N K THUT IN T

KHO ST CM BIN GIA TC

Sinh vin thc hin Cn b hng dn Trn Thanh Sang 1101041 TS. Trn Thanh Hng

Cn Th, thng 11 nm 2013

TRNG I HC CN TH

KHOA CNG NGH

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KHO ST CM BIN GIA TC

Trn Thanh Sang1, Trn Thanh Hng2

ABSTRACT

Nowadays, the acceleration sensor is one of many sensors that are popular in many modern devices. Therefore, this project is researched to survey the data of acceleration sensor in order to provide an overview about this sensor, they are useful for other projects which use the same or different type of acceleration sensor, or the development of related applications (such as control applications, orientation in space,). In this project, the MSP430 microcontroller is used to read out data of acceleration sensor and transmit them to a computer for plotting a graph by Matlab software. The collected data are updated continuously with a high accuracy to meet the requirement of applications, which need high sensitivity, in many areas such as space science, biomedical, automotive industry, electronics civil,...

Keyword: accleleration sensor, I2C interface, UART, MSP430G2452, Matlab GUI,

Title: Survey of Acceleration sensor

TM TT

Ngy nay, cm bin gia tc l mt trong nhng loi cm bin c s dng rng ri trong nhiu thit b hin i. Do vy, ti thc hin kho st d liu ca cm bin gia tc nhm cung cp ci nhn khi qut v cm bin gia tc, cng nh cung cp cc thng tin hu ch cho cc ti khc s dng cng loi hoc khc loi cm bin gia tc, hoc pht trin cc ng dng c lin quan (cc ng dng iu khin, nh hng trong khng gian,). thc hin ti, vi iu khin MSP430 c s dng c d liu ri truyn n my tnh c th v th d liu bng phn mm Matlab. D liu thu thp c cp nht lin tc vi chnh xc kh cao, p ng c yu cu ca cc ng dng i hi nhy cao trong nhiu lnh vc nh khoa hc khng gian, y sinh, cng nghip t, in t dn dng,

T kha: cm bin gia tc, giao tip I2C, UART, MSP430G2452, Matlab GUI,

1 GII THIU

Gia tc l mt i lng vt l quan trng dng m t chuyn ng. Ngy nay, vi s pht trin vt bc ca khoa hc cng ngh, vic o c gia tc tr nn d dng v chnh xc hn nh cc loi cm bin gia tc. Cm bin gia tc c ng dng rng ri trong nhiu thit b nh cc thit b y t hin i, b phn nh hng v iu khin vn tc trong t, b phn nh v trn tn la, tu khng gian, cc thit b o rung, chn ng,Do , ti c nghin cu nhm cung cp nhng thng tin c bn nht v cm bin gia tc, to c s cho nhng nghin cu khc. ti chn cm bin gia tc BMA150 ca hng Bosch Sensortec kho st.

Ngun ti liu tham kho thc hin ti bao gm datasheet ca cm bin gia tc BMA150 v cc thng tin su tm c trn Internet.

1 Sinh vin lp K thut my tnh K36, M s SV: 1101041, S T: 01678767576, email: sang101041@student.ctu.edu.vn 2 B mn T ng ha, Khoa Cng Ngh, H Cn Th

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Kt qu mong mun khi thc hin ti l kho st c d liu ca cm bin bng cch v c th d liu mt cch trc tip trn my tnh.

2 PHNG PHP THC HIN

2.1 S khi tng qut

thc hin kho st d liu ca cm bin gia tc BMA150, ti s dng cc khi chc nng sau:

Hnh 1: S khi tng qut phn cng ca ti

Khi cm bin gia tc: S dng cm bin gia tc BMA150 thu thp d liu gia tc sau gi d liu ny n vi iu khin.

Khi vi iu khin: S dng vi iu khin MSP430G2452 giao tip vi cm bin v my tnh.

Khi my tnh: S dng UART ca my tnh c nhn v phn mm Matlab v th d liu.

2.1.1 Gii thiu v cm bin gia tc BMA150 [1]

BMA150 l cm bin gia tc 3 trc c tm o thp vi ng ra s, c ch to theo cng ngh MEMS (Micro Eletro Mechanical Systems), do hng Bosch Sensortec sn xut.

