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Abstract—A greenhouse monitoring and control system based
on Zigbee networks was developed. This system consists of
greenhouse data acquisition controller and greenhouse remote
monitoring and control software. The system could monitor
temperature and humidity, soil water content and
concentration of carbon dioxide in greenhouse and could save
these greenhouse data to database. Greenhouse acquisition
controller had two kinds of control modes, including local
manual control mode and remote wireless control mode in
monitoring center. Greenhouse remote monitoring and control
software can collect, display and record the collected data, also
can control greenhouse environment. According to the current
indoor temperature, the target temperature and the offset
temperature, PID control method is used for temperature
control in greenhouse. The system is implemented using low
power wireless components, and easy to be installed. A good
wireless solution is provided by this system for centralized
management of the greenhouse group.
INTRODUCTION
At present, China is in the process of transformation from
the traditional agriculture to high quality, efficient and
productive modern agriculture. Greenhouse cultivation
reflects the development direction of modern agriculture
[1,2]. With the continuous development of facilities for
agriculture, the requirements of the greenhouse control
system are also increasing. The greenhouse monitoring and
control system not only can monitor many environmental
factors such as temperature, atmospheric humidity, soil
moisture and CO2 concentration, but also can store, manage
and analyze the collected greenhouse data. So the
greenhouse monitoring system is a multi-tasking system.
Greenhouse cultivation aims basically to protect the
plantations from bad weather, and becomes a mean to
achieve controlled agricultural production in recent years [3].
Most of the greenhouse control system adopted PLC
greenhouse control and field bus control system. These
systems have the shortcomings of wiring time-consuming
and high cost. Zigbee technology is a new wireless communication technology. Relative to Bluetooth and WIFI,
Zigbee technology has the characteristics of low complexity,
low power consumption, low data rate, low cost and ad hoc
networks, et al. [4][5]. Zigbee technology is suitable for the
field of automatic control system and implementing devices
[6].
In our case, greenhouse monitoring and control system
based on Zigbee network was developed. The system can
collect environmental information inside greenhouse by
using temperature sensor,humidity sensor and CO2 sensor.
The system can also realize manual control and automatic
control of greenhouse.
II. SYSTEM OVERALL DESIGN
Greenhouse monitoring and control system was made up
of host system, the central node, wireless collection nodes,
winder reel, CO2 enriching device and solenoid valves. The
host system connects the central node through a serial port.
Wireless collection nodes connect the central node through
Zigbee wireless network. Input terminal of wireless
collection node connects the air temperature and humidity
sensors, CO2 sensor and soil moisture sensor. Wireless
collection node can collect greenhouse temperature and
humidity data and CO2 concentration data. These data are
sent to the host system through the Zigbee wireless network.
Greenhouse monitoring and control system mainly includes
greenhouse remote monitoring and control software and
greenhouse data acquisition controller. Greenhouse data
acquisition controller is mainly composed of a Zigbee
wireless acquisition module, CO2 sensor, soil moisture
sensor, air temperature and humidity sensor.
Zigbee wireless acquisition module includes four
channels of 4-20mA current signal inputs, four channels of
high and low voltage outputs. Two channels of high and low
voltage outputs are used for controlling of opening insulation
film and closing insulation film. One channel is used for CO2
enrichment control, another channel is used for irrigation
control in greenhouse. A wireless acquisition module with an
8-bit address is used to identify the controller.
The CO2, air temperature and humidity integrated sensor
selects TGP-CO2 sensor. This carbon dioxide sensor is a fast,
low power NDIR sensor. The sensor can output 4-20mA
analog signal for CO2 concentration, air temperature and
humidity.
The interval time of the data acquisition controller should
be set primarily when the controller works. The greenhouse
data acquisition controllers periodically send the collected data to the central node. The data formats are as follows: the
data header + data length + terminal address + port number +
function code + valid data.
III. GREENHOUSE REMOTE MONITORING SOFTWARE
DESIGN
The greenhouse remote monitoring and control software
has three function modules, such as greenhouse
environmental information collection, environmental control
and meteorological information collection. The greenhouse
environmental information collection can collect greenhouse
air temperature, humidity, CO2 concentration and soil water
content inside greenhouse. Greenhouse environment control
includes remote control of greenhouse winder reel,
greenhouse irrigation and CO2 enrichment. Meteorological
information collection includes the acquisition of outdoor
temperature and humidity, daily rainfall, wind speed and
wind direction. The software can realize manual control and
intelligent control for greenhouse environment. When the
user double-click the icon of greenhouse manually control in
the main system interface, the greenhouse CO2 enrichment
and the irrigation manual control interface can be entered. In
this interface the manual control of greenhouse CO2
enrichment can be realized by clicking the enrichment button.
The control parameters should be set in greenhouse
intelligent control. The setting parameters include the
varieties of greenhouse planting crop as well as the
appropriate range of temperature. Figure 1 shows the setting
interface of greenhouse intelligent control. After a
greenhouse is selected, the parameters of this greenhouse can
be set.
A. Data protocol analysis
The host computer in greenhouse monitoring center
connects the central node SZ02 of Zigbee wireless network
through the serial port. The data of each greenhouse will be
regularly sent to the central node SZ02.
The data of greenhouse environment is transmitted
through character format. A complete statement includes
data head, data length and environmental data. Fig. 2 shows
the process flow of serial port interrupt function.
Data acquisition
The greenhouse monitoring and control system could
real-time monitor the greenhouse interior environment and
exterior meteorological conditions. The collected data of
interior greenhouse environment includes temperature,
humidity, CO2 concentration and soil moisture. The
collected data of outside meteorological conditions consists
of temperature and humidity. Greenhouse remote
monitoring and control software achieves serial
communication by the serial communication control. When
the serial port receives the data which are reported by
greenhouse acquisition controller, the system can receive
and process the collected data, and then save and display the
data. Fig.3 shows the collected data change with time in
greenhouse. Fig. 4 represents a comparison chart of inside
and outside temperature and humidity.
This system saves data every 8 minutes. The received
temperature, humidity, CO2 concentration and soil moisture
data are the voltage and current value but not available for
using directly, this data need to be processed effectively.
CONCLUSION
A greenhouse environment monitoring and control
system based on Zigbee wireless network was developed.
The system could monitor temperature and humidity, soil
water content and CO2 concentration in greenhouse. The
obtained data by using the system will be able to provide the
data support for vegetable planting in greenhouse. The
system is reliable and runs stably. The man-machine
interface of the software system is friendly. This system
provides a good solution for centralized management of the
greenhouse group.