European Journal of Scientific Research ISSN 1450-216X / 1450-202X Vol. 102 No 3 May, 2013, pp.425-440 http://www.europeanjournalofscientificresearch.com
Greenhouse Automation Based on Wireless Sensor Network with Novel Diagnostic Subsystem Samir Jasim Dept. of Electrical Engineering, University of Babylon – Iraq E-mail:
[email protected] Mahmoud Shaker Dept. of Electrical Engineering, University of Babylon – Iraq E-mail:
[email protected] Ala'a Imran Dept. of Electrical Engineering, University of Babylon – Iraq E-mail:
[email protected] Abstract Greenhouse is a building, which provides controlled climate conditions to the plants to keep them from external hard conditions. Greenhouse technology gives freedom to the farmer to select any crop type in any time during year. This very important issue especially it effected in countries' economies and population food security. Greenhouse needs monitoring and controlling system to operate in its required operation conditions. With great evolution of science in the field of communications technology, wireless automation system becomes the best solution to apply in greenhouse. Wireless sensor network (WSN) is one of the most significant technologies in the last century. In relation to communication protocol, ZigBee is considered as the main popular stander used in WSN because of its good features, low-cost, low power consumption, high capacity, high security and high reliability which they are pushing designer to use it. In this work, we design a greenhouse monitoring and controlling system at same time that meets the needs of Iraqi farmers, cheap, robust, friendly to use and WSN-based. Our designed system supports a lot of functions which the greenhouse manger need them like real-time parameter display, history chart parameter display , upper and lower control threshold set by the user with three control modes of operation and network diagnostic subsystem. The proposed system is implemented practically for monitoring and controlling system to adjust temperature, humidity, and CO2, level and soil moisture inside greenhouse. In which each node consists of arduino platform to process data, XBee S2 as radio transceiver modules and long life rechargeable battery. The monitoring system based on LabView program as Graphical Use Interface (GUI). The prototype is tested on 20mX10m greenhouse available in college of agriculture / University of Babylon and the results obtained are satisfactory according to the recommendation of specialist's staff member in the college.
Keywords: Greenhouse automation, WSN, Zigbee protocol, irrigation control.
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1. Introduction The plant growth is mainly affected by the surrounding environment parameters like Humidity, Temperature, carbon dioxide concentration, Light intensity, water and fertilizers supplied by irrigation. These variables have direct influence on crop healthy and productivity especially in the regions where the climatic conditions are extremely harsh or no plants can be grown outside. To solve this problem, Greenhouse cultivation is used. It provides controlled environment conditions around the plants and Protect crop from external hard conditions. by this job, greenhouse become a very interested technology to obtain optimal growth of plants, improve crop quality far from diseases and it enables farmers to select any plant in any place at any time[1][2]. Compare to the traditional greenhouse, the modern house uses wireless based automation system. Wireless systems have an advantages include cheap, small size devices, mobility, scalability, low cost with respect to instillation or maintenance and it is more convenient and effective. Wireless Sensor Network is one of the most exiting technologies in the recent years. The main concern of this technology is power managing. It use tiny devices (Nodes) consist of microcontroller platform connected to RF module and battery. These nodes have several limitations in terms of processing, memory, and communication range and power resources [3]. In this work, we design a greenhouse monitoring and controlling system that is meet the needs of Iraqi farmers, cheap, robust, friendly to use and WSN-based. The design based on arduino platform, ZigBee wireless module and LabView program to build our system. The system prototype is tested in actual greenhouse and gives the desired results.
