Developing a Hydroponics System with the Incorporation of an Arduino Uno-Powered pH Sensor
JoyKim,SofiaMaciel-Seidman,RiyaSaha
Teacher:NicoleDulaney
From2005to2050,itisexpectedthatcropdemandswillincreaseby100to110%and50%of landwillnotbesuitableforagriculture(Monsees,2019).Thisbecomesamajorissueas populationsareincreasingandcitiesarefurtherdeveloping,reducinglandforfarming.To addressthisissue,therearetwogoalsforthisproject.Thefirstistodesignacost-efficient hydroponicsystemthatissustainabletogrowfreshbasil.ThesecondistodevelopapHsensor withtheuseofArduinoUnothatprovidesaccurateandinstantreadings.Thesensorwillmonitor andrecordthesystem’spH,notifyingwhenthepHisnotinitsoptimalrangeof5.500-6.500.pH wasthefactorchosentoobservebecauseofitsessentialroleinplantnutrition.Thesensorwill beconnectedtoaspreadsheetandLEDlightsoutsideofthehydroponicsystemthatwilllightup whenthepHiselevated,allowingformodificationstobemadeandsotheuserknowstobalance thepH.Thissystemultimatelyoffersanalternativetoimprovethemonitoringofplantnutrition whichisessentialtothequalityofthecropswhilestillbeingfinanciallyaccessibletomost,as hydroponicsystemsthatmonitorthepHcancostupto$2,615.12(HTGsupply).
Introduction
1.1 Reasons for Alternative Farming Methods
In2050,cropdemandswillincreasefrom100%to110%and50%oflandwillnotbe suitableforagriculture(Monsees,2019).Thisbecomesamajorissuewhilepopulationsincrease andcitiesarefurtherdevelopingwhichdecreasesareathatcouldbeusedforfarming.Countries suchasNigeriaandothercountriesintheAfricanregionarefacingafoodandagriculturecrisis andtheseconditionswillbeamplifiedby2050.Inordertoresolvethisissue,foodproduction mustincrease70%tosatisfythisdemand(Liliane,2020).
MalnutritionisalsocommonlyseenindevelopingcountriesinsouthAsianand sub-SaharanAfricancountriesanditcontributesto45%ofdeathsinchildrenundertheageof five(Kramer,2015).Nutritionplaysakeyroleindeterminingproductivityamongworkers, students,andallhumansandwiththelackofnutrientsincorporatedintoone’sdiet,thehuman bodyhasdifficultyfunctioning(Behrman,1993).However,developingcountriessometimeslack theresourcestofulfillanutritiousandoptimaldiet.Notonlyismalnutritionaproblemin developingcountries,butalsochildhoodobesityhasbecomearisingissueindeveloped countries.In2011,obesitywasseenat15%indevelopedcountriesanddoubledgloballysince 1990(Kramer,2015).Oneofthemaincausesofchildhoodobesityisfood-insecurityandalack ofaccesstofruitsandvegetables(Rose,2006).Onepossiblesolutiontotheproblemof malnutritionandchildobesityistheimplementationofahydroponicssystem.
1.2 Hydroponic Systems
Hydroponicsisaformofagriculturethatdoesn’tinvolvesoil.Instead,hydroponic systemsusenutrientsolutionsandwatertogrowcropsorplantsandareagreatalternativeto
traditionalfarmingmethods.Hydroponicsareusedasamethodofagriculturethatdoesnot requiresoilbutneedswater,sunlight,carbondioxide,andnutrientsinordertosurvive.Cropsin thehydroponicsystemsarenotaffectedbyclimatechangeorharshweatherconditionsmeaning thattheycanbeusedasamethodofagricultureallyearround.Hydroponicsalsoofferasolution toairpollutionsincetheydonotuseherbicides.Withstandardagricultureinvolvingsoil, herbicidesnegativelyimpacttheenvironmentbycontaminatingthesoilandrainwaterwith chemicals.However,hydroponicsdonotutilizeharshchemicalslikestandardagriculturebut insteaduseahomogeneousnutrientmedium(NgaNgyuen,2016).Anotherbenefitofusing hydroponicsisthedecreasedriskofsoil-bornediseasesthatcanthreatencropviability.
