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A Wireless Embedded Device For Personalized Ultraviolet Monitoring

Navid AminiJerrid Matthews

Alireza VahdatpourFoad Dabiri

Hyduke NoshadiMajid Sarrafzadeh

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Importance

The skin care product market is growing due to the threat of ultraviolet (UV)

radiation caused: Destruction of the ozone layer

Increasing demand for tanning The tendency to wear less clothing

Potential demand for a personalized UV monitoring device, cancer prevention by

providing measurements of UV radiation intensities and corresponding

recommendations.

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Summary

Based on a novel software architecture, a high-end UV sensor, and conventional PDA (or a cell

phone). short-term applications: calculating the UV

index maximum recommended sun exposure time.

Long-term applications: it displays the amount of UV received over a certain course of time,

from a single day to a month. Low energy consumption and high precision in

estimating the UV index (precision of 0.2).

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UVI precision is ± 0.2 UVI and is extendable to 0.1.

Noise cancellation in hardware Noise cancellation in software

Our Accuracy to estimate the UV index is two and five times higher than current UV index estimators:

EryF from Scitec Oregon Scientific UV Sensor

Exploiting the dynamic power management technique on the UV sensor

Two times longer lifetime relative to EryF from Scitec

Summary

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Did You Know?

The skin is the largest organ of the bodyMost Common Cancer = Skin Cancer!

1.3 Million Cases in the U.S.~ 1 person dies every hour

• Melanoma is considered as the most lethal form of skin cancer.

• In the year 2008, about 62,480 persons are expected to be diagnosed with melanoma resulting in the death of an estimated 8,420 individuals (California).

• Alarmingly, the incidence of melanoma is increasing rapidly in children.

The radiation of UV is about 10% of total solar radiation. It is divided into three ranges based on the wavelength: UV-A (320-400 nm), UV-B (280-320 nm), and UV-C (100-280 nm).

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UV IndexThe Global Solar UV Index (UVI) describes the level of solar UV radiation at the Earth’s surface. The values of the index range from zero upward – the higher the index value, the greater the potential for damage to the skin and eye, and the less time it takes for harm to occur.

/W m40 equal to constant is a k

rumtion spectference acrythema re) is the e(sength λ) at wavel·nmW/(mressed in pex

nceal irradialar spectr is the sowhere E

,dsEkUVI

er

er

λ

nm

nm

erer2

12400

250

)(..

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

250 270 290 310 330 350 370 390 410

Wavelength (nm)

Rela

tive R

esp

onse

(W

n) The calculations are weighted in favor

of the UV wavelengths that human skin is most sensitive to according to the McKinlay-Diffey erythema action spectrum curve

UV Index

UV index Extent

0-2 Low

3-5 Moderate

6-7 High

8-10 Very high

11+ Extreme

The study of the erythemal influence has been frequently based on the minimum dose of UV erythemal radiation that will produce a

noticeable reddening of human skin that has not been previously exposed to solar radiation. This dose is known internationally as the MED (minimum erythemal dose) and is always related to a specific

skin type. If the UV irradiance is 1 MED/hour, then it will take an hour for a person exposed to this irradiance to receive the minimum

erythemal dosage. 1 MED corresponds to a total dose of 210 J/m2. Thus 1 MED/hour = (210 J/m2)/3600 s = 58.3 mW/m2 = 2.33 UVI.

http://www.socialuvwatcher.com/ 8

UVI Versus Location1.  85% increase from snow reflection2.  100% increase at 3000m altitude3.  25% increase from white-water reflection4.  80% of UV rays pass through cloud5.  20% from sand and grass reflection  - and 40% when wet6.  15% reflection from concrete buildings7.  50% can be reflected into shaded areas8.  50% UVB and 80% UVA passes through the upper 50cm of water9.  50% increase from water reflection

Schematic Diagram

Op-amp

UV Sensor

è Current Rf

è Output Voltage

OKI ML8511

10-bit ADC

I/O MCUAtmel

ATmega 128L

EN

Bluetooth AdapterRoving

NetworksRN-24

MicaZ Mote

Nokia N95

Personal UV Monitor Software

UV Index Data

http://www.socialuvwatcher.com/ 10

The world’s first UV sensor IC to be based on SOI-CMOS technology

It integrates a UV light-receiving element and an analog output circuit into a single chip.

This helps to reduce the number of components, cost and size compared to conventional devices.

IC includes an energy-saving standby function, it is perfect for battery driven portable mobile devices which require low power consumption.

Components: UV Sensor

ML8511 from OKI Semiconductor

Introduced 8 months ago

http://www.socialuvwatcher.com/ 11

Features Optical sensor for UV-A and UV-

B Analog voltage output Low supply current ( 300 μA

typ. ) and Low standby current ( 0.1 μA typ. )

Small and thin surface mount package

Functions UV sensor (PN-photodiode) Current-to-voltage converting

amplifier

Components: UV Sensor

ML8511 from OKI Semiconductor

http://www.socialuvwatcher.com/ 12

Components: UV Sensor

0

0.25

0.5

0.75

1

1.25

280 320 360 400 440 480 520 560 600

Wavelength (nm)

Sen

siti

vity

(R

ela

tive

Valu

e)

Spectral sensitivity characterisitics of the ML8511.

