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Li cm n2 nm - mt khong thi gian khng qu ngn, cng khng qu di i vi chng ng ca mi sinh vin chng em. i vi em n thc s l mt k nim qu bu khng bao gi qun. Qua qu trnh hc tp v rn luyn di mi trng i hc Tr Vinh, thy c tn tnh ging dy, s gip ca bn b, s ng vin nui dng ca cha m. Thc s l ng lc, hnh trang mi a em vo i. Vi hnh trang ny em chn thnh bit n qu thy c trng i hc Tr Vinh ht lng truyn t kin thc v kinh nghim cho em trong sut thi gian hc ti trng, mang li cho em mt nn tng kin thc em c th cng tc sau ny. Em xin chn thnh cm n n Th.S V Th ng. Thy tn tnh gip v trc tip hng dn em trong sut thi gian hon thnh chuyn n 2. Em xin chc qu thy c trng i hc Tr Vinh ni chung, thy c khoa Qun tr kinh doanh ni ring di do sc khe, tip bc cho nhng th h ngi Vit Nam sau ny. Cm n ba m, bn b gip ng vin em trong sut thi gian qua. Trn trng knh cho ! Bnh Dng,ngy 15 thng 05 nm 2012. SVTH. ng Quc Tun
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NHN XT CA GIO VIN HNG DN ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... ..................................................... Bnh Dng, ngy thng nm 2012
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MC LC Trang PHN I: M U Chng I: Tng quan 1.t vn ........................................................................................... 03 2.Tnh hnh nghin cu .......................................................................... 03 3.Tm quan trng ca vic nghin cu .................................................. 04 PHN II: NI DUNG Chng II: C s l thuyt: gii thiu s lc v sng siu m 1.Sng siu m l g ............................................................................... 05 1.1Mt s loi cm bin siu m ........................................................... 05 1.2 Cm bin siu m v nguyn tc TOF ............................................. 05 1.3 Tm qut ca cm bin siu m ....................................................... 06 1.4 u im v nhc im ca cm bin siu m ............................... 06 2. Thng s mt s loi cm bin siu m SRF..................................... 06 3. Cc dng pic v cch la chn vi iu khin pic 16F877A .................. Chng III: Thit k phn cng: cm bin siu m HC-SR04 v vi iu khin 16F877A 1.Cm bin siu m HC-SR04 v c im k thut ............................ 09 1.1 Gii thiu ........................................................................................ 09 1.2 Thng s k thut ............................................................................ 09 1.3 Tnh ton khong cch ......................................................................... 1.4 Hot ng pht v nhn phn hi sng m ca HC-SR04 .................. 2. S lc v cc chn ca Pic 16F877A .............................................. 11 3. Giao tip gia cm bin siu m HC-SR04 v vi iu khin 16F877A ................................................................................................ 13 4. ng dng ca cm bin siu m HC-SR04 ....................................... 19 PHN III: Kt lun .............................................................................................. 21
