People spend about three quarters of their time indoors, whether at home, office, entertainment or all kinds of transportation, carrying 24 hours a day of indoor space. Indoor air has pollutants, respirable particles or pollutants such as formaldehyde and in a crowded room, air quality has direct influence on human health, requring the real-time monitoring of indoor air quality.
Described in this paper is an indoor air monitoring system for measuring the Air Quality Index (AQI), a quantitative description of the air quality status of the dimensionless index. Control AQI grading standards determine the air quality level, type and color of said measures, health effects and recommended action.
The indoor air quality monitoring described here is based on wireless sensor networks using the STM32 chip as the core and collects information on temperature and humidity, harmful gases, smoke and other environmental information from the wireless dust sensors. The collected data is transmitted to the wireless transceiver for transmission to a repository on a server.
The hardware part of air quality monitoring system is composed of STM32103 control board monitoring platform, the wireless sensor module and C8051 MCU and nRF24L01 wireless module.
In wireless sensor module, sensor communications is done through an SPI (Serial Peripheral Interface) bus system, which is a high-speed synchronous serial peripheral interface, can make the MCU communicates serially with a variety of peripheral devices to exchange information.
The periphery is provided with a FLASHRAM, network controller, LCD display driver, A/D converter and MCU etc. The communication of SPI operates in a master-slave mode in which there is one master and one or more slave devices. Four lines are used, three of them for one-way transmission of the half duplex.
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