Prepared by : Eric Whittaker Dept. of Electrical and Computer Engineering Utah State University

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Modern Touch Screens Prepared by: Eric Whittaker Dept. of Electrical and Computer Engineering Utah State University E: ; T: (435)797-; F: (435)797-3054 (ECE Dept.) W: http://mechatronics.ece.usu.edu 3/7/2008

2. Outline • Reference list • To probe further • Major applications • Basic working principle illustrated • A typical sample configuration in application (application notes) • Major specifications • Limitations • And many more relevant issues in applications (such as, how to choose, cost information, where to buy etc.) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference list • http://en.wikipedia.org/wiki/Touchscreen • http://computer.howstuffworks.com/question716.htm • http://electronics.howstuffworks.com/iphone3.htm • http://www.mycricket.com/community/cell-phone-info/how-does-touch-screen-phone-work ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. To explore further • http://www.mycricket.com/community/cell-phone-info/how-does-touch-screen-phone-work • http://www.computerweekly.com/blogs/inspect-a-gadget/2012/02/how-do-touchscreens-work.html • http://computer.howstuffworks.com/question716.htm ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Major applications • Cell Phones • PDAs • Industrial human machine interfaces • ATMs • Point of Sale Devices • Computers • Tablets • Many others ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Basic Working Principle (1) • General idea behind all touch screens: c ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Basic Working Principle (2) • These slides will discuss only the four most popular types of touch screens: • Resistive • Capacitive • Surface Acoustic • Infrared – Heat activated • Capacitive-type screens are the most popular in todays cell phones. • Resistive-type screens are most important in ATM’s and other cheaper devices. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Basic Working Principle (3) • Resistive Screens • There is a conductive grid that monitors a change in resistance throughout the screen. • When the grid’s switch is closed, this is a contact point. d ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Basic Working Principle (4) • Capacitive Screens • There is a grid that contains an electrostatic charge; when a finger or something conductive is placed over that grid point, some of the charge is taken from the node. The change is recorded. • The computer finds the node where the touch was sensed. d ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Basic Working Principle (5) • Acoustic Screens • These screen function off of a system of acoustic transmitters and receivers. • When a finger touches the screen, the signal or sound made by the transmitter is dampened and the new sound gradient is recorded • From the recorded data, a finger position is computed. a ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Basic Working Principle (6) • Two Kinds • Heat Sensitive • Measures change in temperature • Optical • Uses a grid o beams to see interference in grid to pinpoint touch location d ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. Typical Sample Application – IPhone c ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Major Specifications • Touch Sensitivity-What can the sensor sense? • Screen Transmissivity– How much of the LCD display can be seen through the sensors? • Durability • Dependability ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Strengths (1) • Resistive Screens • Cheap • Easy to use • Capacitive Screens • Precise • Can detect double touch input • Commonplace ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. Strengths (2) • Acoustic Screens • Precise • Can accept double touch • Infrared • Can accept double touch ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. Limitations • Resistive Screens • Not very durable; screen breaks easily • Not very precise • Cannot sense double touch input • Poorer contrast when compared to other touch sensors ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Limitations (2) • Capacitive Screens • The sensed object must be conductive • Phones will not sense touch when gloves are worn • Cold weather can sometimes disturb sensing • A bit more expensive than resistive screens ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. Limitations (3) • Acoustic Screens • More expensive • Cannot sense a motionless object • Cannot sense small styli • Infrared Screens • Sunlight can disrupt the signal • For heat sensing devices, cold weather or cold hands can stymie the sensor dawg. c ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Cost Information • Priced from High to Low • Acoustic • Infrared - Optical • Capacitive • Infrared - Thermal • Resistive ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. Application Types • Cell Phones • More capacitive than infrared and some resistive and thermal. • Industrial Interfaces • Resistive • Large and Accurate Screens • Acoustic ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators