Sensors

1
Sensors

• TED 384
• Computer Applications in Industry (Robotics
  Education)

2
What are they?

• Sensors help translate physical world attributes
  into values that the computer on a robot can use.
• The translation produces some sort of output
  value that the microcontroller can use.
• http//www.seattlerobotics.org/encod
  er/jul97/basics.html

http//www.gssr.net/communication/images/sensors.j
pg
3
Catagories

• Analog Sensors
• Analog signal measures continuous quantities
  between 0 and 5 volts, such as voltage, current,
  gas pressure, temperature, humidity, light,
  position, force, magnetic field, vibration, etc.
• http//www.active-robots.com/
  products/phidgets/phidgets/Sensors.pdf
• Might be wired into a circuit
• Works like a tuner which can be fine tune by
  turning a knob

http//www.seattlerobotics.org/encoder/jul97/basic
s.html
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Categories

• Digital Sensors
• Generate discrete signals
• A range of values that the sensor can output, but
  the value must increase in steps
• Push button switch
• On or off
• Digital compass
• 9 bit value ranging from 0 to 359

http//www.seattlerobotics.org/encoder/jul97/basic
s.html
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Types of Sensors

• Touch
• Light
• Line Tracking
• Sound
• Optical Shaft Encoders
• Ultrasonic Range Finders
• Tilt

http//www.phytech.co.il/products/images/sensors.g
if
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Touch Sensors

• Completes a circuit that allows electrical signal
  to flow back to the microprocessor indicating
  that the touch sensor has been pressed in

http//www.legoedwest.com/page.php?25
7
Light Sensors

• Output is the inverse of the light level, but
  restricted to fairly narrow current range
• The brighter the light the lower the value
  measured

http//www.generation5.org/content/2004/images/leg
way-ledemit.jpg
8
Line Tracking
http//www.medicine.mcgill.ca/EXPMED/LTSM/photo/20
05/Photos/Slide33.PNG
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Sound Sensors

• Measures sound pressure up to 90 dB, about the
  level of a lawnmower
• The lower the percent the quieter the sound
• 4-5 Silent living room
• 5-10 Someone talking at a distance
• 10-30 Normal conversation close to the sensor
• 30-100 People shouting or music played at a high
  level

www.kidtechnic.com/images/NXT/sensors/sound.jpg
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Ultrasonic Range Finders

• Enables the robot to detect objects, avoid
  obstacles, sense and measure distance, detect
  movement
• Measures in inches and cm precision 3 cm
• Like bats calculates the time it takes for a
  sound wave to hit an object and return, like an
  echo

www.kidtechnic.com/images/NXT/sensors/sound.jpg
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Parallax
http//www.milinst.com/robotics/5_125s.jpg
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Optical Shaft Encoders

• Infrared light sensor and infrared LED
• Measures distances, position and motion sensing,
  increases navigation control
• Greater precision and control

http//www.vexlabs.com/vex-robotics-optical-shaft-
encoder-kit.shtml
13
Tilt Sensors

• Extremely accurate pitch and roll measurements
• WowWee uses a trapped ball bearing
• When tilted the bearing closes the circuit
  between two contacts
• Output that is proportional to rotation
• Shown here 10 to 80 travel

Angle Tilt
Rotary
http//www.positek.com/rotary.htm