Infrared sensors, as a crucial component widely used in the global electronic components industry, play a key role in various fields due to their sensitivity to infrared radiation (i.e., heat). In this article, we will delve into the definition, working principle, types, characteristics, and advantages of infrared sensors.
I. What Are Infrared Sensors?
An infrared (IR) sensor is an electronic device that measures and detects infrared radiation in its surrounding environment. Infrared radiation, discovered by astronomer William Herschel in 1800, is invisible to the human eye because its wavelength is longer than visible light, although it falls within the same electromagnetic spectrum. Anything that emits heat (objects with a temperature above approximately five degrees Kelvin) produces infrared radiation. IR sensors convert detected infrared signals into electrical signals, providing valuable data for analysis and control.
II. Types
There are two primary types of infrared sensors: active and passive.
Active infrared sensors emit and detect infrared radiation. They consist of a light-emitting diode (LED) and a receiver. When an object approaches the sensor, the infrared light from the LED reflects off the object and is detected by the receiver. Active IR sensors act as proximity sensors and are frequently used in obstacle detection systems.
Passive infrared (PIR) sensors, on the other hand, only detect infrared radiation and do not emit it. They consist of:
- Two strips of pyroelectric material (a pyroelectric sensor)
- An infrared filter (to block out other wavelengths of light)
- A Fresnel lens (to collect light from various angles into a single point)
- A housing unit (to protect the sensor from environmental factors like humidity)
PIR sensors are most commonly used in motion-based detection. When a moving object that emits infrared radiation enters the sensor's range, the difference in IR levels between the two pyroelectric elements is measured. The sensor then sends an electronic signal to an embedded computer, which triggers an alarm.
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