touch screen full report

[seminar class]

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INTRODUCING THE TECHNOLOGY
 A touch screen is an input device that allows users to operate a PC by simply touching the display screen.
 The display screen has a sensitive glass overlay placed on 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 overlay and controller) .
HOW DOES A TOUCHSCREEN WORK?
Main touch screen components:
 Touch sensor
 Controller
 Software driver
TOUCH SENSOR
 A touch screen sensor is a clear glass panel with a touch responsive surface which is placed over a display screen so that the responsive area of the panel covers the viewable area of the display screen.
 The sensor generally has an electrical current or signal going through it and touching the screen causes a voltage or signal change. This voltage change is used to determine the location of the touch to the screen
CONTROLLER
 The controller is a small 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
 The driver is a software that allows the touch screen and computer to work together. It tells the 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 the same as clicking your mouse at the same location on the screen.
TOUCH SCREEN DIVERSITY
 Resistive Touch screen
 Surface wave Touch screen
 Capacitive Touch screen
*Surface capacitive
*Projected capacitive
 Near Field Imaging Touch screen
 Infrared Touch screen
RESISTIVE TOUCH SCREEN
1. Polyester Film .
2. Top Resistive Layer.
3. Conductive Transparent Metal Coating.
4. Bottom Resistive Layer .
5. Insulating Dots .
6. Glass Substrate
 Resistive touch screen monitor is composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touch screen controller.
 The inside surface of each of the two layers is coated with a transparent metal oxide coating
 Pressing the flexible top sheet creates electrical contact between the resistive layers, producing a switch closing in the circuit.
 The controller gets the alternating voltages between the two layers and converts them into the digital X and Y coordinates of the activated area.
VS20UA CONTROLLER
 Supply Voltage
5.0V DC
 Maximum Current
20mA (Pick)
 Resolution
12-bit
SURFACE WAVE TECHNOLOGY
 It has a transmitting and receiving transducers for both the X and Y axes.
 The touchscreen controller sends a 5 MHz electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass.
 These waves are directed across the front surface of the touchscreen by an array of reflectors.
 Reflectors on the opposite side gather and direct the waves to the receiving transducer, which reconverts them into an electrical signal—a digital map of the touchscreen
 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 calculated. . The digitized coordinates are transmitted to the computer for processing.
2701RSU CONTROLLER
 Voltaze
+5 VDC
 Baud Rate
9600 (default) and 19200
 Touch Resolution
12bit, size independent
 Conversion Time
10 s per coordinate set
CAPACITIVE TOUCH SCREENS
Surface Capacitive
 It has a an uniform conductive coating on a glass panel.
 During operation, electrodes around the panel's edge evenly distribute a low voltage across the conductive layer & creates an uniform electric field.
 A finger touch draws current from each corner.
 Then the controller measures the ratio of the current flow from the corners and calculates the touch location
5000 RSU SERIAL CONTROLLER
 Supply Voltage :
+5 V DC or +12V
 Baud Rate
9600 (default) and 19200
 Touch Resolution
12bit, size independent.
 Conversion Time
Approximately 15 ms per coordinate set
Projected Capacitive Touch screen
3layers:-front and back protective glass provides optical and strength enhancement options & middle layer consists of a laminated sensor grid of micro-fine wires
 During a touch, capacitance forms between the finger and the sensor grid.
 The embedded serial controller in the touch screen calculates touch location coordinates and transmits them to the computer for processing.
APPLICATIONS..
 Public Information Displays:::
Tourism displays, Trade show display
 Customer Self-Services:::
Stores, Restaurants, ATMs, Airline ticket terminals and Transportation hubs.
 More uses...
Digital jukeboxes, Computerized gaming, Student Registration systems, Multimedia softwares , Scientific applications etc.
Pros & Cons
 Direct pointing to the objects.
 Fast
 Finger or pen is usable (No cable required)
 No keyboard necessary
 Suited to: novices, application for information retrieval etc
 Low precision by using finger
 User has to sit or stand closer to the screen
 The screen may be covered more by using hand
 No direct activation to the selected function
CLOSING THOUGHTS
Though the touch screen technology contains some limitations it’s very user friendly, fast, accurate, easy for the novices & fun to operate. It has been widely accepted. And now by just modifying a little it can replace the mouse and key board completely in near future.