Week 7, Movement Sensor, Group E

This week, our group’s is to explore Movement sensors, here is what I learned from several articles I read. Movement sensor is also known as Motion sensor, it is everywhere around our life today. These sensors were invented during World War II because army needs it to detect of enemy air-crafts, and now it has been developed to apply to our everyday life. Movement sensors are in used in areas such as grocery store doors and security systems. I will give a brief introduction about two type of movement sensors that has been widespread used: radar sensor and infrared sensor.

Radar Sensors:

Radar sensors work by "radiating electromagnetic energy and detecting the echo returned from reflecting objects" [1]. The electromagnetic energy, which is in wave-form, is sent into the environment by a transmitter. When the wave reach to an object, it will reflect and be sent back in the opposite direction, scientists call this an echo. A receiver is used to collect the data from the echo and analysis to see if there is anything changed in the environment. Radar sensors are also called active sensors because they radiate energy in order to detect changes in the environment.

Infrared Sensor:

Unlike radar sensors, infrared sensors are passive; this means that instead of radiating energy in order to detect changes in the environment, they are capable of detecting radiation emitted by other objects, such as thermal energy from human beings [2]. Infrared sensors are made from different materials that sense different ranges of infrared wavelengths. When an appropriate wavelength of infrared radiation strikes one of the material's cells, it changes the cell's resistance. By measuring the resistance of the cell, one can measure its infrared radiation [3]. Since many different objects will emit a certain level of infrared radiation, it is easy for the sensors to detect rapid changes in infrared radiation instead of a particular wavelength. When the sensor detects a change, a device will be triggered to work.

Both Radar sensor and Infrared sensor are movement sensors. Sensor technology has already implemented in a lot of buildings, such as automatic doors, automatic lights and building security systems. And sensor technology will continue to grow and contribute to the modern age.

[1] M.I. Skolnik. Radar Handbook. New York: McGraw-Hill, 1990.

[2] "How PIR Motion Sensors Work". Internet: http://www.gadgetsha​ck.com/motionsensor.​html, [Nov. 10, 2007].

[3] NASA. "Cool Cosmos." Infrared Astronomy. Internet: http://coolcosmos.ip​ac.caltech.edu/cosmi​c_classroom/ir_tutor​ial/irtech.html, [Nov. 10, 2007].

[4] “Motion Sensors” Illumin, University of Southern California. Internet: http://illumin.usc.edu/printer/165/motion-sensors/ [2012]

Comments:

Michael:

Your post discussed pressure sensors that people experience every day but often overlook. I did not know the importance of pressure sensors until I read your post. And I do agree that it could be possible in the future to use the tech behind that in intelligent building design.

Audrey:

Nice introduction about the temperature sensors. You well introduced that temperature sensor has their own advantages and disadvantages. Your post is really technical and professional, but easy to read and understand.