BMA150 c ch to theo kiu t, cho php o gia tc 3 trc trc giao X, Y, Z, hoc ng dng o nghing, hoc o cc chuyn ng hoc cc rung ng. Trn cm bin cn c tch hp sn mt cm bin nhit .

Nguyn tc hot ng:

o c gi tr gia tc, bn trong cm bin tch hp 3 cm bin con bao gm cm bin X (o trc X), cm bin Y (o trc Y) v cm bin Z (o trc Z) hot ng theo nguyn tc thay i in dung. Cu to ca mi cm bin con l mt h khi lng

l xo nh Hnh 2(a), trong khi m gn vi bn t nm gia h 2 t in mc ni tip c khong cch gia hai bn t c th thay i c, nh Hnh 2(b).

(a) (b)

Hnh 2: H khi lng l xo o gia tc (a) v m hnh hai t mc ni tip (b)

CM BIN GIA TC

MY TNH VI IU KHIN

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Di tc ng ca lc bn ngoi lm in dung ca hai t in ny thay i (C = CA CB), c th tnh c dch chuyn ca bn t trung gian da vo cng thc (vi x nh):

Trong : x l dch chuyn, x0 l khong cch gia 2 bn t, C l in dung ca t. Tnh c dch chuyn x, ta c th suy ra gia tc qua cng thc:

Trong : a l gia tc, k l h s t l, m l khi lng cm bin. Do , ch cn o s bin thin in dung ca t l c th tnh c gia tc. Cm bin X, Y, Z c ng ra l gi tr in dung ca t bn trong. Gi tr ny c a vo mt mch chuyn bit (ASIC) x l. Qu trnh ny i qua nhiu mch nh mch dn knh, b lctrc khi c a vo b bin i ADC 10 bit a vo mch logic iu khin v phc v ngt, cui cng l mch phc v cc chun giao tip I2C v SPI (xem Hnh 3). n v ca gia tc ng ra c c lng theo gia tc trng trng g (1g 9.81m/s2).

c im k thut ca cm bin gia tc BMA150:

S dng ngun thp t 1.62 3.6V, dng in khong 200A.

D liu gia tc 3 trc X, Y, Z c l mt s nh phn 10 bit c biu din di dng s b 2, bao gm 3 thang o l 2g ( nhy 256 LSB/g), 4g ( nhy 128 LSB/g) v 8g ( nhy 64 LSB/g), vi g l gia tc trng trng. D liu cp nht lin tc vi tn s 3KHz, phn gii l 4 mg (2g), c th chn bng thng t 25Hz n 1500Hz.

Tch hp cm bin nhit c vi b bin i ADC 8 bit, o nhit trong khong t -30 oC n 97.5 oC, c th thay i thang o theo yu cu s dng.

H tr cc chun giao tip bao gm I2C, SPI vi cc phm ngt c th lp trnh thng bo d liu mi c cp nht.

H tr nhiu loi ngt c th c lp trnh o s chuyn ng hoc nng cao tm o ca cm bin hoc thit lp cc chc nng nng cao.

H tr 2 ch hot ng l normal mode (ch bnh thng) v sleep mode (ch ng) ti u nng lng tiu th.

S cc khi chc nng, s chn v chc nng cc chn ca cm bin BMA150 c hin th ln lt trong Hnh 3, Hnh 4 v Bng 1.

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Hnh 3: S cc khi chc nng bn trong cm bin gia tc BMA150

Hnh 4: S chn cm bin gia tc BMA150

Bng 1: Chc nng cc chn ca BMA150

PIN Tn Chc nng

1 Chn dnh ring Khng kt ni

2 VDD Ngun cung cp

3 GND Ground

4 INT Interrupt

5 CSB Chn chip

6 SCK Ng vo xung clock (giao tip I2C, SPI)

7 SDO Ng ra d liu ni tip

8 SDI Ng vo/ra d liu ni tip

9 VDDIO Ngun cung cp cho giao tip s (I2C, SPI)

10,11,12 Chn dnh ring Khng kt ni

BMA150 c thit k bao gm 127 thanh ghi (c a ch t 00h-7Fh), c chia lm 7 loi: thanh ghi d liu, thanh ghi trng thi, thanh ghi iu khin, thanh ghi ci t, thanh ghi km theo (tng offset ca thanh ghi d liu), thanh ghi dnh ring v mt s thanh ghi khng s dng. Bng 2 trnh by mt s thanh ghi thng dng s dng trong ti.

