[BTL] Cảm biến nhiệt độ

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  1. 1. I HC QUC GIA H NI TRNG I HC CNG NGH BI TP LN GVHD: TS. Nguyn Ngc Linh Nhm thc hin: Nhm 3 Khoa: C hc k thut & T ng ha Lp: K57M H Ni, ngy 10/05/2015 ti: Tm hiu v cm bin nhit v ng dng
  2. 2. Bi tp ln Trang 2 Li m u Trong thi bui cng ngh pht trin nh v bo, ngy cng c nhiu sn phm ra i vi nhng tnh nng a dng, phong ph, v c bit l rt thng minh. Khoa hc pht trin lm cho nhng ngnh khc cng pht trin theo, in hnh l ngnh in t, thng tin, vin thng, c kh ch to, Cc ngnh ny kt hp li vi nhau l tin ca s pht trin cc loi my mc thng minh. Mt h thng my mc thng minh c cu thnh t rt nhiu b phn, cc b vi x l c lp trnh phc tp, cc c cu chp hnh, cc c cu x l cng rt phc tp, C mt b phn v cng quan trng to ln s thng minh khng k n l cc loi cm bin. Nh c cc cm bin, cc robot ngy nay c pht trin nhn bit c cc hnh ng phc tp v d nh tay my nm ly ci cc thy tinh sao cho khng v, hay l h thng t ng ng m ca khi c ngi ra vo cc siu th, C rt nhiu loi cm bin c ch to v s dng theo cc mc ch khc nhau trong i sng nh cm bin cm nhn v nhit , nh sng, m thanh, lc, dng chy, Ty theo mi loi cng vic m mi loi cm bin c cch ch to khc nhau. Mt loi cm bin m chng ta bt gp rt nhiu trong cuc sng hng ngy v ng dng ca n cng v cng rng ri, l cm bin nhit . D dng bt gp nhng loi cm bin ny trong cuc sng nh l nhng my o nhit hin th in t, cc l in tr c iu khin, hay chic ng h lch vn nin, Cm bin nhit c ng dng v cng rng ri v ph bin. Chnh v vy, nhm 3 chng em quyt nh thc hin ti v loi cm bin ny, l tm hiu v cm bin nhit v ng dng trong o nhit n gin. Ni dung chnh ca bi tp ln gm c cc mc sau: Gii thiu chung v cm bin v c im ca chng Nguyn l o c bn ca cm bin Gii thiu v cc loi cm bin thng dng Tm hiu v cm bin nhit Cm bin nhit LM35 v mt mch in ng dng c th. Cc thnh vin ca nhm: STT H v tn M sinh vin Ghi ch 1 Phm Trn Hong 12020162 2 Vn Lc 12020244 3 L Tun Anh 12020004 4 Nguyn Vit Bnh 12020525
  3. 3. Bi tp ln Trang 3 Mc lc I. Gii thiu chung................................................................................................................. 3 1. Khi nim ............................................................................................................................ 4 2. Phn loi cm bin ............................................................................................................. 4 3. ng cong chun ca cm bin ...................................................................................... 5 4. Mt s c trng c bn..................................................................................................... 7 II. Nguyn l o ca cm bin......................................................................................... 11 1. Vi cc cm bin tch cc................................................................................................. 11 2. Vi cc cm bin th ng ............................................................................................... 13 III. Gii thiu cc loi cm bin thng dng................................................................ 14 1. Cm bin quang ................................................................................................................ 14 2. Cm bin nhit ............................................................................................................. 