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Implementation of Wireless Sensors Networkfor Automatic Greenhouse Monitoring

M. Fezari*, A. Khati** and M. S. Boumaza**** Laboratoire de Siga et Automatique ASA), Dpartement d'lectronique

UniversitBai Mokhtar Annaba*Laboratoire de P hysique des Rayonnements (LPR), Dpartement de physique

Dpartement de physique, Facult des sciences, Universit Bai Mokhtar

*** Laboratoire de P hysique de Guel ma (LPG), Dpartement de Gnie lectriqueUniversit 0 ?ai 94 Guelma

Mohmfz@uwcuk kht@yhoof

- hardware design and soware simulation arepresented to control and monitoring greenhouse parameters

such as: air temperature, humidity provision and irrigation bymeans of simultaneous ventilation and enrichment. A set of

smart wireless sensor modules to control and monitoringsystem were designed and tested. The heart of the smart sensoris a microcontroller that receives data on greenhouse

environment conditions from many sensors installed inside andoutside. The smart sensor transfers the data to and from a PCvia a wireless transmission system. Accordingly, it changes the

state of greenhouse command devices, heaters, fans and vapor

injectors to reach the desired condition. A friendly GUI usinghigh level language was developed to carry out the monitoringtasks. The program implements the control algorithmscomparing the received data with set points, sending control

signals to the smart sensors i order to rach the desired

conditions. Performance of the designed system was tested byinstalling it in the model greenhouse with a set of smartsensors.

w; w wk

1. NTRODUCTIONMany research projects study possibilities for

improvement of existing greenhouses anor controlsystems in these greenouses. Oen, it is necessary todevelop an ehanced measurement and control system tofacilitate these studies, snce commercially availablesystems do not provide the necessary exibility for this typeof research. For example, it oen happens that new controllaws cannot be implemented in the available soware, orthat the number of measurements is limited. For instance, nmany advanced contr tudis it is necsary t hve ccesto the low-level manipulators directly [1 - 4].

Apart om developing a completely new control system,one way to handle the limitations of commercially availablesystems is to conect a PC to the commercial climatecomputer. This PC runs

advnced algoritms that generate set-points, which aresent to the climate computer.

II. ATRALS ND THODSOne of the most important tasks of the measurement and

control system is to measure all data needed to study thebehavior of the greehouse and to gain enough information for

modeling of the greenhouse climate and validation of thesemodels. The sensors installed in te greenouse andconsiderations to be taken into account when choosing thesesensors can be mentioned here:

Temperatre is measured outside, in the greeouse, in thesoil and in the water circuits at various locations. For comparabledata the same type of sensor is used at all locations. DS1620sensors were selected, since, at the same level of accacy, thesesensors offer better reliability and long term stability thanalteatives like thermocouples and thermostats. Moisturecontent can be measured very accurately with the principle ofwet/dry bulb temperatures. In our case however most sensorsare dicult to reach, which complicates lling the water

container of the wet bulb sensor. Therefore electronic humiditysensors were selected.

Aer calibration their accuracy is good enough forgreenhouse experiments and they are more reliable th otheroptions since no equent maintenance is required. Mostdominant drawback is that electronic sensors do not nctionwhen condensation occs on the sensor. CO concentration ismeasured with a commercially available CO sensor that worksaccording to the ina red measurement principle, see re [5] and[6]. These sensors are small, do not have a long response time(as some centrally placed analyzers) and do not require equent

maintenance.

Air velocity is measured both inside the heat exchanger asel s utdos (id sd) he atte is esy to measue ithcommercially available wind sensors (rotating turbine wheel) asin gre 1.

Moreover, Wireless Sensor Networks (WSNs) generallyconsist of a large number of low-cost, low-power,multinctional sensor nodes that are smal in size andcommnicate over short distances [1]. Their structure andcharacteristics depend on their electronic, mechanical andcommunication limitations but also on application-specicrequirements. In WSNs, sensors are generally deployed

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randomly in the eld of terest; however, there are someapplications which provide some guidelines and insights,leading to the construction of an optimal architecture terms of network inastrctre limitations and applicationspecic requirements [10 - 13]. So ndamentals to thesuccess of mode agribusess are ecient productionmanagement, high productivity and improved productquality. Nowadays, it is possible to implement sensors node

based on microcontroller, each node integrates some sensorsand possible actuators, by adding to these sensors nodes away to communicate, we will get a Sensors network.

