Crop greenhouse control systems

With the development of society, the number of various horticultural greenhouses and crop greenhouses is constantly increasing. Some of these greenhouses are also installed with various heating, humidifying, ventilation and cooling equipment, but the operation of the corresponding equipment is still mostly done manually.

When the area of the greenhouse reaches thousands of square metres or even larger, the labour intensity of the operators becomes very high and the temperature and humidity regulation in the greenhouse can no longer be completed by hand alone.

A greenhouse is a place where the environment for plant growth can be changed, creating better conditions for plant growth and avoiding the effects of the changing seasons and the harsh climate outside. It uses light-covering material as all or part of the structural material and allows plants to be cultivated in winter or other seasons that are not suitable for open-field plant growth.

Greenhouse production is aimed at regulating the production period, promoting growth and development, controlling pests and diseases and improving quality and yield. The key technology in greenhouse facilities is environmental control, and the ultimate goal of this technology is to improve control and operational precision.

The environment in a greenhouse refers to the space above the ground where the crop grows in the greenhouse. The environment in a greenhouse is made up of factors such as light, temperature, humidity and CO2 concentration. These factors can be regulated by the greenhouse control system, i.e. environmental control, to provide the best growing conditions for the crop.

Greenhouse control is based on the temperature, humidity and light of the external environment, as well as wind speed, wind direction, rainfall and other climatic factors to control the temperature, humidity, ventilation and light in the greenhouse to create a suitable environment for crop growth. In actual control, the controlled quantities such as temperature, humidity and light will affect each other, where a change in one of the controlled quantities will affect the changes in the other controlled quantities.

The PLC converts the relevant parameters collected by the sensors, such as temperature and humidity, into digital signals and stores these data temporarily, compares them with the given values and, after a certain control algorithm, gives the corresponding control signals for control. This system can also send data to the upper computer via a serial communication interface. This allows for more powerful functions such as data management, intelligent decision-making and statistical analysis of historical data, as well as displaying, editing, storing and printing out the data.

The sensor converts the biologically relevant parameters (temperature, humidity, etc.) into voltage signals, which are transformed into the voltage signals required by the voltage to frequency converter by a signal processing circuit consisting of an operational amplifier. The output current of the temperature sensor is proportional to the absolute temperature, and has a fast temperature response, good linearity and high impedance current output, suitable for long distance transmission.