. Cng ngh in t tng t em n cho con ngi nhng ng dng quan trng trong tt c cc nghnh, cc lnh vc. L mt sinh vin khoa Cng ngh, nghnh in t - Vin thng, bn thn em hiu rng vn dng nhng kin thc hc vo thc t l v cng quan trng. Vi suy ngh trn, em quyt nh chn ti Thit k mch phn tch ph tn m thanh. Em xin chn thnh cm n cc thy c gio trong b mn in t - Vin thng, Khoa Cng ngh ging dy cho chng em nhng kin thc v chuyn mn, chng em thc hin tt n thit k mch tng t ny. Do kin thc cn hn ch nn n ny khng th trnh c nhng thiu st. V vy em rt mong c s ch bo ca cc thy c v nhng kin ng gp ca cc bn. c bit em xin chn thnh cm n thy gio ng Thi Sn nhit tnh gip em hon thnh ti ny! Em xin chn thnh cm n ! Vinh, ngy thng.nm 2010 Sinh vin thc hin

Hong Th Mnh 3


Thit k mch phn tch

Chng 1: Tng quan1.1 Gii thiu tng quan v mch phn tch ph m thanh T lu mch phn tch ph xut hin nhiu trong cc dn m thanh. Hin nay ng dng ca mch ny xut hin ngy cng nhiu trong cuc sng nhm phc v gii tr v thm m ca con ngi. Yu cu ca mch phn tch ph tn hiu m thanh l: C kh nng o c gi tr in p ca cc tn hiu tn s m thanh v hin th trn mt ma trn LED. 1. 2. Phn tch h thng 1.2. 1. Kh nng p ng ca h thng: H thng giao tip vi ngi s dng ch bng hin th do vy n hn ch c tc ng ca ngi s dng vo ni dung bn trong mch n nhp nhy theo nhc. - Mch c thit k hin th ph ca cc tn hiu trong cc di tn xc nh. - Mch c thit k theo nguyn tc khi di tn s no ph hp vi thit k mch th hin th tng ng vi dy n LED . 1.2.2. S khi v nguyn tc hot ng: a. S khi:

4


Thit k mch phn tch

Hnh 1: S khi c bn ca mch phn tch ph m tn b. Nguyn l hot ng: Tn hiu t ng vo c a vo tng b lc tn. B lc tn dng loi mch lc tch cc di thng. Mch ch cho cc tn hiu trong mt di tn qui nh i qua v lc b cc thnh phn khc. C th dng transistor kt hp vi cc t in v in tr hnh thnh nn mch lc tch cc hoc dng cc OP-AMP kt hp vi cc linh kin th ng bn ngoi c mch lc tch cc. S mch lc cng nhiu th b phn tch ph tn cng c phn gii tn s cng cao, c th hin trong ch tiu cht lng ca mch cao hn. Mch iu khin dng hin th mc bin ca tn hiu sau khi qua b lc tn. Mch ny c th dng linh kin ri hoc dng cc IC chuyn dng. Cc ng ra cng nhiu th mch c phn gii bin cng ln. Trong s trn ta thy mi b lc tn cn c mt mch iu khin LED cho vic hin th, cng nhiu b lc tn ( phn gii tn s ca mch cng cao) th cng dng nhiu mch iu khin LED. iu ny s gy cho mch 5

n thit k mch tng t Thit k mch phn tch ph tn m thanh s kt ni phc tp. khc phc nhc im ca s trn ta xt nhng ci tin trong s khi sau: 1.3. S khi mch phn tch ph m tn dng hin th dng qut: 1.3.1. S khi:

Hnh 2: S khi ca mch phn tch ph m tn dng hin th dng qut 1.3.2. Nguyn l hot ng: S ny th hin u im l ch dng mt mch iu khin LED bt k s lng mch lc l bao nhiu, s ng ni dy ra mch hin th cng n gin hn do vic s dng ma trn hin th l s kt hp gia hng v ct. S lng ct tng ng vi s lng mch lc tn, cn s hng chnh l s lng u ra ca mch iu khin LED. S ny cng bao gm n b lc tn, cc ng ra ca cc b lc tn c a vo b chuyn mch, ti tng thi im chuyn mch ch cho tn hiu ca mt b lc tn ra m thi. iu khin b chuyn mch c thc hin bi mch m & 6

n thit k mch tng t Thit k mch phn tch ph tn m thanh gii m, tn hiu xung clock ca mch dao ng a vo mch m & gii m, s ng ra ca mch m & gii m tng ng l n. Ng ra ca mch m & gii m cng ng thi c a n mch thc qut cc ct. Nu tn s xung clock nhanh th mt ta s b nh la cho cm gic ng thi cc ct u sng nhng thc ra ti mt thi im th ch c mt ct sng.