2. Overall System Referring to figure (1) the presented design consists of five types of nodes, each node will take its name and position according to its function in the system. These nodes are: sensing, coordinator, control, tank level and Gateway nodes. In general, we established star network topology and each node in our system contains arduino platform as processor unit and XBee S2 with 2mw radiation power as radio transceiver. Other component in the node will be specific to the node function. Sensing nodes are placed inside the greenhouse to measure temperature, humidity and soil moisture as shown in figure (1). In our system design an option is given to the user to set the number of sensing nodes in greenhouse according to its needing. These nodes consist of RHT03 digital output temperature and humidity sensor and EC-5 soil moisture sensors. Sensing nodes connected to coordinator node wirelessly with star topology. One coordinator node collects data from sensing nodes and process them then send processed data to control and gateway nodes. Coordinator node needs online power source. So that, we attached one MG-811 CO2 sensor to this node since this sensor need 200mA current to warm up its cell and start reactions. Control nodes connected to coordinator node wirelessly also, the user has an option to connect more than one node to the system. Control nodes used to drive actuators like fans, cooler, pump and valves. One water level node placed outside greenhouse to sense irrigation water tank level. Finally, gateway node connecting our network to the computer via RS323 port to display the data obtained from network and deliver data which it sets by the user to the network. LabView program was used to great high level user interface application.
3. System Specifications The proposed system in this research is characterized by the following features: • Arduino platform was used. It is open source hardware and software, cheap and easy to use. • Real-time, average value, greenhouse vital parameter (temperature, humidity, Soil moisture and carbon dioxide level) monitoring.
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Zigbee network technology was applied to obtain optimum power saving. Network sleep period is adaptive. This mean, the greenhouse manager can update the value of waiting interval between two network activities. This operation will increase power saving efficiency. New node merging is automatically put in service to the network topology. Sensing node number is configurable. The farmer can add new nodes or remove old one without any effects on system functions. Control node number is changeable also to fulfill irrigation system requirements. Maximum Control node number equal to sensing nodes number plus one. Greenhouse operator can update the upper and lower threshold control values so that the actual measured parameter level follows the threshold values. Control functions in network. This mean the control function of actuators still working even the computer or gateway node removed. The designed system has the following control modes of operation to fulfill farmer requirements: o Automatic actuators control depends on average value of each greenhouse parameters or automatic actuators control depends on single sensing node measured values. o Manually actuators control for emergency cases. The presented design is supported by error diagnostic subsystem for Sensors error indicator, CO2 sensor state indicator, and node life and activity indicator. Figure 1: Overall system layout
4. System Design and Implementation Full functions greenhouse automation system was design in this paper. The work included hardware and software algorithms design for all system components. Figure (2) shows the system architecture which consisted of:
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Figure 2: System architecture
4.1. Sensing Nodes Sensing nodes placed inside the greenhouse. They were responsible to collect climate information and send them to the coordinator node wirelessly on start network topology. Each Sensing node in our design depends on arduino platform, ZigBee wireless module and two types of sensor to do its job. Moreover, sensing node spends a lot of time on sleep mode and it stills waiting a permission from the coordinator node to start its activities. Sensing node contains the flowing components as shown in figure (3): Figure 3: Practical sensing node
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Arduino platform: Arduino is an open-source electronics prototyping platform [4]. It based on ATMEGA328P microcontroller. The ATMEGA328P has 10-bits ADC with four sleep mode options. We used arduino as main processor unit. It acquires output signal from sensors and calculate environment parameters value. After that, arduino will deliver measured values to ZigBee wireless module via UART serial communication to transmit it to coordinator node.
