Development of vehicle air purifier control board
Development of vehicle air purifier control board
Studies have shown that compared with the urban air pollution, the air pollution in the car is more serious. All kinds of harmful gases such as benzene and formaldehyde produced by car decoration are mixed with the air in the car, causing serious harm to the health of passengers. Moreover, because the environment inside the vehicle is usually humid and warm, it is very easy to produce a lot of bacteria, which further worsens the air environment inside the vehicle, which not only affects the physical and mental health of passengers, but also makes the vehicle drivers prone to fatigue, resulting in great driving safety hazards. In view of this, it is necessary to actively take scientific and effective preventive measures, sort out and study the current mainstream vehicle air purifier technology, and point out the development direction of vehicle air purifier in the future.
1、 Development background of vehicle air purifier in China
According to the statistical data of China's air quality survey in 2013, in about 70 key cities with rapid economic development in China, the air pollution index of about 67 cities has exceeded the standard, accounting for 96%. In these cities where the pollution level seriously exceeds the standard, the main air pollutant is PM2.5. With the continuous increase of pH2.5 concentration in the air, the probability of death caused by cardiopulmonary diseases increases greatly, and pH2.5 will also cause a large range of haze, causing serious harm to people's physical health and immunity. Today, with the deteriorating urban air environment, more and more people choose to travel by bus. Therefore, the number of cars in China has increased year by year in recent years. Leather and plastic decorations in the car will emit harmful and toxic substances such as formaldehyde and benzene. Especially for new cars just purchased, the formaldehyde concentration in the car will far exceed that of cars with long service life. The serious urban air pollution and the pollution caused by interior decoration have a great impact on the air in the car. Because the on-board purifier can filter formaldehyde, pH2.5 and other harmful gases in the air to a great extent, it has been greatly developed and applied, and because of its function and concept of health and environmental protection, It further promotes people's market demand for on-board air purifiers.
2、 Analysis on mainstream technology of vehicle air purifier
(1) Normal temperature formaldehyde catalytic oxidation technology: the principle of normal temperature formaldehyde catalytic oxidation technology is to use metal carbonate or metal nitrate for oxidation and precipitation to obtain metal oxides. A small amount of precious metals such as europium and gold are loaded on the formed metal oxides. At normal temperature, europium and gold will react with formaldehyde to produce water and CO2. The normal temperature formaldehyde catalytic oxidation technology can effectively convert the formaldehyde gas in the vehicle into water and CO2, and the air purification efficiency is relatively high, and the purification module can be used permanently.
(2) Electrostatic dust removal technology: the main working principle of electrostatic dust removal technology is to ionize the gas in the high-voltage electrostatic field, so as to gradually deposit the charged dust particles on the anode surface, and then purify the air. Because the electrostatic on-board air purifier can only deal with bacteria, dust and other air impurities in the vehicle, but can not effectively decompose the toxic and harmful chemical gases in the vehicle and can not eliminate the peculiar smell in the vehicle, it is necessary to cooperate with other equipment to achieve better air purification effect in the vehicle. Moreover, when using electrostatic dust removal technology to purify the air in the vehicle, when the suspended particles in the vehicle increase, the purification effect will be greatly reduced.
(3) Filter screen adsorption technology: the main principle of filter screen adsorption technology is to throttle the particles in the air on its surface by using glass fiber material or mesh structure plastic, so as to purify the air. Generally, there are three commonly used filters: activated carbon filter screen, primary effect filter screen and HEPA filter screen. The on-board air purifier made of filter screen adsorption technology can effectively remove bacteria, benzene, formaldehyde and other harmful substances in the vehicle. However, because the service life of the filter screen is limited, and the power of this type of on-board air purifier is generally small and does not have sufficient wind power, the air in the vehicle cannot be completely purified.