In order to make a good decision on WSN, simulation iscarried out using zzy control theor [16-18]. The basic

prciple of zzy controls is: to compare ideal value ofcontrolling quantity with the measuring value t transient,receive input parameter (deviation ), and calculatedeclination variation rate , tu and into zzyquantity and l and then make a decision by zzycontrol regular R and l get zzy control parameter u,nally tu the zzy control one into accurate quantity, acton the target under controlled, circulate like this, and realizethe zzy control of the target. The zzier the zzy targetthat controls is, the more superiority this kind of controlmethod reects than the other methods they are. So that it isvery suitable for the control of the environmental system ofthe greehouse.

RF +I 6 c 2

t

00

Figure 1. Overview of the greenhouse system controller

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S

III. RNHOUS ONTROL ND ONTORNG YSTMConcept of greehouses for controlled enviroment

agriculture is gaing worldwide popularity; thereforegreehouse automation at commercial level is experiencing

attention. Most of the mode automation devices usecomputers and information technology as their basicconstituents. Therefore, automation builds a strong andsuccessl foundation of mechanization d is one of themost welcomed aspects of advanced plant productionsystems in controlled enviroments. Furthermore, theproduction shied to lower cost areas and this speeds up themechanization. The main purpose of a greeouse is toprovide and maintain the environment that will result inoptimum crop production or maximum prot . This includesan enviroment for work eciency as well as for crop

growth. There has been much research and design aboutenvroment control using sophisticated technology (automatedand computerized), but those applications are mostly still inindustrial sectors. In the agricultural sector especially indeveloping countries such as Algeria, the application of theenviroment control tecology is still limited, because it itshigh cost. The designed concept is presented in gure 2. Twosensor nodes are installed side the greenhouse, the infoation

conceing temperature and humidity are sent to the maincomputer via a wireless transmission system, and each node hasa processor ID and can control the motor of a ventilator or heatand a vapor injectors (Humidity System) installed nside thegreehouse. The desired control conditions are forwarded to thenodes by wireless transmission.

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+ .-E-- .I -C-2-V hdy (r, d : \v d ;I-v Mll------

Figure 2. Overview of the greenhouse system controller

VI. MN OMPONNTS of a NSORS ODThe controller was designed to maintain temperatre, relative

humidity and water availability in a desred range.The controller consisted of three temperate sensors and a

number of timers for iigation. The relative humidity wasmeasured using wet bulb temperature sensor. The outputs ofcontrll opet spraer pump to ncease humidt, a dippefor water supply, a fan with ventilation rate of 850 mIto let airin and two fns, each one with a ventilation rate of 280 m I toventilate air out. Mist and fog systems produce tiny waterdroplets that evaporate, thereby cooling and humidiing thegreehouse air. Each sensor node within the proposed designwireless sensors network to control the greeouse is composedof the following parts as shown in gure 3:

A microcontroller om microchip the PIC1676 with8 kilo instrction as program memory, a Ram of 64 bytes , 64

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bytes of EEPROM, Three Parallel ports and one serial portfor communication nd 3 timers [14].

A temperatre sensor, the DS 1620 measrestemperature using a band-gap based temperature sensor. etemperature reading is provided in a 9bit, two'scomplement readg by issuing a read temperaturecommand. The data is transmitted serially through the 3wire serial interface, LSB rst. The DS1620 can measuretemperature over the range of -55 C to +125 C in 0.5 Cincrements.