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Bng 2: Mt s thanh ghi quan trng ca BMA150

a ch Loi thanh ghi Chc nng

02h D liu Byte thp trc X, new_data_x

03h D liu Byte cao trc X

04h D liu Byte thp trc Y, new_data_y

05h D liu Byte cao trc Y

06h D liu Byte thp trc Z, new_data_z

07h D liu Byte cao trc Z

08h D liu Nhit

14h iu khin Thang o, bng thng

ti s dng cm bin gia tc BMA150 c tch hp trn board Inertial One Sensors Xplained [2], v tr ca cm bin v cc chn phc v giao tip I2C c xc nh nh Hnh 5. Board Inertial One Sensors Xplained c tch hp 3 loi cm bin 3 trc, bao gm cm bin gia tc BMA150, cm bin con quay hi chuyn ITG3200 v cm bin la bn AK9875. Board h tr giao tip I2C gia cc cm bin vi vi iu khin qua cc chn SCL v SDA. Trong board Inertial One Sensors Xplained, a ch giao tip I2C (slave address) ca BMA150 l 38h.

Hnh 5: BMA150 trn board Inertial One Sensors Xplained

2.1.2 Gii thiu v vi iu khin MSP430G2452[3] v kit Launchpad

Vi iu khin MSP430G2452 thuc h vi iu khin MSP430 do Texas Instrument (TI) sn xut, c cc c im chung ca h MSP430 nh: thit k theo cu trc RISC 16-bit, l dng vi iu khin siu tit kim nng lng, cng sut tiu th cc thp, in p ngun khong 1.8V 3.6V v mt s tnh nng khc. ti s dng module USI c h tr trong MSP430G2452 giao tip I2C vi cm bin gia tc BMA150.

Kit Launchpad (Hnh 6) l mt kit ng dng nh do TI sn xut, h tr nhiu loi MSP430 np chng trnh v giao tip d liu. ti dng kit Launchpad s dng vi iu khin MSP430G2452 tin hnh giao tip I2C vi cm bin, sau gi d liu nhn c ln my tnh bng giao tip UART c gi lp (do MSP430G2452 khng h tr UART).

BMA150

SCL

VCC

GND

SDA

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Hnh 6: Kit Launchpad s dng MSP430G2452

2.2 Thit k phn cng, phn mm

2.2.1 Phn cng

Thnh phn s dng: ti s dng cc phn cng sn c bao gm cm bin gia tc BMA150 tch hp trn board Inertial One Sensors Xplained, MSP430G2452 trn kit Lauchpad v my tnh c nhn.

Kt ni chi tit: Cc chn VCC, GND, SCL, SDA ca board Inertial One Sensors Xplained ln lt kt ni vi cc chn VCC, GND, P1.6, P1.7 trn kit Launchpad; kit Lauchpad c kt ni vi my tnh qua cng USB. Kt ni phn cng thc t c th hin qua Hnh 7.

Hnh 7: Kt ni phn cng chi tit

2.2.2 Phn mm

Phn mm IAR Embedded Workbench: S dng lp trnh v np chng trnh vo MSP430G2452 thng qua kit Launchpad. Lu gii thut ca chng trnh c d liu cm bin v truyn ln my tnh c th hin Hnh 8. C th chia gii thut ny lm 2 phn: Vi iu khin c d liu cm bin v Vi iu khin truyn d liu nhn c n my tnh v th.

Vi iu khin c d liu cm bin: u tin, MSP430G2452 tin hnh giao tip I2C vi BMA150 thit lp thanh ghi chn thang o v bng thng (a ch 14h) chn rng thang o v bng thng mong mun (c th mc

MSP430G2452