huong dan co ban ve 555

8/9/2019 huong dan co ban ve 555

1/18

555 - Nguyn tc v ng dng

555 l mt loi linh kin kh l ph bin by gi vi vic ddng to c xung vung v c th thay i tn s ty thchvi s mch n gin,iu ch c rng xung. N ng dng hu ht vo cc mch to xung ng ct hay l nhmch dao ng khc.y l linh kin ca hng CMOS snxut .Sau y l bng thng s ca 555 c trn th trng :+ in p u vo : 2 - 18V ( Ty tng loi ca 555 : LM555 NE555, NE7555..)+ Dng in cung cp : 6mA - 15mA+ in p logic mc cao : 0.5 - 15V+ in p logic mc thp : 0.03 - 0.06V+ Cng sut ln nht l : 600mW

* Cc chc nng ca 555:+ L thit b to xung chnh xc+ My pht xung+ iu ch c rng xung (PWM)+ iu ch v tr xung (PPM) (Hay dng trong thu pht hng
http://hoiquandientu.com/read.php?269http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555.JPGhttp://hoiquandientu.com/read.php?269


2/18

ngoi)y ch l nhng thng s c bn ca 555. Cn nhng thngkhc cc bn tham kho datasheet!

1 : Gii thiu, s khi, s nguyn l, chn ca 555

IC thi gian 555 c du nhp vo nhng nm 1971 bng cty Signetics Corporation bng 2 dng sn phm SE555/NE55v c gi l my thi gian v cng l loi c u tin. Ncung cp cho cc nh thit k mch in t vi chi ph tnr, n nh v nhng mch t hp cho nhng ng dng cho n v khng n nh. T thit b ny c lm ra vi tnhthng mi ha. 10 nm qua mt s nh sn sut ngng snloi IC ny bi v s cnh tranh v nhng l do khc. Tuy thnhng cng ty khc li sn sut ra nhng dng ny

Cc dng hnh dng chn ca 555 trong thc t:
http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555-so%20do%20chan.JPG


3/18

Hnh dng ca 555 trong hnh 1 v hnh 2. Loi 8 chn hnh

trn v loi 8 chn hnh vung. Nhng th trng Vit Namch yu l loi chn vung.

Nhn trn hnh 3 ta thy cu trc ca 555 n tng ng vhn 20 transitor , 15 in tr v 2 diode v cn ph thuc vonh sn xut. Trong mch tng ng trn c : u vo kcthch , khi so snh, khi iu khin chc nng hay cng suu ra.Mt s c tnh na ca 555 l : in p cung cp ngia trong khong t 3V n 18V, dng cung cp t 3 n 6mA.
http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555-so%20do%20cau%20tao.JPG


4/18

Dng in ngng xc nh bng gi tr ln nht ca R + R in p 15V th in tr ca R + R .phi l 20M

Tt c cc IC thi gian u c 1 t in ngoi to ra 1 thgian ng ct ca xung u ra. N l mt chu k hu hn t in (C) np in hay phng in thong qua mt in trThi gian ny n c xc nh v n c th tnh c thoqua in tr R v t in C

Mch np RC c bn nh trn hnh 4B Gi thit t in banl phng in.Khi m ng cng tc th t in bt u np
http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555-so%20do%20xung.JPG


5/18

thng qua in tr. in p qua t in t gi tr 0 ln n gnh mc vo t. ng cong np c th hin qua hnh4A.Thi gian n cho t in np n 63.2% in p cu

cp v hiu thi gian ny l 1 hng s. Gi tr hng s thi g c th tnh bng cng thc n gin sau:

t = R.C

ng cong np ca t in

2 :Chc nng ca tng chn ca 555
http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555-duong%20cong%20nap.JPG


6/18

IC NE555 N gm c 8 chn.