Temperature Control with the DS1620, The thermostatoutputs of te DS 1620 allow it to directly control heatingand cooling devices. For example, the THIGH output couldbe used with an exteal latch to tu on a fan as soon as themeasured temperatre exceeds the TH threshold, as shownin Figure 4. This is one possible use of the thermostatoutputs, but it isnt the most efcient way to control a fan,since once the fan ted on, there is no way to t it ofConversely, the TLOW output could be used in a similarfashion to t on a heating device Once again, however,there is no way to the heater off once the desiredtemperature rnge is reached. Using a self-regulating heaterprevents overheating, while the DS 1620 assures that itinitially tus on only if the temperature is cold enough towaant it.

smisior-ntnn

TST

ST

t

c66th

Qt=4h

S620epete

oe Sppy +2 vots

Figur 3a Sensor node Component

,

!

,_ JFigur 3b Temperature sensor DS1620 in control of

ventilation A humidity sensor SHT, When it comes to

precision temperature and humidity measurement, Sensirion

(.sensirion.com) has simplied the process of their SHTxsensor series. Trough a two-wire serial interface, bothtemperature nd hmidity can be read with excellent responsetime and accacy. Parallax has simplied the use of the SHTby mounting it in a user-iendly 8-p DIP module. The moduleincludes a data-line pull-up and series limiter making it possibleto coect directly to the BASIC Stamp or any othermicrocontroller .

A wireless radio-equency transmitter module isadded to the system in order to facilitate the communication.

Each sensor node control a circular area within thegreehouse covered by the accracy of sensors and FR

transmitters, the smar sensor can active vapor injectors electrovane an/or a closer ventilation within the greehouse.

A communication protocol is designed in order to facilitatetransmission of information among closer smart sensors creatinga wireless network of smart sensors.

The sensor node commands the action of a ventilationthrough Motor M and Humidity control tough motor M2 . The communication protocol is mastered by a personalcomputer via wireless components and a Graphique UserInterface as shown in gre 4.

V. F LOC CONTROLLERSThe crop-grow y control system designed in this

paper is a kind of automatic control system, which based on theknowledge of y mathematics and y language nowledgeexpression. It also regards y logic regular reasoning as thetheoretical foundation, and it is a numerical control systemadopting the computer numerical control tecnology of thecloses-ring strcture form one of feedbacks passageway.

The ame diagram of y control system is as Figre 4shows.

A Study on input and output parameter inJuzzy controer

Input parameter is an exteal variable of the ycontroller, and its numeric equals difference betweenmeasurement T(t), H(t) and ideal T, H of moment t. That is

ET = T (t) - To Temperature deviation 1)

CH=EH =H(t) -HoHumidity deviation

Quantitative temperature deviation set XlXl={-5,-4,-3,-2,-1,0, 1,2,3,4,5}. Quantization

temperature deatn Ke = = 5 ,

2)

11 grade, thenfactor of the

EH y control area establishes less than 5%, j value as{NBNNS,ZO, PS,P PB} Quantiation is rade X={-5-4,-3,-2,-1,0,1,2,3,4,5}. Quantiation factor of the t humidity

deviation K = = 5 e In the temperature and humidity control, it does not merely

make temperature rise to the heating of the greehouse, but alsocan increase the greehouse moisture evaporation. It makes thehumidity rise too. When arranged wetly at the same time, it willmake temperatre change too. The coupling phenomenon isnamed cross between the temperature and humidity. To

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introduce solving coupling parameter a] a2 it receivesthe equation of outputting.

Vr= {l-aJxCr+a2 xCHVH = {1-a )xCH +a xCrhere a] and are coecients less th 1

To(ide p

dtyf-iure 4.a. The frame diaram of fuzzy control system

B Outputs quanti described

H

Output vriable is endogenous vriable of zzycontroller for adjust temperature and wet machine it is inputvariable. Because it is coupling output of the inputinformation, its variable classication corresponds tovariable of inputting grade.

Ur is temperature control exporting parameter. Its zzysubset E; value is {NBNNS,20,PS,PPB}. mongthem PB (heat completely): The proporion valve is openedmaximum. PM (mild heat): proportion 1/2 valve tu ondegree, PS (little to heat). 1/3 of proportion valve is openeddegree. 20 (not rise or low the temperature): The proportionvalve closes and the skylight does not open. NS (the littledrop in the temperature): The skylight opened 1/3 degree.NM (mild lowers the temperature): The skylight opened 1/2degree. NB (lower the temperature completely): Theskylight is opened maximum.