Thecropsaresubmergedinwater,keepingtherootsofthecropshydratedandfilledwith nutrients.Thismethodpreventsalotofwaterfrombeingwastedsinceyouareconstantly irrigatingyourlandtomaintainsoilmoistureandhydratingyourplants.Inthehydroponic system,waterandnutrientsareconstantlybeingrecycledwhichuseslesswaterratherthan continuouslyirrigatingaplotofland(Sharma,2018).Thismethodisbeneficialforareasthat experiencedroughtsfrequentlysincethereislessofaconcerntohavewaterforirrigation. Droughtsultimatelyharmcropproductionbecausetheycancauseabnormalplantmetabolismor causetheplanttodie(Dixon,2010).
1.3 pH of Hydroponic Systems
Whendealingwithhydroponics,pHisacrucialfactor.Chemicallyspeaking,pHinvolves theconcentrationofhydrogenions(H⁺)orhydroxylions(OH )insolutionwhichdeterminesthe acidityorbasicityofasubstance.EachplanthasaspecificrangeofpHthatisoptimalforitto grow.Forexample,theoptimalpHrangeofbasilis5.5-6.0(Sharma,2018).ThepHhelps determinetheconcentrationofthenutrientsinthehydroponicssystemwhicharevitalforplant growth.ThepHoftenfluctuateswhentheplantsgrowbecausetheamountofnutrientsgodown quickerthanothers,whichaffectsthepH.MethodstoreadjustthepHmayincludeutilizingpH upordown,addingnutrientsolutions,andchangingoutthewaterinthesystem.
Figure1 Graphicshowingnutrientavailabilityinplants(Ryan,2017)
Figure1displaystheavailabilityofeachvitalnutrientsuchasiron,calcium,andnitrogen inplants.InFigure1,athickerlineindicatesastrongpresenceofthenutrientwhilethinnerline indicatesthelackofaspecificnutrient.Nutrientslikenitrogenarenecessaryforplantgrowth becausetheyhelpcapturelightenergyforphotosynthesis.Whilesomenutrientsmayhavean abundanceinhighlyacidicorhighlybasicsolutions,almosteveryessentialnutrientispresentin aslightlyacidicenvironmentwhichrangesfromaround5.5-6.5.
AmicrocontrollerboardcalledArduinoUNOisbasedontheATmega328P.Itcontains6 analoginputs,a16MHzceramicresonator,14digitalinput/outputpins(sixofwhichcanbe usedasPWMoutputs),aUSBport,apowerjack,anICSPheader,andaresetbutton.Itcomes witheverythingrequiredtosupportthemicrocontroller;togetstarted,justuseaUSBcableto connectittoacomputeroranAC-to-DCadapterorbattery.TheArduinoUnoisawell-liked optionforCreativeprojects,prototyping,andlearningtoprogrammicrocontrollers.Itis designedforusagebybeginnersinelectronics.Itisfrequentlyutilizedinawiderangeof applications,fromtheconstructionofstraightforwardrobotsorinthiscase,hydroponics systems,tomoreintricateoneslikehomeautomationsystems.TheArduinoUnoisapotential optionforpeoplewhoarenewtomicrocontrollersbecauseitisalsoreasonablypricedand simpletouse(UNO R3 | Arduino Documentation,n.d.).
1.5 Purpose
Cropsaresensitiveandvulnerabletoclimatechange.Hightemperaturescancausethe growthofweedswhichcanleadtotheuseofherbicides.Theuseofherbicidescanleadtoan
1.4 Arduino Unoincreaseinpollutionandincreasehealthrisks.Additionallyduetotheincreaseinsoilerosion, landthatoncewasfarmablehasloweredinsoilqualityandisnolongerfertilebecauseofthe impactsofwindandwatermakingthesoildeteriorate(Monsees,2019).Cropsinthehydroponic systemsarenotaffectedbyclimatechangeorharshweatherconditionsmeaningthattheycanbe usedasamethodofagricultureallyearround.Theyaresubmergedinwaterkeepingtherootsof thecropshydratedandfilledwithnutrients.Thismethodpreventsalotofwaterbeingwasted sinceyouareconstantlyirrigatingyourlandtomaintainsoilmoistureandhydratingyourplants (Sharma,2018).Inthehydroponicsystem,waterandnutrientsareconstantlybeingrecycled whichuseslesswaterratherthancontinuouslyirrigatingaplotofland.
