Prepared by:TRAILOKYA NATH SASAMAL


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INTRODUCATION TO THE TECHNOLOGY
A touch screen is an input device to operate a PC by a touch.

Display screen has a sensitive glass overlay placed on it .

Direct onscreen input by an external (pen) 
HOW DOES A TOUCHSCREEN WORK?
Main touch screen components:
Touch sensor
Controller
Software driver

TOUCH SENSOR
A clear glass panel with a touch responsive surface which is placed over a display screen. The responsive area of panel covers the viewable area of the display screen.

An electrical current or signal going through it. Touching the screen causes a voltage or signal change. Change determine the location of the touch.
CONTROLLER
PC card that connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand.
SOFTWARE DRIVER
A software that allows the touch screen and computer to work together.
operating system interpret the touch event information that is sent from the controller.

Touch screen drivers today are a mouse-emulation type driver.
Touchscreen Technology
Resistive Touch screen
Surface wave Touch screen
Capacitive Touch screen
*Surface capacitive
*Projected capacitive

RESISTIVE TOUCH SCREEN
Continued…
Resistive touch screen monitor is composed of a flexible top layer and a rigid bottom layer separated by insulating dots.

The inside surface layers coated with a transparent metal oxide coating
Pressing the flexible top sheet creates electrical contact between the resistive layers.

The controller gets the alternating voltages between the two layers and X, Y coordinates of the activated area.


VS20UA CONTROLLER
Supply Voltage
5.0V  DC
Maximum Current 
20mA (Pick)

SURFACE WAVE TECHNOLOGY
Transmitting and receiving transducers for both axes.

The touchscreen controller sends a 5 MHz electrical signal
Waves are directed across the front surface by an array of reflectors.

Reflectors on the opposite side gather and direct the waves to the receiving transducer.
Continued…
When we touch , we 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 calculated.
2701RSU CONTROLLER
Voltage
+5 VDC
Baud Rate
9600 (default) and 19200

Conversion Time
10 ms per coordinate set

CAPACITIVE TOUCH SCREENS  Surface Capacitive
An uniform conductive coating on a glass panel.
Electrodes around the panel's edge distribute a low voltage across the conductive layer & creates an uniform electric field.
A finger touch draws current from each corner.
Controller measures the ratio of the current flow from the corners.