Transcript What you need to know about Sensors

Sensors you should know
about
Thomas Edwards
http://www.t11s.com
Passive Infrared (PIR) Sensor
• Detects motion of warm
moving objects
• If nothing is moving, there is
no detection
• Commonly used in security
systems
• Very Long range (50 feet)
• Binary or relay opening output
• ~$10
http://www.mpja.com/directview.asp?product=15840+SC
http://www.parallax.com/detail.asp?product_id=555-28027
Microwave Motion Detector
• Uses microwave doppler
shift to detect motion
• Range 10 feet
• May have fewer “false
positives” than PIR detectors
• ~$35 kit
http://www.ramseyelectronics.com/cgibin/commerce.exe?preadd=action&key=MD3C
Active IR Sensors
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Bounces invisible IR beam off of target
Uses triangulation to determine distance
Range up to 5 feet
Analog distance output or binary fixed range
detection output
• ~$10-$20
http://www.acroname.com/robotics/parts/c_Sensors.html
Ultrasonic Sensors
• Uses travel time of sound echos to
detect distance
• Range up to 15 feet
• Outputs can be analog, serial, or
PWM
• Old, expensive Polaroid sensor
• New, cheaper ones today ~$25
http://www.maxbotix.com/
Accelerometers
• New ones based on Micro-ElectroMechanical Systems (MEMS) devices
very small
• Can measure acceleration in up to
three axes
• Even can sense gravitational pull of
earth
• ~$25 and up
http://www.sparkfun.com/commerce/product_info.php?products_id=692
Magnetic Reed Switches
• Magnet in one part causes reed
switch to open/close on second
part
• Commonly used in security
systems
• Range very short (~1 inch)
• Good for limit switch
• ~$5 or under
Force Sensing Resistors
• Pressure reduces resistance
• Analog voltage measured
across resistor divider circuit
• Can measure a few ounces to
100 lbs depending on model
• ~$10-$25
http://www.parallax.com/detail.asp?product_id=30056
http://www.phidgetsusa.com/cat/viewsubcategory.asp?category=5000&sub
category=5210
Touch Sensors
• Measure changes in
capacitance
• Can sense touch through 4
inches of dielectric objects
(glass, plastic)
• ~$10-$20
http://www.phidgetsusa.com/cat/viewproduct.asp?category=50
00&subcategory=5100&SKU=1110
CMU Cam
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Microcontroller and camera combo
Track user defined color blobs
Track motion using frame differencing
Controls up to 5 servos
Other video processing capabilities
Serial I/O
$169
http://www.cs.cmu.edu/~cmucam2/
Laser Range Finder
• Very accurate distance
measurement
• Time-of-flight determines distance
• Range 4m
• 270 degrees of measurement
• 0.36 degrees angular resolution
• RS-232/USB output
• $2695
http://www.acroname.com/robotics/parts/R283-HOKUYOLASER1.html
Sensors you should know
about
Thomas Edwards
http://www.t11s.com