Home air quality monitor based on ESP8266

1 Introduction

In recent years, topics related to air pollution have emerged one after another in my country, and news about air quality issues frequently hit the screens. I once watched the "Under the Dome" program hosted by CCTV reporter Chai Jing and learned that air pollution in our country has become very serious and has even endangered the lives and health of residents. Various reports have been emerging one after another. After some reflection, looking back, when I started to examine my surrounding environment, I found that during the two time periods of 6-7 a.m. and 4-5 p.m. , when I looked out the window, I could clearly feel Everything within sight became gray; I opened the window to soak in the breeze. The breeze should be cool and refreshing, but when it hit my face, it made me cry, cough, and feel vaguely nauseated. It was obvious that something was wrong with the ambient air. Later, I learned by consulting relevant information that this shortening of the visual distance and irritation of the respiratory tract is due to the large number of motor vehicles used by people during the peak hours of commuting. Motor vehicles burn gasoline and diesel and emit a large amount of exhaust gas. The dust raised by driving on the road and these fine particles floating in the air are collectively called PM2.5 . Nowadays, there is a PM2.5 indicator in the daily weather forecast . When the PM2.5 index in the air is high, it means that the air quality outside is very bad, and the air is filled with a large amount of inhalable particulate matter. Respirable particulate matter, as the name suggests, is a type of particulate matter that can be inhaled into the respiratory tract. When a large amount of inhalable particulate matter floats in the environment, if the doors and windows are not closed tightly, even if you are indoors, you will be forced to inhale a large amount of imperceptible PM2. 5. It may cause cough in mild cases, or lead to various diseases or even lung cancer in severe cases. Air pollution is not limited to inhalable particulate matter. Everyone has a warm home. Every happy family is inseparable from careful decoration. There is a special carcinogen in the building materials and paint used in the decoration process: formaldehyde. . As we all know, after decorating the home and painting the walls, it takes a while for the formaldehyde to evaporate almost completely before you can move in. However, there is no fixed time limit for this waiting time, and it can only be judged through personal experience and the intensity of the odor irritation. . But even if the smell dissipates and the air seems to have no strange smell, we still cannot guarantee whether the concentration of formaldehyde residues reaches the relatively safe national standard of less than 0.08 mg / cubic meter. If you check in rashly, you will soon become tearful and drowsy, or even get sick and be hospitalized. Case. There are also some common coughs, colds, and runny noses. Most of these diseases are caused by sudden changes in temperature and are difficult to prevent. We generally can only use our mobile phones to check the approximate temperature and humidity of the local outdoor at that time; while indoors, in addition to being in a fixed place, There is no other better measure or effect than placing an inconvenient thermometer and hygrometer for occasional checking, and it cannot serve as a temperature warning. Therefore, while studying, I used the DHT11 module and ESP8266 chip to design and produce an IoT terminal device that can detect ambient temperature and humidity anytime and anywhere. This graduation topic selection made me realize that the design idea of ​​my previous temperature and humidity detection equipment was relatively single, the plan lacked integrity, and there was still room for improvement and optimization to make it more practical. At the same time, I found that a large number of air quality testing equipment on the market are limited to a certain function, either only monitoring PM2.5 , or only analyzing formaldehyde. Why not integrate these features? This greatly expanded my thinking about design. However, integration alone is not enough. I also realized that modern equipment needs to further refresh its thinking and keep up with the information age, so I finally decided to design and implement a home air quality detector with Internet of Things functions.

2. Significance

The development of the economy and the improvement of living standards have made people pay more and more attention to the air environment and their own health. However, due to the large-scale construction of modern cities, the quality of the air is getting worse. The dust concentration seriously affects the human respiratory system. Coupled with people's demand for indoor decoration, the harm of formaldehyde and dust concentration and the influence of temperature and humidity make semi-enclosed indoor spaces Air quality conditions are even more worrying. In terms of air quality detection, a variety of indoor air quality detectors have been developed at home and abroad. Through all-round comparison, it is found that foreign products have relatively complete functions, high measurement accuracy, and relatively user-friendly system interaction interfaces, but are expensive; domestic products have obvious advantages in price, but compared with foreign products, they are inferior in functionality. There is still a certain gap in terms of completeness, detection accuracy and user experience, and it cannot be popularized in most households.

Based on the above background, this project designs and implements a cost-effective household air quality monitor, which allows home users to fully understand the air quality status of their environment, effectively avoiding unnecessary worries and allowing them to respond and prepare in advance. Corresponding precautions. The main control of this design uses ESP8266 , which can accurately and effectively collect the physical parameters of formaldehyde concentration, dust concentration, temperature and humidity in indoor air through sensors, and upload them to the main control chip for data processing. The main control chip then displays real-time information on the screen. , thereby providing a cost-effective option for the majority of home users to quickly and accurately detect indoor air quality conditions in real time, which has practical significance to a certain extent.

3. Research ideas

By analyzing the factors that affect indoor air quality, and focusing on the four factors that have the greatest impact on the human body, namely formaldehyde, dust, temperature and humidity, we researched and designed a portable detector based on ESP8266 , which can accurately and effectively measure indoor air. formaldehyde concentration, dust concentration and temperature and humidity. The implementation of this home air detector system is divided into processing layer and application layer. As shown in Figure 1-1 below , the processing layer mainly includes the ESP8266 main control board, DHT11 temperature and humidity sensor module, PM2.5 dust sensor module, GY-SGP30 gas sensor module, OLED display module, active buzzer alarm module and power supply Module composition; the application layer includes the server and user interface established by ESP8266 . After the equipment is initialized, the three sensor modules process the detected environmental data and transfer it to the main control board; after analysis and processing by the main control , it is judged whether the detected data meets the national standard value in the "Indoor Air Quality Standard" ( GB18883-2002 ) , when the value exceeds the standard, the user is prompted through an active buzzer alarm, and the data is displayed on the OLED display after friendly processing; the power module is responsible for the power supply of the entire system; the server sends the processed data to the web client interface display. This testing instrument has the characteristics of strong practicability, fast measurement speed, simple operation and friendly user interface. Compared with other professional equipment, this testing instrument is more suitable for the general public to quickly and accurately detect indoor air quality in real time for the majority of home users. situation, providing a compromise between simplicity, reliability and professionalism.