Automated Watering System for Greenhouse … · The topic of this project is an automated watering...

ECE498ReportQianyue(Nancy)Guo

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Automated Watering System for Greenhouse Qianyue (Nancy) Guo

ECE498 – Electrical Engineering Capstone 2 Supervisor: Professor Hedrick

November 24, 2015


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REPORTSUMMARY

The topic of this project is an automated watering system for greenhouse at

Schenectady ARC Maple Ridge Center1 (will be referred as ARC later).

The goal is to upgrade the current watering system at ARC. Ideally the system

should run automatically on holidays, weekends, or whenever the individuals and staff

at ARC are occupied. More importantly, the system will have customized user interface

for individuals with disabilities so that they could easily operate the system without

supervising. The system will also have multiple soil moisture sensors employed so that

the plants would not be over watered or under-watered.

Figure1ARCGreenhouseOverview

The project consists of four major components, the microcontroller, the user

inputs, the sensor system and the water delivery system. The structure of it is shown

down below.


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Figure2BlockDiagram

Controller receives inputs from both the User Inputs and the Sensor System. User

inputs are for example, water level controls or buttons to set time for watering. They

control the regular watering schedule for the plants depending on what mode the user has

chosen and what weather of the year or what time of the day it is. There will be different

modes imbedded in the microcontroller that the users can choose from by using a 12-

button keypad. There will also be a 16*2 LCD that gives simple instructions on the

choices that the users are going to make.

Figure3LCDScreenFigure412-ButtonKeypad

Sensor System will be mainly soil moisture sensors. It monitors the whole process

of watering and prevents the system from over-watering or under-watering the plants.


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Figure5ASoilMoistureSensor

The water delivery system will distribute the water to all the plants. There will be

three waterlines, accordingly for dripping tubes, misting heads, and overhead baskets.

The prototype of the system will be built in the greenhouse on campus. It will be

designed and coded for using on one bench of seeding table and one row of hanging

basket. Watering needs for four types of most popular spring plants will be taken into

consideration since the system will be first put into use in spring. The size of the watering

zones and the genres of the plants will be able to be expanded.


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Tableofcontents

TableofContents

REPORTSUMMARY.................................................................................................................................2

TABLEOFCONTENTS............................................................................................................................5

TABLEOFFIGURESANDTABLES......................................................................................................6

INTRODUCTION...................................................................................................................................7

BACKGROUND.........................................................................................................................................9

DESIGNREQUIREMENTS...................................................................................................................11

DESIGNALTERNATIVES....................................................................................................................13

MOISTURESENSOR................................................................................................................................................14

CONTROLLER...........................................................................................................................................................14

USERINTERFACE....................................................................................................................................................14

WATERDELIVERY..................................................................................................................................................14

PRELIMINARYPROPOSEDDESIGN................................................................................................15

MOISTURESENSOR................................................................................................................................................15

CONTROLLER...........................................................................................................................................................17

USERINTERFACE....................................................................................................................................................17

WATERDELIVERY..................................................................................................................................................17

OTHERS....................................................................................................................................................................19

REFERENCES.........................................................................................................................................20


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Tableoffiguresandtables

Figure1ARCGreenhouseOverview.................................................................................................2

Figure2BlockDiagram...........................................................................................................................3

Figure3LCDScreenFigure412-ButtonKeypad...........................3

Figure5ASoilMoistureSensor..........................................................................................................4

Figure6HosewithExchangeableWand.........................................................................................8

Figure7DrippingTubesforOverheadBaskets...........................................................................8

Figure8AnExampleofIrrigationControllersontheMarket...............................................9

Figure9TensiometerFigure10Transducer....................................13

Figure11DetailedBlockDiagram...................................................................................................13

Figure12SolenoidDriver...................................................................................................................19

Table1WateringNeedsforPlants..................................................................................................12

Table2Comparisonforsoilmoisturesensors..........................................................................16

Table3partsforthisproject.............................................................................................................20


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Introduction

The Schenectady ARC Maple Ridge Center is a local chapter of NYSARC, Inc,

which is a non-profit organization dedicated to supporting individuals with intellectual

and other developmental disabilities and their families throughout New York State. The

greenhouse plays a significant role for the development of ARC because on the one hand

ARC is partially funded by the plants that are sold, i.e. the local airport purchased their

big plants from ARC, while on the other hand, the individuals are being trained when

they are engaging in the greenhouse work.