7


Thit k mch phn tch

Chng 2: C s l thuyt2.1. Mch lc tn s: 2.1.1. Gii thiu v cc loi mch lc: Thng trong cc thit b in hoc in t cn chn hoc cn cho qua nhng tn s no ngi ta thng dng b lc tn s. Trc kia n c dng ch yu bng nhng phn t in cm L v in dung C. Ngy nay IC khuch i thut ton (OP AMP) c kch thc nh, c nhiu c tnh u vit, gi thnh h, tnh ton thit k n gin nn c a chung dng cc b lc tch cc RC.C nhiu loi mch lc tch cc khc nhau chng hn nh mch Butterworth v Chebyshev. Trc khi xt n cc b lc ta cn xt n bc ca b lc. Bc ca b lc xc nh dc ng ct. S bc cng cao, ng ct cng dc. Bc lc gia tng theo 6dB/oct. Mch lc tch cc n gin nht l mch lc bc nht vi dc l 6db/oct. Cc mch lc tch cc cao cp hn c th c bc cao hn, v d mt b lc bc hai c dc ng ct l 12dB/oct. Phn di, do yu cu ca ti, trnh by ch yu v mch lc di thng. Sau y l gii thiu cc loi mch lc: 2.1.2. Mch lc thng thp: Mch lc Butterworth c thit k c p ng bin tn phng trong di thng v c c tnh ng cong trn tru. Hnh di trnh by biu p ng tn s ca mt mch lc Butterworth bc nht in hnh.

8


Thit k mch phn tch

Hnh 3: c tuyn mch lc thng thp Mt loi ph bin khc ca p ng lc c th hin bi mch lc Chebyshev. Biu p ng bin tn ca mt mch lc thng thp Chebyshev c trnh by hnh di:

Hnh 3: c tuyn mch lc thng thp Chebyshev p ng bin tn ca mch lc khng phng tn s thp hn tn s ct nh trong b lc Butterworth. Trong b lc Chebyshev, c mt s gim v bin pha trc tn s ct v bin li tng tr li trc khi ng suy gim bt u. Thun li ch yu ca mch lc Chebyshev l c c tnh ng suy gim rt dc.Cc mch din thc s ca mch lc Butterworth v Chebyshev thng th kh ging nhau. Thng 9

n thit k mch tng t Thit k mch phn tch ph tn m thanh thng, s khc bit duy nht trong hai mch lc l gi tr cc linh kin thc s c s dng. 2.1.3. Mch lc thng cao:

Hnh 4: c tuyn mch lc thng cao v mch lc thng cao Chebyshev V mt chc nng, mt mch lc thng cao ng vai tr i lp vi mt mch lc thng thp. Nu b qua ng cong suy gim, nhng ci c cho qua bi mch lc thng thp s b chn li bi mch lc thng cao v ngc li. Cc mch lc tch cc thng cao kh ging cc mch lc tch cc thng thp. ngoi tr v tr ca mt s linh kin b thay i. Cng ging nh mch lc tch cc thng thp, mt mch lc tch cc thng cao cng c c p ng Butterworth ln p ng Chebyshev c trnh by di y. 2.1.4. Mch lc thng di: Ni chung cc mch lc di thng phc tp hn nhiu so vi cc mch lc thng thp v thng cao. Theo mt mt no , cc mch lc thng thp v thng cao cng l mt loi mch lc di thng. Trong mt mch lc thng thp, tn s ct di l mt im tng tng nm di 0Hz. i vi mch lc thng cao, tn s ct trn c xc nh bi p ng tn s ca 10

n thit k mch tng t Thit k mch phn tch ph tn m thanh khuch i thut ton (hay cc linh kin tch cc khc) c dng trong mch lc. Mt mch lc di thng c th c to ra bng cch mc ni tip mch lc thng thp v mch lc thng cao. Cc mch lc di thng phc tp hn v c nhiu thng s hn v v th linh hot hn. Cc thng s bao gm nh: li (K),bc lc (n), tn s trung tm (Fc), v bng thng (BW) ngoi ra cn c mt thngs na l h s phm cht Q, c suy ra t Fc v BW.

