1 Clever Pointer Device Samer Aamar Post PC Course – 2002.
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Transcript of 1 Clever Pointer Device Samer Aamar Post PC Course – 2002.
2
It would be great to be able to…
move next/previous without the need to be near your PC/Laptop
mark important words / draw basic shapes (circles, arrows, etc.) with his pointer device
press on buttons on the screen, activate shortcuts, surf in WEB…
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How does it work?
The pointing device will plot a virtual ray! The intersection with the projection screen
will be calculated (3D space) The computer will translate the intersection
3D point into a 2D point on the screen. Mouse Move events will be fired to the
system
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Some mathematics
The points p1, p2 are in 3D space The ray vector p2-p1 It would be easy to calculate the intersection point with the
screenBUT, before all
the coordinates of the projection screen should be defined
p1 p2
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Components
Basic components:
2 Tri-Axis Accelerometers
Three buttons
Transmitter/Receiver (wireless)
3D Accelerometers
buttons
Transmitter
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Buttons
The device has three buttons: ‘Activate’ button:
When down the MOUSE_MOVE event is fired
‘LButton’ / ‘RButton’ button: samples the Left/Right Button on the regular
mouse
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Accelerometers
We need: 3-Axis Accelerometer
MEMS (Micro Electro Mechanical Systems) Acc. :SmallLight
Ability to measure hand motion (next slide)
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Measuring Hand Motion
Parameter Target Value
Frequency Range 0.1 to 25 Hz
Acceleration Amplitude +/- 5 g
Acceleration Resolution 1 mg
g ~ 9.8 m/sec2
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Accelerometers (II)
Good enough (according to the sheets)
Analog Device iMEMS accelerometers ADXL105 ADXL150
Microsystems Technology Laboratory (MTL) 3-Axis accelerometers:
TG Series Accelerometers: CXL10TG3 (crossbow tech.) ACCELEROMETERS by Vernier
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Analog Devices Performance
Resolution of ADI accelerometer sensors over
time
Cost of performance in ADI accelerometer sensors
over time
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Relevant Thesis
Graham B.; Using an Accelerometer Sensor to Measure Human Hand Motion; Massachusetts Institute of Technology; 2000.
He achieved the following: Frequency: 0.1 – 25 Hz Amplitude: ±10g Mass: 4.88 grams Size: (17mm)^3
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Transmitter/Receiver
Frequency: 25 Hz
Data (bits): 2 x 3 x 32 (X, Y, Z) 3 (buttons)
Total (per second)25 x 194 = 4850 = 4.8 Kb per sec
PossibilitiesBluetooth – too much!Radio transmitter/receiver – simple: 10 Kb per sec is OK!
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Summary
Required Existing
3-Axis Accelerometers
Three single-axis accelerometers (Analog Devices)
Receiver/Transmitter Radio
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Open Issues!
CPU Consuming? Sudden movements – like sharply putting the
device on the table (20g) What happens if the connection between
transmitter and receiver was interrupted temporarily for some reason (example by moving to another room)
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Related Sites
http://www.analog.com http://shop.store.yahoo.com/crossbow/index.html http://www-mtl.mit.edu/MEngTP/Graham_Thesis.pdf