Currently the watering system at ARC not only does not work properly, but also

is extremely time consuming. The ARC now only has a hose with two Y-connected

Nozzles. The one that goes to the overhead baskets does not work. The other one that

waters the seeding tables has two exchangeable wands for watering the greenhouse. One

of the wands is for misting, which increases the moisture in the air, and the other one for

soaking, which delivers water into the soil. Either way, the wand has to be carried by

someone and watering the whole greenhouse could take up to 2 hours every time. It is

exceptionally time-consuming and especially for individuals who cannot hold the wands

on their own, they require hand over hand supervising. Hence, it can cost at least double

the time and labor force. Therefore, the upgraded system must be able to be used by all of

the individuals and their supervisors.


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Figure6HosewithExchangeableWand

Figure7DrippingTubesforOverheadBaskets

The purpose of this project is to upgrade the current watering system at ARC. The

system would be mainly operated by the individuals and sometimes their supervisors at

ARC. Hence, the accessibility to the individuals is crucial to the project. The users would

be ideally able to operate the system simply by pressing pushbuttons on a 12-button

keypad. The system would also be able to run automatically on weekends and holidays or


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whenever the people at ARC are occupied. Moreover, the watering delivery system

would be upgraded in order for a better functionality. Lastly, soil moisture sensors would

be implemented to ensure that the plants get watered properly.

Background

Presently there are irrigation controllers for the greenhouse on the market.

However, they are not specifically designed for people with disabilities. The operation

process is complicated even for people who do not have disabilities and whoever does not

have experience in the past would need to spend some time reading the manual guides

and take some time to learn. For the ARC, the individuals who operate the system would

not be the same person all the time and it will spend a tremendous amount of time if the

supervisors learn how to use the controllers first and then teach every single individual

how to use them.

Figure8AnExampleofIrrigationControllersontheMarket


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Economically speaking, a 12-station irrigation controller can go from 500 U.S

dollars to 1000 U.S dollars and that is merely the controller, excluding from the water

delivery system. For example, the weathermatic bundle SL1612-SLW5 from Sprinkler

Warehouse is priced for $517.932. It is a 4-zone base model, expandable to 16 zones, it is

able to run up to 4 programs concurrently, and it can have up to 8 start times per program.

However, this controller comes with a number of features that would not match what the

ARC is looking for. I.e. the wireless weather station it comes with is useless in this case.

On the other hand, there are features that are not included in the controller, for example

the soil moisture monitoring. This will decrease the death rates of the plants in the

greenhouse. Therefore it is not ideal to buy or modify from the irrigation controllers that

are on the market now.

For the future development of the project, it could be implemented in all kinds of

organizations that are involved with the disabled, the elders, or even households that have

greenhouses. Once you have it implemented, it could last a long time. The users only

need to change the coding or have people change the coding to accommodate to all kinds

of plants, season, and watering zones. Because of the simplicity of the user interface, it is

very hard to mess up and have the program changed by accident. Hence, the system is

low maintenance and the users will only have to pay the company to come to their

greenhouses once every season to change up the coding or whenever they changed the

layout of the plants and their watering zones.

Shock hazard has already been taken into consideration during the designing

process. All the wires and electronics will be enclosed in waterproof enclosures. The only

part that is involved with the users is the 12-button keyboard and there should not be any


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incidents happening if operated properly.

DesignRequirements

The most important element of the system is the accessibility of it. The system

must be usable by all the individuals and supervisors. Since the disabilities of the

individuals differ hugely from each other, the user interface has to be as simple as

possible so that even the person with the greatest disabilities would be able to use it under

supervising.

The water delivery system consists of three waterlines, two for the seeding bed

and one for the overhead basket. One of the two waterlines that provide watering for the

seeding bed will be used for soil soaker and the other one will be used for mister. The

plants need both types of watering methods because the soaker increases the moisture

inside the soil and make sure the roots of the plants get watered enough and the mister

increases the air humidity.

To prevent the plants from over watering and under watering, the soil moisture

level must be remained in certain range. The prototype will be designed for four types of

plants, two for overhead baskets and two for seeding bench. The watering needs differ

from the periods of their growth, the seasons of the year, and the types of soil they are

planted in. However, plants have general watering needs and it is shown down below.


