Mc Lc1.Gii thiu ti21.1Yu cu chc nng21.2Yu cu phi chc nng21.3S khi21.4K hoch thc hin32.Thit k h thng32.1Khi ngun32.2Khi cm bin32.2.1Cm bin nh sng32.2.2Cm bin nhit 42.2.3Cm bin m t52.3Khi iu khin62.3.1Khi qut chc nng cc cng ca PIC62.3.2iu ch PWM.82.3.3Kt ni pic vi cc khi khc.92.4Khi thc hin iu khin92.4.1Khi iu khin ng c92.4.2Khi iu khin nh sng.92.5S nguyn l v mch layout102.5.1S nguyn l102.5.2S mch layout103.Sn phm thc t10

1. Gii thiu ti1.1 Yu cu chc nng Mch o m, nh sng, nhit hin th ln LCD v lin tc c cp nht theo chu k khong 1 pht. Da vo cc kt qu nhn c t cc cm bin a ra cc tn hiu iu khin: Khi cng nh sng thp th bt n vi mc nh sng tng ng Khi cy c m thp phi kim tra nhit mi trng, nu nhit mi trng qu co th cng khng bt my bm nc. Khi t iu kin bt my bm nc ti cho cy. m phi c cp nht mt cch nhanh chng, trnh trng hp bm nc qu nhiu.1.2 Yu cu phi chc nng Thit k mch gn gng, b tr hp l. C m hnh thc t. Mch chy n nh.1.3 S khi

Chc nng cc khi: Khi ngun: cung cp ngun cho ton mch Khi iu khin: tip nhn kt qu t khi cm bin v thc hin ra lnh cho iu khin khi thc hin: hin th kt qu cm bin, bt n, bt my bm. Khi cm bin: o cc gi tr bin ca mi trng nh: cng nh sng, nhit , m ca t. Khi thc hin: thc hin cc yu cu t khi iu khin.1.4 K hoch thc hin2. Thit k h thng2.1 Khi ngun Chc nng: cung cp ngun nui cho ton b mch Yu cu : ngun ra n nh, cng cp cng sut cho ton b mch. S nguyn l:

Mch ngun cung cp ra hai in p: 5v: cung cp cho khi iu khin, cm bin 12v: cung cp cho ng c my bm nc.

2.2 Khi cm bin2.2.1 Cm bin nh sng Chc nng: o v tr v cng ca nh sng, s dng cm bin Bh1750. Cm bin BH1750: c u ra l s nh phn 16 bit xc nh c cng nh sng qua giao tip I2cS khi ca cm bin:

PD: l 1 con photo diode, c nhim v cm bin nh sng AMP:B khuych i thut ton, c nhim v chuyn i tn hiu t photodiode sang tn hiu in. ADC: B chuyn i AC, chuyn i tn hiu tng t( tn hiu in) sang tn hiu s 16 bit. Logic + I2C interface: Tnh ton cng nh sng xung quanh cm bin v cung cp giao tip I2C giao tip vi khi iu khin. Kt qu s c ghi vo cc thanh ghi (thanh ghi d liu, thanh ghi thi gian quy nh qu khi no c v ghi d liu t thanh ghi d liu). OSC: Xung dao ng ni cung cp cho qu trnh tnh ton logic.2.2.2 Cm bin nhit Chc nng: o v tr v nhit ca mi trng, s dng cm bin nhit LM35 S

Chn 1: chn cp ngun 5v cho IC hot ng. Chn 2: chn ni t. Chn 3: Chn tn hiu ra. Tn hiu dy l tn hiu AC. Tn hiu in u ra c quy c cho s thay i cho nhit .2.2.3 Cm bin m tCu to ca 2 chn cm bin:

Mch nguyn l o m:

Phng php o: Mt chn ca sensor c ni vo ni ly tn hiu AC, chn cn li c ni t. Ta cm 2 chn ca sensor vo khu vc t trng cn o.Cm bin khi c cm vo t trng s tng t nh mt bin tr thay i gi tr theo m ca t. t cng m th in tr cng nh ngc li khi t kh in tr s ln v cng. Tn hiu AC c ly ra t mch phn p, in tr ca cm bin thay i th tn hi AC cng thay i. Ta c gi tr AC ny qua vi iu khin v thc hin tnh ton ta thu c m ca t hin ti m cm bin o c.Trc u vo AC ta c mt t in, t ny c tc dng chng nhiu cho tn hiu AC ta thu c.2.3 Khi iu khin

