Tuesday, March 29, 2011

Sensor Research

(WEEK 5)


Motion Sensor


There are several types of motion sensors such passive infrared sensors (PIR), ultrasonic (active), microwave (active).


Basically motion sensors transform the detection of moving object within the field of view and converts  an electric signal which acts like a switch. Once detected, the switch will stay closed as long as any movement is detected by the sensor.
PIR sensor diagram
The motion sensor acts as a switch
Source: http://coopy.sproutlab.com/projects/rain-umbrellas/



How Infrared Technology Works

In general, infrared sensors work by emitting an invisible pulsed light signal. The receiver then looks for the reflected signal back and reacts to changes in the reflection of the signal that indicates a presence in its detection area. There are two types of infrared technology: Diffused and Distance Measuring Infrared.
Diffused Infrared Sensors work by flooding pulsed infrared light over a specific area below the sensor down to floor level. It then uses the reflected infrared as its base of reference. Foreign objects entering the detection area alter the infrared base reference level and trigger activation.



Motion Sensor

Building a sound trigger motion sensor trigger

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