May do tu truong sii* dung sensor GMI trong vung nano-Tesla
Dirong Quang Hd^"\Vo Dire Trgng^">, Vii Diic Du/'^ Biii Vi?t Kh6i^'\ Phi Hda Biiih^"^
(ei)Viin Khoa hge Vdt li?u, Vi?n KH&CN Viit Nam (h) Khoa Diin tir-Vien thong, Dgi hge Bdch khoa Hd ngi
Tdm tdt:
Hieu irng tro khdng tir khong id (Giant magneto impedance- GMI) dugc klidm phd tir 1994 tren cdc vdt lieu hgp kim vd mdng mdng vd dpih hinh vd cdu true nano, vd da bdt dau dugc irng elung lam sensor tir trong viing tir trudng co nano-Tesla (nT). Trong vung tir truong ndy sensor bdn ddn diing hiiu irng Hall ndm ngodi khd ndng do dugc, gidi hgn d 0,1 niTva phu thugc manh vdo nhi?t dg so vd^sensor GML Mdy do tir truong dugc nghiin ciru che tao diing sensor GMI - AMI 204 tich hgp cong nghg vi xir ly cho phep do dugc cuong dg tit truong thdp toi nT voi dg dn dfnh vd tin cay cao trong ddi tdn so bien thien tdi 1 Khz. Vai kich thudc hogt dgng nhd ciia sensor GMI cd 20 micrometer, thiet bj cho phep phdt hien bien thien tir tnrdmg trong vdt the kich thuoc nhd nham dua toi nhieu muc dich img dung khdc nhau : nghien ciru tinh chdt tir cua vdt lieu tir, spintronics do bien thien tir truong trdi ddt, phdt hien kim logi sdt tir vd nhieu img dung khdc.
I. Gidi thieu chung
Hien nay, mdy do tir trudng dang chiem vai trd quan trgng vd dugc su dyng rgng rai trong cudc sdng cua con ngudi. Vai trd cua cdc sensor tir trudng la vd cung can thiet trong nhidu ung dyng thye te nhu trong bd nhd cua mdy tinh ca nhan PC, trong cac phuong tien giao thdng nhdm myc dich dinh vi vd ddn dudng,... Hau het cac ky thuat do tiJ trudng deu dya tren cdc hieu ung dien tir trudng nhu hieu ung Hall, GMI, GMR, SQUID,... vdi do nhay khdc nhau. Trong bdi bdo ndy, chiing tdi trinh bdy thiet ke mdy do tir trudng cam tay sii dung sensor tir trudng AMI204 sir dung hidu iirng tir trd khdng Id GMI dya tren cdng nghe PSoC.
Sensor AMI204 dugc xdy dyng tren sgi FeCoSiB vd djnh hinh vdi dg nhay cao co thS sir dung cho cdc iimg dung vimg tir trudng cd nano-Tesla (nT).
Hieu img tir trd khdng Id (Giant Magnetoimpedance - GMI) Id sy thay ddi manh tdng trd dudi tdc dung cua tir trudng ngoai [1]. Khi ddng dien AC (viing tdn sd 1-lOMhz) tiem vao cdu tnic, ddng dien phan bd tren bd mat day dan lam thay ddi dien trd va trd khang cua day dan. Vi vdy, tdng trd ciia day dan phy thugc manh vao phan bo ddng dien bl mat va do tu thdm cua vdt lieu lien q^uan ddn chuydn dgng quay cua momen tir. Hieu ung tii trd khdng 16 thudng dugc ddnh gid bang he sd tir trd MIR (Magneto-Impedance Ratio) [2]:
Trong Ihiel ke cac Ihiel bi do ludng va dieu khidn cd sd lugng Idn, de giam gia thanh san pham, cdng nghe PSoC duoc uu lien lua chon vi nhung uu diem ndi bai ciia nd: Ifch hgp bd vi xir ly vdi cac khdi xir ly sd va luong ly, kha nang lai cau hinh linh hoal va phan mdm thidl kd.
lap trinh lien dung.