Thepurposeofthisstudyistodesignaspaceefficient,low-costhydroponicsystemthat growsbasil,aswellasanArduinoUnopHsensortodetectandalerttheuserofdangerouspH levels.ThepHsensorwillmonitorandrecordthesystem’spH,notifyingwhenthepHisnotin itsoptimalrangeof5.5-6.0.TheArduinoUnopHsensorwillallowformoreclearandaccurate measurements.Furthermore,itwillenabletheuserofthehydroponicsystemtoinstantlyknowif thepHlevelsaretoohighortoolow,whichhelpspreventplantexposuretoimproperpHlevels.
2.1 Engineering Goals
Methodology
1. Designahydroponicssystemthatissuitableforgrowingmint,basil,andbabylettuce. 2. DesignanArduinopHsensortotestthepHofthesystem’swater.4. CreateanimmediatewarningsystemonthedevicetoindicatedangerouspHlevelsinthe system.
5. Makethissystemspaceefficient.
HydroponicSystem:
pHSensor:
6. Makethissystemcostefficient. 2.2 Materials 1. Opaquestoragecontainer(3.75gallons) 2. Netpots 3. Airpumpwithairstone 4. pHup 5. pHdown 6. Drill 7. Seedtray 8. Rapidrooters 9. Growlight 10.Gloves 11. Googles 12.Basilseeds 13.Ruler2.3 Code Description
ThesourcecodeforthepHsensorwaswritteninPythonlanguage.The pHsensoruses theSoftwareSeriallibrary Thetestingcodetakesareadingevery20minutes,butisadjustablein thecodeifanotherfrequencyoftimeisneeded.Thefollowingparametersarerecordedafter eachreadingistaken:thecurrentpHofthewaterofthehydroponicssystemandthe correspondingLEDcolor.TheprogramstoresthedatainArduSpreadsheetincolumnform.The dataisthenmanuallysavedanddownloaded.TheRGBLEDlightisprogrammedtolightred, yellowandgreenwhichcorrespondtocertainpHvaluesofthewaterofthehydroponicssystem. TheRGBlightturnsredwhenthepHvalueisgreaterthan6.500;thelightturnsyellowwhenthe pHvalueislessthan5.500;thelightturnsgreenwhenthepHvalueisbetween5.500and6.500. ThesepHvaluesareoptimalfortheplantsgrowninthishydroponicssystem,whichisbasil.The sourcecodeforthedevicecanbefoundinAppendixA.
2.4 Spreadsheet Description
ThespreadsheetthatcolorcodesandpresentsthedatacollectedbythepHsensorisbased inGoogleSheets.ThespreadsheetisprogrammedwithArduSpreadsheet.Utilizingthe
2. ELEGOOUNOProjectSuperStarterKitwithTutorialandUNOR3Compatiblewith ArduinoIDE SoftwareandProgramming: 1. ArduinoIDE 2. SoftwareSeriallibraryconditionedformattingrulesshowninTable4,thespreadsheetautomaticallytellstheuserthe coloroftheLEDlight,thusallowingtheusertoinstantlyknowifthepHlevelofthesystemisat dangerouslevels.IfthepHlevelisabove6.500,thepHofthesystemistoohighandthecellwill sayred.IfthepHlevelisbetween5.500and6.500,thesystemisattheappropriatepHleveland thatcellwillsaygreen.IfthepHislessthan5.500,itistoolowandthecellwillreadyellow. Thesevaluesarearangethatbasilplantsfallunder,andissupportedbyresearchfromthe (Sharma,2018)TherangescanbeeasilyadjustedtoaccommodatethepHlevelsfordifferent cropsthatfarmersmaybegrowingintheirsystem.
2.5 Protocols
Figure2: Stepstakentobuildandsetupthehydroponicssystem.
Table1:Theblanktableusedtocalculatethetotalcostsofallthematerialsthatwereusedtobuildthehydroponic system
2.6 Safety Precautions
Inthisexperiment,pHupanddownwereused.Thesearebuffersthatcanhelpbalance thepHofthesystem.pHuphaspotassiumhydroxide(KOH )andpotassiumcarbonate(K₂CO₃).
