Artificial climate chamber is to move the uncontrollable natural environment into the laboratory, artificially realize the simulation of the natural environment with the three main factors of temperature, humidity, and light related to the growth and development of organisms, create local artificial climate, and seek various The best growing conditions for crops, exploring the laws of their growth and development, cultivating new varieties, and obtaining new technologies of high quality, stable production and high yield. In computer-aided agricultural production techniques, artificial climate chambers are an effective tool for agricultural scientific research.
The artificial climate simulation system introduced in this paper consists of a sensing system, a measurement and control circuit, and a software system. In the process of developing the artificial climate box, it has been widely applied to the sensing technology and the single chip microcomputer technology.
1 The composition of the sensing system The environment in the climate chamber is mainly measured by the three parameters of temperature, humidity and light. The three parameters are obtained by the respective sensors, and the non-electrical temperature, humidity, and light are converted into continuously variable analog quantities by the sensors. In this way, three probes for detecting environmental parameters are designed in the signal acquisition part of the system:
1.1 Temperature probe The NTH5D153A thermistor was chosen according to actual conditions. Its performance parameters are as follows:
Nominal resistance -15 000 Ohm B constant - 4 100
Temperature coefficient - 4.6 maximum allowable power -0.56W
Thermal time constant -20 seconds Operating temperature -30~+125°C
1.2 The humidity probe uses a zinc oxide-chromium oxysulphide ceramic humidity sensor that does not require electrothermal cleaning. The resistivity of the humidity sensor hardly changes with temperature, the aging phenomenon is very small, and the resistance change after a long-term use is only a few percent. The response speed of the component is fast, about 10 seconds for (0~100)%RH, and 2 seconds for humidity change ±20%; there is almost no hysteresis when absorbing moisture and dehumidifying.
1.3 The light probe uses a silicon photocell to convert light parameters into photocurrent. The device has high sensitivity, good stability, and a linear relationship between output current and light brightness. Under natural light conditions, the photocurrent is about 0.1~10mA, which can be amplified and I/U converted by preamplifier output.
2 The measurement and control circuit is due to the logarithmic relationship between the resistance value of the thermistor and the humidity sensitive resistor and the relative temperature change. For the convenience of software design, the logarithmic diodes are used to represent them at equal intervals. Therefore, the output ends need to be connected with the logarithmic diodes. Then through the preamplifier circuit output. The output of the silicon photocell itself is linear and can be directly connected to the preamplifier. Then through the zero adjustment circuit and sensitivity adjustment circuit to send ADC0809 A / D conversion. Through the master chip 8031, the measured data is divided into two output channels here: All the way to the display, using three three-and-a-half LED display, respectively display the current temperature, humidity, light parameters. The other channel data is compared with the standard preset value of the memory. If the error exceeds the error range, it is fed back to the control device such as a humidifier, a heating pipe, etc., and the environmental parameters are adjusted to suit the actual needs.
The composition of the circuit modules is shown in Figure 1.

Fig. 1 The principle of the measurement and control circuit The temperature simulates the 24-hour temperature change in the natural environment. The temperature at different times of the year is preset in the memory with an error of ±0.5°C. When the difference between the measured ambient temperature and the standard temperature is exceeded and the difference exceeds ±0.3°C, heating/cooling is performed to achieve feedback control.
The humidity value detected by the humidity sensor is actually the relative humidity in the climate chamber. The relative humidity in the natural environment is generally between 30% and 80%. When the relative humidity of the environment is lower than the preset standard relative humidity of 1%, the humidifier is activated by the 8031; otherwise, the drying fan is started to dry.
Using a simulated light source, the lighting time can be set as required (spring, summer, autumn, winter). Illuminance changes according to the natural law of simulation. The incandescent lamp combination light source with adjustable brightness close to the sunlight spectrum is used to turn on/off each group of light sources according to a set time, and the simulation of natural light changes from weak→strong→weak→dark→weak and repeated. Its switching time and brightness are controlled by the microcontroller.
3 Modular programming combined with the design of the hardware circuit, the adjustment of the environmental parameters is controlled by the software to achieve the effect of simulating the natural environment. The following tasks were added to the software design:
(1) Exchange standard temperature, humidity and light parameters;
(2) data sampling, filtering and processing;
(3) Keyboard input and display output functions;
(4) Alarm function;
(5) Real-time clock timing function.
Based on the overall design of the program modules, the injection uses interrupt service routines, subroutine calls or direct connections, and the structure of each module program is shown in Figure 2.

Figure 2 Artificial climate box application software block diagram 4 Conclusion This system has been tested and observed for a long time, and it is running well. It has certain experience in setting various parameters of the artificial climate box and has certain practical significance in guiding scientific agriculture. With the advancement of sensors and computer technology, as well as the deepening understanding of climate models, the design of artificial climate chambers will be closer to real natural effects.

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