Khac vdi cac chip kha trinh khao nhu ASIC (Application Specific Integrated Circuit) hay FPGA (Field Programmable Gale Amiy) chi cho phep tao ra cac IC cd chuc nang ridng le, vdi su tfch hgp mdt bd vi xir ly 8 bit ciing cac bd nhd ROM, RAM va cac khdi xir ly tin hieu tuomg ty, tfn hieu sd, PSoC that su la mdt hg vi he thdn^ don chip manh me cho phep limg dung vao hau het cac he thdng nhung. Ddi vdi cac sdn phdm do ludng, sir dung PSoC td ra hidu cjua vi no tfch hgp bd chuydn ddi tuofng ty sd (ADC) len den 14 bit, bd khudch dai vdi he sd khuech dai cd the lap trinh dugc dong thdi cac sai so vd dien dp va nhidu rc4t thap.
Ngodi ra, PSoC con cung cdp nhidu khdi tuong ly va sd khac dk tao ra cac thidt bj ngoai vi nhu: bd chuyen ddi sd tuong tyc (DAC), bd Igc, bg so sanh, bd ddm, bd tao xung PWM, truyen thdng ndi tidp SPI, ket noi dj bg UART. Vdi giao dien tryc quan, thao tac lya chgn, keo thd, phdn thiet kd, cdu hinh PSoC trd nen nhanh chong vd de ddng horn
Tom lai, trong thiet ke mdy do tii' trndng cam tay nay, chiing tdi sir dung PSoC vi khd ndng linh hoat ciia no, gid thanh hgp ly, nhd ggn do tfch hgp nhieu thdnh phan bdn trong chip vd phdn mem phdt trien nhanh.
II. Nguyen ly hoat dong
Thiet bl bao gom cdc khdi co ban Id: khdi ngudn cdp ngudn dn djnh cho PSoC vd sensor, khoi xu ly Id chip PSoC dugc tdng cudm^ them bd nhd EEPROM ngodi, sensor GMI do nhay cao, khdi giao tidp vdi ngudi diing vd khdi giao tiep vdi mdy tfnh qua chudn USB.
Trong thidt bj ndy, chip PSoC cd chuc ndng lien ket cdc thdnh phdn khdc vdi nhau. PSoC ddm nhdn vide nhdn tfn hieu dien tu sensor GMI vao vd chuyen thdnh gid trj cudng do tu trudng dya vao dac tuydn da bidt trudc ciia sensor. Cdc gid trj tir trudng do ndy se dugc hien thj tren man hinh LCD cho ngudi dung biet ddng thdi cd the luu cdc gid trj ndy vdo EEPROM khi cdn thiet vd chuyen dir lieu sang mdy tfnh qua chuan USB.
Phdn chuang trinh viet cho PSoC cho phep ngudi diing lya chgn chd do do trung binh trong mdt khodng thdi gian hodc do tire thdi vd nhieu lya chgn khdc thdng qua khdi giao tiep vdi ngudi su dung (mdn hinh LCD vd cdc phfm bdm).
Keys
LCD * — 1 —
1 User Interface 1
'»•
EEPROM
*
1 T
I2C
LCD -
PSoC
CPU RAM FLASH Firmware
UART
ADC
/
a
Power Supply
L
GMI Sensor AMI-204
4
System
USB Module
Hlnh 1. Sa d6 khoi hf th6ng Sensor GMI:
Sir dung hieu img tir trd khdng lo, tap dodn thdp Aichi Nhat Ban [5] da san xudt cdc loai sensor tir nhay d dang IC nhd cd thd tich hgp vdo cdc thidt bj dien tu mgt cdch de ddng. San phdm AMI-204 chii:a hai sensor GMI d^t vudng gdc, di?n dp tuydn tfnh ddu ra se tuong iing vdi cudng do tir trudng theo hudng cua mdi sensor. Su dung hai sensor dat vudng gdc khdng nhirng cho phep do dugc timg thdnh phan cudng dg tir trudng md cdn cho phep tinh toan hudng tir trudng chi'nh xac hom.