2.3.1 Khi qut chc nng cc cng ca PIC Cng A: Cng A gm 6 chn I/O. y l cng c th xut v nhp d liu. thit lp chc nng vo ra cho cc chn ca cng ny s dng thanh ghi TRISA c a ch l 85h. Khi mun cho mt chn no ca cng A l chn input th ta thit lp cho bit iu khin chn trong thanh ghi TRISA ln mc logic 1. Khi mun l chn output th thit lp bit v mc 0. i vi cc cng B, C, D, E ta cng thao tc tng t. Cng A cn c mt s chc nng quan trng sau y: Ng vo tng t ca b ADC. Thc hin chuyn i tn hiu t tng t sang s. Ng vo xung ng h ca TIMER(). Thc hin cc nhim v m xung thng qua Timer(). Ng vo ca b giao tip MSSP. Ng vo in th so snh. Mt s thanh ghi c lin quan: PortA: c a ch 05h, cha gi tr cc chn trong cng A. TrisA: c a ch 85h, c vai tr iu khin xut nhp d liu ra cc cng. ADCON1: c a ch 9Fh, iu khin b ADC. CMCON: c a ch 9Ch iu khin b so snh. CVRCON: c a ch 9Dh iu khin b so snh in p. Cng B: Cng B gm c 8 chn xut nhp d liu. Thanh ghi iu khin xut nhp ra cc chn l TRISB. C ch iu khin ging nh trong cng A. Cng B cn c chc nng quan trng l lin quan n ngt ngoi vi v b ngt Timer() (ngt trong). V d trong ti ny, cc chn RB4-RB7 phc v ngt ngoi dng trong iu khin ng c bng bn phm. Cc thanh ghi lin quan: PORTB: cha gi tr cc chn ca cng B. TRISB: iu khin xut nhp d liu trn cc chn ca cng B. OPTION_REG: iu khin ngt ngoi v ngt Timer(). Cng C: Cng c 8 chn xut nhp d liu. Thanh ghi iu khin l TRISC hot ng ging cc cng trn. Mt chc nng quan trng c s dng cng C trong ti ny l b PWM c chc nng iu xung lp trnh c tn s v duty cycle gip iu khin tc cng nh chiu quay ca ng c. Cng D: Cng c 8 chn vo ra d liu. Cng ny cng l cng xut d liu ca chun giao tip song song PSP. Cc thanh ghi lin quan: Thanh ghi iu khin l TRISD. Thanh ghi PORTD: cha gi tr cc chn ca cng D. Cng E: Cng c 3 chn tng ng thanh ghi iu khin l TRISE. C cc chn iu khin ca chun giao tip PSP. Cc thanh ghi lin quan: PORTE: cha gi tr cc chn ca cng. TRISE: iu khin xut nhp d liu v phc v cho chun giao tip PSP. ADCON1: iu khin khi chuyn i tng t s ADC2.3.2 iu ch PWM.Nh trnh by trn, bng cch thit lp cho b PWM cng C m ta c th iu khin c tc cng nh chiu quay ca ng c. Khi nim v PWM - PWM (Pulse Width Modulation) hiu mt cch n gin l thay i khong thi gian xung mc cao (duty cycle) trong mt chu k khng i, dn n s thay i in p trung bnh ra ti. ng dng iu khin ng c.S minh ha:

Nu ta c: Ts l chu k ca xung. T l khong thi gian xung mc cao trong 1 chu k. Umax: l in p ln nht cp cho ti. D l h s iu chnh: D = T/Ts in p cp cho ti Ut = D * Umax iu ch PWMi vi PIC 16f877a c hai chn 16 v 17 c iu khin bi hai thanh ghi CCPR1/2 c chc nng a ra tn hiu iu khin ng c. Qu trnh iu ch PWM gn lin vi b TIMER2 ca PIC.iu ch PWM th cn quan tm n cc thng s tn s v thi gian xung mc cao trong mt chu k tn s cho.Fo l tn s ca Pic v Fx l tn s iu ch PWM th ta c biu thc: Fx = Fo / (4*mode*(period + 1))) Cc n mode v period s c thit lp thng qua b Timer2 ca PIC

2.3.3 Kt ni pic vi cc khi khc.2.4 Khi thc hin iu khin2.4.1 Khi iu khin ng cKhi o m ca t, khi iu khin nhn thy: m ca t thp( b kh) v nhit mi trng khng cao so vi 1 ngng t trc( c ly ngay lc y qua cm bin nhit ) th khi iu khin xe xut xung PWM iu khin ng c bm nc.ng c s bm nhanh bn u v tc ca bm xe gim dn khi m o c tng cao.Khi m o c t ngng th dng my bm. trnh bm qu nhiu nc, do tc cp nht m chm, ta t ngng m khi c my bm thp hn so vi ngng nc.2.4.2 Khi iu khin nh sng.

Khi nhn c kt qua o c t cm bin nh sng, khi iu khin tnh ton cng nh sng c hay khng, t xut xung PWm ph hp ra iu khin nh sng ca led cho ph hp vi cng yu cu.2.5 S nguyn l v mch layout2.5.1 S nguyn l2.5.2 S mch layout3. Sn phm thc t