(4) Ozone sterilization and decomposition technology: compared with other vehicle air purifier air purification technologies, ozone sterilization and decomposition technology has very strong sterilization effect. Because ozone is a strong oxidant, it has very strong oxidation ability, especially for bacteria, nicotine and amine. In addition, ozone can also oxidize and decompose benzene, VOC, etc. However, the use of ozone sterilization and decomposition technology to purify the air in the vehicle also has certain limitations, because ozone is a gas harmful to human body, and the state has very strict requirements for its use. Therefore, when using ozone on-board air purifier, it is necessary to ensure that there is no one in the vehicle.
(5) Negative ion technology: negative ions have a certain charge, which can make small dust particles in the air gather together to form larger particles and settle, so as to purify the air. In addition, when ionized, negative ions will also produce a very small amount of ozone in the air, which can kill various microorganisms and bacteria mixed in the air, so as to make the air more fresh and refreshing, which is very beneficial to improving people's immunity. The purification effect of the vehicle air purifier made of negative ion technology is very significant, but it also has obvious disadvantages, that is, when its concentration is high, it will have certain side effects on the human body, and its decomposition effect on formaldehyde, VOC and other impurities in the air in the vehicle is not obvious.
(6) Nano photocatalyst technology: nano photocatalyst technology is an air purification technology rising in recent years. The on-board air purifier made by this technology is usually called ultraviolet on-board air purifier. It uses the irradiation of ultraviolet to kill various microorganisms and bacteria in the air in the car, so as to achieve the effect of disinfection and sterilization. Generally speaking, UV vehicle air purifier integrates nano photocatalyst technology and negative ion technology, which has the significant advantage of complete sterilization.
3、 Development trend of vehicle air purifier
Through in-depth investigation, it can be seen that the development trend of on-board air purifier in the future is mainly reflected in two aspects: intelligence and Internet. The specific conditions are as follows: (1) intelligence of on-board air purifier. Restricted by its own hardware conditions, the performance of traditional vehicle air purifier in algorithm processing and human-computer interaction is not satisfactory. In the future, with the continuous progress of intelligent hardware and the gradual popularization of short-range communication technology, people can bind all data of on-board air purifier with mobile phones. At that time, people can track and control all monitoring and purification data of on-board air purifier by using mobile phones. In the intelligent process of vehicle air purifier, how to effectively realize the stable transmission of interactive data by short-range wireless communication technology is the key link. (2) Internet of on-board air purifier. In the process of gradually promoting the intellectualization of vehicle air purifier in the future, as an Internet product, mobile phone will inevitably drive the vehicle air purifier to develop in the direction of Internet. In addition to realizing the function of tracking and controlling various monitoring data of on-board air purifier by using Internet mobile phones, it is bound to derive richer and diversified Internet services. For example, push air cleaner advertisements for users in combination with the characteristics of pollutants in the vehicle.
With the increasing popularity of automobile households in China, the impact of automobile dust, volatile organic compounds and air pollutants entering from the air inlet of automobile air conditioning on human body has been paid more and more attention. Moreover, the relatively closed inside the car will lead to excessive exhaust gas and insufficient oxygen supply in the small area, which is easy to cause the driver's inability to concentrate and fatigue. Being in this environment for a long time will pose a threat to human health. Most of the existing on-board air purifiers are evolved from filter screen household purifiers, which are usually small and placed in the vehicle. Although the purifier can effectively purify bacteria, dust and other harmful substances, because of its small size, the product has few functions and low purification efficiency.
4、 Hardware design of vehicle purifier control system
This design takes stc15w401as single chip microcomputer as the core, combined with temperature and humidity sensor, ozone purifier, electrostatic precipitator, negative ion purifier and humidification device, designs vehicle air purifier. The hardware part adopts the module design, and the relay is used to control the opening and closing of each module. The structure diagram of the system is shown in Figure 1.