Hnh 5: c tuyn mch lc thng di 2.1.5. Mch lc chn di: Mt mch lc di chn cho hu ht mi tn s i qua n ngoi tr nhng tn s nm trong mt khong c xc nh (thng l hp). Cc mch lc di chn thng c dng loi b nhng thnh phn tn s khng mong mun. Cc tn s cao hn v thp hn di chn u c mch lc di chn cho qua d dng. Trong th p ng bin tn ta thy c mt l hng hay lm xung v th mch ny thng c gi l mch lc Notch. 11


Thit k mch phn tch

Hnh 6: c tuyn mch lc chn di

2.1.6 Chi tit v mch lc thng di Mch lc di thng c bn c minh ha bn di:

Hnh 7: S nguyn l mch lc tch cc thng di dng KTT Mch ny c th c thit k cho li t thp ti trung bnh v gi tr Q c th cao ti 20, gi tr thp hn ca Q c th c chn la bng cch dng cc gi tr linh kin thch hp. Trong mch chn C 1 = C2 = C d tnh ton. Cc thng s cho trc l tns trung tm (Fc), li (K) v Q. Trong hu ht cc trng hp, gi tr Q c th c suy ra t 12

n thit k mch tng t Thit k mch phn tch ph tn m thanh tn s trung tm v bng thng ca b lc di thng.Q= FC BW

Vi cc thng s cho trc, ta c cc cng thc tnh R1, R2 v R3:R1 = Q R2 = Q R = 2Q 2FC C (2Q K ) ; 3 2FC C

2FC CK ;

li c xc nh bng t s gia R1 v R3:K= R3

2R1

Mt hn ch quan trng cho mch ny l nu c li (K) cao th Q cng phi cao. Khng th thit k mch lc vi li cao v Q thp bi v gi tr ca R2 s m. Trong mch, bc lc c xc nh bi gi tr Q. Gi tr Q cng cao, ng ct cng dc. Khi cho trc cc gi tr C, R1, R2, R3, c th tnh c:FC = 1 2C R1 + R2 ; R1 R2 R3 Q = FC CR3

13

n thit k mch tng t ph tn m thanh 2.2. Mch iu khin LED

Thit k mch phn tch

2.2.1. Mch iu khin LED dng linh kin ri: 1. Mch dng Transistor

Hnh 8: Mch iu khin LED dng KTT Trong s trn, Q1 v Q2 to thnh b khuch i hai tng. Khi u vo khng c tn hiu, Q1 hu nh ng (trng thi ny c xc nh bi bin tr R4), st p trn R2 nh, khng m Q2 bi vy trn cc C ca Q2 khng c dng ra, cc LED tt.Khi c in p dng t u vo, Q1 m, in p vo cng ln, Q1 m cng nhiu. Do Q2 cng m v c dng in ra cc C. Dng in ny cng ln. Khi in p u vo cng mnh. Khi c dng in th cc LED ln lt sng, bt u t LED cui cng (LED7) Khi c dng in t cc C ca Q2 th dng in ny hu 14

n thit k mch tng t Thit k mch phn tch ph tn m thanh nh hon ton i qua R12 v LED7 v to nn st p trn on ny (ti anod LED6 so vi mass). Vi mt dng in xc nh LED7 sng v in p st trn n khong 1,8 n 2V. Trong qu trnh dng in tng ln, in p ny khng i. Mt cch khc LED7 ng vai tr ca mt n p. Nhng dng in tng dn n vic tng in p ti anod LED 6.Khi in p ny t gi tr bng tng in p st trn LED 7 v diode m D6 (0,7V) tc l khong 2,5 n 2,7V th LED6 pht sng. LED5 s sng tip theo khi dng cc C ca Q2 tip tc tng, khi m in p ti anod LED5 t n gi tr bng tng in p st trn LED ang sng v cc diode m D5, D6. Tm li LED tip theo ch sng khi tng in p anod ca chng (so vi mass) ln khong 0,7V so vi in p trn anod ca LED trc . Khi dng in ra trn cc C ca Q2 gim th cc LED tt theo th t t trn xung di. tuyn tnh ca LED ch bo ph thuc vp vic chn la chnh xc cc in tr R7 n R12 cng nh cc tham s ging nhau ca cc LED. Mch ny khng ch lm vic c vi ngun tn hiu in p khng i u vo m cn vi ngun tn hiu l m tn. Trong trng hp ny, mch ch lm vic vi cc na chu k dng ca tn hiu. 2. Mch iu khin LED dng cc khuch i thut ton:

