Tm hiu so d khi v so d nguyn l cua mach do Sp02 I.So d khi cua mach do Sp02 1.So d khi

Hinh 1:so d khi mach do Sp02 . M ta hot dng Khi LED DRIVER duoc diu khin thng qua 2 duong: duong tin hiu diu khin vic sang tt cua led va duong din khin dong qua LED dua vao b DAC1.Khi cam bin gm2denLEDdovahngngoaivamtPhotodetector.AnhsangtruyntuLEDqua ngon tay s duoc thu lai o Photodetector d theo di su hp thu Hb va Hb02 Tin hiu tu Photo Detector duoc cho qua khi khuch dai ln 1 ( dung OPA381) voi h s4.7M.TinhiusaubkhuchdainaycvaiVngmtrn99lathanhphnmt chiu Tin hiu sau b khuch dai ln 1 duoc s hoa qua b ADC1 va thu vao vi diu khin, gia trinaychobitgndunggiatrimtchiucuatinhiu(vidongmtchiuchim99 cua ca tin hiu) Dua vao gia tri cua b ADC1 vi diu khin s cp dong mt chiu co gia tri xp xi bng vao b khuch dai ln 2 ( dung OPA333) thng qua b DAC2. Vic cp dong mt chiu tuongduongvaochncuabkhuchdaicoynghialoaibophnlonthanhphnmt chiu khoi tin hiu. Tin hiu sau khi khuch dai ln 2 s duoc cho di qua khi loc gm loc thng thp, loc thng cao va loc thng dai d loai bo nhiu va thanh phn mt chiu con lai Saukhi loc tin hiu la thanh phn xoay chiu, s duoc cho qua b ADC2va dua vao xu li.. D dam bao tinh n dinh ta s ly trung binh cua 1020 gia tri tinhSp02 lin tip va loai bo nhung gia tri co su sai bit dt ngt ( thuong la do mach chua n dinh).BvidiukhinstinhtoangiatriSp02duavaotinhiuthuduoc,giatrinayduoc hin thi ln LCD 3.Chi tit cc khi 3.1 Khi cam bin D thit k cac du do do o du ngon tay (dai tai) nho gon, chung ta cn ngun anh sangva b detectornho. Cac diode phat sang (LED) phat ra cac anh sang do Red va hng ngoai InIra Red. Tuy nhin, cng sut trung binh co th nhn duoc tu cac LEDssbihanchvabdetectorcodnhaycaosrtcnthitdphathin luonganhsangnhoduoctruynquadungontay.Vndnaycothkhcphuc duocbngcachdungcacdiodephatsangLEDchuynbitdangphattrin:Cac diodephatsangphatraanhsangdoduocsanxutvoihthngthukinhbn trongdtaoranhungduracodnhaycao.Tuongtunhuvy,cacdiodephat sang phat ra anh sang hng ngoai co dong lon duoc thit k d tao ra xung sao cho dinh cuaxung co ththay diduoc tu chung, co th tng bin dxungma khng cn tng cng sut trung binh.Diu nay lam cho b detector co th phat hin duoc anh sang truyn qua du ngon tay mt cach don gian. Nhu vy khi cam bin gm co hai den LED va mt Photodetecter duoc b tri di dinnhauquangontay.Trongmachsudung2denLEDsncotrndudocua hng MMIC 3.1.1.Diode pht quang ( LED) Du do MMIC su dung 2 LED o hai buoc song 660nm va 940nm duoc mc nguoc nhau d dam bao chi co mt LED sang tai mt thoi dim, tuy vao chiu din ap thi do co th la LED do hay hng ngoai

Hinh 2. B tri Leds va Photodiode trong du do|11| Cu to cuadiode phtquang:Diode phatquanggmmtloptipxucPNva hai chn cucAnodeva Cathode.Anode duocnivoi ban dnloai P con Cathode duoc ni voi ban dn loai N. Vt liu ch tao Diode phat quang du la cac lin kt cua cac nguyn t nhom 3 va nhom5trongbangtunhoannhuGaAs,hockthop3nguyntnhu GaAsP..Dy la cac vt liu tai hop truc tip co nghia la su tai hop xay ra giua cac din tu o sat day dai dn va cac l trng o sat dinh dai hoa tri. Hnh 3: Cu to diode pht quang guyn l lm vic:Khi LED phn cuc thun, cac hat dn da s khuch tan at qua lop tip xuc PN, chung gp nhau s dn dn tai hop va giai phong nng luong duoi dang cac photon anh sang. Tc d tai hop ty l voi nng d din tu trong phn ban dn P va nng d l trng trong phn ban dn N va nng d din tu trong phn ban