The document discusses various sensors used in mobile phones. It describes proximity sensors which detect how close the phone is to the user's face and turn off the screen to save battery during calls. It also explains GPS sensors which track location using satellites, ambient light sensors which adjust screen brightness based on light levels, accelerometers which detect orientation changes, compass sensors which indicate direction using magnetism, gyroscopes which detect motion, and back-illuminated image sensors which improve low-light photography. These sensors power many smart features in phones and help differentiate them from conventional devices.

1. DEPARTMENT OF ELECTRONICS AND TELECOMMUNICATION ENGINEERING
(2015-2016)
TAE- 1
Activity Based Learnig
Subject:
“Sensor and Transducer”
TOPIC
“Mobile Sensors”
Year/Semester:
3rd Year | 6th Sem
Guided By:
Prof. Abhijit S. Titarmare
Assistant Professor
Submitted by:
Ashish M. Pandey (C- 30)

2. Introduction to Sensors
Since the beginning of race in mobile communication, a new model is being launched every day
into the world with different features. These new features and specifications gain enough fame of
users to survive in the competition of mobile technology. Today different manufacturers like
Samsung, Apple, Sony, HTC and many more manufactures of smartphones and became
competitors. One of the feature that attracts the mobile phone buyer is the smart work it does.
Different types of sensors like accelerometer, ambient light sensor, GPS sensor, compass, proximity
sensor, pressure sensor, gyroscope etc are behind these smartphones. Let us understand how each
sensor works with respect to its operating principle.
ProximitySensors
The main function of this proximity sensor is to detect how close your smartphone's screen is to
your body. When you use your smartphone, it detects the position of ear with respect to screen
and turns off the light of screen and saves battery. Also proximity sensor stops the accidental
touch, unwanted input during talk. This sensor also detects the signal strength, interference sources
and amplify or filter by use of Beam Forming Technique. Thus, in a nutshell, proximity sensor detect
the presence of body like cheek, face or ear and stops the web surfing, music or video during
talk/calling and save the battery. After the conversation, it resumes the same function which was
stopped earlier during talk.
GPS (Global Positioning System) sensor
GPS short form of Global Positioning System, originally developed and setup for military operations
and was made available for everyone in 1980s by Government. GPS is a system which tracks the
target or 'navigate' the things by map or picture with the help of GPS satellites. Nowadays
smartphones come with assisted GPS or A-GPS which does the same work with the help of
intermediate server in case of disconnection with main GPS satellite. iPhone 4S, iPhone 5, HTC One,
HTC Droid DNA, HTC One X, Samsung Galaxy series smartphones, Sony Xperia,Nokia
Lumia 620,820,920 and 822 and many more smartphones support GLONASS (Globalnaya
Navigatsionnaya Sputnikovaya Sistema) GPS system for navigation purpose.
Ambient Light Sensor
This sensor optimize the light of screen when it exposed to normal light with different intensity.
Ultimate function of ambient light sensor is to adjust the display brightness, which at the end saves
the battery power and life too. Ambient light sensor senses and adjust the light based on principle
of "superposition". They contains photo diodes which are sensitive to different spectrum of light
and combined mathematical effect adjusts the gain and output changes of the light intensity on
the screen.

3. Accelerometer Sensor
The main function of accelerometer is to sense the changes in the orientation of smartphone with
respect to datum and adjust the orientation to suits the viewing angle of operator. For example,
when you are looking for web-page with increased width, you can get this landscape view from
changing the orientation of phone to horizontal. Similarly camera mode also changes the portrait
to landscape or landscape to portrait mode when we change the orientation of phone/camera.
Ultimately this accelerometer sensor sense the change in orientation by 3D (X,Y & Z axis)
measurement of acceleration of the device with respect to free fall. One can better use this
feature/sensor while playing racing games where he/she can steer the car in the desired direction
by leaning the phone in that direction.
Compass Sensor
We all know that the function of compass is to give right direction with respect to the north-south
pole of earth by use of magnetism. But due to interference in communication, smartphone does
not use the magnet as one of the component in compass sensor but it uses new technology which
does the same work as conventional compass does. If ultra low frequency signal coming from
specific direction like North or South and with the help of accelerometer, the sensor can calculate
the orientation and direction. This can be possible by 'Hall effect'. Thus, by use of multiple sensors
put across different orientation and using disk/magnetic concentrator (with high permeability
material)which bends the lines of magnetic field which are parallel to the plane of sensor plane this
can be attained.
GyroscopeSensor
This sensor's function is to maintain and control the position, level or orientation based on the
principle of angular momentum. When 'Gyros' used along with accelerometer senses motion from
six axes i.e. right, left, up, down, forward and backward. It also detects the roll, pitch and yaw
motions. Yaw, Roll and Pitch are the angular moments seen from three axes i.e. X, Y and Z. Using
MEMS(Micro Electrical and Mechanical System) technology, (iPhone 4 uses this technology)
gyroscopic sensors helps in navigation purpose and detecting the gesture recognition systems
used in smartphones and tablets.
Back Illuminated Sensor
Back-illuminated sensor is one of the new feature that every camera contains. It is a type of digital
image sensor which changes or increase the light captured while capturing a photograph. Earlier it
was designed for security cameras and astronomical purposes. Sony is the first company to
implement this technology in 2009.
Thus, at the end, one can say all these sensors serve as the back-bone of recently developed
smartphones and also Quick Response (QR)Code, Data Encryption and these smart sensors made
our conventional phone become Smart.