14 3. Cm bin o v tr v dch chuyn.................................................................................... 14 4. Cm bin o bin dng ..................................................................................................... 15 5. Cm bin o lc ................................................................................................................ 15 6. Cm bin o vn tc, gia tc v rung............................................................................... 16 7. Cm bin o p sut cht lu........................................................................................... 17 8. Cm bin o lu lng v mc cht lu......................................................................... 17 9. Cm bin thng minh ....................................................................................................... 18 IV. Tm hiu v cm bin nhit .................................................................................. 18 1. S lc cc vn lin quan............................................................................................ 18 2. Cm bin nhit . ............................................................................................................ 20 V. Cm bin nhit LM35 v mt mch in ng dng o nhit ..................... 32 1. Tm hiu v cm bin LM35............................................................................................. 32 2. Mch o nhit dng LM35 kt hp vi IC ADC0808 v vi iu khin 8051. ........... 35 Ti liu tham kho................................................................................................................... 40
  4. 4. Bi tp ln Trang 4 I. Gii thiu chung 1. Khi nim Cm bin l thit b dng cm nhn, bin i cc i lng vt l v cc i lng khng c tnh cht in cn o thnh cc i lng in c th o v x l c Cc i lng cn o (m) thng khng c tnh cht in (nhit , p sut, khong cch, nh sng, m, ) tc ng ln cm bin cho ta mt c trng (s) mang tnh cht in (in tch, in p, dng in, tr khng) cha ng thng tin cho php xc nh gi tr ca i lng o. c trng (s) l hm ca i lng cn o (m): s = f(m) (1.1) Trong cng thc (1.1), s l i lng u ra hoc l phn ng ca cm bin, x l i lng u vo hay kch thch (c ngun gc l i lng cn o), thng qua o c (s) cho php nhn bit gi tr ca kch thch (m). 2. Phn loi cm bin C rt nhiu loi cm bin c ch to v ng dng trong thc t, ta c th phn loi cm bin theo cc c trng c bn nh sau: Theo nguyn l chuyn i gia p ng v kch thch + Hin tng vt l o Nhit in o Quang in o Quang t o in t o Quang n hi o T in o Nhit t + Hin tng ha hc o Bin i ha hc o Bin i in ha o Phn tch ph + Hin tng sinh hc o Bin i sinh ha o Bin i vt l o Hiu ng trn c th sng Theo dng kch thch + m thanh o Bin pha, phn cc o Ph o Tc truyn sng + in o in tch, dng in o in th, in p o in trng (bin, pha, phn cc, ph) o in dn, hng s in mi, + T o T trng (bin, pha, phn cc, ph) o T thng, cng t trng o t thm + Quang o Bin, pha, phn cc, ph o Tc truyn o H s pht x, khc x o H s hp thc, h s bc x + C o V tr o Lc, p sut o ng sut, cng o Moment o Khi lng, t trng o Vn tc cht lu, nht + Nhit o Nhit o Thng lng
