TOUCH SCREEN

SENSOR

Created By:- VIKRAM TYAGI

SHAHNUL HAQUE CHOUDHURY

CS IInd YEAR

How Does a Touchscreen Work?  A basic touchscreen has three main components:

1. Touch sensor.

3. Software driver.

2. Controller.

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

What is TOUCHSENSOR ?? “A Touchscreen is a display which can

detect the location of touches within the display area. This allows the display to be used as an input device, removing the keyboard and/or the mouse as the primary input device for interacting with the display's content.”

CONTROLLER

The controller connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand. The controller determines what type of interface/connection you will need on the PC. Controllers are available that can connect to a Serial/COM port (PC) or to a USB port. Specialized controllers are also available that work with DVD players and other devices.

SOFTWARE DRIVERThe driver allows the touchscreen and computer to work together. It tells the computer's operating 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 as same as clicking your mouse at the same location on the screen. This allows the touchscreen to work with existing software and allows new applications to be developed without the need for touchscreen specific programming.

TOUCHSCREEN TECHNOLOGY

RESISTIVE

CAPACITIVE

INFRARED

SURFACE ACOOUSTIC WAVE (SAW)

RESISTIVE TOUCHSCREEN

Composed of several layer including two metallic layers separated from each other.

When metallic layers are connected (touched) change in voltage occurs.

Change in electric current is sent to controller and the location is determined.

CHARACTERS :-

Cost effective solutions .

Activated by a stylus, a finger or gloved hand.

Not affected by dirt, dust, water, or light .

75%~85% clarify.

Resistive layers can be damaged by a very sharp object.

CAPACITIVE TOUCHSCREEN Coated with a current conducting material. Sensor has a precisely controlled field of

stored electrons in horizontal and vertical directions.

Humans also exhibit capacitance. A controller detects when there is a

disturbance in the electric field (touch). The controller then determines the location.

WORKING• During a touch, capacitance forms between the

finger and the sensor grid. The embedded serial controller in the touchscreen calculates touch location coordinates and transmits them to the computer for processing.

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

CHARACTERS :-

Durable and resistant to scratches for demanding applications .

Faster and more responsive.

Immune to surface contaminants .

Superior optical clarity, brighter display and less surface reflection .

Must be touched by finger, will not work with any non-conductive input .

INFRARED TOUCHSCREENInfrared (IR) technology relies on the interruption of an IR light grid in front of the display screen. The touch frame contains a row of IR-light emitting diode (LEDs) and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light.

The IR controller sequentially pulses the LEDs to create a grid of IR light beams. When a stylus, such as a finger, enters the grid, it obstructs the beams. One or more photo transistors from each axis detect the absence of light and transmit signals that identifies the x and y coordinates.

CHARACTERS :-

Clear as glass.

Most durable surface.

Improves reading ability.

SAW TOUCHSCREEN

Surface waves are readily absorbed when a soft object such as a fingertip touches the substrate. SAW Touch Screen use pure glass with transmitting and receiving piezoelectric transducers for both the X and Y axes.

The touch screen controller sends an electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass.

When you touch the screen, you absorb a portion of the wave traveling across it. The received signal is then compared to the stored digital map, the change recognized, and a coordinate calculate.

CHARACTERSDurable glass construction.

High optical clarity.

Activated by a finger, gloved hand or soft tip.

Not completely sealable, can be affected by large amounts of dirt, dust, and / or water in the environment.

COMPARISONTECHN-OLOGY

Transparence

Resolution

Durability SensorSubstrate

DisplaySize

TouchMethod

RESISTIVE 75-85% Good Resistant to moisture but not to scratches.

Polyester top,glasssubstrate with ITO coating.

Upto 19” Can use any pointing device.

CAPACITIVE >92% Good Resistant. Glass with ITO coating.

Upto 21” Human Touch.

INFRARED >92% Limited Resistant Any substrate

Upto 60” Can use any pointing device.

SAW >92% Good Adversaly affected by moisture.

Glass with ITO coating.

Upto 30” Finger,Gloved Tip.

CURRENT USES -ATMs, Self Checkout Counters, Airport Check-in, etc.

PDAs

Tablet PCs

Mobile Phones

Handheld Gaming Consoles

MULTI TOUCH TECHNOLOGYMulti-touch is a method of input on a touchscreen that allows two or more fingers to be used on the screen at one time. It allows pinching and stretching gestures on the screen to control zooming. Multi-touch is something typically associated with capacitive touchscreen displays rather than with more common resistive touchscreen displays.

References:-

http://en.wikipedia.org/wiki/Touchscreen

http://www.touchscreens.com/intro-anatomy.html

Research Note on Touch Screen Sensors by Andrew Nathanson

http://www.wisegeek.com/what-are-touch-screen-monitors.htm