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• Soil Moisture Sensor: We used EC-5 soil moisture sensor from (Decagon Devices, Inc.) to measure water contain in soil. EC-5 sensors measure the dielectric constant of bulk soil and use that measurement to infer volumetric water content (VWC) of the soil [5]. This type of sensors is characterized by high accuracy, no affected by soil salinity and texture, low power consumption, 10 ms time response, linear scale and low cost. The maximum and minimum values of the analog output from EC-5 sensor proportion to excitation voltage [6]. So that excitation voltage stability is a very important factor in the sensor measurements accuracy. To solve this problem, we designed electronic circuit to ensure excitation voltage stability as shown in figure (4). Microcontroller will calculate VWC% from sensor output voltage by using sensor response mathematical equation. We estimated this equation from curve fitting of Laboratory experience. The result compared with calibrated soil moisture device form Decagon Devices to ensure that our results are correct. • Temperature and Humidity sensor: RHT03 digital-output sensor was used to measure temperature and relative humidity inside the greenhouse. The feature of this sensor includes high precision, full range temperature compensated, low power consumption, calibrated digital signal output and low-cost. It has measuring range from -40 to 80 Celsius with accuracy ±0.5 Celsius for temperature and from 0 to 100% with accuracy ±2% for humidity [7] .Each sensor of this model has temperature compensation technology to correct measurement of relative humidity because Relative humidity reading strongly depends on temperature. We use this type of sensor whose installation is shown in figure (5) to measure temperature and relative humidity inside greenhouse. It is more convenient to use digital output sensor compare to the traditional analog output sensors. Also, the integrated circuit inside generates error message if error occurs. Finally, Sensing nodes perform control function. This function optionally set by the user. It enables sensing node to talk to partner control node through the coordinator node. Figure 4: Practical circuit of EC-5 soil moisture sensor
Figure 5: DHT03 temperature & humidity sensors
4.2. Irrigation Water Tank Node The objective of this node was to maintain water level inside irrigation system water tank. Measured value from this node was sent to coordinator node to modify pump actuator state . This node was fixed at irrigation water tank and it has four Non-contact Liquid Level Switch. It advances technology in liquid monitoring. Unlike traditional liquid level sensors, it does not need to be flooded into liquid. So, in this way, liquid will not be contaminated and the life of the sensor will not be reduced so fast because of the contact between liquid and sensors [8]. In our design, if this node takes permission from coordinator node, tank node arduino start to enable each sensor individually and read its output. When
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it finished from level estimation process, tank node sends measured value to coordinator node which takes decision about actuator state. 4.3. Coordinator Node We used one coordinator node inside the greenhouse. Communication master or coordinator or main controller node is the heart of our network. It is the central node in our design without this node the network inactive and other nodes still waiting permission to send from him. Coordinator node has the flowing tasks: i. Zigbee network coordinator. ii. Mange nodes communication. iii. Collect sensing nodes data and calculate average value of each greenhouse parameter. iv. It Takes decision about actuator state depending on average value and control predefined upper and lower limits of each greenhouse parameter. v. It Routs received information from each node to individual control node. The user can optionally set this function if he needs to control actuators depending on specific sensing nodes measured values. vi. Coordinator node needs online power supply.so that we decided to attach CO2 sensor to this node because CO2 sensor needs 200mA to warm up and to start cell reactions. It starts to send series of beacon signals, each beacon hold unique destination node address, with this beacon, node has permission to begin collecting data and send them back to coordinator node. When the coordinator node receives data from individual node, it inspects incoming data to decide which control mode will use. Then it prepares collected data to monitoring process after finishing, it encodes processed data in data frame and send them to gateway node. Gateway node passes this information to computer to display in human interface program. Figure (6) shows coordinator node with CO2 sensor. • Carbon dioxides Sensor: MG811 sensor onboard from sandbox electronics Inc. was used to measure carbon dioxide level inside the greenhouse. It has Good sensitivity and selectivity to CO2 [8]. MG811 sensor cell needs to warm up to start correct sensing so that, 200mA heater component attached internally to cell [8]. Our work at this sensor includes sensor response equation estimation. We put under pressure CO2 container inside enclosed room and we started to increase CO2 level and record output voltage form sensor. We found that the Sensor produces analog voltage linear to the common logarithm of CO2 level, by fitting output curve we could estimate that equation. Finally, CO2 levels reading compared with calibrated CO2 meter. The difference was acceptable in this application. Figure (7) shows MG811 sensor and heating circuit. Figure 6 a: Coordinator node
