The electrical and control system of the greenhouse is based on the environmental information inside and outside the greenhouse detected by the information detection system installed inside and outside the greenhouse or observed by the operator, through the strong current control cabinet, environmental controller or computer operation drive / actuator (such as fan system, window opening system, wet curtain water pump system, curtain pulling system, CO2 fertilization system, artificial lighting system, heating system, irrigation and fertilization system, etc.), adjust and control the environmental climate (such as temperature, humidity, light, CO2, etc.) and irrigation and fertilization in the warm room to meet the growth and development needs of cultivated crops (Among them, the artificial lighting system, fan system and irrigation and fertilization system can visit mobile grow system com to know more).
1. Classification of greenhouse electrical and control systems
The electrical and control system of greenhouse can be divided into manual control system and automatic control system according to the degree of personnel participation in operation. The automatic control system can be divided into digital controller control, controller control and computer control according to different functions and composition.
A. Manual control system the manual control system is mainly based on the temperature and humidity measured by the thermometer and hygrometer in the greenhouse and the information observed by the grower indoors and outdoors. It is a system that manually operates the strong current control cabinet to control the drive / actuator. The manual control system is mainly composed of strong current control cabinet.
B. Digital controller control system this control system often only controls a certain environmental factor of the greenhouse. The controller monitors a certain environmental factor in the temperature chamber through the sensor and sets the upper and lower limit values, and then the controller automatically turns on or off the driving equipment, so as to control the environmental factor of the greenhouse within the set range. For example, the temperature controller can be connected The temperature of the greenhouse is regulated by the fan, wet curtain cooling device, etc. due to the low cost, this system is very suitable for the greenhouse with low operation requirements. The digital controller control system is mainly composed of strong current control cabinet, sensor (information detection) and digital controller.
C. The digital controller of the controller control system adopts single factor control. In the control process, it only controls one element without considering the influence and change of other elements, which has great limitations. In fact, many environmental factors affecting crop growth restrict and cooperate with each other. When a certain environmental element changes, other relevant elements should also change accordingly In order to achieve the optimal combination of environmental elements. The controller control system adopts comprehensive environmental control. This control method automatically changes and adjusts other elements when one element changes according to the cooperation relationship between crops and various environmental elements, which can better optimize the environmental combination conditions.
The controller control system is composed of strong current control cabinet, sensor (information detection) and environment controller. The environment controller usually adopts single chip microcomputer or programmable controller as the control core component.
D. Computer control system the difference between computer control system and controller control system is that computer equipment is used. Generally, it can be divided into two categories. One is composed of environmental controller and computer. The computer only needs to complete monitoring and data processing, and greenhouse managers can use the computer for word processing and other work; the other is special equipment, which is control equipment As the core of the system, it can not be used for other work. The greenhouse environment control software is installed in the computer. The computer control system often adopts a variety of sensors, which constitute the information detection system.
2. Common equipment constituting the control systemA. Strong current control cabinet strong current control cabinet generally includes circuit breaker, relay, contactor, button, limit switch and other electrical components. Strong current control cabinet is the basis of greenhouse electrical and control system. Both manual control system and automatic control system need to be controlled through strong current control cabinet.
In the manual control system, the fan, window opener, wet curtain water pump, raising machine, CO2 fertilization equipment, manual lighting equipment, heating equipment and irrigation are turned on or off by operating the button on the panel of the control cabinet. In the automatic control system, the operation of strong current control cabinet has two modes: manual control and automatic control. In case of computer failure or manual operation, the manual control mode can be selected. That is, the control cabinet can perform manual control operation independently of the computer control system.
B. Information detection sensor information detection sensor is an important component to realize the automatic control of greenhouse. The commonly used sensors in greenhouse include temperature sensor, humidity sensor, CO2 concentration sensor, EC concentration measurement sensor, pH measurement sensor, light sensor, outdoor weather station, etc.
Temperature sensor temperature is the most important greenhouse meteorological environment parameter. There are many temperature detection methods and devices. Commonly used temperature sensors include thermocouple type, thermal resistance type, thermistor type, etc.