+ Chn s 1(GND): cho ni GND ly dng cp cho IC haychn cn gi l chn chung.+ Chn s 2(TRIGGER): y l chn u vo thp hn inp so snh v c dng nh 1 chn cht hay ng vo ca 1 tso p.Mch so snh y dng cc transitor PNP vi mc ip chun l 2/3Vcc.+ Chn s 3(OUTPUT): Chn ny l chn dng ly tn hiura logic. Trng thi ca tn hiu ra c xc nh theo mc 0

1. 1 y l mc cao n tng ng vi gn bng Vcc nu(PWM=100%) v mc 0 tng ng vi 0V nhng m tronthc t mc 0 ny ko c 0V m n trong khong t (0.35->0.75V) .+ Chn s 4(RESET): Dng lp nh mc trng thi ra. Khichn s 4 ni masse th ng ra mc thp. Cn khi chn 4 n
http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555_chan.JPG


7/18

vo mc p cao th trng thi ng ra ty theo mc p trn chv 6.Nhng m trong mch to c dao ng thng hani chn ny ln VCC.

+ Chn s 5(CONTROL VOLTAGE): Dng lm thay imc p chun trong IC 555 theo cc mc bin p ngoi haydng cc in tr ngoi cho ni GND. Chn ny c th khngni cng c nhng m gim tr nhiu ngi ta thngchn s 5 xung GND thng qua t in t 0.01uF n 0.1uFcc t ny lc nhiu v gi cho in p chun c n nh+ Chn s 6(THRESHOLD): l mt trong nhng chn uvo so snh in p khc v cng c dng nh 1 chn cht+ Chn s 7(DISCHAGER): c th xem chn ny nh 1 khain t v chu iu khin bi tng logic ca chn 3 .Khi ch mc p thp th kha ny ng li.ngc li th n m ra.Chn 7 t np x in cho 1 mch R-C lc IC 555 dng nhtng dao ng .+ Chn s 8 (Vcc):Khng cn ni cng bt l chn cung cpp v dng cho IC hot ng. Khng c chn ny coi nh IC

cht. N c cp in p t 2V -->18V (Ty tng loi 555thp nht l con NE7555)

3: Cu to bn trong v nguyn tc hot nga) Cu to:


8/18

Nhn trn s cu to trn ta thy cu trc ca 555 gm : 2OPAM, 3 con in tr, 1 transitor, 1 FF ( y l FF RS):- 2 OP-amp c tc dng so snh in p- Transistor x in.- Bn trong gm 3 in tr mc ni tip chia in p VCC th3 phn. Cu to ny to nn in p chun. in p 1/3 VCvo chn dng ca Op-amp 1 v in p 2/3 VCC ni vo cm ca Op-amp 2. Khi in p chn 2 nh hn 1/3 VCC, chS = [1] v FF c kch. Khi in p chn 6 ln hn 2/3 VCchn R ca FF = [1] v FF c reset b) Nguyn tc hot ng:
http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555-%20cau%20tao.JPG


9/18

trn mch trn ta bt l H l mc cao v n gn bng VcL l mc thp v n bng 0V. S dng pc FF - RSKhi S = [1] th Q = [1] v = Q- = [ 0].Sau , khi S = [0] th Q = [1] v =Q- = [0].Khi R = [1] th = [1] v Q = [0].Khi S = [1] th Q = [1] v khi R = [1] th Q = [0] bi v Q-= [1transisitor m dn, cc C ni t. Cho nn in p khng nvo t C, in p chn 6 khng vt qu V2. Do li ra caamp 2 mc 0, FF khng reset.

Khi mi ng mch, t C np qua Ra, Rb, vi thi hng(Ra+Rb)C.* T C np t in p 0V -> Vcc/3:- Lc ny V+1(V+ ca Opamp1) > V-1. Do O1 (ng ra caOpamp1) c mc logic 1(H).- V+2 < V-2 (V-2 = 2Vcc/3) . Do O2 = 0(L).
http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555-%20cau%20tao1.JPG


10/18

- R = 0, S = 1 --> Q = 1, /Q (Q o) = 0.- Q = 1 --> Ng ra = 1.- /Q = 0 --> Transistor hi tip khng dn.