  5. 5. Bi tp ln Trang 5 o Nhit dung, t nhit + Bc x o Kiu o Nng lng o Cng Theo tnh nng ca b cm bin + nhy + chnh xc + phn gii + chn lc + tuyn tnh + Cng sut tiu th + Di tn + tr + Kh nng qu ti + Tc p ng + n nh + Tui th + iu kin mi trng + Kch thc, trng lng Theo phm vi s dng + Cng nghip + Nng nghip + Mi trng, kh tng + Thng tin, vin thng + Dn dng + Giao thng + Nghin cu khoa hc + V tr + Qun s Theo thng s ca m hnh mch thay th + Cm bin tch cc c u ra l ngun p hoc ngun dng + Cm bin th ng c c trng bng cc thng s R, L, C, tuyn tnh hoc phi tuyn. 3. ng cong chun ca cm bin ng cong chun ca cm bin l ng cong biu din s ph thuc ca i lng in (s) u ra ca cm bin vo gi tr ca i lng o (m) u vo. ng cong chun c th biu din bng biu thc i s di dng s = f(m). Da vo ng cong chun ca cm bin, ta c th xc nh gi tr mi cha bit ca m thng qua gi tr o c si ca s. d s dng ngi ta thng ch to cm bin c s ph thuc tuyn tnh gia i lng u ra v i lng u vo, khi phng trnh s = f(m) c dng s = am+b, trong a, b l cc h s, khi ng cong chun l ng thng. Hnh 1. ng cong chun cm bin
  6. 6. Bi tp ln Trang 6 Cc phng php chun cm bin: Chun cm bin l php o nhm mc ch xc lp mi quan h gia gi tr s o c ca i lng in u ra v gi tr m ca i lng o c tnh n cc yu t nh hng, trn c s xy dng ng cong chun di dng tng mnh ( th hoc biu thc i s). Khi chun cm bin, vi mt lot gi tr bit chnh xc mi ca m, o gi tr tng ng si ca s v dng ng cong chun. Hnh 2. Phng php chun cm bin - Chun n gin: Trong trng hp i lng o ch c mt i lng vt l duy nht tc ng ln mt i lng o xc nh v cm bin s dng khng nhy vi tc ng ca cc i lng nh hng th dng phng php chun n gin. Thc cht ca chun n gin l o cc gi tr ca i lng u ra ng vi cc gi tr xc nh khng i ca i lng o u vo. Vic chun c tin hnh theo hai cch: + Chun trc tip: cc gi tr khc nhau ca i lng o ly t cc mu chun hoc cc phn t so snh c gi tr bit trc vi chnh xc cao. + Chun gin tip: kt hp cm bin cn chun vi mt cm bin so snh c sn ng cong chun, c hai c t trong cng iu kin lm vic. Khi tc ng ln hai cm bin vi cng mt gi tr ca i lng o ta nhn c gi tr tng ng ca cm bin so snh v cm bin cn chun. Lp li tng t vi cc gi tr khc ca i lng o cho php ta xy dng c ng cong chun ca cm bin cn chun. - Chun nhiu ln Khi cm bin c phn t b tr (tr c hoc tr t), gi tr o c u ra ph thuc khng nhng vo gi tr tc thi ca i lng cn o u vo m cn ph thuc vo gi tr trc ca i lng ny. Trong trng hp nh vy, p dng phng php chun nhiu ln v tin hnh nh sau: + t li im 0 ca cm bin: i lng cn o v i lng u ra c gi tr tng uwgns vi im gc m = 0 v s = 0. + o gi tr u ra theo mt lot gi t tng dn n gi tr cc i ca i lng o u vo. + Lp li qu trnh o vi cc gi tr gim dn t gi tri cc i. Khi chun nhiu ln cho php xc nh ng cong chun theo c hai hng o tng dn v o gim dn.
  7. 7. Bi tp ln Trang 7 4. Mt s c trng c bn a. nhy ca cm bin i vi cm bin tuyn tnh, gia bin thin u ra s v bin thin u vo m c s lin h tuyn tnh vi nhau: s = S.m (1.2) i lng S xc nh bi biu thc s S m c gi l nhy ca cm bin. Trng hp tng qut, biu thc xc nh nhy S ca cm bin xung quanh gi tr mi ca i lng o xc nh bi t s gia bin thin s ca i lng u ra v bin thin m tng ng ca i lng o u vo quanh gi tr : im m s S m (1.3) php o t chnh xc cao, khi thit k v s dng cm bin cn lm sao cho nhy S ca n khng i, ngha l t ph thuc nht vo cc yu t sau: - Gi tr ca i lng cn o m v tn s thay i ca n - Thi gian s dng - nh hng ca cc i lng vt l khc (khng phi l i lng o) ca mi trng xung quanh. Gi tr S thng c cung cp bi nh sn xut tng ng vi iu kin lm vic nht nh ca cm bin. nhy trong ch tnh v t s chuyn i tnh ng chun cm bin xy dng trn c s o cc gi tr si u ra tng ng vi cc gi tr khng i mi ca i lng o khi i lng ny t n ch lm vic danh nh c gi l c trng tnh ca cm bin. Mt im Qi(mi, si) trn c trng tnh xc nh mt im lm vic ca cm bin ch tnh. Trong ch tnh, nhy S xc