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Table1WateringNeedsforPlants

Plant Positions Plant Types Watering Needs

Overhead Basket

Wave Petunia3 Medium

Blue Fan Flower (scaevola) Medium

Seeding Bench

Rosemary Low

Geranium (Pink) Medium

Detailedsoilmoisturedatawillberequiredwhencodingforthesystem

besidesthegeneralwateringneedsIlistedabove.Tensiometerkitwillbeemployed

formeasuringthecut-offmoisturefortheplants.Tensiometerisaninstrumentthat

worksasavacuumgageandessentiallymeasuresthetensionthatsoilapplieson

thetensiometer.Thetensiometerwillbefollowedbyatransducerthatconverts

mechanicalsignalsintoelectricalonessothatthedatawouldbereadableforthe

microcontroller.Thewateringneedsaboveareconcludedwhentheplantsare

plantedintheground.Soilincontainersdryoutfasterthaningroundbedssothe

plantsneedtobewateredmorefrequently.Thetimeofthedaywhentheplants

needtobewateredwouldvarygreatly,butgenerallyspeakingthebesttimewould

beearlymorningbeforethesunfullyrisessothatthewetleaveswouldnotbeburnt

fromthesun’shotraysandtheycouldalsoavoiddevelopingmoldandfungus.


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Figure9TensiometerFigure10Transducer

TheprototypewillbebroughttotheARCinwinterfortestingontheplants

toensurethesystemworksproperly.Atensiometerwillbeemployedtocheckthe

measurementofthesoilmoistureandtocalibratetheSoilMoistureSensor.

DesignAlternatives

Figure11DetailedBlockDiagram


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MoistureSensor

There are three ways to measure the soil moisture, using a tensiometer followed

by a transducer, a soil moisture sensor, or homemade soil moisture sensor probes. The

plants at ARC will be in 4’’ pots and 6’’ overhead baskets. The tensiometer is way too

big to be placed into them. Besides, there will be multiple sensors placed in the pots and

baskets to provide even watering. A full kit of tensiometer and transducer will be over

$400 dollars and it is not practical to use tensiometers for all of the sensors.

The homemade moisture sensor probes essentially exploit the same principle as

the off-shelf moisture sensors. They both have resisters for the metal parts and depending

on the moisture of the soil, they will be resulting in different conductivities.

Controller

Themosttwocommonandeasy-to-usehardwareplatformsareRaspberryPi

andArduino.ThereisonetypeofRaspberryPithathasitsowndisplayscreenbutit

istoosmallforwhatIwaslookingfor.ThereforeIdecidedtoseparatethecontroller

anddisplay.Also,personallyIhavepastexperiencewithArduinosoIchosetouseit.

UserInterface

Theuserinterfacehastobeassimpleaspossiblefortheproject.Therearea

lotofoff-shelfkeypadsandLCDscreensoutthere.Ijustchosethemostcommon

ones.

WaterDelivery

Therearefourmaintypesofgreenhouseirrigationmethodsonthemarket.

Thefirstoneisdriptubing.Itbringsthewaterdirectlytotherootsoftheplantsbut


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itisconsideredtimeconsuming.Thesecondoneisoverheadmister.Itisbetterused

forgreenhousethathasthesameplantspecies.Sprinklersheadscouldbeconnected

tooverheadwaterpipesandemitamistysprayacrosstheentiregreenhouse.This

methodisextremelybeneficialforlargegreenhouses.Howeverusingoverhead

mistersdowastealotofwater.Thirdlythereismatirrigationanditisbestforthe

plantsthatareconstantlythirsty.Byusingthismethod,plantswouldbeplacedona

specializedmatthatstaysperpetuallymoist.Thelastoneisperimeterirrigation.

Essentiallyitisamixtureofdriptubingandoverheadmistinginacertainarea.

PreliminaryProposedDesign

MoistureSensor

The moisture sensors oversee the whole system. They stop the running programs

when the moisture detected exceeds the cut-off moisture and start to run the pre-coded

programs if the moisture does not reach the minimum moisture programmed. The outputs

of the sensors are analog signals and they will be converted into digital after going into

the micro controller.