* T C tip t np t in p Vcc/3 -> 2Vcc/3:- Lc ny, V+1 < V-1. Do O1 = 0.- V+2 < V-2. Do O2 = 0.- R = 0, S = 0 --> Q, /Q s gi trng thi trc (Q=1, /Q=0- Transistor vn ko dn !

* T C np qua ngng 2Vcc/3:- Lc ny, V+1 < V-1. Do O1 = 0.- V+2 > V-2. Do O2 = 1.- R = 1, S = 0 --> Q=0, /Q = 1.- Q = 0 --> Ng ra o trng thi = 0.- /Q = 1 --> Transistor dn, in p trn chn 7 xung 0V !- T C x qua Rb. Vi thi hng Rb.C- in p trn t C gim xung do t C x, lm cho in p

nhy xung di 2Vcc/3.* T C tip tc "X" t in p 2Vcc/3 --> Vcc/3:- Lc ny, V+1 < V-1. Do O1 = 0.- V+2 < V-2. Do O2 = 0.- R = 0, S = 0 --> Q, /Q s gi trng thi trc (Q=0, /Q=1- Transistor vn dn !

* T C x qua ngng Vcc/3:- Lc ny V+1 > V-1. Do O1 = 1.- V+2 < V-2 (V-2 = 2Vcc/3) . Do O2 = 0.- R = 0, S = 1 --> Q = 1, /Q (Q o) = 0.- Q = 1 --> Ng ra = 1.


11/18

- /Q = 0 --> Transistor khng dn -> chn 7 khng = 0V na vt C li c np in vi in p ban u l Vcc/3. Ni tm li cc bn c nn hiu l :

Trong qu trnh hot ng bnh thng ca 555, in p trnC ch dao ng quanh in p Vcc/3 -> 2Vcc/3. (Xem dngc tnh t in phng np trn)- Khi np in, t C np in vi in p ban u l Vcc/3, kt thc np thi im in p trn C bng 2Vcc/3.Np ivi thi hng l (Ra+Rb)C.- Khi x in, t C x in vi in p ban u l 2Vcc/3, vthc x thi im in p trn C bng Vcc/3. X in vihng l Rb.C.- Thi gian mc 1 ng ra chnh l thi gian np in, mc x in.

3 ) Cng thc tnh tn s iu ch rng xung ca 555

Nhn vo s mch trn ta c cng thc tnh tn s , r
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12/18

xung.+ Tn s ca tn hiu u ra l :

f = 1/(ln2.C.(R1 + 2R2))

+ Chu k ca tn hiu u ra : t = 1/f

+ Thi gian xung mc H (1) trong mt chu k :

t1 = ln2 .(R1 + R2).C

+ Thi gian xung mc L (0) trong 1 chu k :

t2 = ln2.R2.C

NH vy trn l cng thc tng qut ca 555. Ti ly 1 v dnh l : to c xung dao ng l f = 1.5Hz . u tin tchn hai gi tr c trng l R1 v C2 sau ta tnh c R1Theo cch tnh ton trn th ta chn : C = 10nF, R1 =33k --> R= 33k (Tnh ton theo cng thc)

4 ) Cc dng mch dao ng t 555a ) Mch bo ng m thanh dng SCR


13/18


14/18

d) Cnh bo mt in
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15/18

e ) My nhp iu m thanh

f) Dao ng CW
http://hoiquandientu.com/images/stories/Dien-tu-can-ban/555-timer/555ex5.gif


16/18

g) Trigio Smith


17/18

h) Dao 2 IC 555 trog th nghim m thanh

i) Mch nhp nhy 2 LED


18/18

Nh trn ti gii thiu qua v iC 555 v nhng mch ng

dng ca n!Bi vit trn ti c s tham kho hnh nh ca nhng ti liunc ngoi v ti liu nc ngoi!

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huong dan co ban ve 555