Figure4:UARTConnection(Interfacing Atlas Scientific Ph Sensor With Arduino via UART/I2C,nd)pHdowncontainsphosphoricacid(H₃PO₄),citricacid(C₆H₈O₇),andmonoammonium phosphate(NH₄H₂PO₄).Protectiveequipmentsuchasglovesandsafetygoggleswereworn whilehandlingpHupanddown.Additionally,protectiveequipmentsuchasgoggleswasworn whiledrillingtheholesintothelidofthecontainer Anadultsupervisorwasalsopresentwhen thedrillwasused.
Results
Figure5showstheentiresystem.Inthisfigureitcanbenotedthatthebasilhas successfullygrown.TheimageinFigure7,whichwastakentwoweeksbeforetheimagein Figure5showsthebasilatamuchsmallersizeandshorterheight.However,afterbeinginthe hydroponicssystemfortwoweeks,thebasilgrewtoanoptimalheightandsizeandcanbe consumed.Thegrowlights,pHsensor,airpump,andplantscanallbeseeninFigure7.ThepH sensorasshowninFigure7issubmergedinthesystemandisconstantlytakingreadingsofthe system’spH.Figure6showsasideviewofthesystemandsensor.Figure7showsatopviewof thesystemandsensor.ThefrontviewofthesystemisshowninFigure5.Figure8showsthe EZO™pHCircuitwhichisconnectedtothepHsensorandtheArduinoUnoshowninFigure9.
TheArduinoUnoinFigure9isamicrocontrollerthatcontrolsthepHsensorandallowsitto takeaccurateandclearreadings.Thebreadboardmakeselectricalconnectionsbetweenthe resistors,theRGBLED,andtheArduinoUnoinorderforthesensorandLEDlightstooperate properly.TheRGB LEDlightisonthebreadboardandlightsupaccordingtothereadingstaken bythesensor.Figure10depictsthefullsetupofthepHsensorandallofitscomponents, includingthebreadboard,ArduinoUno,andEZO™pHCircuitwithcarrierboard.Figure11
showstheactualsensorthatwasplacedinthesystemandtookreadingsofthewaterinthe system’spHlevels.
Table2showspHlevelsinArduSpreadsheetasanexampleofhowthecolor-codedcells operate.GreencellsindicateapHlevelbetween5.500and6.500. YellowcellsindicateapH levelbelow5.500.Redcellsindicateaphlevelabove6.500. Additionally,acorrespondingLED lightturnedonaccordingtothepHlevelofthesystem.Forexample,ifthepHwas4.495,a yellowlightwouldturnon.IfthepHwas6.495,agreenlightwouldturnon,andfinally,ifthe pHwas6.505,aredlightwouldturnon.Table2 showsthecolorcodedspreadsheetgenerated duringoneofthedaysoftesting.
Figure8:EZO™pHCircuitwithCarrierBoard
Figure10:Fullset-upofpHsensor
Table2:Color-codedspreadsheetgeneratedafterthepHsensordetectedappropriatepHlevelsand highpHlevels inthesystem,respectively
Table3:Color-codedspreadsheetgeneratedafterthepHsensordetectedlowpHlevelsand appropriatepHlevelsin thesystem,respectively
Table4:Conditionalformattingrules
Discussion
Usability
Thedurabilityofthesystemensuresthatitrequiresveryfewrepairsandmaintenance.
Thesystemandthespreadsheetweredesignedtobeeasilyusedbyavarietyofpeople,ina varietyofareas.TheArduSpreadsheetprogramautomaticallylogsandsavesthepHreadings
fromthesensor.ThecellsinthespreadsheetcontainthepHlevelofthesystemandthecolorof theLEDlight.AsstatedinMethodology,theLEDlightisarrangedinthreecolorcategories (yellow,green,andred)accordingtobasil’sappropriatepHlevels.YellowindicateslowpH, greenindicatesappropriatepH,andredindicateshighpH.ByhavingacoloredLEDlightlight up,theuserinstantlyknowsifthesystem’spHisataninappropriatelevelandhowtheyneedto adjustthepH.Forexample,ifauserseesayellowlight,theyknowtheymustaddpHuptothe system.IfauserseesthattheLEDlightisred,theyinstantlyknowtheyhavetoaddphdownto thesystem.Althoughusershaveaccesstothedatainthespreadsheet,theuseofLEDlights allowsuserstoknowtheapproximatepHleveloftheirsysteminaquickandeasymanner.