dn P. Cac hat dn nay la rt thp trong cac cht ban dn do do nguoi ta thuong cy thm cac hat dn vao. Cuong d dong din qua Diode ti l thun voi cuong d cua cac hat dn va do do cng ty l thun voi cuong d anh sang phat ra. Cc thng s cua LED: DongquaLED:DyladongkhiLEDhoatdngchaytuAnodesangCathode. Trong truong hop du do dang xet thi dong nay vao c 210mA Din ap su dung: Dy la din ap roi trn 2 du LED, d LED hoat dng n dinh thi din ap nay co th nm trong khoang 0,93V. Luu y la vi anh sang hng ngoai truyn qua tay nhiu hon nn din ap cp cho LED hng ngoai thuong s thp hon din ap cp cho LED do .1.2. Photodiode ( Photodetecter) Photodiodebindianhsangthuduocthanhtinhiudin,cuthodyladong din. Hnh 4 : Dc tuvn J-I cua mt Photodiode Si[1j Photodiode hoat dng o ch d phn cuc nguoc, theo do dong din thu duoc s ty l tuyn tinh voi cuong d anh sang theo cng thuc: I SE Trong do: S la ty l nhay sang cua photodiode E la cuong d anh sang chiu vao photodiode DhiurhonhoatdngcuaPhotodiode(PD)ochdphncucnguoc xem hinh minh hoa trn dy v dc tuyn IV cua mt SiPD din hinh Tn hiu thu duoc o Photodiode: Hnh 5: S hp thu cua nh sng khi di qua ngn tav[j Tin hiu thu duoc o Photodiode th hin cuong d sang ma photodiode nhn duoc. Trong tin hiu nay s gm 2 thanh phn: Thanhphnmtchiudctruongchoanhsangtruynquaxuong,da,co,tinh mach Thanh phn xoay chiu dc trung cho anh sang truyn qua dngmach va bi hp thu boi Hemoglobin Thanhphnmtchiulathanhphnchimchuyu(99hochon)va khng mang thng tin, thanh phn xoay chiu la thanh phn nho ( xp xi 1) mang thng tin v nng d Hb va Hb02 Bang sau cho bit kt qua do duoc tai du ra sau khi duoc khuch dai voi h s 1M Orhm va din ap cp vao Led la 1.5V Bang 1: Cia tr din p ti du ra Photodetector( k1M) Mt chiuXungxoaychiu( Vpp) Nhiu ( Vpp) Led do 0.5V8 mV58 mV Led hng ngoai 1.3V53mV810 mV Tu bang trn suy ra bang thanh phn tin hiu sau du ra cua PD voi V led 1.5V : Bang : 1hnh phn tin hiu Mt chiu Xungxoaychiu( App) Nhiu( App) Led do 0.5uA8 pA58pA Led hng ngoai1.3uA 53pA810pA .2. Khi Led Driver 3..1So d nguyn l Hnh : so d nguvn l khi Led Driver 3.. ta chc nng MachLeddriver co chucnng diu khinled dovaledhngngoai tt, sang theo dung chu ky, dng thoi diu khin d sang cua led cho phu hop. Q1vaQ2:ktnigiuavidiukhinvoiQ3vaQ4ddiukhinQ3vaQ4 thng hoc ngt. Q3, Q4, Q5, Q6 : duoc mc nhu mach cu H (HBridge) co chuc nng diu khin tt, sang cho led. U3 (TLV5637) : co chuc nng chuyn di tu s sang tuong tu voi du ra la din ap va thng qua do diu khin d sang cua led. .2..guyn l hoat dng SW1 va SW2 duoc ni voi 2 chn I/O cua vi diu khin atmega16L. Do do, khivi diu khin chua cp din ap vao du SW1 thi transistor Q1 dong, din ap o cuc B va E cua transistor Q3 bng nhau va bng 12V (ngun cp).VB(Q3) VE(Q3) 12 V Khi do Q3 dong, khng co dong din chay qua led do va led do khng sang. Khi vi diu khin cp din ap vao du SW1 thi Q1 thng, khi do co dong din chay tungun 9V qua R6, R3 , Q1 xung dtva tao ra din ap o cuc B cua Q3 be hon 9V. VB(Q3) VE(Q3) 12 V Do do Q3 thng, dong din chay tu ngun qua Q3, led do va dn cuc C cua Q5.DngthoivoiviccpdinapvaoduSW1,vidiukhindiukhinU3 (TLV5637) cp din ap vao cuc B cua Q5 d Q5 thng. Khi do dong din s chay qua Q5 xung dt va lam led do sang. Tuongtu,khiSW2duoccpdinap,Q2thngkeotheoQ4thng.Dng thoikhidodinapduoccpvaocucBcuaQ6thngquaDAClamQ6thng. Dong din s chay qua led hng ngoai xung dt. Nhu vy, Led do sang khi : SW1 duoc