UH is humidity control exporting parameter. Its zzysubset F value is {NBNNS,20,PS,PPB} among themPB (the whole humidication): All hydrant open. PM (mildhumidication): hydrant open of half, PS (littlehumidication): hydrant tu on 1/3. 20 (no increase orlower humidication): hydrant close and skylight close. NS(little lower temperature): 1/3 of skylight is opened. NM(mild lowers the temperatre): 1/2 of skylight is opened. NB(lower the temperatre completely): The skylght is opened

biggest. Quantication output amount 11 grade, soX6={-5,-4,-3,-2,-1,0,1,2,3,4,5} .

Obviously, when a] and a2 are all 0, Ur= r, UH = H,equal to two single circuits control at this moment. When

they are all 1, Ur= H, UH = r, then it is limit coupling atthis moment as in[20. The real a] and a2 are among O1.

The concrete methods are to hypoesize a] and a2 to be

equal to and carry on the experiment to the greehouse.Whenever heat or eliminate damp, it will make the temperatureand humidity in the greeouse have greater uctuations. Then

gradually increase a] and a2 it makes the uctuation reduce,achieve the goal of solving coupling, thus get the optimumvalue.

Membership FunctionsMembership nctions of temperature and humiditycontrolled output are shown in Figure 4.b and Figure 4.c.

Stability is ne. The form of Membership nction adopts the

triangle or bell has small inuence on control nction. We

choose the triangle form of Membership nction for the purpose

to achieve simplied calculation [17-19. Temperature and

humidity deviation membership nction, the Membership

nctions of temperature and humidity controlled output are

showed in Figure 4.b and Figure 4.c.

j

B V\! NS I PS P.\! P,- -6 5 -3 - - 0 3 5 6

iure 4.b. The temperature and humidity deviation Membership nctions

fC)' p(Czo

2 iiure 4.c. The Membership nctions of temperature nd humiditycontrolled output

VI. MULATON ND ALDATONThe model greehouse has a oor of 10 by 20 m

, covered

with 200mm polyethylene lm. The set of experiments werecarried out dring the autumn season at the university BadjiMokhtar in the city of naba: rst of all, a simulationtecnique based on zzy logic controller were designed andtested then in second part, a practical conception of two Nodeswere installed in the greehouse and a communication protocolis implemented with PC based on the uncontrolled mode ofoperation ( where the node sensors control the greehousedepending on reference values preregistered for temperature and

humidity levels) and the controlled mode ( where all theinformation is provided to the PC and then the PC takes thedecisions and forward the control command to the node sensors).The communication of the greeouse parameters to the host is

presented by each node as a tree byte infoation: the rst byteconstitute the sender address (JD) in rst four bits and thedestination address (the host) n four bits, the second byte is thetemperature information and the third byte is the humidityinformation. The simulation results achieved for these cases forthe air temperate and relative humidity are shown in table 1.

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Table 1. Iitial results of the system

Set 10/10/08 151008 20/1008 221008datesT 25 28 27 27DayTempR H. 48 50 60 55%Offset

ValuesT I I I 1CR.H. 2% 2% 2% 2%

The formatio take om sesors is simulated usigzzy loic cotroller . The greehouse si;ulator with zzylogic cotroller is illustrated i gure 5.a ad 5.b.

1" 'C _e

. .- , 1::1.uM.

r - . I J.

Figure 5.a: simulation of fuzzy logic temperature control

have a better cotrol of the iside coditios. Through zzilycotrollig ad regulatig the crop growth eviromet of thegreehouse, it will play a eormous role to improve the outputad quality of the crops. More experimets o special vegetatioare programmed i ear ture.

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" -. j

Figure 5.b: Simulation of Fuzzy logic temperature Humidity and lightcontrol

VII. ONCLUSONFrom the experimets, it ca be cocluded that the

overall performace of the system to maitai thetemperature ad withi the give rage is satisfactory.However, the time costat of mist fog system is rather log, about 30m , i reachg to the desired hidity level. sesor with quicker respose time as well as usig a

better sprayer system could improve respose time of thesystem. For large greehouse, more odes are ecessary to

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