1. Samuel Delesalle EP413 How Things Work Oct 12 2017
Computer Mouse
Samuel Delesalle
EP413 How Things Work
Oct

2. Introduction Brief History Different forms of mice and how they work
Transducers in a computer mouse
Hardware and Software required
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3. A Short History 1926: Joystick invented
1952 First Trackball in use, used a 5 pin bowling ball
1968 First mouse, Engelbart mouse, used two wheels
1972 Mechanical (ball) mouse become popularized
1980 Optical mouse introduced to market
1998 Laser mice developed but not popularized till 2004
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4. Mechanical Mice 3-rollers with steel ball
Each tracking rotor is attached to a 2-bit encoder
Early mice sent these logic signals directly to the computer
Later mice used internal IC
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5. Optical Mice Use an LED and an array of imaging photodiodes
Generally red or infrared LED
Early versions required special “gridded” mousepads
Thousands of pictures per second
Use CMOS sensor
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6. Photodiode Sense Electromagnetic radiation
Use p-n junction semiconductor
Photons excite electrons from valence band to conduction band
This creates an electron hole pair
When a minority charge carrier drifts to the depletion region it is swept across by the electric field resulting in a current
Silicon has a bandgap of 1.1eV ~ 1128nm
Silicon diodes operate from ~200nm -~1100nm
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7. CMOS Sensor Complementary-symmetry Metal–Oxide–Semiconductor
Uses complementary n and p type MOSFETs
An array of pixels each containing a photodiode
Scans pixels in a top to bottom range
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8. Laser Mice Very similar to Optical mice Also use imaging CMOS sensor
Use VCSEL, Vertical cavity surface emitting laser
Laser wavelength is generally infrared
Lasers penetrate surface providing a different range of mousepad materials

9. VCSEL, Vertical Cavity Surface Emitting Laser
Semiconductor laser diode
Perpendicular emission
Produces coherent photons
Quantum well holds electrons of similar energy
N-type and P-type layers act
as mirrors forming a waveguide
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10. Optical Mice Vs Laser Mice
Laser mice have a higher intensity beam resulting in higher maximum sensitivity / DPI
Laser mice see into surfaces and feel jittery at slow motions
Optical mice 1% variation
Laser mice 5% variation
Laser mice work on almost any surface
Optical mice function best on mousepads
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11. Mouse Buttons Miniature snap action switch or micro switch
3-pin switch
All or nothing response
2 conductive springs
The flat spring is held in place by the curved spring
When enough pressure is applied the flat spring starts to move
This motion reduces the force applied by the curved spring resulting in an over the center motion referred to as a click
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12. Scroll Wheel First developed in 1985, first commercial model in 1995
Potentiometers or optical encoders
Potentiometer must be able to do multiple loops
Also use a micro switch on the bottom and possibly on the sides

13. Hardware in a Mouse Microprocessors
New Logitech mouse uses a 32-bit ARM microcontroller
Runs LED screen
Use SROM, secure read only memory, newer mice are flash able for updates

14. Software Uses microprocessors to process data from optical sensor
CMOS sensor produces analog output for each pixel
These are converted into digital signals and the X and Y coordinate shifts are measured for each picture
The X and Y shifts are converted into mouse motion based on DPI settings of the mouse
Storing and controlling macros and key bindings
Control lighting
Power saving mode

15. Drivers Drivers are used for the mouse to interact with the OS
Converts I/O from the mouse to signals the computer can understand
Most Computer Mice will work without drivers but no extra features
Interact with software on the mouse
Enable special keys on the mouse
Most Games in the past 15 years use direct input

16. Wire Vs Wireless Computer Mice
In the past wired mice were faster but now wireless mice are catching up
Wireless mice need internal battery
Mice have a polling rate you can set between 125Hz and 1000Hz
Higher polling rate has a higher power draw
Monitors have a refresh rate of 120Hz and now up to 240Hz

17. Summary Many developments in the past 50 years
Optical mice and laser mice both have their own benefits
A computer mouse has many components each playing their own role
Modern computer mice require complex hard and software for optimal operation
Hardware is getting excessive

18. Questions?

19. References https://en.wikipedia.org/wiki/Main_Page
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