cp din ap tu vi diu khin. SW2 khng duoc cp din ap. U3 xut din ap ra OutB. OutA cua U3 ngt. Led hng ngoai sang khi : SW2 duoc cp din ap tu vi diu khin. SW1 khng duoc cp din ap. U3 xut din ap ra OutA. OutB cua U3 ngt. Hnh 7 : Chu k bt tt Leds[4j Cahailedduocdiukhinnhayvoitns100Hzvoithoigiansangla/ chu ky(2,5ms). Led hng ngoai sang sau khi led do tt duoc / chu ky. .2.4 Linh kin su dung .2.4.1 :204 a.Gii thiu chung. DylamtloaitransistorNPNcuahngFairChild,duocthitkchomuc dichcobanlakhuchdaihockhoadintu.Daihoatdnglntoi100mAkhi dong vai tro khoa din tu va 100MHz khi dong vai tro khuch dai. nh 8: 204 -.Bang thong s. Bang 3 1hng s co ban cua 394 K hiuTham sGi triDon vi VCEO Din ap CollectorEmitter40V VCBODin ap CollectorBase60V VEBODin ap EmitterBase6V IC Dong cuc Collector200mA TJ, Tstg Dainhitdhoatdngvabao quan 55 toi 150 oC .2.4.2206 a.Gii thiu chung. DylamtloaitransistorPNPcuahngFairChild,duocthitkchomuc dichcobanlakhuchdaihockhoadintuvoidongquaCollectorctu10A dn 100mA. Hnh 9: 39 -.Bang thong s. Bang 4: 1hng s co ban cua 39 K hiuTham sGi triDon vi VCEO Din ap CollectorEmitter40V VCBODin ap CollectorBase40V VEBODin ap EmitterBase5V IC Dong cuc Collector200mA TJ, Tstg Dai nhit d hoat dng va bao quan55 toi 150 oC .2.4..TLV56 a.Gii thiu chung. TLV5637 co chuc nng chuyn di tu s sang tuong tu voi du ra la din ap. Nohoatdngduatrnchuntruynthngnitiptcdcao(SPI)dohng Motorola d xut. Voi d phn giai 10 bit va 2 knh du ra, TLV5637 phu hop voi voi chuc nng diu khin dong qua led trong mach spo2. Hnh 1 : So d chn cua 1LJ537 [1j Bang 5: Cc chn cua 1LJ 537 Tn chnSI/O/PM ta AGND5PChn dt *CS3IChn chon chip. Tich cuc thp. DIN1IDu vao du liu s OUTA4ODu ra din ap tuong tu cua DAC A OUTB7ODu ra din ap tuong tu cua DAC B REF6I/ODin ap tham chiu tuong tu SCLK2IDu vao xung giu nhip VDD8PNgun duong -. Tinh nng. Hai knh du ra din ap voi d phn giai 10 bit. Din ap tham chiu ni lp trinh duoc. Thoi gian thit lp lp trinh duoc : 0.8s o ch d nhanh (Fast Mode). 2.8 s o ch d chm (Slow Mode). Tuong thich voi cac cng serial SPI. c.Hot dng. Din ap du ra duoc tinh theo cng thuc : VOUT 2*REF*CODE0x1000 |V| (4.1) VOUT : Din ap du ra. REF : Din ap tham chiu. CODE : gia tri du vao s trong khoang 0x000 dn 0xFFF\ Khung du liu: D15D14D13D12D 11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 R1SPD PWR R012 bit du liu SPD : bit diu khin tc d1Fast Mode0 Slow Mode PWR : bit diu khin cng sut1Cng sut thp 0Hoat dng binhthuong Bit chon thanh ghi: Bang : Bit chn thanh ghi cua 1LJ537 R1R0Thanh ghi 00Ghi du liu ra DAC B va b dm 01Ghi du liu vao b dm 10GhiduliuraDACAvacpnhtDACBvoidu liu o b dm 11Ghi du liu vao thanh ghi diu khin Ynghiacua12bitphuthucvaothanhghi.Numttrongnhungthanh ghi hoc b dm duoc chon thi 12 bit du liu s quyt dinh gia tri moi cua DAC. Bit du liu : DAC A, DAC B, B dm D11D10D9D8D7D6D5D4D3D2 D1D0 Gia tri DAC moi00 Bit du liu : Diu khin D11D10D9D8D7D6D5D4D3D2D1D0 XXXXXXXXXXREF1REF0 NuthanhghidiukhinduocchonthibitD1vaD0trong12bitduliu duoc dung d thit lp din ap tham chiu. REF1 va REF0 xac dinh ngun din ap tham chiu va gia tri nu din ap tham chiu ni duoc chon. Bang 7: Xc dnh din p tham chiu REF1REF0Din ap tham chiu 00Ngoai 011.024V 102.048V 11Ngoai .2.4.4 DAC651 a.Gii thiu chung. DAC6571cochucnngchuynditussangtuongtuvoiduraladin ap.Nohoatdngduatrnchuntruynthngnitipdngb(TWI)duatrn chuntruynthngI2CdohngPhilipsSemiconductorsanglpvaxydung thanhchunnm1990.Voidphngiai10bit,1knhduravatiuthuitdin nng, DAC6571 duoc lua chon voi muc dich cp din ap diu khin duoc vao du vao khng dao cua opa333. Hnh 11: So d chn DAC571 Bang 8: Cc chn cua DAC571 STnM ta 1VOUT Din ap du ra cua DAC 2GNDDt 3VDD Ngun 4SDADu vao du liu ni tip 5SCLDu vao xung dng b 6A0Chn chon dia chi linh kin -.Tinh nng . Hoat dng voi nng luong thp: 125A, 3V Tc d cp nht nhanh: 188kSPS Khi cp ngun thi du ra la 0V Ngun tu 2.7V dn 5.5V Giao tip I2C ln toi 3.4MBPS Giai nhit d hoat dng tu 40oC dn 105oC c.Hot dng . Din ap du ra duoc tinh theo cng thuc : VOUT VDD*D1024 |V| VOUT : Din ap du ra. VDD : Din ap ngun. D : Gia tri thp phn duoc tinh toan tu gia tri nhi phn trong thanh ghi DAC, no nm trong khoang tu 0 dn 1023 Co 3 ch d hoat dng: Ch d chun : 100kBPS Ch d nhanh : 400kBPS Ch d tc d cao : 3.4MBPS Giao thuc truyn du liu giua hai ch d chun va nhanh la ging nhau. Giao thuc o ch d nhanh/chun: * Master bt du truyn du liu bng cach tao mt trang thai bt du. Trang thai btdulakhicosuchuynditumuccaoxungmucthpoduongSDAtrong khi duong SCL vn giu omuc cao. Tt ca cac linh kin tuong thich I2C du chp nhn trang thai bt du nay. * Master sau do truyn xung SCL va 7 bit du liu cung 1 bit diu khin huong o duong SDA. Caclinh kin snhn cac bit dia chi duoc gui boimasterva so sanh no voi dia chi duoc c dinh sn bn trong. Chi linh kin nao co cung dia chi voi dia chinhnduocmoidapunglaibngcachkeochnSDAxungmucthptrong sut chu ky muc cao cua xung SCL thu 9. Khi nhn duoc dap ung nay, master bit rng kt ni giao tip voi slave(linh kin DAC) d duoc thit lp. *MastertaocacxungSCLdtruynduliudnslavehocnhnduliutu slave. Bn nhn cn phai xac nhn du liu duoc gui tu bn truyn. Do do, mt tin hiu xac nhn duoc tao boi master hoc slave tuy thuc vao bn nao la bn nhn. 9 bit du liu chun dng b la cn thit bao gm 8 bit du liu va 1 bit xac nhn. *Dktthucquatrinhtruynduliu,masterkhoitaomtdiukinktthuc bngcachkeochnSDAtumucthplnmuccaotrongkhiduongSCLomuc cao. Vic nay giai phong cac bus va ngung giao tip voi slave. Tt ca cac linh kin tuong thich I2C phai chp nhn diu kin kt thuc nay. Khi diu kin kt thuc duoc nhn, tt ca cac linh kin bit rng bus d duoc giai phong va doi diu kin bt du tip theo bng cach so sanh voi dia chi cua minh. SSlaveaddress 0ACtrl/MSByte ALSByte A/*AP A: Acknowledge *A : Not acknowledge S: Diu kin bt du Sr: Diu kin bt du lp lai P : Diu kin kt thuc Giao thuc o ch d tc d cao: * Khi bus ri, ca duong SDA va SCL duoc keo ln cao. * Master khoi tao diu kin bt du theo sau do va mt chui bit 00001XXX * Sau domastertao diu kin bt dulplai. Sau diu kinbt dulplainay giao thuc tuong tunhu o ch d nhanh/chun,ngoai truvic tc d truynln toi 3.4MBPS duoc cho phep. Diu kin kt thuc kt thuc ch d truyn tc d cao va chuyn tt ca cac thit lp bn trong slave v ch d nhanh/chun. SHSMaster code *ASrSlave address 0ACtrl/MSByte ALSByte A/*AP Bvte da ch. MSBLSB 100110A00 Byte dia chi la byte du tin duoc nhn tu master sau diu kin bt du. Sau bit du tin (MSBs) la dia chi duoc nha san xut dt truoc la 100110. Bit tip theo la bit chon linh kin (A0). Chn vao A0 co th duoc ni voi ngun, dt hoc co th duocdiukhinboicacmuclogicTTL/CMOS.Diachilinhkinduocdtboi trang thai cua chnnay trong sut qua trinh cpngun cho DAC6571. Co th kt noi 2 linh kin DAC6571 trong cung bus I2C ma khng cn thm lin kt logic. Bvte quang -E. MSBLSB 