So dd khdi cua AMI-204 nhu sau:
Pulse Generator Synchronous
Detection
Control
r"x il
T
Sample Hold (X-Y Selecti^on)
r"
l^U,
LVYjrt^?^
Xaxls sensor
-m-
Y axis sensor
Reference Voltage
GND2
Cac thdng sd ky thuat ciia mdt sensor AMI-204 (No.501):
Bang 1. Cdc thdng sd ciia sensor AMI-204 Dieu kicn thii' righicm
Do nhay true X
Dien ap ra d OGauss (true X) Dd nhay true Y
Dicn ap ra d OGauss (true Y)
Vcc=3V
255.6 mV/Gauss 1476.4 mV 248.7 mV/Gauss 1420.3 mV
HI. Thiet ke chip PSoC
.AMdy do sir dung chip PSoC CY8C27443 vdi tai nguyen gdm cd 8 khdi sd vd 12,khdi tuong ty trong dd chi su dung 7 khdi so vd 1 khdi tuong ty.
Mdt sd khdi chi'nh dugc cdu hinh trong PSoC:
- ADC: Bg chuyIn ddi tuomg ty sd len ddn 14 bit hd trg sdn ben trong PSoC Id mdt dilm ndi bat khidn PSoC dugc sir dung trong cdc thidt bj do ludng nhdm thay thd cho vide su dung vi xii" ly ket hgp vdi ADC ben ngodi.
LCD: Khdi dilu khiln hidn thj theo chudn LCD HD44780 ciia Hitachi, cimg vdi cdc phim bam tao thanh bd phdn giao tiep vdi ngudi sii dung.
UART: Khdi giao tidp vdi module USB dk chuydn cdc gid trj do dac sang may tfnh qua chudn giao tidp USB dung trong cac trudng hgp luu trii, ve dd thj, ... Xung ddng ho su- dung trong giao tiep UART dugc lay ra tir khdi Counter 8 bit.
- I2C: Giao tidp I2C kit ndi PSoC vdi bd nhd md rdng EEPROM, du lieu co thd dugc luu tam thdi trong EEPROM tiirdc khi chuydn sang mdy tfnh, tdng tfnh di ddng cho thidt bj.
Cdc thdng sd dugc lya chgn chung cho chip PSoC :
Bang 2. Cac thong CI CPU Clock
Sleep Timer Analog Power
Ref Mux AgndBypass Op Amp Bias A Buff Power Switch Mode Pump
Supply Voltage Watchdog Enable
so chung ciia PsoC PU
24 MHz 512 Hz SC On/Ref Low (Vdd/2) -h/- (Vdd/2)
Disable Low Low OFF 5V Disable
IV- Ket luan
Vdi uu didm ggn nhe, tidt kiem ndng lirgng, gia thdnh thdp, dp nhay cao, thidt bj cho phep umg dung irong nhilu linh vuc khac nhau: nghidn cuu tfnh chdt tir cua vat lieu tir, do bien thidn tir t'ludng trai dai, phat hien kim loai sdt tir vd nhieu irng dung khdc. Vdi nhirng uu dilm tren, thidt bi do tir timdng sir dyng sensor AMI-204 la mgt san phdm tin cay phii hgp vdi thi trudng Viet Nam.
Mgt phdn kinh phi nghien ciru ndy dugc thue lii?n trong khudn khd Di tdi nghien ^ini cobdn vai md .so 103.03.49.09 ciia Quy phdt trien khoa hge & cong ngh? quoc gia (NAFOSTED).
Tai lieu tham khao
[1] Phf Hda Binh, Nguyen Huy Hieu, Nguyen Hodi Nam, Ducmg Qudc Diing, Ung dung
cong nghi PSoC trong thiet ke module do tir trudng vd ddng dien tren sensor hieu Umg tir tro khong Id, Tuyen tap cac bao cao khoa hge: Hgi nghi to^n quoc lan thir VI ve ty
dgng hoa- 2005.tr. 58-63
[2] C.Tannous, and J.Gieraltowski, (2003) Giant Magneto-Impedance and its applications [3] L. V. Panina and K. Mohri, Appl. Phys. Utt. 65, 1189 (1994)
[4] R. S. Beach and A. E. Berkowitz, Appl. Phys. Lett. 64, 3652 (1994) [5] AICHI STEEL CORPORATION, http://www.aichi-steel.co.jp/