15


Thit k mch phn tch

Hnh 8: Mch iu khin LED dng KTT Trong mch, cc u vo khng o c ni vo mch phn p ly mc in p mu, trong khi in p tn hiu vo cng lc cc u vo o. Mch so p s so snh cc mc in p vo v lm sng cc LED tng ng. 2.2.2. Mch iu khin LED s dng IC LM3915: 1.Gii thiu chung IC LM3915 l mt mch tch hp n khi c th cm nhn c cc mc in p tng t v iu khin hin th trn 10 led hoc mn hnh tinh th lng hay l cc thit b hin th hunh quang chn khng, cung cp cho mt b khuch i lgarit 3dB/bc in p tng t hin th. Mt chn thay i hin th t biu ct sang hin th cc im di ng. Dng trn led c iu khin v c th lp trnh c m khng cn n cc tr hn dng. Tt c h thng hin th c th hot ng nh ngun cp nm trong khong 3V cho n 25V. IC bao gm mt in p tham chiu c th iu chnh c v ng mt b chia p 10 mc chun. B m 16

n thit k mch tng t Thit k mch phn tch ph tn m thanh nhp trng thi tr khng cao nhn tn hiu t mt n trong di 1.5V ca ngun dng. Hn na, n khng cn phi bo v cc tn hiu u vo. B m nhp iu khin 10 b so ring l c tham chiu ti cc b chia vi chnh xc. chnh xc thng thng tt hn 1dB. S hin th 3dB/bc ca LM3915 l mt dy cc tn hiu ng vi di rng,nh l mc m thanh, in, cng chiu sng hoc dao ng. Cc chng trnh m thanh trung bnh hoc l cc b ch bo mc cc i, ng h in nng v ng h o cng tn hin cao tn. Thay th cho cc ng h o thng thng bng kt qu hin th nhanh dn trn mt biu led. IC LM3915 rt d p dng nh l mt ng h o 1.2V bng tht m ch i hi mt in tr cng vi 10 led. Mt in tr lp trnh vi ngun p bt k t 1.2V n 12V. sng ca led c th c iu khin bi mt bin tr ring. IC LM3915 rt a nng. cc u ra ca n c th iu khin hin th trn cc mn hnh tinh th lng, cc bng hunh quang chn khng, v bng n dy tc tt nh cc led mu. Nhiu thit b c th c ghp ni hin th cho mt im hay l mt ct vi rng 60 dB hoc 90 dB. Lm3915 cng c th c ghp ni vi LM3914 hin th mt di/biu hoc vi Lm3916 cho mt m lng k m rng. Cc c im ca Lm3915: - 3dB/bc, bin 30 dB - iu khin hin th cc led, mn hnh tinh th lng, bng hunh quang chn khng. 17

n thit k mch tng t Thit k mch phn tch ph tn m thanh - Hnh thc hin th ct hay im c th do ngi dng chn c bn ngoi. - in p tham chiu bn trong t 1.2V n 12V. - Hot ng vi in p ngun n t 3V n 25V. - Dng ra c th lp trnh t 1mA n 30mA. - in p vo chu ng 35V m khng gy tn hi hoc sai kt qu u ra. - iu khin trc tip TTL hoc CMOS. - B chia bn trong 10 bc, v c th c tham chiu ti mt bin rng ca in p - LM3915 c nh gi cao nht khi hot ng t 00C n +700C.

Hnh 1: ng dng tiu biu ca IC LM3915 2. S d khi v chc nng cc chn LM3915 a. S khi S khi c n gin ca LM3915 bao gm mt b m vo trng thi tr khng cao, hot ng vi tn hiu t t n 12V va c bo v chng ls o chiu 18

n thit k mch tng t Thit k mch phn tch ph tn m thanh v qu p. Tn hiu ny sau c p dng cho mt lot 10 b so snh, mi b nh vy c thin p so snh mc khc nhau bi tr bng.

