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

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

CAPACITIVE SYSTEM

CAPACITIVE SYSTEM

Examples:

- Ipods, Ipads, Iphones etc…

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