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ADC Output and Corresponding UV Indices Sensor output

voltageADC output

UV index

0.993 320-345 0

1.073 345-370 1

1.153 370-395 2

1.233 395-420 3

1.313 420-445 4

1.393 445-470 5

1.473 470-495 6

1.553 495-520 7

1.633 520-545 8

1.713 545-570 9

1.793 570-595 10

1.873 595-620 11

1.953 620-645 12

2.033 645-670 13

2.113 670-695 14

2.193 695-720 15

2.273 720-745 16

2.353 745-770 17

2.433 770-795 18

2.513 795-820 19

2.593 820-845 20

(Vcc = 3.0 V)

..ADC

UVI OUTPUT 20)5

320(

It should be noted that the Maxim1678 DC-DC converter which is located on the MICAz mote provides a solid 3V supply operated off a pair of AA batteries.

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The flowchart of the software

T = Maximum recommended exposure time

Is SPF = 0?

Read the Bluetooth data (current UVI)

Enter your sunscreen’s SPF

Enter the skin type (1 to 4)

No T = T × SPF

Yes

Start

Current UV? (or

accumulated UV)

Yes

No

Enter the period of time (1 to 3 for day, week and month)

End

Show the UV history and total UV

exposure

Show current UVI and T

If you use a sunscreen, the exposure time will be multiplied by the sun protection factor (SPF) of the applied sunscreen.

Maximum Exposure Algorithm:

Exposure Time * SPF

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Examples Skin types and corresponding tolerated MEDs and maximum exposure time.

Skin type

Color, burning and tanning in the sun

Tolerable MEDs

Maximum exposure time

1White, always

burns, never tans2 hecto

J/m267 min / UVI

2Yellow and white,

usually burns, sometimes tans

4 hecto J/m2

100 min / UVI

3Yellow and black, sometimes burns,

usually tans

5.75 hecto J/m2

200 min / UVI

4Black, rarely

burns, always tans8.5 hecto

J/m2300 min / UVI

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A person with a skin type of 3, in a UV index of 10, will start to sunburn

after just 20 minute of unprotected exposure to the sun:

[200 (min) / 10 (UVI) = 20 min]

If this person uses an SPF 30 sunscreen this becomes 600 minutes, or 10 hours:

[20 (min) × 30 (SPF) = 600 min].

Experimental Results

UV Dose = Average UV × Exposure time.

The data were gathered on a partially cloudy day in June in Los Angeles and we kept the device fixed on the roof of an eight-story building.

Time 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00

UV index(ending on the hour)

1.2 2.2 4 5.4 6.2 9 5.6 5.8 4.6 2.4 1.2 0.0

Hourly mean UV index 1.6 3.1 4.2 5.4 7.8 7.4 6.1 5.5 3.9 2.2 0.8 0.0

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Energy Consumption

Operation / component

Average power

Sensing / UV sensor

Sensing mode: 900 µW

Standby mode: 0.3 µW

Processing / microcontroll

er

Busy mode: 29.95 mW

Idle mode: 14.88 mW

Communication / Bluetooth

adapter

Connected mode: 120 mW

Idle mode: 3 mW

Average power consumption for different parts of personalized UV monitoring device.

The calculation of the UV index is performed every 15 seconds and in order to get an accurate estimation of the UV index, the average of four consecutive sensor measurements is taken into account.

in this embedded device, we achieved an energy saving of up to 60% in the sensing part as opposed to an always-on sensor system

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Accuracy

Due to noise cancellation in software, and also considering the fact that ML8511 is less sensitive to the angle with respect to the sun, we were able to extract the UV index with the precision of 0.2 which is 2 and 5 times more accurate than previous tiny devices produced by (OS 2008) and (EPP 2008).

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Future Work

The gathered data show that unlike similar UV sensors, ML8511 is less sensitive to the angle with respect to the sun.

20 degrees rotation 10 percent decrease in the UV Index

1- Integrating the system with a gyro to correct the error caused by rotation.

2- Putting a specified number of sensor on a Half Sphere and taking the maximum over their outputs.

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References Ferguson, K., 2005, Melanoma (Clinical updates). Journal of Continuing Education in Nursing, Vol. 36, No. 6, pp.

