Our power ful devicesUse of internal sensors of tablets and smartphones in physics

#scichallenge2017 Matouš Pikous

What is hidden in our devices?

• Accelerometer

• Gyroscope

• Magnetic field sensor

• Proximity sensor

• Ambient light sensor

• Other sensors

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.

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)

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.

Uses of magnetic field sensor

• Measures magnetic flux density and its direction• Detects magnets• Determines north• Better orientation of the device

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.

Proximity sensor & Ambient lightsensor

• 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.

Other sensors• Microphone

• Barometer

• Hearth rate sensor

• Thermometer

• Pressure sensor

• UV light sensor

• Fingerprint reader

(Depends on your device)

Applications

• Measures 2 • This app features 15 functions as

teslameter, decibelmeter, plumb bob, seismometer, barometer and altimeter

Applications

• Sensor Kinetics • This app let’s you use gyroscope,

accelerometer and magnetic field sensor. Also this app does charts of measured values.

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

Physics experiments

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)

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.

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.)

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=√(Bhor2+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.

ResourcesMagnetické pole [online].[cit. 2015-09-22]. Dostupné z: http://fyzweb.cz/materialy/fyzika_Zeme/magpole/magpole.phpArduino 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.pdfSmartphony 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

The original project

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