What Is a Dust Sensor?
Dust sensors, as the name suggests, are elements that detect dust, and are used to detect particles floating in space in general home environments and particle-controlled clean rooms. Dust sensors are widely known for general household use, such as in air purifiers and air conditioners with built-in dust sensors.
A particle counter is similar to a dust sensor. These detectors detect suspended particles based on the light scattering principle. It can detect cigarette smoke, house dust that causes allergies, etc.
Applications of Dust Sensors
Dust sensors optically detect airborne particles such as house dust and tobacco smoke. They are used in air purifiers, air conditioners, ventilation fans, environmental monitors, and other sensors that use light to detect various types of dust, cigarette smoke, house dust, and other particles.
Duct sensors are often used in air purifiers and air conditioners that detect particles suspended in the air and monitor their condition, or change their operation according to the state of particles in the air.
Principle of Dust Sensors
Dust Sensors consist of a light-emitting diode that emits light and a photodiode that receives light reflected from dust. In addition, a lens is used to collect the light efficiently, and a heater is used to generate a weak updraft of air inside the sensor, which draws in dust and smoke from the air intake. Dust and smoke are then discharged from the exhaust port.
The light-emitting diode (e.g., infrared) emits light in pulses in response to an external input signal. A photodiode, which is the light-receiving element, receives the incident light from the light-emitting diode and outputs a pulse current in response to the amount of incident light.
Aspheric lenses are installed on all surfaces of the light-emitting and light-receiving elements to narrow directivity. The area where the optical axes of the emitting and receiving elements intersect is the area where dust, smoke, etc. are detected. To prevent unnecessary light from entering the light-receiving element as stray light, a slit, or the like, is added to the sensor case to reduce stray light.
Cigarette smoke and house dust can be distinguished by looking at the temporal transition of the output voltage. If the output voltage is detected continuously, it can be identified as cigarette smoke, and if the output voltage is detected intermittently, it can be identified as particles such as house dust.