TOUCH SCREEN TECHNOLOGY
What is a touch screen?What is a touch screen?
An electronic visual An electronic visual display that locates display that locates the coordinates of a the coordinates of a users touch within users touch within display areadisplay area
Works independently Works independently of what is being of what is being displayed on screendisplayed on screen
TOUCH SCREEN TECHNOLOGY
Four different technologies used to make touch screens today: Resistive
Capacitive
Surface Acoustic Wave (SAW)
Infrared LED or Optical
RESISTIVE SYSTEM
Consists of a glass panel with two layers, conductive and resistive metallic layers
Electrical current runs between both layers when operational
The two layers make contact when touched, sending coordinates to the driver
RESISTIVE TOUCH SCREENS
Two layers of Two layers of conductive conductive materialmaterial
Touch creates Touch creates contact between contact between resistive layers resistive layers completing circuitcompleting circuit
RESISTIVE TOUCH SCREENS
Voltage in Voltage in circuit changes circuit changes based on based on positionposition
Controller Controller determines determines location based location based on voltageson voltages
Any material Any material can trigger can trigger sensorssensors
RESISTIVE SYSTEM
• Examples:Examples: Palm Pilot PDAs Palm Pilot PDAs
Certain GPS systems Certain GPS systems
CAPACITIVE TOUCH SCREENS
Glass panel with Glass panel with conductive layer conductive layer (Indium Tin Oxide)(Indium Tin Oxide)
Small amount of Small amount of voltage applied to voltage applied to four corners of four corners of touch screentouch screen
CAPACITIVE TOUCH SCREENS
Touch draws minute Touch draws minute amount of current amount of current creating voltage dropcreating voltage drop
Coordinates of point of Coordinates of point of contact calculated by contact calculated by controllercontroller
CAPACITIVE SYSTEM
One layer that stores electrical charges on the panel
When touched with a finger, the electrical charge is transferred to user
Computer then coordinates where touch took place
WHAT CAN TRIGGER THE SCREEN?
~ Resistive
- Anything from a finger to a pen
~ Capacitive
- Only things with a conductive
input
PricePrice ClarityClarity Damage Damage Resistance Resistance
ResistiveResistive CheapestCheapest Low ClarityLow Clarity Easiest to Easiest to damage with damage with sharp objectssharp objects
CapacitiveCapacitive More More expensiveexpensive
High ClarityHigh Clarity Less prone to Less prone to damage by damage by sharp objectssharp objects