Figure 6 b: Coordinator node with co2 sensor
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Samir Jasim, Mahmoud Shaker and Ala'a Imran Figure 7: MG811 onboard CO2 sensor
4.4. Control Nodes Since the presented designed system supports multi control node, so the total number of control nodes equal to the sensing nodes number plus one. To explain this function, each sensing node can assign to individual control node, and all sensing nodes can takes part to control one node. With first control mode, coordinator node will route a copy of the received data from sensing node to unique control node. If this mode is an activated in sensing node, sensing node will compare each own measured value with the upper and lower control threshold which received from beacon signal and generate control signal to modify actuator state directly. By using variable resistance the user can select any sensing node form the network to work with specific control node directly. On the other hand, in the second mode, coordinator node sends control signal depends on the average value of each parameter to control node. We used relay shield which compatible with arduino platform to drive actuators as shown in figure (8). 4.5. Gateway Node Gate way node works as bridge to connect ZigBee protocol with UART protocol. It receives data from coordinator node and rout them to user interface program and Vice versa. Arduino platform has one serial port only, so that we needed to develop relay shield to switch between TX/RX of ZigBee wireless module and arduino platform TX/RX. Figure (9) illustrates gateway node and relay shield. • Gateway operation: During coordinator node activity cycle, relay shield is connecting arduino platform to ZigBee module and the gateway node works in similar way to sensing node but without sensors. It still waits permission from coordinator node to send its packet. The data sent from gateway represented user defined values of the network. After that, when coordinator node finished collecting and processing data, it sends monitoring data packet to gateway node. After node received this packet, the microcontroller will enable relay shield to switch arduino serial port to computer and disconnect ZigBee module; in this situation, gateway is ready to send own information to user interface program. User interface program will response to that packet by sending back a new network setting data packet. When gateway received this packet it tunes off the relay shield and the operation repeated.
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Figure 8: Control node
Figure 9: Gateway node with relay shield
4.6. Communication Module A lot off wireless technologies are avialable in the markets and can be applied to greenhouse automation system but the working under the umbrella of wireless sensor network imposes to use low data rate and low power consumption techniques . There are many technologies produced to fulfill this requirements. However, Zigbee technologie is the populer one. It produced by Zigbee alliance and reprecented upper layers in OSI protocol stack .Zigbee technology depends on physical and MAC layers provided by IEEE 802.15.4 standard . The IEEE 802.15.4 Working Group focuses on developing a short-range communication system in Wireless Personal Area Networks (WPANs) so that, The main features of the IEEE802.15.4 wireless technology are low complexity, low cost, low power consumption, low data rate transmissions, to be supported by cheap devices[9]. We used two modules XBee 2mW U.FL Connection - Series 2 (ZigBee Mesh) and XBee 2mW Wire Antenna - Series 2 (ZigBee Mesh) from Digi International as radio transceivers. As shown in figure (10). These modules characterized by [10]: • Indoor/Urban range: up to 133 ft. (40 m). • RF data rate: 250,000 bps. • Transmit Power Output: 2mW (+3dBm), • Operating frequency: 2.4 GHz. • Receiver sensitivity: -96 dBm. • Operating Frequency: Band ISM 2.4 GHz. • supported both AT and API serial interfaces.
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We used X-CTU program to configure the modules in AT (transparent) mode. In this mode, the modules act as a serial line replacement [9]. It is more convenient to work with AT mode than API mode and AT mode fulfills our requirements. 4.7. Networking We established start topology. Star topology network supports optimum power saving with low network latency. our Zigbee network contains one Zigbee network coordinator and Zigbee end devices as shown in figure (11). Coordinator node acts as Zigbee network coordinator, network manager, routing device and preparing data for monitoring. It has broadcast function by setting DL to 0xFFFF while the other nodes (sensing, gateway and control) represented Zigbee End devices. They are responsible to collect data and send it to the coordinator only. Figure 10: XBee module
Figure 11: Star topology of system
As it is mantioned before, we configured our XBee modules in AT mode. So, to make star network topology we needed two things, i. We must work with Network Data Frames shown in figure (12). ii. Communication master node. To ensure that one node has the air at a time. Figure 12: Network data frame.