Humidity sensor humidity can be expressed by absolute humidity and relative humidity. The relative humidity can be detected by the dry wet bulb method. If the water vapor in the air does not reach the saturation state, there is a difference between the dry bulb temperature and the wet bulb temperature. The relative humidity of the air can be obtained according to the difference between the dry bulb temperature and the wet bulb temperature.
CO2 concentration sensor the sensors for detecting CO2 concentration include gas sensitive resistor CO2 concentration sensor, electrochemical CO2 sensor, infrared CO2 concentration detector and impedance piezoelectric CO2 sensor. Gas sensor is a kind of semiconductor sensitive element. It uses the mechanism of CO2 adsorption to change the conductivity of semiconductor itself to detect CO2 concentration. Electrochemical CO2 sensor is a sensor that converts CO2 concentration into electrical signal through electrochemical reaction. Impedance piezoelectric CO2 sensor is a CO2 sensor based on the sensitive response of series piezoelectric crystal to solution conductivity and dielectric constant. The infrared CO2 concentration detector is made according to the specific absorption wavelength of CO2 gas in the infrared region.
PH meter pH is a function of the hydrogen ion concentration of the solution, which represents the pH of the solution. For irrigation, fertilization and nutrient solution cultivation systems, it is very important to detect the pH of the solution.
EC measuring instrument EC refers to conductivity. In the solution, the higher the ion concentration, the stronger the conductivity and the greater the EC value; The lower the ion concentration, the smaller the EC value. In nutrient solution, nutrients exist in the form of ions. If the nutrient content is high, the EC value is large. Therefore, the total concentration of nutrients in nutrient solution can be obtained by measuring the EC Value of nutrient solution.
Light intensity sensor light intensity is a very important greenhouse environmental parameter and the main parameter to control the external and internal shading of greenhouse.
Outdoor weather station outdoor weather station includes wind speed sensor, wind direction sensor, temperature sensor, humidity sensor, light sensor and rainfall sensor.
C. Digital controller digital controller is usually the control equipment used in the control room for single environmental factors in the greenhouse.
The digital controller and the sensor form a control system together. For example, the temperature sensor and the temperature controller form a temperature control system. The temperature information collected by the temperature sensor is transmitted to the temperature controller, and the control signal is sent to the control cabinet to control the opening and closing of relevant equipment according to the upper and lower temperature limits preset by the temperature controller.
D. Many environmental factors affecting crop growth in greenhouse environmental controller restrict and cooperate with each other. When a certain environmental factor changes, the relevant other factors should also change accordingly in order to achieve the optimal combination of environmental factors. The controller control system adopts integrated environmental control. According to the cooperation relationship between crops and various environmental elements, when one element changes, other elements will automatically change and adjust accordingly, which can better optimize the environmental combination conditions.
3. Main functions of automatic control system
A. Measurement and storage functions (data input and storage)
The function of measurement is to detect various environmental parameters of various agricultural facilities according to the inspection mode specified by the operator or the default of the system, including automatic monitoring of environmental factors such as air temperature, humidity, CO2 concentration and light intensity. The measured parameters can be automatically stored in the database online, and all data can be backed up automatically or manually.
B. Data management function
All online monitoring data and manually typed data are stored in various databases according to data types. Operators can quickly retrieve the data meeting certain constraints, display and print them in forms or other forms, and query, count, tabulate and draw curves for these data at any time.
C. Data display and printing function
The main functions of the display are: the measured parameters can be displayed in real time on the projector or computer, and the dynamic change diagrams of various environmental parameters can be output.
D. Regulation function
The equipment to be controlled in the system can be set on the environment controller through the system setting window to realize automatic regulation; It can also be adjusted and controlled on the computer.
E. Fault handling function
Fault processing is divided into two parts: fault alarm and fault diagnosis. When any measured parameter exceeds the preset range, the system adopts multimedia technology to automatically give audible and visual alarm, and access relevant data into and out of the database. The fault diagnosis function indicates the location, nature and solution of the fault, so as to effectively speed up the maintenance progress.
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