Touchscreen 29

7/31/2019 Touchscreen 29

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Submitted By :-Md Nazish Aslam

0832EC071029

Submitted To :-Mr. Amit Malik

DEPARTMENT OF ELECTRONICS & COMMUNICATION

SEMINAR

ON

TOUCHSCREEN TECHNOLOGY


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INTRODUCING THE TECHNOLOGY

HOW DOES A TOUCHSCREEN WORK?

TOUCH SCREEN DIVERSITY

COMPARISON

APPLICATIONS

CONCLUSION


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A visual display unit screen that allows the user to givecommands to the computer by touching parts of the screeninstead of using the keyboard or a mouse.

The display screen has a sensitive glass overlay placed on itand 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.


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A basic touchscreen has three main components:1 Touch sensor;

2 Controller;

3 Software driver.

The touchscreen is an input device, so it needs to becombined with a display and a PC or other device to make acomplete touch input system.


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A touch screen sensor is a clearglass panel with a touchresponsive surface which isplaced over a display screen sothat the responsive area of thepanel covers the viewable areaof the display screen.


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The controller is asmall PC card thatconnects between the

touch sensor and thePC. It takesinformation from thetouch sensor andtranslates it intoinformation 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 the

screen the same as clicking your mouse at the samelocation on the screen.


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Resistive Touch screen

Capacitive Touch screen

*Surface capacitive

*Projected capacitiveSurface Acoustic wave (SAW) Touch screen

Near Field Imaging Touch screen

Infrared Touch screen


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Resistive touch screen monitor iscomposed of a flexible top layerand a rigid bottom layer separatedby insulating dots, attached to atouch screen controller.

The inside surface of each of thetwo layers is coated with atransparent metal oxide coating

Pressing the flexible top sheetcreates electrical contact betweenthe resistive layers, producing a

switch closing in the circuit. The controller gets the alternating

voltages between the two layersand converts them into the digital

X and Y coordinates of theactivated area.


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(Reading a 4-Wire Screen)


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StructureSurface capacitive technology consists of auniform conductive coating on a glass panel.

Electrodes around the panels edge evenlydistribute a low voltage across the conductivelayer, creating a uniform electric field.


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Working principleA human body is an electric conductor, so when you touch the screen witha finger, a slight amount of current is drawn, creating a voltage drop. Thecurrent respectively drifts to the electrodes on the four corners.Theoretically, the amount of current that drifts through the four electrodesshould be proportional to the distance from the touch point to the fourcorners. The controller precisely calculates the proportion of the currentpassed through the four electrodes and figures out the X/Y coordinate of atouch point.


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Infrared (IR) technology relies on theinterruption of an IR light grid infront of the display screen. The touchframe contains a row of IR-lightemitting diode (LEDs) and photo

transistors, each mounted on twoopposite sides to create a grid ofinvisible infrared light.The IR controller sequentially pulsesthe LEDs to create a grid of IR lightbeams. When a stylus, such as a finger,

enters the grid, it obstructs the beams.One or more photo transistors fromeach axis detect the absence of lightand transmit signals that identifiesthe x and y coordinates.


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Technology Capacitive SAW Infrared ResistiveTransparence Very good >92% Very good >92% Very good >92% 75%~85%Resolution Good Good Limited due to

spacing of IR

sensorsgood

Surface

Contaminants/durability

Resistant to

moisture andother surface

contaminants

Adversely

affected bymoisture or

Surface

contaminants

Potential for

False activationor dead zones

From Surface

Contaminants

Unaffected by

Surfacecontaminants.

Polyester top

sheet is easily

scratchedSensor substrate Glass with ITO

coating Glass with ITO

coating Any substrate Polyester top

sheet, glasssubstrate with

ITO coatingDisplay size 8.4"-21" 10.4"-30" 10.4"-60" up to 19"Touch method Human touch finger, gloved

hand or soft tipCan use any

pointing device Can use anypointing device

Comparison


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The user must sit within arms reach of the display

Possible arm fatigue

Difficult to select small items

Possible retrofit problem (the touch screen must be fitted

on the screen)

Limitations:


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Public Information Displays:::Tourism displays, Trade show display

Customer Self-Services:::

Stores, Restaurants, ATMs, Airline ticketterminals and Transportation hubs.

More uses...

Digital jukeboxes, Computerized gaming,Student Registration systems, Multimediasoftwares , Scientific applications etc.


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Though the touch screen technology containssome limitations its very user friendly, fast,accurate, easy for the novices & fun to operate.It has been widely accepted. And now by justmodifying a little it can replace the mouse andkey board completely in near future.


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Any queries???

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Touchscreen 29