Hnh 2: s khi ca IC LM3915

19

n thit k mch tng t Thit k mch phn tch ph tn m thanh b. Chc nng cc chn LM3915 IC LM3915 c tt c 18 chn, mi bn 9 chn, c trnh by nh hnh v di y.

Hnh 3:Ss chn ca IC LM3915 Chc nng cc chn Chn 2 (V-): chn ni t. Chn 3 (V+): chn cp ngun. Chn 5 (Signal input): chn a tn hiu vo. Chn 7 (Reference output): chn tham chiu ra. Chn 8 (Reference adjust): chn iu chnh tham chiu. Chn 9 (Mode select): chn la chn ch , u vo la chn ch cho php kt ni cc Lm3915 vi nhau, v iu khin ch hot ng hin th ct hay im. C cc cch c bn s dng u vo ny nh sau: Cc chn 10 ->18, chn 1 l cc u ra cho php kt ni vi thit b hin th.

20


Thit k mch phn tch

Chng 3: Thit k v ch to mch phn tch ph m thanh3.1. S khi:Trong n ny, mch phn tch ph m tn c phn tch l tn s 10, phn tch bin cng l 10. Trong mch s dng mch hin th dng qut mch gn nh, cc ng kt ni t cng nh s lng cc linh kin c gim.

Chia mch thnh cc phn chnh nh sau: khi mch lc vi cc chuyn mc in t; khi mch dao ng, m, thc vi mch 21

n thit k mch tng t Thit k mch phn tch ph tn m thanh iu khin LED; v khi mch ma trn LED hin th.

22

n thit k mch tng t Thit k mch phn tch ph tn m thanh 3.1.1. Khi mch lc v chuyn mch in t:

Tn hiu t ng vo c a ng thi vo tt c cc b lc, ti ng ra ca cc b lc ny c a vo chuyn mch in t vi cc ng vo d liu iu khin chuyn mch. Ti mt thi im ch c tn hiu ra ca mt b lc. iu ny c thc hin bng cch a vo cc d liu chuyn mch thch hp. 3.1.2. Khoi mach dao ong, em, thuc vi mach iu khin LED:

Trong khi ny, mch iu khin LED l c lp vi nhng phn khc nhng cho gn nn c gp chung vo phn ny. Tn hiu c a vo mch iu khin LED c c d liu tng ng ng ra hng. 23

n thit k mch tng t Thit k mch phn tch ph tn m thanh Mch dao ng to xung clock cp cho mch m kt hp vi mch gii m,cc ng ra ca mch gii m chnh l cc ng ra d liu chuyn mch cho b chuyn mch, ng thi cc ng ra ny cng c a vo mch thc cho ra cc ng ra ct dng qut cc ct. 3.1.3. Khi mch ma trn LED hin th: Khi ny l khi n gin nht so vi cc khi. y l mt ma trn gm cc hng v cc ct. Giao im ca hng v ct chnh l LED c gn vo. D liu c a vo hng ti tng thi im tng ng vi ct c chn hin th.

3.2. Thit k, tnh ton: 3.2.1. Khi mch lc v chuyn mch in t: 3.21. Thit k v tnh ton mch lc: Ty theo tng cp my, ta c th gp cc mch phn tch ph m tn c phn chia thnh nhng tn s trung tm ca cc b lc nh 20Hz, 30Hz, 60Hz, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 8KHz, 16KHz, 20KHz,.... cc mch phn tch ph m tn n gin hn, ta c th gp tn s trung tm ca cc b lcch c 5 tn s, mt s loi chuyn dng, s tn s trung tm ln n 10, 15, 16,32,... v d nhin s lng tn s trung tm cng nhiu th 24

n thit k mch tng t ph tn m thanh mch cng c cht lng cng cao.

