Touch

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Touch Free Typer ECE 445 Senior Design
Project

• Sherlyn Lim
• Matthew Schiel
• Abigail Fontes
• April 26th 2006

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What is Carpal Tunnel Syndrome?

• A disease that restricts hand movements due to
  immobilization of tendons
• Caused by stress to tendons
• Activities that result in stress
• Typing at a very high speed
• Excessive video gaming
• Playing a musical instrument vigorously

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Treatment

• Wrist brace
• Surgery
• Steroids
• Ergonomic Designs

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Motivation

• They will have constant difficulty in typing
• Our proposed solution The Touch Free Typer
• Capable of giving such individuals a means of
  typing

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Objective

• Such a Typer will be activated by light instead
  of pressure or other tactile forces
• It will detect light signals on the indicated key
  and trigger the appropriate serial key code
• This data will be sent to the computer via PS/2
  port

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Features

• Glove which emits a laser beam
• Portable - can be hooked up to any computer via
  PS/2 port
• 19 button keypad, including numbers 0-9,
  arithmetic symbols, Enter and Backspace
• Basic design can be expanded to full keyboard

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Benefits

• Requires minimum hand movements
• The beam pointing on the keys is sufficient to
  make the circuit work
• Easy, cheaper and efficient route to typing
• Recommend that a study be carried out to prove
  this

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System Overview
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Glove

• Laser emitter attached to finger tip
• Already possesses a battery, switch and circuit
  board
• 3V battery used
• Used a toggle switch to turn the emitter on and
  off

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Glove
Circuit Board
Battery Holder with 3V Battery
Laser Emitter
Toggle Switch
Glove
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Keypad Layout

• 4 columns and 5 rows of keys
• First area left open for design considerations
• For each key
• 2 rows of photodiodes
• Dimensions 2 cm by 3 cm
• For each photodiode
• Dimensions 0.9 cm by 0.9 cm

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Photodiode Quantum Efficiency

• QE Percentage of photons that will create an
  electron-hole pair
• Function of wavelength
• Radiometric Sensitivity Ratio of short circuit
  photocurrent to the energy of incident light
• QE 1240 Radiometric Sensitivity (A/W)
• Wavelength (nm)

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Calculation of VTP1188S QE

• Wavelength of red laser 670 nm
• QE (1240 0.46)
• 670
• 85
• Comparison
• CCDs gt90
• Photo film lt10

QE 85
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Sensor Circuit
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Measurements
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Simulations
4.996V
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Keyboard
5.1kO Resistor Array
Connection to PIC
SN74LS153 Muxes
VTP1188S Silicon Photodiode Array
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Controller

• PIC16F877A
• Takes its inputs from MUXes
• Determines which key has been triggered
• Sends appropriate serial code to the computer

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PIC
MJ66FJF 6-pin DIN cable
PIC 16F877A
15kO pull-up resistors and 390O current-limiting
resistors
20 MHz oscillator
Row outputs from keypad
Column select inputs to keypad
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Flowchart
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State Diagram
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Software

• Used PIC program to achieve optimal reset delay
  for key states
• Modified delay between cycles of main program
  loop
• Modified number of states before reset
• Serial output to PS/2 port required start and
  stop bits as well as a synchronized clock signal
• Programmed our own output coding (did not use
  USART or SPI on PIC)

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Implementation
Analog signal from an activated sensor
Output from oscillator 19.531 MHz
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Implementation
2 column select bits from the PIC to the MUXes (4
columns) time between select cycles 2.66 ms
Column Select bit 0 with row output from MUX
while sensor is activated
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Implementation
3 bytes transmitted for each key Make code and
Break code
Make code of 2 11 bits Time 904 us
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Implementation
Make code and break code for 6
Make and break codes for ? One extra byte
needed
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Testing Procedures

• Visual inspection to see if light from laser is
  on
• Found that a 1s time window was reasonable
• Indefinite window gets reset if and only if you
  go off key
• Accuracy effected if angle is changed
• Laser beam tested at a distance of 15ft away
• Correct character displayed when sensors are
  activated

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Design Considerations

• Time lag between the 2 sensors optimum reset
  time
• Erratic hand movements
• Size of key
• Portability of device
• Power supply

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Costs Involved
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Other Possible Applications

• Can be used on any part of the body that can be
  controlled
• Examples head, shoulder
• Possible replacement for the mouse during
  presentations

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Successes

• Able to establish communication between laser
  beam and sensors
• Circuit worked!
• Low costs maintained throughout

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Challenges

• PIC programming
• No previous knowledge of C programming language
• Tracks on PCB were too close to one another
• Implementing the correct serial format to
  communicate with the PC

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Recommendations

• Extend keypad to incorporate whole keyboard
  layout consisting of alphabets, function keys,
  arrow keys
• Extend glove unit so that laser emitters can be
  attached to all five fingers
• Carry out an in-depth clinical experiment
• Possible research project

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Conclusion

• Valuable learning experience
• Acknowledgements
• Hyesun Park
• Alex Spektor
• Peter Dragic
• All the guys at the machine and parts shops Jim
  Brownfield and Mark Wayne Smart
• PCB makers

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Questions and Comments?