The system adopts stc15w401as single chip microcomputer. The single chip microcomputer adopts 8051 core. It has 2K bytes of storage space, two independent serial ports, high-speed 10 bit converter and 8 channels. It is high-speed and reliable. The single chip microcomputer belongs to 1t single chip microcomputer, which is 8 to 12 times faster than the traditional 12t single chip microcomputer. The processor meets the requirements of low cost, high speed and good reliability.
4.1 power conversion module
Because the rated working voltage of stc15w401as single chip microcomputer is 3.3V, and the relay needs 5V DC power supply. Therefore, the power conversion module adopts lm2576 to convert the vehicle DC 12V voltage into 3.3V and 5V DC through lm2576, which are respectively supplied to the single chip microcomputer and relay after filtering, as shown in Figure 2.
Lm2576 is a commonly used voltage stabilizing chip, with a maximum current of 3a, which can fully promote the work of the relay. Lm2576 can produce high reliability single chip microcomputer power supply. Therefore, the power supply demand of the system is met by using voltage stabilizing chips of 3.3V and 5V.
4.2 temperature and humidity sensor module
DHT11 is a common temperature and humidity detection module. DHT11 integrates control and calibration circuits internally and does not need any other components externally. At the same time, DHT11 has been calibrated in the accurate humidity calibration room, so there is no need for calibration in use, which simplifies the use process of making on-board air purifier. It can be seen that DHT11 has very good stability and reliability and is very suitable for this control system.
The data pin in DHT11 communicates with MCU as a serial bus. In order to solve the problem of insufficient driving ability of MCU pin, 4.7K pull-up resistance is used as compensation.
4.3 relay drive module
The relay is connected with the I / O output of the single chip microcomputer through sn7404n. The single chip microcomputer outputs commands to control the opening and closing of the relay, and then control the opening and closing of each working module. The setting of sn7404n plays an isolation role and can effectively protect the single chip microcomputer from accidental burning.
5、 Software design of vehicle air purifier control system
In order to achieve the effect of air renewal, purification and dust removal in the vehicle, the main program should realize the cycle of air exchange, ozone sterilization, anion and electrostatic dust removal. In addition, in order to meet the comfort in the vehicle, it is necessary to meet the free setting of the personnel in the vehicle, such as the wind speed and humidity of the air supply.
After the air purifier is started, wait for automatic mode or manual mode to be selected. If the automatic mode is selected, the machine waits for manual input of parameters, such as wind speed, humidity, temperature and other requirements. After waiting for the parameters to be loaded, the purifier completes humidification based on the data collected by the temperature and humidity sensor DHT11. During ventilation, the ozone sterilization module and electrostatic dust removal module ensure that the air entering the vehicle is clean and fresh. Then, in the process of small air circulation in the vehicle, the function of dust removal and purification is continuously implemented. After completing the whole working state, check and compare the parameters. If the parameters are not updated, it means that the purifier has completed the initial preset, and the whole program can be ended. If the parameters are updated, the parameters will be reloaded to continue to perform functions such as ventilation and purification.
If the manual mode is selected, the machine will wait for the user's setting, such as the size of air supply, the degree of humidification, etc., until the user turns off and maintains the set state.
summary
The system control design of the vehicle air purifier is based on stc15w401as series single chip microcomputer, which has the advantages of stable operation and low cost. Through the cooperation of multiple modules, the functions of air renewal, purification, dust removal, sterilization and humidification in the vehicle can be realized. It has the advantages of powerful functions and can provide a good environment for the vehicle. In addition, the system design is humanized, the parameters are set by the user, and the wind speed, temperature and humidity are adjustable. Manual and automatic modes are available for users to adjust. If the automatic mode is selected, the air in the vehicle and the air entering the vehicle can be purified automatically, which can not only reduce the entry of outdoor polluting gases and bacteria into the vehicle, but also realize the self circulation and purification in the vehicle. This is a function that most on-board air purifiers do not have. Through modular design, the system can realize more functions by adding modules. For example, after adding an independent power supply, you can continue to work after the car stalls, and prevent the fire caused by too high temperature in the car in summer by ventilation.