Moreover,thisspreadsheetprogramcanbetailoredtothepHlevelsofeachuser’s specificcrop.Theusercaneasilychangethecolor-codedconditionalformattingofthe ArduSpreadsheetsdisplaytoaccountfordifferentoptimalpHlevelsforadifferentcrop.For example,ausergrowingbroccolithatgrowsoptimallyinanacidicenvironment,couldadjustthe conditionalformattingvaluesinordertohaveamorebasicoptimalrange.Additionally,users caneasilyusethedatainArduSpreadsheettocreategraphs,charts,andeasilyanalyzetrends.
Notonlyisthespreadsheeteasytouse,butthehydroponicssystemasawholeisvery simpleandveryuserfriendly Afterusershavegerminatedtheirseedsandplacedtheseedlingsin thesystem,theplantsnolongerrequireanypersonalcare.Unliketraditionalfarmingmethods, cropsinahydroponicsystemdonotneedtobecaredforonadailybasis.Theydonotevenhave tobewateredsincetherootsofthecropsareconstantlyabsorbingwaterthroughthesystem.The onlythingusershavetodoisaddnutrientsolutionstothesystemevery7to10days.Theother conditionusersshouldmonitoristhepHofthesystem.OurArduinoUnopHsensor,however, makesthisverysimpleforusers.
Cost-Benefit Analysis
Table4:Thecostofalltheequipmentusedforthehydroponicsystem Thetotalcostofthissystemwas$31895
Notonlyisthesystemspace-efficientandeasytouse,itisalsoverycostefficient.The totalcostofthesystemis$318.95,whichisdrasticallylessthanothersystemsonthemarket.
ThereareveryfewhydroponicsystemsonthemarketwithsimilarpHsensortechnologyasours. AlthoughyoucanpurchaseahydroponicsystemandseparatepHsensor,therearenoneavailable tothepublicthatutilizethesamecolor-codedspreadsheetandLEDlightingsystemlikeours. However,ourentiresystemisstilllessexpensivethansomehydroponicsystemsonthemarket.
Forexample, theUnderCurrentUCE9XXL13systemcosts$2,615.12(HTGSupply Hydroponics&GrowLights).AlthoughthissystemdoesmonitornutrientsandpHlevels,itis stillmuchmoreexpensivethanoursystem.OursystemalsomonitorspHandcostsover$2,000 lessthantheUnderCurrentsystem.Furthermore,ourlowpricehelpsmakethesystemmore easilyaccessibletousersinunderdevelopedand underservedareas.Thisisvitalinhelping providepeopleinavarietyofareasandcommunitieswithaccesstofreshproduce.Purchasingan
expensivesystemsuchastheUnderCurrentwouldnotbeanaffordableoptionforusersin underservedcommunitieswhomweaimtohelpprovideaccesstoproduceandnutritiousfoods.
Conclusion
Allengineeringgoalsforthisprojectweremet.Thehydroponicsystemsuccessfullygrew basil,thepHsensorsuccessfullytookreadingsofthesystem’spH,andtheLEDlightsturnedon accordingtothepHlevels.ThedatarecordedbythepHsensorwassenttoanArduSpreadsheet thatcontainedthecorrectcolorbasedonthesystem’spHlevel.Thesystemwasalsospace efficientasitwasabletoeasilyfitinanapartmentwithouttakinguptoomuchspace.The system’sareais150in²anditsareais900in²,makingitmuchsmallercomparedtosome systemsonthemarketthatcanbeupto224ft².Thismakesthesystemveryaccessibleforpeople wholiveinanurbansettingandmaynothavelandorayardtogrowproducein.Furthermore, thissystemwasfoundtobecosteffective,andismoreaccessibleforfarmers,botanists, agriculturalists,andevenordinarypeoplewhocannotaffordtopurchaseand/ormaintainlarger scale,moreexpensivetechnologies,suchascommercialhydroponicsystemsandpHmonitors.
Inadditiontotheaffordablecostofthissystem,thespreadsheetalsomakesiteasyforusersto monitor,analyze,andadjustthepHlevelsoftheirsystem.Thissystemisavaluabletoolfor farmersandeverydaypeoplewhowanttoeasilyandinexpensivelygrowfreshproducewithout anysoilorland.