Thit k mch phn tch

Thng thng, cc tn s trung tm c bin thin theo qui lut Octave (tn s tng gp i), chnh l do vn x l hi (harmonic). iu ny quyt nh rt ln i vi r, cht lng ca cc ngun m a dng nh cc bi nhc ha tu vi nhiu loi nhc c khc nhau. V d nh: thng thng ta phn bit c nt La cng bt ca mt n guitar v ca piano c chnh l nh cc hi cc bt cao hn ca nt La chun m ta phn bit c hai nhc c. Ta c th din t mt s tn s m loi nhc c c th t c nh sau: - tn s 30Hz: thng nghe cc loi Bass violin, Bass Tuba, Contrebass,... - tn s 60Hz: thng nghe cc loi Trombone, Bassoon, Cello,... - tn s 100Hz: thng nghe cc loi Viola, ging ni con ngi, Kettle drum, cc guitar bass, trng,... - tn s 330Hz: thng nghe a s cc m c bn ca cc nhc c v ging ni con ngi. - tn s 1KHz: vng tp trung cc m thanh ca cc loi nhc c, cc m cao ca con ngi. - tn s 3,3KHz: tp trung cc m thanh do cc loi n dy to ra. nt dy tn s ln cn ny. - tn s 10KHz: tp trung hi bc cao ca m c bn ca cc loi nhc c, ting x ca bng t gy ra. - tn s cao hn 10KHz: hi bc cao ca cc m c 25

n thit k mch tng t Thit k mch phn tch ph tn m thanh bn v ca mt s nhc kh c bit. T cc thng k tng i trn, ta c c mt s nim v cng dng ca cc b lc. Vic thit k b lc c th phn chia thnh nhiu b lc di thng c lp c tn s trung tm ring bit tnh ton. Mt b lc di thng loi tch cc dng khuch i thut ton, ta c th s dng cc cng thc sau l kt qu ca hm truyn t mch: - Tn s trung tm Fc c xc nh vi t C1 = C2. - in tr R1, R2 xc nh tr khng vo ca mch: Z = R1 + R2. - li in p ca mch c xc nh bng: 2R1 - H s phm cht: Q = FC CR3 K = R3/

26

n thit k mch tng t Thit k mch phn tch ph tn m thanh - Tn s trung tm c xc nh bng cng thc:FC = 1 2C R1 + R2 R1 R2 R3

- Cc gi tr R1, R2 va R3:R1 = Q 2FC CK ; R2 = Q R = 2Q 2FC C (2Q K ) ; 3 2FC C

Hnh 15: B lc thng di dng KTT Khi tnh ton b lc, c th chn trc mt vi thng s, sau suy ra cc gi tr cn li nh vo cc cng thc trn. Trong thit k, chn AV =12dB l li ca mch tng ng vi K = 4, h s phm cht Q = 2, in tr R1 = R2 = 120K, ta suy ra cc thng s khc nh: R2 = 120K => R3 = 960 KQ = FC CR3 FC = 0,63610 .10 6 C = FC Q 2 CR3 = 10 6 C

t c cc tn s trung tm khc nhau cho cc b lc, ta c th thay s Fc tnh ra gi tr C1 = C2 = C. Trong thit k, ta chn 10 b lc vi cc tn s trung tm nh sau: 32Hz, 64Hz, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 27

n thit k mch tng t ph tn m thanh 8KHz, 16KHz.

Thit k mch phn tch

Kt qu tnh ton c cho bng sau: C1 = C2 (l thuyt) 19.87 nF 9.93 nF 5.08 nF 2.54 nF 1.27 nF 636 pF 318 pF 159 pF 79.5 pF 39.7 pF C1 = C2 (thc t) 22 nF 10 nF 4.7 nF 2.2 nF hoc 2.7 nF 1.2 nF hoc 1.5 nF 620 pF 330 pF 160 pF 82 pF 39 pF

Fc (Hz) 32 64 125 250 500 1K 2K 4K 8K 16K

Tr khng vo ca khuh i thut ton cao nn cc b lc hu nh rt t ph thuc vo s hiu khuch i thut ton (ngoi tr p ng tn s). Tr khng vo ca b mch lc ny l Z = (R 1 + R2)/10 (do co 10 mach loc rieng le ghep song song). Cc khuch i thut ton trong mch s dng loi ngun i. V c 10 mch lc nn s dng 2 vi mch c 4 khuch i thut ton bn trong v 1 vi mch c 2 OP AMP. Cc vi mch c s dng l LM 324 (4 khuch i thut ton) va TL082 (2 khuh i thut ton).