10010000 Dia chi quang ba duoc h tro cho DAC6571. Dia chi quang ba co th duoc su dung d cp nht dng b. Khi su dung dia chi quang ba, DAC6571 khng quan tm dn trang thai cua chn A0. HS-Mode Master Code . MSBLSB 00001XX0 Ctrl/MS-Bvte . MSBLSB 00PD1PD0D9D8D7D6 LS-Bvte . MSBLSB D5D4D3D2D1D0XX CEc ch d nng luong thap . DAC6571baogm4chdhoatdngringr.Cacchdnayduoclp trinh thng qua 2 bit (PD1 va PD0). Bang 9: Ch d hot dng cua DAC571 PD1PD0Ch d hoat dng 00Hoat dng binh thuong 011kO ni voi dt, PWD 10100kO ni voi dt, PWD 11Tro khang cao, PWD .. Khi khuch dai ln 1Khikhuchdailn1cotacdungkhuchdaidongdurartnhocua Photodetector (PD).Tinhiu sau PD cogia tri chivaiuAdivoi dongmt chiu vavaidnvaichucnAdivoiphnxoaychiu.Dodokhikhuchdailn1va dam bao duoc tinh cht it nhiu, d chinh xac cao va cng sut tiu thu rt thp. Co haiphuongansudunglinhkincothluachonody:Mtlasudungmtb khuch dai roi va mc ni tip ngay sau PD. Truong hop nay co th dung OPA381 cuahngTexasInstruments,lamtlinhkinduocthitkchuynbitchochuc nng khuch dai va bin dng dongap sau cac PD. Hai la su dung cac PD co tich hop sn b khuch dai. Trong truong hop nay co th dung OPT101 cng cua hang Taxas Instruments. Hai cach su dung la tuong duong v mt nguyn ly , tuy nhin chung ti khuyn nghi su dung OPT101 vi han ch duoc nhiu, tng d chinh xac tuygiathanhcodthon.Trongtailiunaychungticngstrinhbayduatheo phuong an su dung OPT101 VicphathinvasudungOPT101divoichungtilatinhconhungco nhung uu dim rt lon. Linh kin nay thuc su giai quyt duoc rt nhiu vn d kho khncuadtaivalamchonoddanghondangk.TuynhinOPT101khng duocthitkchomucdichdoSp02dodocomtsdimcnphailuuykhisu dungd tranh cac sai sot. Duoi dy chung ti s trinh bay kiv linh kinnay, chi ra nhung uu dim ni tri cua no cng nhu cac vn d cn hiu chinh ..1 OPT101 OPT101 cua hng Texas Instruments la mt linh kin gm mt PD tich hop sn voi b khuch dai ( transimpedance). Din ap du ra ty l tuyn tinh voi cuong d cua anh sang chiu vao PD. Linh kin co th hoat dng o ch d cp ngun don hoc ngun kep va co th su dung ngun Pin. Bang duoi dy cho bit cac thng s hoat dng chinh cua OPT101 Bang 1: 1hng s hot dng cua OP111 Thong siu kinMin TvpMaxon v S AP NG Dong PD in Ep ra 650nm 650nm 0.45 0.45 A/W J/uW DAI NHIET Nhit d lam vic Nhit d -ao quan 0 -25 70 85 C C IEN AP CP in Ep lam vic Dong thu dng Ti. JPIN30J 2.7 120 36 240 J uA So d nguyn ly cua OPT101: Hnh 1 : So d nguvn l cua OP111[1j OPT101duocthitkvoimucdichcambinanhsangmitruong(anh sangnhiu buoc song) do do divoi ungdungdo Sp02 comt s vn d cn luu y: - Pho dEp ng cua OPT101 Ph dap ung cho bit su thay di cua kha nng dap ung theo buoc song anh sang. Hnh 13 : Ph dp ng cua OP111[11j Trong d thi trn, truc ngang la buoc song va truc dung la h s dap ung. Ta thy h s dap ung( r) cua OPT101 la khng ging nhau tai nhung buoc song khac nhau.Cuthdivoi2buocsonganhsangmatasudungodudola640nmva 940nm thi h s dap ung nay ln luot la 0,72 va 0,87. Su khac bit nay co y nghia cuc ki quan trong vi su tuong quan cua din ap thu duoc khng chi phu thuc vao cacthanhphnHbvaHb02tacntinhmaconphuthucvaohsdapungcua tung buoc song Luc do cng thuc tinh R s phai hiu chinh lai theo cac h s nay vi: Tai buoc song 21(do): I1 0,72 Iin1l Cr Cor) (1 0110- -(4.2) Tai buoc song 22(hng ngoai):I2 0,87Iin2l Cr Cor) (2 0210- - (4.3) Luu y la nu mach su dung khi tu dng diu chinh d sang cua Leds thi su hiu chinh la khng cn thit.

