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INTRODUCTION TO THE TECHNOLOGY
HOW IT WORKS ?
TOUCH SCREEN DIVERSITY
CONTROLERS USED
APPLICATIONS
CLOSING THOUGHTS
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Touch screen is an input device that allows users tooperate a PC by simply touching the display screen.
The display screen has a sensitive glass overlay placedon it and we could give the desired input by touching it.
A touch screen is based on CRT (Cathode Ray Tube)technology, that accepts direct onscreen input.
The ability for direct onscreen input is facilitated by an
external (light pen) or an internal device (touch overlayand controller).
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Main touch screen components:Main touch screen components: Touch sensor
Controller
Software driver
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A touch screen sensor is a clear glass panel witha touch responsive surface which is placed over adisplay screen so that the responsive area of thepanel covers the viewable area of the display
screen.
The sensor generally has an electrical current orsignal going through it and touching the screencauses a voltage or signal change. This voltagechange is used to determine the location of thetouch to the screen.
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The controller is asmall PC card thatconnects between
the touch sensor andthe PC. It takesinformation from thetouch sensor andtranslates it into
information that PCcan understand.
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The driver is a software that allows the touchscreen and computer to work together. It tells theoperating system how to interpret the touch event
information that is sent from the controller.
Most touch screen drivers today are a mouse-emulation type driver. This makes touching thescreen the same as clicking your mouse at the samelocation on the screen.
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Resistive touch screen
Surface wave touch screen
Capacitive touch screen
*Surface capacitive*Projected capacitive
Near Field Imaging touch screen
Infrared touch screen
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1. Polyester
Film
2. Top Resistive
Layer
RESISTIVE TOUCH SCREENRESISTIVE TOUCH SCREEN
3. Conductive
Transparent
Metal Coating
. Insulating
Dots
6. Glass
Substrate
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Resistive touch screen monitor is composed of aflexible top layer and a rigid bottom layerseparated by insulating dots, attached to a touchscreen controller.
The inside surface of each of the two layers iscoated with a transparent metal oxide coating
Pressing the flexible top sheet createselectrical contact between the resistive layers,producing a switch closing in the circuit.
The controller gets the alternating voltagesbetween the two layers and converts them intothe digital X and Y coordinates of the activatedarea.
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Supply Voltage5.0V DC
MaximumCurrent20mA (Pick)
Resolution12-bit
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It has a transmitting and receiving transducers forboth the X and Y axes.
The touch screen controller sends a 5 MHz electricalsignal to the transmitting transducer, which converts
the signal into ultrasonic waves within the glass.
These waves are directed across the front surfaceof the touch screen by an array of reflectors.
Reflectors on the opposite side gather and direct thewaves to the receiving transducer, which reconvertsthem into an electrical signal³a digital map of thetouch screen.
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When you touch the screen, you absorb a
portion of the wave traveling across it. Thereceived signal is then compared to thestored digital map, the change recognized,and a coordinate calculated. The digitizedcoordinates are transmitted to the
computer for processing.
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Voltaze+5 VDC
Baud Rate
9600 (default) and19200
Touch Resolution12bit, size independent
Conversion Time10 ms per coordinate
set
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It has a an uniform conductive coating on a glasspanel.
During operation, electrodes around the panel'sedge evenly distribute a low voltage across theconductive layer & creates an uniform electricfield.
A finger touch draws current from each corner.
Then the controller measures the ratio of thecurrent flow from the corners and calculates thetouch location
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Supply Voltage :+5 V DC or +12V
Baud Rate:9600 (default) and
19200
Touch Resolution:12bit, sizeindependent.
Conversion Time:Approximately 15 msper coordinate set.
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3layers:- front and
back protective glass
provides optical and
strength enhancementoptions & middle
layer consists of a
laminated sensor grid
of micro-fine wires
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During a touch,capacitanceforms betweenthe finger andthe sensor grid.
The embeddedserial controllerin the touchscreen calculatestouch locationcoordinates andtransmits themto the computerfor processing.
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Public Information Displays:::Public Information Displays:::Tourism displays, Trade show display.
Customer SelfCustomer Self--Services:::Services:::Stores, Restaurants, AT Ms, Airline ticketterminals and Transportation hubs.
More uses...More uses...Digital jukeboxes, Computerized gaming, Student
Registration systems, Multimedia softwares,Scientific applications etc.
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Direct pointing tothe objects.
Fast.
Finger or pen isusable
(No cable required).
No keyboardnecessary.
Suited to: novices,application for
information retrievaletc.
Low precision byusing finger.
User has to sit orstand closer to the
screen.
The screen may becovered more by
using hand.
No direct activationto the selected
function.
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Though the touch screen technology contains somelimitations it·s very user friendly, fast, accurate,easy for the novices & fun to operate. It hasbeen widely accepted. And now by just modifying
a little it can replace the mouse and key boardcompletely in near future.
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