OFweek smart home network news: With the rapid development of sensor technology, more and more sensors have begun to be applied in the field of smart home, and in the system to play an increasingly important role in control judgments. The organic integration of temperature, humidity, illuminance, human infrared, door and window magnetism, flooding, smoke, gas, and other sensor devices builds an integrated sensing network for smart homes, which is embodied in data in smart home systems. In the imaginable space, in the humanized application that the future smart home can realize, the acquisition ability of the sensor will certainly surpass all that human beings can perceive. This site has launched a special theme for sensor applications, which provides a detailed understanding of sensor technology and application functions.
What is a sensor?
In fact, the sensor is a detection device that can sense the measured information and transform the sensed information into electrical signals or other desired forms of information output to meet the information transmission, processing, storage and display. , recording and control requirements. There are many types of sensors, which can be divided into three categories: physical quantity, chemical quantity, and biomass. In each category, there are many small categories. At present, sensors are needed in many fields such as industrial production, space development, ocean exploration, environmental protection, resources investigation, medical diagnosis, biological engineering, and even cultural relic protection. It can be said that almost every modern project lacks sensors.
MEMS sensor
Since the development of sensors, miniaturization, intelligence, and integration have become a trend. The full name of MEMS is a micro-electromechanical system. Micro-electro-mechanical systems refer to mass production. Micro-mechanisms, micro-sensors, micro-actuators, and signal processing and control circuits, as well as interfaces, communications, and power supplies, are integrated on one or more chips. Micro devices or systems.
Field of application
MEMS sensors are new sensors made using microelectronics and micromachining technology. Manufacture of sensors, actuators or microstructures using MEMS technology is characterized by miniaturization, integration, intelligence, low cost, high efficiency, mass production, high productivity, and high yield. As an important symbolic industry of international competition strategy, MEMS sensors are widely used in countries all over the world due to their high technological content and broad market prospects. In the past decade, the MEMS sensor industry ecosystem in China has also been gradually improved. From the R&D, design, foundry, and packaging and testing to application, a complete industrial chain has basically taken shape.
Sensor classification
Sensors can generally be divided into thermal sensing elements, photosensitive elements, gas sensors, force sensors, magnetic sensors, humidity sensors, acoustic sensors, radiation sensitive sensors, color sensors, and flavor sensors according to their basic sensing functions. Big class. Similar to human sensory organs, sensors can be divided into:
· Haptics - pressure sensitive, temperature sensitive, fluid sensors
·Sense of smell - gas sensor
· Vision - photosensitive sensor
·Hearing - acoustic sensor
· Taste - chemical sensors
According to the measured physical quantity is divided into: force, pressure, displacement, temperature, angle sensor and so on.
According to the working principle of the sensor is divided into: strain sensor, piezoelectric sensor, piezoresistive sensor, inductive sensor, capacitive sensor, photoelectric sensor.
Pressure Sensor
According to the way the sensor converts energy, it is divided into:
Energy conversion type: piezoelectric, thermocouple, photoelectric sensor, etc.
· Energy control type: Resistive, inductive, Hall-type sensors and thermistors, photoresistors, moisture sensitive resistors, etc.
· According to the working mechanism of the sensor is divided into:
Structure type: Inductive, capacitive sensors, etc.
Physical type: piezoelectric, photoelectric, various semiconductor sensors.
In accordance with the form of sensor output signal is divided into:
Analog: The sensor output is analog voltage;
Digital: The sensor output is digital, such as an encoder sensor.
According to the principle of energy conversion can be divided into:
Active sensors: Active sensors convert non-electrical energy into electrical energy, such as electromotive force, charge-type sensors, etc.
• Passive sensors: Passive sensors do not function as energy converters, but simply convert measured non-electrical energy into electrical parameters, such as resistive, inductive, and capacitive glow sensors.
Smart home mainstream sensor application classification
In the smart home application, the traditional sensors connected to the bus are expensive, the cost of the sensor networking is huge, and the wiring is difficult in some areas, and the protocols between different types of sensors and control systems are incompatible. Therefore, with the development and maturity of wireless sensor network technology, wireless sensor network products began to gradually replace the traditional wired sensor products with their unique advantages, and penetrated into all aspects of the smart home field.
Temperature and humidity sensor
The temperature sensor is mainly used to detect indoor and outdoor ambient temperatures. Thermistors are the most widely used in home environments. Thermistors are a type of sensitive element that is divided into a positive temperature coefficient thermistor (PTC) and a negative temperature coefficient thermistor (NTC) according to different temperature coefficients. Thermistors are typically temperature sensitive and exhibit different resistance values ​​at different temperatures. The positive temperature coefficient thermistor (PTC) has a higher resistance at higher temperatures, and the negative temperature coefficient thermistor (NTC) has a lower resistance at higher temperatures, and they all belong to semiconductor devices.
Humidity sensors are mainly used to detect indoor and outdoor ambient humidity. Humidity sensor is the simplest humidity sensor. Humidity sensors are mainly resistive and capacitive. Humidity resistance is characterized by covering the substrate with a film made of a moisture sensing material. When the water vapor in the air adsorbs on the moisture sensing film, the resistance and the resistance of the element change, and this characteristic is utilized. Measure humidity. Humidity-sensitive capacitors are generally made of polymer film capacitors. Commonly used polymer materials include polystyrene, polyimide, and cellulose acetate. When the humidity of the environment changes, the dielectric constant of the humidity sensitive capacitor changes, and its capacitance also changes. The amount of capacitance change is proportional to the relative humidity.
Infrared sensor
Objects that exist in nature, such as the human body, flames, and ice, emit infrared light, but their wavelengths are different. The human body temperature is 36 to 37 degrees Celsius, and the infrared wavelength emitted is 9 to 10 micrometers, which is a far-infrared region. A heating element of 400 to 700 degrees Celsius emits an infrared wavelength of 3 to 5 micrometers and belongs to the mid-infrared region. Pyroelectric infrared sensor is not affected by day and night, can be used for monitoring day and night, widely used in burglar alarm.
Infrared sensor
Materials with high pyroelectric coefficients include lead zirconate titanate ceramics, lithium niobate, and triglycidyl sulfate. Pyroelectric body infrared sensors generally use a differential balance structure, which consists of sensitive components, field effect transistors, and high-value resistors.
Smoke sensor
Smoke detectors are detectors that mainly respond to combustion or pyrolysis of solids, liquids, particles, or smoke particles. They are mainly used to detect visible or invisible combustion products and initial fires with slow fires. Can be divided into ion type, photoelectric type, laser type and infrared beam type four.
PM2.5 dust sensor
The dust sensor is generally measured optically. Its working principle is that when particles are irradiated with light, particles of different sizes and concentrations will have different scattering images, and the dust concentration can be measured through the detection of scattered light distribution.
Visible light sensor
The visible light sensor is mainly used to measure the brightness of visible light in the room and is used to adjust the brightness of the room. The sensor converts the optical signal into an electrical signal output. Through sensor detection and driving control, it can be realized that when the room is bright enough, the preset lamp switch is actively closed; and when the room brightness is insufficient, the preset lamp switch can be actively turned on.
Pyroelectric infrared sensor
It can convert infrared signals with a wavelength of about 10 microns into electrical signals. When no human body moves, the sensor detects only the background temperature of the site. If the human body enters the detection zone, it is detected by the sensor through the Fresnel lens. It is the difference between human body temperature and background temperature. Pyroelectric infrared sensors can be widely used in automatic alarm devices, sensor faucets, automatic flush toilets, automatic lighting and automatic curtains.
Pyroelectric infrared sensor
Gas sensor
Nowadays, air quality is becoming more and more a concern for people, so wireless gas sensors have attracted more and more manufacturers' interest. The gas sensor can detect the content of special gas components in the air. The sensor uses the principle of positive correlation between the surface acoustic wave velocity and frequency and the external environment change, that is, when the gas sensitive membrane interacts with the gas to be measured, the gas film layer quality When the conductivity changes, the wave frequency of the acoustic surface of the piezoelectric crystal shifts. When the gas concentration changes, the film quality and the conductivity change also change. By detecting changes in the surface acoustic wave frequency, it is possible to accurately reflect changes in gas concentration.
Sound sensor
Sound sensors are mainly used to test indoor sound and achieve sound control. Specifically speaking, a small shrapnel is used to sense the sound and a sound signal is converted into an electric signal through a relay. When the sound is loud enough, the electric signal is large enough. At this time, the electric signal is transmitted to the contact of the switch. Turn the circuit on or off.
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