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Alarm circuit diagram using pyroelectric sensor

2015-03-02 02:37  
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Alarm circuit diagram using pyroelectric sensor
The circuit is composed of amplifier, comparator and an output control part. According to Faraday's law, person's body temperature is about 37 ℃, radiation infrared wavelength is about 10μm, the pyroelectric sensor selects P7178 with 7 ~ 20μm sensitive wavelength range. A1 and A2 are selected low noise, low loss CMOS op amp μPC358, and it is connected to band-pass filter composed of RC to prevent the entry of the noise and error signal, extracting only a signal when the human body moves. A3 and A4 constitute a comparator.