4.8. Graphical User Interface (GUI) We used LabView to create a user-friendly monitor interface program that enables operator to perceive, modify the environment conditions of greenhouse and also monitoring the status of the network as shown in figure (13). GUI includes greenhouse real-time parameters display, history chart display, setting upper and lower controlling limits, system control mode, network node number setting, current network Values and Network diagnostic. "Measured values" zone in GUI program displays real-time average value of greenhouse temperature, humidity, soil moisture and irrigation water level. At the same time, the program draws historical chart to these parameters. Our design gives an option to the user to modify environment parameters of greenhouse as he needs. This feature is represented in "threshold Values Setting" zone in the GUI. The operator can set new parameters control levels from "level setting" and see the current value in the network from "Net. Values" indicators. "System status: Auto. or man." Zone is using to change control mode between
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automatic and manual. System default mode is automatic but the operator can change it to manual for emergency reasons. This zone is containing button for each actuator to turn it ON/OFF in manual mode. Also, there is two LED indicators to display actuator state. Our design supported "self-system diagnostic". It is important issue to the operator to know if node is dead or still work put with error. The system provides to the operator the number of nodes which still life and active. The operator compares between "Nodes in Network" and" life & Active nodes" values to estimate network conditions. If they are different, this means that the network topology has been changed for some reason and he/she should check system nodes. Also, CO2 sensor state and tank node life indicators are presented in our diagnostic design. Figure 13: Graphical User Interface front panel
5. System Operation In the following points, we summarized our system operation starting from sensing physical parameter until we reach to display variables and controlling actuators .these steps are: a) Sensing node responsible to collect greenhouse environment data and send them to coordinator node. Sensing nodes must have permission from coordinator node to start collecting data and send them. b) The system starts to collect climate information when coordinator node turns on. After coordinator node active, it takes five second to establish ZigBee network and joining its child devices. c) After five seconds, coordinator node starts to send first beacon signal which hold gateway destination address. Gateway node will response to that signal by sending network setting signal which consists of user defined control threshold values, automatic control mode and network node number. d) When coordinator node receives setting signal, it immediately modifies both the node number in the network and the beacon signal contains. Beacon signal will hold the new control threshold values. e) Then, coordinator node start to send series of beacon signals with different destination addresses to collect information from sensing nodes and water level node. Total beacon number = number of nodes set by user + 2
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If single node controlling mode was selected in any sensing node, the coordinator will make a copy of the received signal from that sensing node and it routs this copy to a specific control node directly. f) While coordinator node receives the response of beacons from each node, it preforms averaging algorithm. The process Includes the addition of one parameter measured values from different sensing nodes and divided result by the number of nodes. Our design support adaptive average value calculation. This mean, when the number of nodes changes for any reason like nodes dead the average value still correct for active and life node only. g) After that, coordinator node read CO2 sensor voltage and calculates CO2 level. h) At this point, all information are available to the coordinator node to preform control functions. It starts to compare each parameter average value with its upper and lower limits which set by the user. By this method, the coordinator node takes decision to turn actuator ON or OFF. i) Coordinator node sends control signal to control node to modify actuator state. j) Coordinator node will send computer signal to the gate way. Gate way node routs this type of signal to computer directly. GUI will display this information to the operator. k) Finally, coordinator node inters waiting interval. This period is configurable and during this interval the network will be inactive and sensing nodes enter sleep mode to achieve power saving. l) During waiting period, GUI response to computer signal coming from gate way by sending back signal contains modified values which they are set by the user. At this point the system will ready to begin new cycle.
6. Irrigation Control Functions The presented design is supported by three types of irrigation control function namely: a) Automatic actuators control which depends on the average value of each parameter in the greenhouse. b) Automatic actuators control depends on a specific single sensing node measured value. c) Manual actuators controlling for control mode which depend on average value. This mode for emergency cases.
7. Diagnostic Subsystem The presented greenhouse automation system supported with diagnostic subsystem. As shown in figure (14), diagnostic subsystem introduces the following services: a) Sensing node number. b) Tank node life indicator. c) CO2 sensor error. After the system nodes deployment, greenhouse manager needs to know the operation conditions of the network. Node life and error in node are the main important matters which the user needs to check. The presented design covers these issues and if any error occurs like node dead, the diagnostic system will sense this change in topology and give an alarm to the user as shown in figure (15). At the same time, coordinator node responses to this error in topology by flashing red LED as shown in figure (16). At the same way, diagnostic subsystem will response to any error occurs inside sensing node itself.
