The infrared detector in a smart home system is a device that utilizes the infrared radiation beam between the transmitter and the receiver, which is completely or greater than a detection principle that can generate an alarm state when a given percentage is interrupted. It is divided into active and passive, let us talk about active infrared detectors.
The active infrared intrusion detector generally consists of a separate transmitter and receiver. The transmitter and receiver are installed separately. The infrared radiation spectrum of the transmitter should be outside the visible spectrum. The infrared transmitter usually adopts complementary self-excited multi-harmonic. The oscillating circuit is a modulating power supply that produces a very high duty cycle pulse waveform. The infrared light emitting diode is modulated by a large current narrow pulse signal, and the pulsed infrared light is emitted. The infrared receiver usually adopts a photodiode as a photoelectric sensor, and converts the received infrared light signal into an electrical signal, and after the signal processing circuit amplifies and shapes, the relay contact is driven to generate an alarm state signal.
Active infrared intrusion detectors should pay attention to the following aspects when using.
1 Active infrared intrusion detector is a line-controlled detector, which is suitable for proper camouflage.
2 Active infrared intrusion detectors are greatly affected by climate when used outdoors. In the case of fog, snow, rain, sand and other harsh climates, the visibility of the atmosphere is reduced, the active infrared intrusion detector is shortened, and the system is prone to false alarms.
3 The sensitivity of the active infrared intrusion detector is generally adjusted at the factory, the user can not adjust it himself. Once the sensitivity is too high (prone to false alarm) or too low (easy to leak alarm), the relevant personnel should be notified in time for maintenance.
4 When the wind scraping tree shakes the infrared beam, it is easy to cause the system to false alarm.
5 When the indoor infrared active intrusion detector is used, the curtain movement can easily block the infrared beam, causing false alarm of the system. Be sure to insert the window after going out.
6 The lens surface is exposed to the air and is susceptible to contamination. It should be wiped frequently with lens paper to ensure the normal operation of the detector.
After talking about the active smart home infrared detector, let me talk about the passive infrared intrusion detector.
When the human body moves within the detection range, the detection device that causes the received infrared radiation level to change and can generate an alarm state is called a passive infrared intrusion detector. It has two key components, one is a Fresnel lens and the other is a pyroelectric sensor. Any object in nature that is above absolute zero (-2730C) will produce infrared radiation, and objects of different temperatures will emit different wavelengths of infrared energy. The human body has a constant body temperature and is different from the ambient temperature. When the human body moves, this change in the difference is detected by the pyroelectric sensor through the Fresnel lens, thereby outputting an alarm signal. Passive infrared intrusion detectors should pay attention to the following aspects when using.
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