With the development of urban economy, central air-conditioning has become an indispensable refrigeration appliance for various large-scale commercial buildings such as office buildings, large shopping malls and hotels. However, one problem that can be caused by the use of all air conditioners is that the indoor closed environment for a long time is internally circulated, the air is not circulated, the indoor air quality is degraded, and the situation such as "air conditioning disease" is caused. According to statistics from relevant experts, in air-conditioned closed rooms, after 5 to 6 hours, indoor oxygen decreased by 13.2%, E. coli increased by 1.2%, Rhodobacter sphaeroides increased by 1.11%, and diphtheria bacteria increased. 0.5%, other harmful bacteria in the respiratory tract have different degrees of increase. It is the people who have been working and living in this environment for a long time, and they often get the "air conditioning disease" unconsciously. It is based on the idea of ​​"air circulation." By letting the outdoor air pass through the purification of the garden plants and the oxygen-enriched treatment, the fresh air and humidity are suitable for the air, and the control circuit is built up to provide the user with the air update at the right time and under the appropriate air renewal demand conditions. service. Improve indoor air quality. At the same time, centralized air conditioning is economically more affordable, and users only need to install air ducts and air valves.
1 system structure and hardware circuit design
The system takes STC's 51 enhanced MCU STC12C65A60S2 chip microcontroller as the core, considering that the performance of STC12C65A60S2 is enough to meet the needs of circuit operation and low cost. The STC12C65A60S2 is the best solution; the conceptual model is divided into: 1) the display part (12864 display), which is used to display the greenhouse degree of the garden and the room in real time, the soil moisture inside the garden, and the user room number that is performing the air update. Parameters; 2) The control detection part (the upper computer written in VB language) is used to display various parameters of the air freshness inside the air storage chamber in real time: temperature, humidity, CO2 concentration, negative ion concentration, and the air obtained through the algorithm. The parameter value of the comprehensive freshness level. By actually dividing the values ​​into categories, we divide the processed air levels with high, good, poor, and poor, and display the air quality levels with different color indicators. The upper machine has control buttons for controlling the mode of operation of the system, objects, and setting the working time. 3) Sensor circuit part for detecting air quality parameters. The overall system plan is shown in Figure 1.
1.1 DS1302 digital clock circuit
Here, the DS1302 clock circuit is used to set the time point of the gas replacement system to change the gas, and the length of time for setting the ventilation work.
The DS1302 is a high-performance, low-power, real-time clock chip with RAM from DALLAS. It can time the year, month, day, week, hour, minute and second, and has leap year compensation function. The voltage is as wide as 2.5 to 5.5 V. The clock can work in 24-hour format or 12-hour (AM/PM) format. The interface between the DS1302 and the microcontroller uses synchronous serial communication, which is connected to only three lines. It is possible to transmit a plurality of bytes of clock signals or RAM data at a time by transmitting one byte or burst at a time. The DS1302 has a 31 x 8 RAM register for temporary data storage. The DS1302 is an upgraded version of the DS1202 that is compatible with the DS1202, but adds dual power pins for the main power/back power supply and provides the ability to charge the back power supply with a fine current.
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