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CY3236A-PIRMOTION: Pyroelectric Infrared (PIR) Motion Detection Evaluation Kit (EVK)

CY3236A-PIRMOTION: Pyroelectric Infrared (PIR) Motion Detection Evaluation Kit (EVK). Agenda. PIR Theory PIR Motion Detection—The PSoC Way. PIR Theory. PIR Theory - Basics. Humans at normal body temperature radiate most strongly in the infrared spectrum at an approximate wavelength of 10uM

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CY3236A-PIRMOTION: Pyroelectric Infrared (PIR) Motion Detection Evaluation Kit (EVK)

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  1. CY3236A-PIRMOTION:Pyroelectric Infrared(PIR) Motion Detection EvaluationKit (EVK)

  2. Agenda • PIR Theory • PIR Motion Detection—The PSoC Way

  3. PIR Theory

  4. PIR Theory - Basics • Humans at normal body temperature radiate most strongly in the infrared spectrum at an approximate wavelength of 10uM • To detect this signal, a transducer is required that converts the infrared signal to current or voltage

  5. PIR Theory – PIR Sensors • A PIR sensor is made of ceramic material that generates surface charge when exposed to infrared radiation • As the amount of radiation increases, the surface charge generated increases • A FET is used to buffer this signal

  6. PIR Theory – PIR Sensors • As the sensor is sensitive to a wide range of radiation, a filter window is added • This window limits the infrared rays falling on the ceramic pickup to 8um-14um range • Also, a resistor is added to the source of the FET to convert the charge to voltage Filter Window Ceramic Substrate

  7. PIR Theory – PIR Sensors • The output of the sensor is the function of infrared radiation • But the output is also affected by vibration, radio interference, sunlight etc What is the solution? Filter Window Ceramic Substrate

  8. PIR Theory – PIR Sensors • Dual Sensors are used • Both sensors are connected out of phase such that any excitation that is common to both the sensors cancel out • A body passing before the sensors excites first one and then the other sensor Two Sensors connected out of phase Physical Construction of a dual sensor

  9. PIR Theory – Fresnel Lens • To improve the range and detection angle, Fresnel Lens are used • A Fresnel lens is a plano convex lens that has been collapsed on itself to form a flat lens that retains its optical characteristics, but is thinner and has lesser absorption losses

  10. PIR Theory – Fresnel Lens • There are many types of Fresnel Lens available, each having a different angle of coverage, focal length etc

  11. PIR Theory – Detection • When an object moves in front of the sensor, the dual elements are excited one after other • The resultant output is a +ve signal followed by a –ve signal

  12. PIR Theory – Detection • The signal is first amplified using an amplifier and then fed to a comparator • The comparator produces an output when the sensor detects a movement • This comparator output can be further processed to control electrical loads

  13. PIR Motion Detection Applications • Automatic Lighting Controls • Automatic Door Openers • Security Systems • Activating Wireless Cameras

  14. PIR Motion Detection—The PSoC Way

  15. PIR Detection – The PSoC Way • The Amplifier is implemented in 2 stages with capacitive coupling between stages • ADC measures the output of amplifier stage

  16. PIR Detection – The PSoC Way • Digital High Pass Filter and Decision logic in firmware • All Hardware and Firmware implemented in One PSoC Device Refer to AN2105 on www.cypress.com/designresources

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