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# Use of internal sensors of tablets and smarphones in physics #scichallenge2017

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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

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### Use of internal sensors of tablets and smarphones in physics #scichallenge2017

1. 1. Our powerful devices Use of internal sensors of tablets and smartphones in physics #scichallenge2017 Matouš Pikous
2. 2. What is hidden in our devices? • Accelerometer • Gyroscope • Magnetic ﬁeld sensor • Proximity sensor • Ambient light sensor • Other sensors
3. 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. 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. 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. 6. Uses of magnetic ﬁeld sensor • Measures magnetic ﬂux density and its direction • Detects magnets • Determines north • Better orientation of the device
7. 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. 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. 9. Other sensors • Microphone • Barometer • Hearth rate sensor • Thermometer • Pressure sensor • UV light sensor • Fingerprint reader (Depends on your device)
10. 10. Applications • Measures 2 • This app features 15 functions as teslameter, decibelmeter, plumb bob, seismometer, barometer and altimeter
11. 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. 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. 13. Physics experiments
14. 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. 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. 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. 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. 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. 19. The original project • https://www.slideshare.net/MatouPikous/vyuziti-internich-sond-tabletu-a-chytrych- telefonu-pri-vyuce-fyziky