The off-shelf Moisture Sensors will be used in this project because they are cheap,

they fit in the pots and baskets, and they are relatively accurate. The off-shelf sensors

have better quality with slightly higher price, but they are rust-proof and generally a lot

easier to use and considerably more presentable. Also, with the amount of sensors

needed in this project, the time that will be spent making the homemade ones would not

be worth it. Hence, the off-shelf soil moisture sensors will be used for the project.


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Table2Comparisonforsoilmoisturesensors

Size Price Accuracy

Tensiometer5

6 inch*2 inch

>$400

High

Soil Moisture Sensor

2.5 inch*1 inch

$4.95

Medium

Homemade Moisture Sensor probe

2.5 inch*1 inch

<$1

Low


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Controller

FormicrocontrollerIchoseArduinoinsteadofRaspberryPibecause

Arduinocomeswithbuilt-inanalogtodigitalconverterbutRasberryPidoesnot.

Furthermore,onthewebsitethatIboughtmostofthepartsfrom,alotofthe

librariesforprogramminginArduinoareprovidedbutnotinRaspberryPi.

UserInterface

Theprojectisdesignedforindividualswithvariouskindsofdisabilities

thereforetheaccessibilityoftheuserinterfaceiscrucial.A12-buttonkeypadwillbe

usedfortheindividualstochoosethewateringmodefortheplantsandtheLCD

displaywillhaveshortsimplephrasesthatnavigatethemtodosoevenifwithout

theirsupervisors.Bothsignalsaredigitalsignalssothatitdoesnotneedtogo

throughanyconverters.

WaterDelivery

The perimeter irrigation method will be exploited in the project. Dripping is the

most efficient way of delivering water since all the dripping tubes go directly into the soil

to the roots of the plants and there would not be any evaporation occurred before the

water gets to the plants. Since the dripping tubes will be going through every single one

of the pots and baskets, it would not take so long because of the sizes of them. The plants

at ARC Maple Ridge Center are in small containers for sale uses so that it is very

important that plants in different parts of the watering zones are being watered

equivalently. By using dripping tubes, the rate of being watered equivalently can reach


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95% whereas using other methods are so much lesser, i.e. using sprinklers only have 75%

similarity.

The plants also need certain level of air humidity, so it is necessary to use misters

too to increase the air moisture. However, in case for the water not to be wasted, the

angle of the misters will be adjusted so it would mist the area of the plants that people

expect them to be misted.

The solenoid driver part of the system will be consisting of three solid state relays

and three solenoid valves that control the water. There will be one solid state relay and

one solenoid valve on each one of the waterline. The three waterlines are for soaker for

the seeding table (dripping tube), mister for the seeding table, and overhead baskets

(dripping tube). The solid state relays act as switches of the circuit. They also protect the

circuit from overheating and short-circuiting. They control the solenoid valves, which are

in charge of the amount of water released and distributed to the plants. Solenoid valves

are followed by manifolds, which break up the main stream of water to certain zone of

watering through dripping tubes and misters. Both solid state relays and solenoid valves

are very commonly used in greenhouses so I chose the off-shelf products that would work

with the voltage in the greenhouse.


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Figure12SolenoidDriver

Others

Allthewires,microcontroller,orotherelectronicdevicesofthisprojectwill

becoveredwaterproofenclosurestopreventanykindsofshortcircuitandusers

gettingshocked.ThewaterproofenclosuresarewidelyusedingreenhousessoI

purchasedthesizethatlooksreasonabletoputthecontrolsystemoftheproject.


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Table3partsforthisproject

Item: Stage:

Soil Moisture Sensor

Sensor System Tensiometer - 6inch

Service Kit - Tensiometer

Soil Moisture Transducer

Sparkfun 12-button keyboard User Inputs

Serial Enabled 16*2 LCD

Arduino Controller

Solenoid Valve-110V Water

Delivery System Dripping Tube

Manifold

Mister

Solid State Relay

Waterproof Enclosure Others

Cable Management & Venting

References1. http://www.arcschenectady.org/index.html 2. http://www.sprinklerwarehouse.com/Weathermatic-Bundle-SL1612-SLW5-p/sl1612-slw5.htm 3. http://www.landscape-america.com/gardens/wave-petunias.html 4. http://www.smgrowers.com/resources/Irrigation.asp 5. http://www.specmeters.com/tensiometers/?keyword=WatchDog Data Loggers and Stations with

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