Althoughallengineeringgoalsweremet,thissystemisaprototypeandhassome limitations.Theoperationofthesystemasawholeisdependentontheuseofelectricity.The growlightsandairstoneandairpumpmustbepluggedintoanoutletandrunonelectricity
Additionally,thepHsensorreliesonaccesstoacomputer.Acomputerisrequiredtoprogram thesensorandtodisplaythedatainaspreadsheet.Furthermore,thespreadsheetrequiresan internetconnectionandcannotbeusedoffline.Similartoanytechnologicaldevice,thissystem canrequiremaintenanceandrepair,butthesizeanddesignofthesystemallowsittobequickly andinexpensivelyrepairedsoitcancontinuetooperate.
Inthefuture,improvementstothissystemcanhelpaddressitsfewlimitations.To addresstheprototype’srelianceonelectricity,solarpowercouldbeusedinthefuture.This wouldincreasetheportabilityofthesystem,andmakeitmoreenvironmentally-friendly.
Additionally,aportablecomputingdevicecouldalsobeusedinplaceofthecomputerthatthe prototypecurrentlyuses,whichwouldalsoaidinmakingthesystemmoreportableand accessibletousersofalleconomicbackgrounds.Furthermore,anofflinespreadsheetwillenable userstoaccessthedatawithoutconnectiontotheinternet.Thiswillenableusersinmoreremote areasorareaswithnoWiFiaccesstomoreeasilyusethesystem.Moreover,anotherfuture improvementtothesystemcanincludeaddingwheelstoincreaseitsportability.Theadditionof wheelswouldallowthesystemtobetransportedfurtherdistanceswithouttheneedtocarrythe containerthatholdsallofitscomponents.Thiswouldhelppreventdamagetothesystemwhenit isbeingtransportedandincreasethesystem’soverallusability
Thesystemanditstechnologyhastheabilitytonotonlyimproveagriculturalmethods, butitalsohasthepotentialtosignificantlyimprovetheaccesstofreshproduceformembersof underservedcommunitiesandunderdevelopedareas.Hydroponicscanplayavitalroleinthe futurebecauseofitsabilitytoproducecropswithoutsoiloranyland.Inaworldwherelandis rapidlydepletingduetofactorssuchasclimatechange,extremeweatherconditions,and drought,beingabletogrowcropswithoutsoilisahugeadvancementthatcanbeutilizedona
largerscaletomeetrisingfooddemands.Furthermore,thesystem’ssmallsizeenablesittobe usedinurbansettingswhereresidentsmaynothaveaccesstoanareaoflandtogrowproduceor cannotaffordtopurchasefreshproduce,thusincreasingaccesstofreshproduceforresidentsof urbansettings.Moreover,thesystem’sinexpensivecostallowsmembersofunderprivilegedand disadvantagedcommunitiestogrowtheirownproduceandhaveaccesstofresh,nutritiousfoods.
Acknowledgements
Wewouldliketothankourparentsforalwayssupportingandaidingusinallour endeavors.ThankyoutoourresearchteacherMs.Dulaneywhoguidedus, encouragedus,andmonitoredourprogressthroughoutthisentireprocess.ThankyouMr. Pollatos,ourpreviousscienceresearchteacherandcurrentDirectorofScience,forhis support.ThankyoutoMr.Laspina,BethpageHighSchoolRoboticsMentor,forgivingus permissionandsupervisinguswhenusingresourcesoftheBethpageHighSchoolRoboticsLab.
WewouldalsoliketothankNYITandSAAWAforawardinguswithresearchgrantstohelp fundthisproject.Thisprojectwouldnothavebeenpossiblewithoutthepeopleacknowledged above.
References
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Dixon,G.R.,&Tilston,E.L.(2010).Soil-bornepathogensandtheirinteractionswiththesoil
environment.InSoilmicrobiologyandsustainablecropproduction(pp.197-271).
Springer,Dordrecht
HTG supply: Hydroponics & Indoor Garden Supply Store.HTGSupplyHydroponics&Grow Lights.(n.d.).RetrievedJanuary1,2023,fromhttps://www.htgsupply.com/
Interfacing Atlas Scientific Ph Sensor with Arduino via UART/I2C.(n.d.).HowToElectronics. RetrievedJanuary2,2023,from
https://how2electronics.com/interfacing-atlas-scientific-ph-sensor-with-arduino-via-uart-i 2c/
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MonseesH,SuhlJ,PaulM,KloasW,DannehlD,etal.(2019)Lettuce(Lactucasativa,variety Salanova)productionindecoupledaquaponicsystems:Sameyieldandsimilarqualityas inconventionalhydroponicsystemsbutdrasticallyreducedgreenhousegasemissionsby savinginorganicfertilizer PLOSONE14(6):e0218368.
https://doi.org/10.1371/journal.pone.0218368
Ngyuen,NgaT.,etal."Hydroponics:AVersatileSystemtoStudyNutrientAllocationandPlant ResponsestoNutrientAvailabilityandExposuretoToxicElements."USNational Libraryof Medicine,13July2016,www.ncbi.nlm.nih.gov/pmc/articles/PMC5091364/.