- Quan h gia din Ep dau ra va cong suat chiu sEng cua OPT101 Hnh 14 : Quan h gia din p ra v cng sut chiu sng[1j Tu d thi trn ta thy OPT101 co su bin di tuyn tinh giua cng sut chiu sang va din ap ra - Quan h gia dEp ng din Ep va tan s chiu sEng Tnschiusangodyslnnhaycuangunsangtrongmtgiy.V nguyntcdnmttnslonnaodothicaclinhkinPDskhngcondapung duoc hoan toan voi anh sang chiu vao nua. Hnh 15: Quan h gia dp ng din p v tn s chiu sng[1j Tu d thi trn ta thy la trong khoang ly mu dang xet ( 100Hz) thi su dap ung cua linh kin la n dinh ( phai ln dn hon 10kHz thi su dap ungmoi bi giam sut ) - Quan h gia goc chiu sEng va s dEp ng Cng mt cuong d sang nhu nhau thi r rang goc chiu cng co anh huong dn dap ung cua din ap ra Hnh 1: Quan h gia gc chiu v dp ng din p[1j Trongdtaidangxetthigocchiuduocbtribng0divoithanhphn chinh ( thanh phn anh sang truyn qua) - Quan h gia dong din ti va nhit d DongdintiladongdincongaycakhiPDkhnghduocchiusang. Dong din ti noi chung gy ra sai lch v tin hiu va khng co loi. Dong din ti cang nho thi mach hoat dng cang chinh xac Hnh 17 : Quan h gia din p dng ti v nhit d[1j Nhudtrinhbayobang1thidinapdurakhihoatdngvaoc0.51V. Nhu vy thanh phn din ap ti o dy chi c 7mV la khng co y nghia gi nhiu - Quan h gia dong hoi tip va nhit d Donghi tip co dlon bnghiugiua dong dinphn cuc ( Ibias ) va dong din ti ( Idark). Dong hi tip duoc cng vao dong ID va do do cng gy ra sai lch tin hiu Hnh 18: Quan h gia dng hi tip v nhit d[1j Tathyrngvoinhitdphongbinhthuong(25)thidonghitipc 160pA, chim ty l khng dang k so voi thanh phn ID ( c uA) .4. Khi tu dng diu chinh cung d sng cua Leds Nhu d noi o muc 2.5 vic dam bao du ra sau b khuch dai cua tin hiu do va hng ngoai bng nhau s don gian hoa qua trinh ly mu cng nhu tinh toan. D thuchinvicnaytacokhitudngdiuchinhhskhuch dai.Khinaybao gm mt b ADC d theo di tin hiu sau tng khuch dai va mt b DAC d diu khin cuong d dong din qua Led. Khi thy d lon tin hiu vuot qua muc qui dinh truoc(3V)thicuongddongdienquaLedsduocgiamxung.Nguoclaikhi thy d lon tin hiu nho hon 3V thi cuong d dong din qua Led s tng ln tuong ung. Nhu vy khi nay cho phep giu n dinh tin hiu o mt ngung cho truoc. Luu yrngquatrinhtheoditinhiuquaADCchicodchinhxactuongdivino khngphnbitduocthanhphnmtchiuhayxoaychiu.Tuynhintrong truonghopnayvithanhphnmtchiuchimdnhon97cua tinhiunnd chinh xac trong hoat dng cua khi la hoan toan chp nhn duoc .5. Khi khuch dai ln 2 Sau khidi qua khi khuch dailn 1 ta thy tinhiu chua thxuly(loc.) ngay vi 2 ly do sau: mt la thanh phn mt chiu con chim chu yu va hai la thanh phn xoay chiu qua nho. D khc phuc diu nay ta cn tng khuch dai thu 2 voi hai chuc nng sau Khuch dai thanh phn xoay chiu ln muc tuong di lon d co th loc va xu ly tip. H s khuch dai cua tng nay duoc chon khoang 2530 ln Locbophnlonthanhphnmtchiu.Dthuchinchucnngnaytascp vaomtducuakhuchdaimtdongdinmtchiucogiatrignbngnhung nho hon gia tri cua tin hiu sau tng khuch dai thu nht nho vao b ADC1 va b DAC2 ( dung DAC 6571) Hnh 19 : Khi khuch di tngdng OPA333 TrongtngkhuchdainaythiOPA333cuahngTexasInstrumentduoc khuyn nghi su dung .5.1 OPA Ung dung b chuyn di Do nhit d Thit bi kim tra cm tay Thit bi do dac y t Dong OPA333 la khuch dai thut toan duoc ch tao theo cng ngh CMOS su dung k thut kim chun