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PHN I: M U Chng I : TNG QUAN1. t vn Ngy nay vi s pht trin vt bc ca x hi, c bit l trong cc ngnh k thut. Khi m cc sn phm mi lin tc ra i, nhng vt liu ni tri hn, cng ngh mi cng ra i Song song th nhu cu ca con ngi i vi s tin b ca x hi cng ngy cng khc khe hn. c bit khi ngnh cng ngh s, tr tu nhn to ra i n cng len li mi lnh vc ca x hi. ng dng ca vi iu khin vo cc ngnh cng ngh ny l rt ln. Tuy nhin o c nhng gi tr ca cc linh kin hay thit b ta phi s dng mt thit b chuyn dng l o khong cch bng sng siu m. Trong ti ny ta ch tm hiu v nghin cu v sng siu m bng cch dng Vi iu khin. Trong qu trnh lm d rt c gng nhng vn khng trnh nhng sai v thiust Rt mong nhn c nhng ng gp chn thnh ca qu thy c v cc bn c th thc hin tt hn cho cc ln tip theo. 2. Tnh hnh nghin cu: Da trn phng php nghin cu v phn tch c tnh chc nng ca cc linh kin in t c bn ( transistor, in tr, t in,....) cc IC s (m, gii m,...) v p dng kin thc hc, nhng ti liu c c trn tp ch, sch, v internet.....v vi s hng n nhit tnh ca gio vin hng dn xy dng ln mt mch c chc nng o khong cch, hot ng tt v ng vi yu cu ti. 3. Tm quan trng ca vic nghin cu Mch o khong cch bng song siu m thuc ti n 2, y cng l nghin cu v gip em lm quen vi vic lm n 2, lm quen vi cch hc t nghin cu, hc tp v lm vic chung vi nhm, gip sinh vin vn dng cc kin thc hc v cng vi s hng dn ca gio vin thc hin tt mch 4. Lnh vc ng dng: - R b con, camera, laser...SV: ng Quc Tun MSSV: 120710029 Page 4
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CHNG II: C S L THUYT GII THIU PHN S LC V SNG SIU M1/ Sng siu m l g : V bn cht, sng siu m l sng c hc, do n tun theo mi quy lut i vi sng c, c th to ra sng siu m bng cch tc ng mt lc c hc vo mi trng truyn m. Sng siu m (Ultrasound): f > 20kHz Cc ngun sng siu m c trong t nhin: Di, mt vi loi c bin pht sng siu m nh hng Ni chung cc sng ny nm trong vng tn s 20 100 kHz. Sng siu m ng dng trong y hc c tn s t 700 KHz n 50 MHz trong siu m chn on s dng cc tn s t 2 MHz n 50 MHz. 1.1/ Mt s loi cm bin siu m:
Cm bin siu m c nhiu loi, ty theo cng dng nhn bit vt trong khong cch gn hay xa, nhn bit cc vt c tnh cht khc nhau v trong nhng iu kin hot ng khc nhau m ngi ta cng ch to cc loi cm bin siu m khc nhau. 1.2/ Cm bin siu m v nguyn tc TOF (Time Of Flight) Sng siu m c truyn i trong khng kh vi tc khong 343m/s. Nu mt cm bin pht ra sng siu m v thu v cc sng phn x ng thi, o c khong thi gian t lc pht i ti lc thu v, th my tnh c th xc nh c qung ng m sng di truyn tring khng gian. Qung ng i ca sng s bng 2 ln khong cch t cm bin ti chng ngi vt, theo hng pht sng ca siu m. Hay khong cch t cm bin n chng vt s c tnh theo nguyn l TOF: d=v*t/2.
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1.3/ Tm qut ca cm bin siu m. Cm bin siu m c th c m hnh ha thnh mt cnh qut, trong cc im gia dng nh khng c chng ngi vt, cn cc im trn bin th dng nh c chng ngi vt nm u .
1.4/ / u im v nhc im ca cm bin tim cn siu m U IM:khong cch m cm bin c th pht hin ln ti 15m Sng phn hi ca cm bin khng ph thuc vo mu sc ca b mt i tng hay tnh cht phn x nh sng ca i tng V d:b mt knh trong sut ,b mt gm mu nu,b mt plastic mu trng hay b mt cht liu nhm sng trng l nh nhau Tn hiu p ng ca cm bin tim cn analog l t l tuyn tnh vi khong cch.iu ny c bit l tng cho cc ng dng nh theo di cc mc vt cht,mc chuyn ng cu i tng
