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