dc quyn d dng thoi cung cp din ap oIIset rt thp( lon nht la 10) va d tri nhit rt nho. Kich thuoc nho, d chinh xac cao,dim lam vic tinh thp yu cu tro khang du vao cao va o ch d thng thuong thi din ap ra hut khoang 100mV so voi ngun cp va voi railtorail thi d hut nay khoang 50mV. Ch d ngun cp don hoc kep la thp nhu nhau duoc su dung khoang 1.8V( 0.9V) dn 5.5V( 2.75V), chung duoc ti uu hoa cho din ap thp va mach cp ngun don. Ho OPA333 cung cp d loi dng pha(CMRR) rt tt ma khng lin quan toi diu kin b sung tng du vao. Tt ca cac phin ban OPA333 du duoc quy dinh lam vic o nhit d tu 40dn 125 Mt s cac thng s cua OPA333 ang 11 : Cc thng s cua OPA Thng sDiu kinMinTypMaxDon vi DIEN AP OFFSET Din ap oIIset vaoVos Voi nhit d dVos/dT Voi ngun cpPSRR Vs5V Vs1.8V 5.5V 2 0.02 1 10 0.05 5 /V DONG DINH THIN DAU VAO Dong dinh thin du vaoI

Nhit d Dong oIIset du vao IOS pA pA pA NHIU Din ap nhiu du vao I0.011Hz Din ap nhiu du vao I0.110Hz Dong din nhiu du vao I10Hz in 0.3 1.1 100 pp pp IA/H KHOANG DIEN AP DAU VAO Khoang din ap thng thuong VCM H s nen dng phaCMRR (V)0.1VCM(V)0.1 (V)0.1 106 130 (V) 0.1 V dB So do chan cua OPA333. nh 20: so d chn OPA SO-8 [10] Mt s biu d biu din dc tinh cua OPA333 duoc cung cp trong datasheet: nh 21:D loi vng ho v tn s [10] nh 22:uc dp ng vi tn hiu ln nh 2:uc dp ng vi tn hiu nho [10] nh 24:Su phuc hi sun duong din p [10] nh 25:Su phuc hi sun m din p [10] nh 26:hiu 0.1-10 [10] nh 2:Ph mt d nhiu din p v dng din vi tn s [10] .6 Khi loc .6.1 Dinh nghia v mach loc Machlocduocdinhnghiachungnhtlamachdintaoradctuyntns mamuc tiu cuanola cho phepmt s tn snht dinh di qua dngthoiloai bot nhungtnskhachaynoicachkhaclabindcuanhungtinhiucotnscho phep di qua duoc giu nguyn con bin d cua nhung tin hiu khng duoc di qua s bi trit tiu .6.2 Phn loai mach loc Theo cau to. Mach loc thu dng Mach loc tich cuc Theo chc nng. Mach loc thng thp Mach loc thng cao Mach loc thng dai Mach loc trit dai .6. Cc thng s dc trung .6..1 Dc tuyn bin d tn s Dc tuyn bin d tn s la d thi cua ham duoc xac dinh nghia la ty s giua din ap ra trn din ap vao cua b loc goi la ham truyn dat, ham nay v co ban s phu thuc vao tn s cua tin hiu vao : K(I)Ura(I)/Uv(I)( 4.4) Hnh 8: Dc tuvn bin d tn s [4j .6..2 Dc tuyn pha tn s Dctuynphatnscuablocladthibiudinmiquanhgiuapha cua tin hiu ra so voi tn s cua tin hiu du vao. Vi vy, thng thuong pha cua tin hiu ra s bi lch so voi pha cua tin hiu vao. .6.. D suy giam Khixacdinhcacdiukinloc,thngthuongnguoitahaysudungkhai nim v d suy giam cua ham truyn dat hay dc tuyn bin d. Gia su gia tri cuc daicuahamtruyndatcuamtblocbtkinaodolaM0,nugiatricuaham truyndattaitnsIlaM(I)thikhainimvdsuygiamtuongdicuadc tuyn bin d duoc dinh nghia nhu sau :udB(I) 20lg(M0/M(I))(4.5) .6..4 Tn s ct Tnsctcuabloclytuonglagiatritnsmataidohamtruyndat chuyn tu gia tri 1 v gia tri 0 hoc nguoc lai, tu 0 ln 1. Tuy nhin, tn s ct cua cacblocthuctduocdinhnghialatnsmadctuynbindtaitnsdo giam di 3dB .6..5 Dai thng v tn s trung tm Tuong tu nhu tn s ct , dai thng cua mt b loc ly tuong duoc dinh nghia la dai tn s ma tai do gia tri cua ham truyn dat bng 1. Tuy nhin voi b loc thuc t, gia tri cuaham truyn dat tai dai thngs la gia trigiam di 3dBvoi gia tri cuc dai. Tn s trung tm cua b loc duoc dinh nghia la cn bc hai