ECDC Embedded

8/7/2019 ECDC Embedded

http://slidepdf.com/reader/full/ecdc-embedded 1/21

Current touch-pad

Technologies

An overview of the problemstatement



Problem statement

• To design a touchpad for a computer/laptop which thus includes both hardware and softwarepart

• Implementing features such as multi-touch andother user friendly features such as zoom in/out

shall be considered at utmost level.



Restrictions

• One is not allowed to add hard wares or soft wares which involve image processing

• The hardware should not contain any specialIC’s except 8 bit microcontrollers and otheressential IC’s like LDO, Buffers. Any other IC’s if necessary should be intimated to thecoordinators before use.



Current touch pad technologies

• Underlying principle- Human Finger - The tissue of the human body is filled

with conductive electrolytes covered by a layer of skin,a lossy dielectric.

Other Examples - Stylus but not pen

• In modern world prevalent touch sensorsare Resistive touch

Capacitive touch

Infrared touch

SAW (Surface Acoustic Wave) Touch



Resistive touch

• Sensor has two layers–not in contact▫ An outside flexible layer, coated on

the inside with a conductor, e.g. ITO,

(Indium Tin Oxide),▫ non-conductive separator "dots",

e.g. mica or silica, small enough tonot be noticeable,

▫ an inside supporting layer of glass,coated on its face with conductor(ITO).

• Around the outside of the viewing

area is a printed circuit pattern.



Resistive touch

• WorkingRefer to the diagram givenalongside

• Pros▫ Simple and inexpensive

• Cons▫ Requires pressure for

touch▫ Reduces visibility by 10-

20%



Capacitive touch

• Idea exactly similar toresistive touch

• Though it has just one

coated layer.• Working



Capacitive touch

• Pros

▫ Since single layer no pressure, and more brightness

• Cons

▫ Little expensive because of the touch detectiondevice



Infrared touch

• Infrared touch consists of ▫ a glass face in front of the LCD

to touch down on,

▫ Emitters/sensors along all

four edges of the viewing area, built into a raised bezel.

• The sensor simply detects when

the beam is broken/changed when a finger or other objectenters the space.



Infrared touch

• Pros▫ Can support any object touch

▫ No contact pressure

▫ Long life device

• Cons

▫ Raised bezel increases thickness

▫ Cannot be used in areas where darkness isrequired



SAW Method

• Method uses▫ Ultrasonic pulses▫ piezo-electric crystals

bonded to the glass,

▫ Reflectors• Working▫ When the finger touches the

glass, some of the sound isabsorbed or redirected. The

separate sensors see thiseffect differently, so theposition of the touch can becalculated.



SAW Method

• Pros

▫ No coating hence no obstruction to light

▫ Operational even at high temperature

• Cons

▫ Expensive

▫ Glass needs to be loosely fitted so that all soundenergy is not absorbed



Feasible touch pad technologies

In this section we shall try to bring down currenttouch sensor based technologies to feasiblemethods that can help in solving the problemstatement



Wire grid detection

• A vertical set of wires carrying +1 separated by anon conducting sheet with holes overlapped by aset of horizontal wires serving as input.

Outputlines

Shortdetecting lines



Wire grid detection

• Working

▫ The paper helps in keeping distance between the

output and input wires thus preventingunnecessary short and whenever one touches ashorting occurs at the place of the hole in thepaper thus detecting a touch



Led as a sensor• Photovoltaic operation of LED

• The IN pin is an ADC which showsapproximately 3.3 V in dark and 0 in full brightness

Refer to the video



Human Charge

• The charge in a human body can be amplifiedusing amplifiers and brought within logicalrange

• One can use a potentiometer at the output to bring touch in logical range



Infrared Touch

• Infrared touch ( discussed in the previous slides)can also be used along with TSOPs to work as amulti-touch screen.



Controlling keyboard and mouse

• Programming drivers of mouse or keyboard is a very tough task

• At this point MATLAB/java comes to our aid.



Robot class

• It is inbuilt java class that helps control mouseand keyboard

• For details visit:▫ http://www.mathworks.com/support/solutions/e

n/data/1-2X10AT/index.html?solution=1-2X10AT

http://www.mathworks.com/support/solutions/en/data/1-2X10AT/index.html?solution=1-2X10AT










Comments

• For details and explanation of the pointsmentioned in the presentation stay tuned for thelecture that shall be conducted in first week of

January whose videos shall be uploaded

• For any suggestions, comments or queries dropin a mail at [email protected]

• Hope you found it informative!!!

mailto:[email protected]

mailto:[email protected]

ECDC Embedded

Documents

Transcript of ECDC Embedded