With the continuous progress of science and technology, people’s requirements for the quality of life not only stay in the continuous satisfaction of material conditions, and gradually derive a smart home system with the characteristics of safety, convenience, efficiency, speed, intelligence and personalization. It is of great significance to create a comfortable, convenient and efficient living space for the quality of modern human life.
While smart home has attracted much attention, its various internal automatic control, detection, air conditioning equipment and other systems have also received attention. Almost all electronic components used in this system are inseparable from special ceramics, such as those in automatic temperature control equipment. Applied heat-sensitive ceramics, humidity-sensitive ceramics used in automatic humidity adjustment equipment, photosensitive ceramics in light detection elements, etc.
1 The working principle of sensitive ceramics
Thermal ceramics, humidity sensitive ceramics and photosensitive ceramics are a small branch of special ceramics, and they all belong to semiconductor ceramics (also known as sensitive ceramics) in functional ceramics. Semiconductor ceramics refer to ceramic materials with semiconductor properties. Semiconductor ceramics are mainly used to make various sensitive components and are the key materials for various information sensors, so they are also called sensitive ceramics.
Thermal ceramics are a class of ceramics whose resistivity changes significantly with temperature. Generally, according to the temperature coefficient, it can be divided into positive temperature coefficient (PTC) in which the resistance increases with temperature, negative temperature coefficient (NTC) on the contrary, and critical temperature coefficient (CTR) in which the resistance changes sharply within a specific temperature range, etc. Thermal ceramics.
Humidity-sensitive ceramics are a class of ceramics whose resistance changes significantly with humidity.
Sensitive ceramics can be used as multi-function sensors to detect two or more parameters at the same time. For example, thermal ceramics can be used in the form of thermistor sensors, temperature sensors, etc.; humidity-sensitive ceramics are mainly used in the form of humidity sensors.
2 Application examples of sensitive ceramics in smart home systems
In a complete smart home, the most basic systems that are often encountered are the air conditioning ventilation system and the fire smoke exhaust system. In this working system, there are strict accuracy requirements for each working element, such as the test accuracy and accuracy of humidity sensors and temperature sensors.
2.1 Air conditioning and ventilation system
The main function of the air conditioning and ventilation system in the smart home is indoor air conditioning. Air conditioning regulation refers to the adjustment and control of the air environment (temperature, humidity and air flow speed) in a specific space by using certain technical means to achieve and maintain it within a certain range to meet the requirements of the process and Human comfort requirements. Comfort air conditioning generally refers to the indoor temperature of 24℃~28℃ in summer and the relative humidity of 40%~65%; the indoor temperature of 18℃~22℃ in winter and the relative humidity of 40%~60%. In the smart home system, air conditioning can create a suitable indoor climate environment to facilitate people’s life, study and rest.
When the air conditioning and ventilation system is working, in the summer with relatively high humidity, it mainly adopts the method of supplying cold air to make the indoor temperature reach the ideal value, and in the winter when the temperature is relatively low, the air is heated to achieve the purpose of heating. Cold air in summer and warm air in winter are treated. In winter, the air is generally dry and the required air needs to be humidified. Air conditioning systems require a variety of sensors, and at the same time, these sensors have high process requirements. Humidity sensors and temperature sensors should be able to automatically and real-time detect the humidity temperature of fresh air, supply air, return air and the controlled environment; pressure sensors and flow sensors should be able to automatically and real-time detect steam pressure and flow; at the same time, the temperature sensor should also measure heat. The water temperature and the temperature of the cooling water; it should also be able to automatically adjust and switch each valve according to the meteorological parameters and different control requirements, so as to control the fresh air treatment state and the indoor state of the all-air air conditioning system.
In the smart home system, there are high requirements for the temperature and humidity of the air entering the room, and the temperature and humidity in the room will change with the change of the outside temperature, which requires the sensor to respond quickly and automatically adjust. Here the sensor plays the role of monitoring. After receiving the signal, it will be locked to the total control system and debugged by itself.
2.2 Fire water fire extinguishing system
In fire and smoke exhaust systems, the application of sensitive ceramics in sprinkler systems:
1) The automatic sprinkler system is a fire-extinguishing system that uses a fixed pipe network and sprinklers to automatically sprinkle water and send out a fire alarm signal at the same time.
2) It uses the light, heat and pressure signal sensing generated during the fire to automatically start, and sprinkle water to the fire area to extinguish the fire or control the spread of the fire.
3) It not only has the function of detecting fire and alarming, but also has the function of spraying water and controlling the development of fire. It plays the role of monitoring the fire situation at any time and automatically starting the fire extinguishing device.
Components prepared from sensitive ceramics are mainly used in closed nozzles, wet alarms and alarm devices.
The closed sprinkler is composed of a spout, a temperature-sensing release structure and a splash plate. In the system, it is responsible for the task of detecting fire, starting the system and sprinkler. The temperature is mainly tested by a temperature sensor made of thermally sensitive ceramics.
The alarm control valve is a special valve for controlling the water source, starting system and hydraulic alarm bell and other alarm equipment in the sprinkler system. The alarm control device plays the role of monitoring, control and alarm in the automatic sprinkler system, and can emit sound, light and other signals. It is mainly composed of a controller, a detector and an alarm.
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