28


Thit k mch phn tch

Ta c s ca ton b 10 mch lc nh sau:

V c in p trung bnh a n cc chuyn mch in t nn ti ng ra ca cc b lc phi c thm mch chnh lu.

Hnh 17: Mch chnh lu mc ti ng ra b lc

29


Thit k mch phn tch

T C1 c chn bng thc nghim c c s hin th ti u (tc ln v xung ca ct n phi khng c nhanh qu cng nh chm qu so vi ting nhc, thng thng chn C1 = 1uF). Do mc DC ti ng ra ca cc mch lc coi nh l 0V, khi qua mch chnh lu s b st p 0,6V trn diode chnh lu. V th ng ra ca cc mch lc phi c nng mc DC ln 0,6V b li s st p khi qua mch chnh lu. iu ny c thc hin nh sau:

Hnh 16: Mch b st p trn Diode 3.2.2 Thit k chuyn mch in t: Trong cc mch in t, cc chuyn mch hay cn c gi l kha in (SW) c s dng kh a dng. Cc chuyn mch ny c th dng diode, transistor,... Phn ny ch trnh by v cc chuyn mch dng transistor. Yu cu mch ca ta l c ng vo v ng ra ring. Ta xt s sau:

30


Thit k mch phn tch

Hnh 18: Mch kha in t dng Transistor Ng iu khin khi mc in p cao s lm cho transistor dn, lm thng mch gia ng vo v ng ra. in tr R phi c chn dng IB ng vo khng nh hng n ng ra (IE) khi khng c tn hiu vo ti ng vo. R c chn bng thc nghim. Q l transistor cng sut nh c ln. Ta c s nguyn l hon chnh ca khi mch lc v chuyn mch in t nh sau:

31


Thit k mch phn tch

32

n thit k mch tng t Thit k mch phn tch ph tn m thanh 3.2.3. Khi mch dao ng, m v gii m, mch thc v iu khin LED a. Mch dao ng: Mch dao ng to xung clock c th c to t 2 cng o. Mch c s nh sau:

Hnh 18: Mch to dao ng dng cng NOT Trong mch dng hai tng o IC1A v IC1B rp thnh mt mch dao ng a hi pht ra dng xung vung. Ng ra ca tng IC1B cho lin lc thng vo tng C1A. T C1 to ng hi tip thun gia tng IC1A v tng IC1B. R1 v C1 l mch nh thi. Vi mch dao ng ny, tn s ra c tnh theo cng thc:f = 1 1.4 R1C1

Trong mch, xung nhp kim sot tc qut ca chuyn mch v hin th. Trong mt chu k xung nhp th ch c mt tn s c so snh bin v ch c mt ct LED sng vi chiu cao tng ng vi bin . Nu ta cho ct LED sng hn hoc bng 25 ln trong 1 giy th mt ta khng cm nhn c s nhp nhy ca ct LED tc l tn s ca mch dao ng a hi to xung phi ln hn hoc bng 10 x 25 = 250Hz. b. Mch m & gii m: Mch m c nhiu loi, trong thit k do yu cu cn 10 33

n thit k mch tng t Thit k mch phn tch ph tn m thanh ng ra. Ta c th dng mt IC m BCD ri t cc ng ra BCD ny a vo mt IC gii m BCD ra tng ng ring bit nhng cho gn nh ta dng thng mt IC c chc nng m ln chc nng gii m. IC ny ch cn xung clock vo v cho ra cc ng. Ta dng IC 4017 l mt IC n phin c ch to theo cng ngh CMOS, c 16 chn. Trong IC c 5 tng m Johnson, IC dng m cc xung vo theo h c 10. Cc c tnh ca 4017: - Mc ngun lm vic 3 n 18V. - Tc lm vic c th ln n 12MHz. - ng vo dng mt cng NAND trigger nn khng cn chun ha dng xung kch ng vo. S o chan IC 4017:

Hnh 18: S chn IC 4017 Chc nng cc chn nh sau: - Chn 14: xung clock vo, xung ny dn vo mt cng NAND dng trigger, do vy n khng cn cc xung vo c cc dc ln v xung qu thng, ngha l khng cn phi vung ha cc xung kch thch bng cch thm mch ngoi. 34

n thit k mch tng t Thit k mch phn tch ph tn m thanh - Chn 13: l ng vo ca mt tng o, ng ra ca tng o ni vo mt cng vo ca cng NAND. Nh vy khi chn ny mc cao, n s t mt cng vo ca tng NAND mc thp, iu ny s kha cng NAND v v hiu cc xung m a vo trn chn 14. Lc hot ng bnh thng, chn ny c ni mass. - Chn 15: l ng vo ca mt tng o v ng ra ca tng ny cho ni vo cc chn R\ (cc chn lm phc nguyn cc tng FF). Nh vy khi chn 15 mc cao, n s to mc logic thp trn chn R ca cc FF v c tc dng phc nguyn. Lc thng, chn ny phi mc thp hay thng c ni mass. - Cc chn ra c ly theo th t t chn 3, 2, 4, 7, 10, 1, 5, 6, 9, 11. Trn cc ng ra ny u c tng khuch i m, nh vy dng ng ra c th ly cao n 10mA. Cc chn ny ra tc ng mc cao. - Chn 12: l ng ra trn s. Lc mi cp in, IC cn phi c RESET, c RESET mt cch t ng, ta cn mt mch AUTO-RESET nh sau:

Hng s thi gian:

= RC

35

n thit k mch tng t ph tn m thanh Hnh 19: Mch AUTO RESET cho IC 4017 S mch ca 4017 nh sau:

Thit k mch phn tch

Hnh 20: S kt ni IC 4017 Cc ng ra c a ti chuyn mch in t ng thi c a n mch thc qut cc ct. c. Mch thc:

Hnh 21: S mch thc Mch thc c tc dng nng dng ng ra iu khin cc LED. Cung cp dng t Vcc cho cc ct LED. Cc cng o dng cch ly vi tng trc cng nh o pha d liu ra t mch m & gii m. d. Mch iu khin LED: Mch iu khin LED s dng vi mch LM3914 c xt phn trn. 36


Thit k mch phn tch

Hnh 22: S mch iu khin LED Sau y l s nguyn l hon chnh ca khi mch dao ng, m & gii m, v mch iu khin LED:

37


Thit k mch phn tch

38


Thit k mch phn tch

3.2.4 Thit k khi mch ma trn LED hin th: Ma trn LED bao gm 10 hng v 10 ct. C s nguyn l nh sau:

39


Thit k mch phn tch

40

n thit k mch tng t ph tn m thanh3.3. Thit k mch in: 1. Mch lc tn v chuyn mch: Mch in

Thit k mch phn tch

41

n thit k mch tng t ph tn m thanhS b tr linh kin

Thit k mch phn tch

42


Thit k mch phn tch

2. Mch dao ng, m & gii m, v mch VU-LED: Mch in

S b tr linh kin

43

n thit k mch tng t ph tn m thanh3. Ma trn LED:

Thit k mch phn tch

Lp trn:

Lp di:

S b tr linh kin

44


Thit k mch phn tch

Kt lunSau mt thi gian thc hin ti: Thit k mch phn tch ph m thanh em thit k thnh cng mch tha mn cc yu cu t ra, kt qu c kim chng bng cch m phng hot ng ca robot trn my tnh bng phm mm Proteus. Mch phn tch ph tn p ng c nhng yu cu ca mt mch phn tch ph tn chuyn dng. Tuy nhin vic hin th cha th hin tnh thm m v vic s dng cc LED, nu dng ma trn hin th tinh th lng th vic hin th s c kt qu tt hn. Nu kt hp mch phn tch ph m tn vi mt mch iu chnh m sc (tone equalizers) th ta s c mt thit b iu chnh m sc dng th (Graphic Equalizer). Thit b ny c s dng kh ph bin trong cc dn m thanh t trung ti cao cp. Vic kt hp hai mch cng chnh l hng pht trin cho ti. Em rt mong nhn c kin ng gp ca cc thy c v cc bn pht trin ti ny c tt hn.

45


Thit k mch phn tch

Ti liu tham kho[1] [2] Tu. [3] [4] K thut mch in t phi tuyn Ti liu trn Internet. Phm Minh Vit, Trn Cng Nhng. K thut mch in t - Phm Minh H. L Thuyt mch - Phng Xun Nhn, H Anh

46

Documents

Mach Phan Tich Pho Am Thanh