In my project I tried to find how tablets and smartphones can be used in physics lessons and then how many advantages they can bring. I focused on two of the internal sensors measuring quantities. I described those two sensors to details and I figured out two experiments which could be practised at school lessons. The first sensor is an accelerometer, which is a common sensor in most portable devices and which can be used in many different ways. The second sensor is magnetic field sensor because students do not know it but it can be useful in physics lessons. #scichallenge2017

1. Our powerful devices
Use of internal sensors of tablets and smartphones in physics
#scichallenge2017 Matouš Pikous

2. What is hidden in our devices?
• Accelerometer
• Gyroscope
• Magnetic field sensor
• Proximity sensor
• Ambient light sensor
• Other sensors

3. Accelerometer
• Movable and static part
• When you move your device, the movable part rests
in its position according to Newton’s first law about
inertia.
• Capacitive Accelerometer
• Highly used in phones and tablets
• Movable and static parts are anodes and cathodes
of a capacitor. When you apply acceleration, the
distance between cathodes and anodes changes,
so does the capacity.The change of capacity can
be measured and then you can count the
acceleration.

4. Uses of accelerometer
• Measures the acceleration in
3 axis
• Gravitational acceleration
• Counts velocity and distance
(according to formula v = a . t and
distance according to formula s = v . t)

5. Magnetic field sensor
• The Hall effect sensor
• It is a tiny sheet of metal semiconductor of
two pairs of contacts.The first pair brings
current to the sheet. In magnetic field the
current goes to one side and it creates
voltage which can be measured with the
second pair of contacts.Then you can count
the magnetic flux density.

6. Uses of magnetic field sensor
• Measures magnetic flux density and
its direction
• Detects magnets
• Determines north
• Better orientation of the device

7. Gyroscope
• Measures the angular rotational
velocity
• Tracks rotation and twist
• How gyroscopes works in general
• There is a rotor with its stable axis.The heavier the
rotor is the more resistant to overturn it is and so
the more accurate it is. Change of the angle
between current position and gyroscope can be
measured. Change of the angle per time is the
angular rotational velocity of device.

8. Proximity sensor & Ambient light
sensor
• Measures proximity
between the device and
other objects
• How it works
• There is an emitter and detector.The
emitter emits infrared radiation.The
radiation reflects from nearby object.
Reflected radiation is detected by
detector. If you know the velocity of
the radiation and time of traveling
you can count the distance.
• Analyses ambient light
• How it works
• There is a photoresistor with
photoconductive layer in the device.
When a photon hits an electron in the
layer the photon gives the electron its
power. So the electron leaves its atom
and the layer becomes more
conductive. Because you know change
of the conduction, you can analyse
ambient light.

9. Other sensors
• Microphone
• Barometer
• Hearth rate sensor
• Thermometer
• Pressure sensor
• UV light sensor
• Fingerprint reader
(Depends on your device)

10. Applications
• Measures 2
• This app features 15 functions as
teslameter, decibelmeter, plumb
bob, seismometer, barometer and
altimeter

11. Applications
• Sensor Kinetics
• This app let’s you use gyroscope,
accelerometer and magnetic field
sensor. Also this app does charts of
measured values.

12. Applications
• Compass
• It is an app built in all iPhones and it
is very easy to use. It features
compass and spirit level. It can
determine geographical and true
north.
• Decibel Ultra
• This app measures volume and
frequency of sounds

13. Physics experiments

14. Measuring free fall
• Tools
• Phone or tablet with an app measuring
acceleration (I used Sensor Kinetics),
pillow.
• Workflow
• Put pillows on the floor. Launch the
app. Drop your device in one axis on
the pillow. Note the acceleration into
table. Repeat. (Most of apps show
progress of acceleration in time in
graphs)

15. Measuring magnetic flux density of the Earth
• Tools
• Phone or tablet with an app
measuring magnetic flux density in 3
axis (I used Sensor Kinetics) and app
determining the magnetic north,
paper, a pencil, a ruler, a tape, a
calculator.

16. Measuring magnetic flux density of the Earth
• Workflow
• Tape the paper on table. Put your
phone on it and launch the app to
determine geographical north. Draw a
line pointing to the north (let’s call it x).
Draw a perpendicular line (let’s call it y).
Put your device on y line so that x axis
of the phone is parallel with x line.
Launch the app measuring magnetic flux
density. Measure the values of magnetic
flux density 5 times and write down the
measurements. Count diameters. (I
recommend you to take screenshots.)

17. Measuring magnetic flux density of the Earth
• Calculation
• To count the magnetic flux density
you will need first to count the
horizontal vector from x and y values.
Bhor=√(x2+y2) Then you can count
magnetic flux density as B=√(Bhor
2+z2).
To count declination of magnetic flux
density you should use this formula:
tan𝛼 = y/x. For inclination you should
use this formula: sin𝛽 = z/B.

18. Resources
Magnetické pole [online].[cit. 2015-09-22]. Dostupné z: http://fyzweb.cz/materialy/fyzika_Zeme/magpole/magpole.php
Arduino Nano a akcelerometr [online]. 2011 [cit. 2015-09-22]. Dostupné z: http://www.josefnav.cz/images/Arduino/Akcelerometr/osy.GIF (upraveno)
Akcelerometry [online]. [cit. 2015-09-22]. Dostupné z: http://www.micro.feld.cvut.cz/home/x34ses/prednasky/08%20Akcelerometry.pdf
Smartphony mají 19 smyslů. Znáte je všechny? [online]. 2013 [cit. 2015-09-22]. Dostupné z: http://www.mobilmania.cz/clanky/smartphony-maji-19-smyslu-znate-
je-vsechny/sc-3-a-1329584/default.aspx
Techbox: váš telefon je prošpikovaný senzory [online]. 2013 [cit. 2015-09-21]. Dostupné z: http://mobilenet.cz/clanky/techbox-vas-telefon-je-prospikovany-
senzory-12496
Magnetic Field Calculators [online]. 2015 [cit. 2015-09-22]. Dostupné z: http://www.ngdc.noaa.gov/geomag-web/#igrfwmm
Magnetická indukce [online]. [cit. 2015-09-22]. Dostupné z: http://www.realisticky.cz/ucebnice/02%20Fyzika%20S%C5%A0/04%20Elekt%C5%99ina%20a
%20magnetismus/05%20Magnetick%C3%A9%20pole/04%20Magnetick%C3%A1%20indukce.pdf
Základy elektroniky [online]. [cit. 2015-09-22]. Dostupné z: http://www.spsemoh.cz/vyuka/zel/neelektricke.htm
Měření magnetického pole [online]. x, 2012 [cit. 2015-09-22]. Dostupné z: https://www.vutbr.cz/www_base/zav_prace_soubor_verejne.php?file_id=53861.
Bakalářská práce.Vysoké učení technické v Brně.Vedoucí práce Ing. Jiří Fialka.
Elektrická kapacita. Wikipedia: the free encyclopedia [online]. San Francisco (CA):Wikimedia Foundation, 2001- [cit. 2015-09-22]. Dostupné z: https://
cs.wikipedia.org/wiki/Elektrick%C3%A1_kapacita
Hallova sonda [online]. 2014 [cit. 2015-09-22]. Dostupné z: https://cs.wikipedia.org/wiki/Hallova_sonda
How a Smartphone Knows Up from Down (accelerometer) [online]. [cit. 2015-09-21]. Dostupné z: www.youtube.com/watch?v=KZVgKu6v808

19. The original project
• https://www.slideshare.net/MatouPikous/vyuziti-internich-sond-tabletu-a-chytrych-
telefonu-pri-vyuce-fyziky