A Wireless Embedded Device For Personalized
Ultraviolet Monitoring
Navid Amini
Jerrid Matthews
Alireza Vahdatpour
Foad Dabiri
Hyduke Noshadi
Majid Sarrafzadeh
1
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.
2
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).
3
Summary
 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
4
Did You Know?
 The skin is the largest organ of the body
 Most 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).
5
UV Index
The 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.
Relative Response (Wn)
1.00E+00
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
1.00E-01
1.00E-02
1.00E-03
1.00E-04
250
270
290
310
330
350
370
390
410
Wavelength (nm)
where E λ is the solar spectral irradia nce

2
1
ex
p
ressed
in
W/(m
·nm
) at wavelength λ
400nm

UVI  ker .  E .ser ( )d , ser() is the erythema reference action spectrum
250nm
k is a constant equal to 40 m 2 /W
 er

6
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.
UVI Versus Location
1. 85% increase from snow reflection
2. 100% increase at 3000m altitude
3. 25% increase from white-water
reflection
4. 80% of UV rays pass through cloud
5. 20% from sand and grass
reflection - and 40% when wet
6. 15% reflection from concrete
buildings
7. 50% can be reflected into shaded
areas
8. 50% UVB and 80% UVA passes
through the upper 50cm of water
9. 50% increase from water reflection
http://www.socialuvwatcher.com/
8
Schematic Diagram
Personal UV
Monitor Software
UV Index Data
OKI ML8511
Current
Nokia N95
Rf
Op-amp
10-bit
ADC
Output
Voltage
EN
UV Sensor
I/O
MicaZ Mote
MCU
Bluetooth
Adapter
Atmel
ATmega
128L
Roving
Networks
RN-24
Components: UV Sensor
 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.
http://www.socialuvwatcher.com/
ML8511 from OKI Semiconductor
Introduced 8 months ago
10
Components: UV Sensor
 Features
ML8511 from OKI Semiconductor
 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
http://www.socialuvwatcher.com/
11
Components: UV Sensor
Sensitivity (Relative Value)
1.25
1
0.75
0.5
0.25
0
280
320
360
400
440
480
520
560
600
Wavelength (nm)
Spectral sensitivity characterisitics of the ML8511.
http://www.socialuvwatcher.com/
12
ADC Output and Corresponding UV Indices
(Vcc = 3.0 V)
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.
Sensor output
voltage
ADC
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
 ADCOUTPUT  320 
UVI  (
)  0.2.
5


13
The flowchart of the software
Start
No
Current UV?
(or
accumulated
UV)
Yes
Enter the period of
time (1 to 3 for day,
week and month)
Enter the skin type
(1 to 4)
If you use a sunscreen,
the exposure time will
be multiplied by the sun
protection factor (SPF)
of the applied
sunscreen.
Enter your
sunscreen’s SPF
Read the Bluetooth
data (current UVI)
T = Maximum
recommended
exposure time
Show the UV history
and total UV
exposure
Maximum Exposure Algorithm:
Exposure Time * SPF
Is
SPF = 0?
No
T = T × SPF
Yes
Show current UVI
and T
End
14
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
1
White, always
burns, never tans
2 hecto
J/m2
67 min / UVI
2
Yellow and white,
usually burns,
sometimes tans
4 hecto
J/m2
100 min / UVI
3
Yellow and black,
sometimes burns,
usually tans
5.75 hecto
J/m2
200 min / UVI
4
Black, rarely
burns, always tans
8.5 hecto
J/m2
300 min / UVI
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].
15
Experimental Results
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
UV Dose = Average UV × Exposure time.
Energy Consumption
Average power consumption for different parts of
personalized UV monitoring device.
Operation /
component
Sensing / UV
sensor
Processing /
microcontroll
er
Communicati
on / Bluetooth
adapter
Average power
Sensing mode: 900
µW
Standby mode: 0.3
µW
Busy mode: 29.95
mW
in this embedded device, we achieved
an energy saving of up to 60% in the
sensing part as opposed to an alwayson sensor system
Idle mode: 14.88 mW
Connected mode: 120
mW
Idle mode: 3 mW
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.
17
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).
18
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.
19
References
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References
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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.
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OKI, 2008, OKI Semiconductor, ML8511 UV sensor, http://www.oki.com/.
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