cua tich 2 tn s ct trn va ct duoi cua b loc. I0II (3.6) .6..6 S cuc cua mach loc S cuc cua bloc thuong duocxac dinh bng sluongmach RChay stu co trong b loc. S cuc cua b loc cang lon thi d dc cua dc tuyn bin d trong vung dai chuyn tipcang lon. Do do nu b loc co s cuc cang lon thi cht luong cuamachloc cang tt. Tuynhin , khi s cuc cua b loc canglon thi d phuc tap va kha nng mt n dinh cang cao. Hnh 9:Bc cua b lc cng cao th d dc cua bin d cng ln [4j .6.4 Thit k b loc cho mach do Sp02 Dloaibocacthanhphnnhiutnsthpvanhiucngnghipchotin hiu ra duoc n dinh, trongmach su dung b loc thng cao 0.5Hz va b loc thng thp 10Hz. .6.4.1 ach loc thng cao 0.5 Machlocthngcao0.5Hzstrittiunhiutnsthp,loaibocacthanh phn tn s nho hon 0.5 Hz a.Chon tu C1C2C100nF b.Tinh toan gia tri din tro R1 la din tro ni voi cuc khng dao cua b khuch dai thut toan: ta co tn s ctIc121-2-C1-C2 chon R12R2 voi Ic0.5Hz R122-n-0.5-C=.H c.Tu do ta co R2R1/2 2.2MO d.Chon R3R22.2 MO la din tro ni vao cuc dao cua b khuch dai thut toan Su dng du giua cac din tro s lam giam su sai lch xung nho nht Hnh 3: So d mch lc thng cao .5Hz .6.4.2 ach loc thng thp 10 V nguyn tc khi xy dung b loc thng thp ta chi cn hoan chuyn vi tri giua cac cp gia tri din tro va tu din tuong ung a, Chon C1100nF, C247nF b, Ta cng co cng thuc tinh tn s ct Ic121-2-C1-C2 voi gia tri tu din d chon va tn s ct Fc10Hz ta co duoc R1R2220kO Hnh 31: so d mch lc thng thp 1Hz .. Khi xu l tnh ton Dthuchinchucnngxulitinhtoanchomachtasudungmtvidiu khin Atmega16 thuc ho AVR AVRlahovidiu khin 8 bit theo cngnghmoi,voinhung tinhnng rt manhduoctichhoptrongchipcuahngAtmeltheocngnghRISC,nomanh nganghangvoicachovidiukhin8bitkhacnhuPIC,PSoC.Doradoimun hon nn ho vi diu khin AVR co nhiu tinh nng moi dap ung ti da nhu cu cua nguoi su dung, so voi ho 8051, 89xx s co d n dinh, kha nng tich hop, su mm deo trong vic lp trinh va rt tin loi. CEc tinh nng mi cua h AJR. - Giao din SPI dng b. Giao tip I2C B bin di ADC 10 bit. Cac knh bm xung PWM. 3 b Timer/Counter 8 bit. Timer/Counter 16 bit. 1 b so sanh analog. B nho EEPROM. Giao tip USART..vv. Atmelga32codydutinhnngcuahoAVR,vgiathanhsovoicacloai khac thi gia thanh la vua phai khi nghin cuu va lam cac cng vic ung dung toi vi diu khin. Tinh nng : B nho 32KB Flash co kha nng doc, ghi 10000 ln 1024 byte EEPROM co kha nng doc, ghi 100000 ln. 2KB SRAM. 8 knh du vao ADC 10 bit. H tro cac giao tip UART, SPI, I2C. 1 b so sanh analog, 4 knh PWM. 2 b timer/counter 8 bit, 1 b timer/counter1 16 bit. 1 b dinh thoi Watchdog. Hnh 3:So d chn Atmega1 Mo ta chc nng cEc chan cua atmega16 Vcc va GND 2 chn cp ngun cho vi diu khin hoat dng. Reset dy la chn reset cung khoi dng lai moi hoat dng cua h thng.2chnXTAL1,XTAL2cacchntaobdaodngngoaichovidiukhin,cac chnnay duoc ni voi thach anh (hay su dung loai 4M), tu gm (22p). Chn VreI thuong ni ln 5v(Vcc), nhung khi su dung b ADC thi chn nay duoc su dung lam din th so sanh, khi do chn nay phai cp cho no din ap c dinh, co th su dung diode zener: ChnAvccthuongduocnilnVccnhungkhisudungbADCthichnnay duoc ni qua 1 cun cam ln Vcc voi muc dich n dinh din ap cho b bin di II.So d nguyn ly: Tu cac khi thit k nhu trn ta co so d nguyn ly cu th So d nguyn l cua mach do SpO2 Hnh 33: So d nguvn l 1 Hnh 33 : So d nguvn l