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Appendix
APPENDIXA:pHSENSORSOURCECODE
#definetx3
//definewhatpintxisgoingtobe
SoftwareSerialmyserial(rx,tx);
//definehowthesoftserialportisgoingtowork
//astringtoholdincomingdatafromthePC Stringsensorstring="";
Stringinputstring="";
//astringtoholdthedatafromtheAtlasScientific product
booleaninput_string_complete=false; //havewereceivedallthedatafromthePC booleansensor_string_complete=false; //havewereceivedallthedatafromtheAtlas
Scientificproduct floatpH; //usedtoholdafloating-pointnumberthatisthepH intred_light_pin=11; intgreen_light_pin=10; intblue_light_pin=9; voidsetup()
Serial.begin(9600);
//setbaudrateforthehardwareserialport_0to9600 myserial.begin(9600);
//setbaudrateforthesoftwareserialportto9600
//setasidesomebytesforreceivingdatafromthePC sensorstring.reserve(30);
inputstring.reserve(10);
Scientificproduct
//setasidesomebytesforreceivingdatafromAtlas
pinMode(red_light_pin,OUTPUT);
pinMode(green_light_pin,OUTPUT);
pinMode(blue_light_pin,OUTPUT);
} voidserialEvent()
{
inputstring=Serial.readStringUntil(13); //readthestringuntilweseea<CR>
input_string_complete=true; //settheflagusedtotellifwehavereceiveda completedstringfromthePC
}
voidRGB_color(intred_light_value,intgreen_light_value,intblue_light_value)
{
analogWrite(red_light_pin,red_light_value);
analogWrite(green_light_pin,green_light_value);
analogWrite(blue_light_pin,blue_light_value);
} voidloop() {
//ifastringfromthePChasbeenreceivedinits entirety
if(input_string_complete==true)
myserial.print(inputstring);
//sendthatstringtotheAtlasScientificproduct myserial.print('\r');
//adda<CR>totheendofthestring
inputstring=""; //clearthestring
input_string_complete=false;
//resettheflagusedtotellifwehavereceiveda completedstringfromthePC
if(myserial.available()>0)
//ifweseethattheAtlasScientificproducthassenta character
charinchar=(char)myserial.read();
//getthecharwejustreceived
sensorstring+=inchar; //addthechartothevarcalledsensorstring if(inchar=='\r')
//iftheincomingcharacterisa<CR>
sensor_string_complete=true; //settheflag
//ifastringfromtheAtlasScientificproducthas beenreceivedinitsentirety
if(sensor_string_complete==true)
//Serial.println(sensorstring); //sendthatstringtothePC'sserialmonitor
//Serial.println('\t');
floatphValueInDouble=sensorstring.toFloat();
//Serial.println(phValueInDouble);
//RGB_color(255,255,255);//White
//delay(1000);
if(phValueInDouble>6.500)
Serial.println(sensorstring);
//Serial.println('\t');
Serial.println("RED");
RGB_color(255,0,0);//Red delay(1200000);
if(phValueInDouble<=6.500&&phValueInDouble>=5.500)
Serial.println(sensorstring);
//Serial.println('\t');
Serial.println("GREEN");
RGB_color(0,255,0);//Green delay(1200000);
/**if(phValueInDouble==3.572)
Serial.println(sensorstring);
Serial.println('\t');
Serial.println("BLUE");
RGB_color(0,0,255);//Blue delay(1000);
if(phValueInDouble<5.500)
Serial.println(sensorstring);
//Serial.println('\t');
Serial.println("YELLOW");
RGB_color(255,255,0);//Yellow delay(1200000);
sensorstring="";
//clearthestring
sensor_string_complete=false; //resettheflagusedtotellifwehavereceiveda completedstringfromtheAtlasScientificproduct