242–243. Sue, N., Roberta, S., 2002, The management of high-risk melanoma: Staging, treatment, and nursing issues,

Journal of Dermatology Nursing, Vol. 14, pp. 363. Hall, H. I., Miller, D. R., Rogers, J. D., Bewerse B., 1999, Update on the incidence and mortality from melanoma in

the United States, Journal of the American Academy of Dermatology, Vol. 40, pp. 35–42. Boscoe, F., Schymura M., 2006, Solar ultraviolet-B exposure and cancer incidence and mortality in the United

States, BMC Cancer Journal, Vol. 6, pp. 264. ACS, 2008, American Cancer Society, Cancer facts and figures, http://www.cancer.org/. Strouse, J. J., Fears, T. R., Tucker, M. A., Wayne A. S., 2005, Pediatric melanoma: Risk factor and survival analysis

of the surveillance, epidemiology and end results database, Journal of Clinical Oncology, Vol. 23, pp. 4735–4741. Hu, S., Ma, F., Collado-Mesa, F., Kirsner, R. S., 2004, UV radiation, latitude, and melanoma in US Hispanics and

blacks. Archives of Dermatology, Vol. 140, pp. 819–824. Jemal, A., Devesa, S. S., Fears, T. R., Hartge, P., 2000, Cancer surveillance series: Changing patterns of cutaneous

malignant melanoma mortality rates among whites in the United States, Journal of the National Cancer Institute, Vol. 92, 811–818.

DeFabo, E.C., Noonan F.P., 1983, Mechanism of immune suppression by ultraviolet radiation in vivo. I. Evidence for the existence of a unique photoreceptor in skin and its role in photoimmunology, The Journal of Experimental Medicine, Vol. 158, pp. 84-98.

Herlihy, E., Gies, H.P., Roy, C.R. Jones, M., 1994, Personal dosimetry of solar UV radiation for different outdoor activities, Journal of Photochemistry and Photobiology, Vol. 60, pp. 288-294.

Wong, C.F., Toomey, S., Fleming, R.A., Thomas, B.W., 1995, UV-B radiometry and dosimetry for solar measurements, Journal of the Health Physics Society, Vol. 68, No. 2, pp. 175–184.

RMI, 2008, The Royal Meteorological Institute of Belgium, http://www.meteo.be/. Solar, 2008, Solar Light Company, 501 UV-Biometer, http://www.solar.com. OS, 2008, Oregon Scientific Company, UV Monitor with Exposure Timer, http://www.oregonscientific.com. EPP, 2008, ePlus premium Ltd., UV Index Meter, http://www.eplus-premium.com Maddodi, N., Setaluri, V., 2008, Role of UV in Cutaneous Melanoma, Journal of Photochemistry and Photobiology,

Vol. 84, No. 2, pp. 528–536. Liu, C.M., 2000, Surface erythemally weighted UVB flux in Taiwan, Terrestrial Atmospheric and Oceanic Sciences,

Vol. 11, No. 4, pp. 879–894. HKO, 2008, Hong Kong Observatory, UV index forecast, http:.www.hko.gov.hk. WMO 2008, World Meteorological Organization, UV index, http://www.wmo.int. Gies, P., 2000, Photoprotection by clothing, Photodermatol Photoimmunol Photomed, Vol. 23, No. 6, pp. 264-274. OKI, 2008, OKI Semiconductor, ML8511 UV sensor, http://www.oki.com/.

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References UNEP, 2008, United Nations Environment Programme, UV index, http://www.unep.org/. Kramer, M., Geraldy, A., 2006, Energy Measurements for MicaZ Node, http://vs.informatik.uni-kl.de/. Vanicek, K., Frei, T., Litynska, Z., Schnalwieser, A., 2000, UV-Index for the Public, COST-713 Action (UV-B

Forecasting), Office for Official Publications of the European Communities, pp. 27. Parisi, A. V., Kimlin, M. G., Wong J. C. F., Wilson, M., 2000, Diffuse component of the solar ultraviolet

radiation in tree shade, Journal of Photochemistry and Photobiology B: Biology, Vol. 54, pp. 116–120. HKO, 2008, Hong Kong Observatory, UV index forecast, http:.www.hko.gov.hk. WMO 2008, World Meteorological Organization, UV index, http://www.wmo.int. UNEP, 2008, United Nations Environment Programme, UV index, http://www.unep.org/. Kramer, M., Geraldy, A., 2006, Energy Measurements for MicaZ Node, http://vs.informatik.uni-kl.de/. Vanicek, K., Frei, T., Litynska, Z., Schnalwieser, A., 2000, UV-Index for the Public, COST-713 Action (UV-B

Forecasting), Office for Official Publications of the European Communities, pp. 27. Parisi, A. V., Kimlin, M. G., Wong J. C. F., Wilson, M., 2000, Diffuse component of the solar ultraviolet

radiation in tree shade, Journal of Photochemistry and Photobiology B: Biology, Vol. 54, pp. 116–120. Gies, P., 2000, Photoprotection by clothing, Photodermatol Photoimmunol Photomed, Vol. 23, No. 6, pp. 264-

274. OKI, 2008, OKI Semiconductor, ML8511 UV sensor, http://www.oki.com/.