Greenhouse Automation Based on Wireless Sensor Network with Novel Diagnostic Subsystem Figure 14: Diagnostic subsystem.
Figure 15: Node no. diagnostic.
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Figure 16: Error indication.
8. Results The experimental work has installed in the greenhouse available in the college of agriculture / university of Babylon with (20mX10m) dimension in order to measure and control greenhouse environment parameters, temperature, humidity, soil moisture and CO2 level inside greenhouse. According to the greenhouse dimension and requirements and the discussion with greenhouse manager we conclude that only three sensing nodes are sufficient to let the greenhouse operates at high efficiency. Figure (17) illustrates system deployment. According to the following results obtained, the designed system presented in this paper gives a very excellent results and the greenhouse control operation is very efficient. a) Monitoring Greenhouse Parameters. We measured real-time temperature, humidity, soil moisture, CO2 concentration inside greenhouse and irrigation water level successfully as shown in figure (17). The system still work for 24 continuous hours. During this period, the monitoring system was stable; no error detected and power saving concept was achieved. Figure (18) shows 40 minutes of monitoring only. b) Control of Greenhouse Parameters As mentioned above, we used three types of actuators to modify greenhouse climate, fan actuators for controlling temperature, humidity and CO2 level. Solenoid valves to control irrigation process and water pump to control water level inside irrigation tank. We decided to separate control result for temperature, humidity and CO2 level because we have one actuator controlling these variables. But the system stills support separate actuator for each parameter. Figure 17: Practical system deployment
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Figure 18: Temperature, Humidity, Soil moisture, CO2 level monitoring, Irrigation water level of the greenhouse
• Greenhouse humidity control We could perfectly control greenhouse humidity value between 27%RH for upper limit and 18%RH lower limit as shown in figure (19). • Greenhouse temperature control We could perfectly control greenhouse temperature value between 32 Celsius for upper limit and 29 Celsius lower limit. Figure (20) shows the obtained results. Figure 19: Greenhouse humidity control
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Figure 20: Greenhouse temperature control
• Carbon dioxides control To control CO2 level, we fixed coordinator node near fan actuators and we increase CO2 level inside the greenhouse by using CO2 container. We could perfectly reduce greenhouse CO2 level to the user defined value. We recoded the result as shown in figure (21). • Soil moisture control Our design successfully manages greenhouse irrigation system. All irrigation modes in our system work properly. We could perfectly control the amount of irrigation water between the user defined values depending on average parameters value or single sensing node measured value. Figure (21) shows the control of Solenoid valve depending on the average VWC of each sensing node. Figure 21: CO2 level and Soil moisture control.
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• Irrigation water level controlling An excellent control can be performed for greenhouse irrigation water storage tank level between 90% for upper limit and 20% lower limit. We obtain good actuator pump stability by selecting this upper and lower range. Figure (22) shows the obtained results. Figure 22: Irrigation pump control.
9. Conclusions In this work, we presented a design of greenhouse automation system based on WSN technology. The system has the ability for real-time monitoring and control of the necessary environmental conditions (temperature, humidity, soil moisture, and CO2) necessary for the correct operation of the greenhouse. The system depends on advanced technology, high accuracy and short time response sensors to collect climate information. The system provides the capability to change network sensing and control nodes number after deployment. This option support greenhouse size extension and increase automation system efficiency. Wireless ZigBee network is used for greenhouse technology produced low cost in both installation and maintenance, removed limitation of wire and increase power consumption efficiency. The system used "control in network" method this means that the computer can be disconnected from the system without any effect. Greenhouse climate conditions depend upon the type of plant and greenhouse surrounding environments so that, the system provide the ability to user to modify inside conditions of greenhouse as he/she needs. The system supported with diagnostic subsystem to make greenhouse manger to monitor system status especially if he sits far from system deployment. System diagnostic functions include sensing error, error correction and send feedback alarm. The system tested practically in 20m*10m prototype greenhouse and the gateway node is placed at 35m distance far from coordinator node. The prototype system is implemented in the greenhouse of agriculture faculty / Babylon University, according to many college professors specialists praised the results and they tell us that the system is very efficient.
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