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Using Pyroelectric Infra-Red (PIR) sensors for motion detection | Cypress Semiconductor

Using Pyroelectric Infra-Red (PIR) sensors for motion detection

Last Updated: 
Sep 23, 2008

Motion detection of an object can be achieved by using some stimulus and sensing its reflection as in RADAR, or by sensing the natural signals generated by an object. This article discusses motion detection of an object by sensing the infrared signal radiated from the object.

Infrared radiation exists in the electromagnetic spectrum at a wavelength that is longer than visible light. Infrared radiation cannot be seen but it can be detected. Objects that generate heat also generate infrared radiation and those objects include animals and the human body, whose radiation is strongest at a wavelength of 9.4 μm. To detect this signal, a transducer is required that converts the infrared signal to a form detectable with conventional circuitry. To read more on this topic, click the link to the pdf above or visit:

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