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Nhc im:cm bin siu m yu cu i tng c mt din tch b mt ti thiu(gi tr ny ty thuc vo tng loi cm bin) Sng phn hi cm bin nhn c c th chu nh hng ca sng m thanh tp m Cm bin tim cn siu m yu cu mt khong thi gian sau mi ln sng pht i sn sng nhn sng phn hi.kt qu cm bin tim cn siu m nhn chung chm hn cc cm bin khc Vi cc i tng c mt vt cht thp nh bt hay vi qun o rt kh pht hin vi khong cch ln Cm bin tim cn siu m gii hn bi khong cch pht hin nh nht S thay i ca mi trng nh nhit (vn tc m thanh ph thuc vo nhit ) p sut,s chuyn ng khng u ca khng kh,bi bn bay trong khng kh gy nh hng n kt qu o Nhit ca b mt i tng nh hng n phm vi hot ng ca cm bin,hi nng ta ra t i tng c nhit cao lm mo dng sng,lm cho khong cch pht hin ca i tng ngn li v gi tr khong cch khng chnh xc B mt phng phn hi nng lng ca sng m thanh tt hn b mt g gh,tuy nhin b mt trn phng li c i hi khc khe v v tr gc to thnh gia cm bin v mt phng i tng 2/ Thng s mt s loi cm bin siu m SRF. Cm bin SRF02 SRF04 SRF05 SRF08 SRF10 SRF235 Thng tin I2C/Serial K thut s K thut s I2C I2C I2C Range Ti thiu Ti a 15cm 6m 3cm 3m 3cm 4m 3cm 6m 3cm 6m 10cm 1,2m Angle * 450 450 450 450 600 150 Echoes ** Mt Mt Mt 17 Mt Mt Thi gian khc nhau 70 ms 100s 36 ms 100s 36 ms 65 ms 65 ms 10 ms Ghi ch A
BC AB AD
Ch thch: *: c tnh gc ca hnh nn cm bin cm bin. **: S vang ghi li bi cm bin. y l nhng ting vng ghi t c gn y nht v c ghi mi bng mi ln khc nhau. A: Nhng cm bin nh hn in hnh (SRF 05/04/08) kch thc. B: Phm vi thi gian c th c iu chnh xung bng cch iu chnh c.SV: ng Quc Tun MSSV: 120710029 Page 7
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C: Cm bin ny cng bao gm mt photocell mt trc pht hin nh sang. D: Hot ng mt tn s 235kHz cao hn. 3/ CC DNG PIC V CCH LA CHN VI IU KHIN PIC Cc k hiu ca vi iu khin PIC:- P I C 1 2 x x x x : d i l n h 1 2 b i t -PIC16xxxx: di lnh 14 bit -PIC18xxxx: di lnh 16 bit C: PIC c b nh EPROM (ch c 16C84 l EEPROM) F: PIC c b nh flash LF: PIC c b nh flash hot ng in p thp LV: tng t nh LF, y l k hiu c Bn cnh mt s vi iu khin c k hiu xxFxxx l EEPROM, nu c thm ch A cui l flash (v d PIC16F877 l EEPROM, cn PIC16F877A l flash). Ngoi ra, cn c thm mt dng vi iu khin PIC mi l dsPIC. Vit Nam ph bin nht l cc h vi iu khin PIC do hng Microchip snxut. Cch la chn mt vi iu khin PIC ph hp: - Trc ht cn ch n s chn ca vi iu khin cn thit cho ng dng. Cnhiu vi iu khin PIC vi s lng chn khc nhau, thm ch c vi iukhin ch c 8 chn, ngoi ra cn c cc vi iu khin 28, 40, 44, chn. - Cn chn vi iu khin PIC c b nh flash c th np xa chng trnhc nhiu ln hn. Tip theo cn ch n cc khi chc nng c tchhp sn trong vi iu khin, cc chun giao tip bn trong. - Sau cng cn ch n b nh chng trnh m vi iu khin cho php. - Ngoi ra mi thng tin v cch la chn vi iu khin PIC c th c tmthy trong cun sch Select PIC guide do nh sn xut Microchip cung cp.
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S iu khin:
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CHNG III: THIT K PHN CNG CM BIN SIU M HC-SR04 V VI IU KHIN PIC 16F877A1/ Cm bin siu m HC-SR04 v c im k thut. 1.1/Gii thiu. - HC-SR04 l mt bin pht trin t SRF05 c thit k tng tnh linh hot, tng phm vi, ngoi ra cn gim bt chi ph. HC-SR04 l hon ton tng thch vi SRF05. Khong cch c tng t 3 mt n 4 mt. - HC-SR04 cho php s dng mt chn duy nht l cho c kch hot v phn hi, do tit kim c gi tr trn chn iu khin. - HC -SR04 l tt chn. Hiu sut n nh v chnh xc khc nhau, cao lm cho n mt m-un ph bin trong th trng in t. - So vi cc m-un Shap khc nhau, IR, HC-SR04 l r tin hn. Nhng n c chnh xc khc nhau, v khong cch xa hn phm vi. 1.2/ Thng s k thut:
Ngun cung cp: 5V DC hot ng g hin nay:
