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+SChttp://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/cgi-bin/commerce.exe?preadd=action&key=MD3C
Active IR Sensors
• 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 ~$25http://www.maxbotix.com/
Accelerometers
• New ones based on Micro-Electro-Mechanical 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-$25http://www.parallax.com/detail.asp?product_id=30056
http://www.phidgetsusa.com/cat/viewsubcategory.asp?category=5000&subcategory=5210
Touch Sensors
• Measure changes in capacitance
• Can sense touch through 4 inches of dielectric objects (glass, plastic)
• ~$10-$20http://www.phidgetsusa.com/cat/viewproduct.asp?
category=5000&subcategory=5100&SKU=1110
CMU Cam
• 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-HOKUYO-LASER1.html
Sensors you should know about
Thomas Edwards
http://www.t11s.com