Download pdf - Burnaby, British Columbia RE: ENSC 440 Post …whitmore/courses/ensc305/projects/2009/...their homes, as well as lock or unlock their door remotely. Chickadee Tech has successfully

SchoolofEngineeringScienceSimonFraserUniversity8888UniversityDriveBurnaby,BCV5A1S6

May6,2009Mr.SteveWhitmoreSchoolofEngineeringScienceSimonFraserUniversityBurnaby,BritishColumbiaV5A1S6RE:ENSC440PostMortemforWatchbird™HomeMonitoringSystem.DearMr.Whitmore,“TheWatchbird™RemotePeaceofMindSystem:PostMortem”,attachedtothisletter,detailsthewrap‐upcommentsfortheWatchbird™system.ThegoalfortheWatchbird™prototypewastocreatea“proofofconcept”peace‐of‐mindhomemonitoringsystemtoallowuserstoremotelycheckthestatusofvarioussensorsintheirhomes,aswellaslockorunlocktheirdoorremotely.ChickadeeTechhassuccessfullybuiltthisprototypeanddemonstrateditsfunctionality.ThisdocumentfirstpresentsthemannerinwhichtherealizedWatchbird™prototype’sdesigndiffersfromthatpresentedin“TheWatchbird™RemotePeaceofMindSystem:DesignSpecifications”.Itthenpresentssomeideasforfutureworkonthesystemtoprepareforproductionlevelmanufacturing.Pleaseletmeknowifyouhaveanyquestions,comments,orconcernsregardingthisdocument.Icanbecontactedat604.837.4009orbyemail([email protected]).ThankyouverymuchforyourtimeinreviewingtheWatchbird™postmortem.Regards,

SamanthaGristPresidentChickadeeTech

TheWatchbirdTMRemotePeaceofMindSystem:

PostMortem

SamanthaGristDerekLowesAndraSt.QuintinShiouMin(Eric)ShenMay6,2009

TheWatchbirdTMRemotePeaceofMindSystem:PostMortem

iii

TableOfContentsTOC .............................................................................................................................................................................................IIILISTOFFIGURES ..................................................................................................................................................................... VLISTOFTABLES....................................................................................................................................................................... V1 INTRODUCTION ................................................................................................................................................................12 CURRENTSTATUS ............................................................................................................................................................23 DEVIATIONFROMSPECIFICATIONS...........................................................................................................................43.1 TIMINGDESIGN ...................................................................................................................................................................................43.2 CELLPHONE–OERVERCOMMUNICATIONPROTOCOL................................................................................................................ 43.3 SERVER.................................................................................................................................................................................................. 53.3.1 Hardware ........................................................................................................................................................................................ 53.3.2 Software .......................................................................................................................................................................................... 5

3.4 SERVER/BASESTATIONCOMMUNICATIONPROTOCOL............................................................................................................... 53.5 BASESTATION .....................................................................................................................................................................................53.5.1 Hardware ........................................................................................................................................................................................ 63.5.2 Software .......................................................................................................................................................................................... 7

3.6 RFTRANSCEIVERS.............................................................................................................................................................................. 73.7 RFTRANSCEIVER/SENSOR/ACTUATORCIRCUITRY....................................................................................................................83.8 SENSORMODULES............................................................................................................................................................................ 113.9 LOCKACTUATOR .............................................................................................................................................................................. 113.10 SETUPANDUSERINTERFACE...................................................................................................................................................... 12

4 FUTUREPLANS............................................................................................................................................................... 124.1 FULLSYSTEM .................................................................................................................................................................................... 124.2 CELLPHONE–OERVERCOMMUNICATIONPROTOCOL............................................................................................................. 124.3 SERVER............................................................................................................................................................................................... 134.3.1 Hardware ......................................................................................................................................................................................134.3.2 Software ........................................................................................................................................................................................13

4.4 SERVER/BASESTATIONCOMMUNICATIONPROTOCOL............................................................................................................ 134.5 BASESTATION .................................................................................................................................................................................. 134.5.1 Hardware ......................................................................................................................................................................................134.5.2 Software ........................................................................................................................................................................................14

4.6 RFTRANSCEIVERS........................................................................................................................................................................... 144.7 RFTRANSCEIVER/SENSOR/ACTUATORCIRCUITRY................................................................................................................. 144.8 SENSORMODULES............................................................................................................................................................................ 154.9 LOCKACTUATOR .............................................................................................................................................................................. 154.10 SETUPANDUSERINTERFACE...................................................................................................................................................... 16

5 BUDGETANDTIMELINEOVERVIEW....................................................................................................................... 175.1 BUDGET.............................................................................................................................................................................................. 175.2 TIMELINEOVERVIEW ...................................................................................................................................................................... 18

6 GROUPREFLECTIONS .................................................................................................................................................. 196.1 SAMANTHAGRIST ............................................................................................................................................................................ 196.2 ERICSHEN ......................................................................................................................................................................................... 206.3 DEREKLOWES .................................................................................................................................................................................. 21


iv

6.4 ANDRAST.QUINTIN........................................................................................................................................................................ 227 CONCLUSION ...................................................................................................................................................................23


v

ListofFigures

FIGURE1:SYSTEMOVERVIEW ..................................................................................................................................................................................................2FIGURE2:REVISEDBASESTATION‐RFINTERFACE ...............................................................................................................................................................6FIGURE3:REVISEDRFCIRCUITRYATBASESTATION. ..........................................................................................................................................................7FIGURE4:REVISEDTIMEDELAYCIRCUIT. ...............................................................................................................................................................................8FIGURE5:ORIGINALLYEXPECTEDPULSESWITHORIGINALCIRCUITDESIGN.....................................................................................................................9FIGURE6:PULSESSOMETIMESOBSERVEDWITHORIGINALCIRCUITDESIGN:THETRANSMITTEDPULSEISNOLONGERLONGENOUGH. ............. 10FIGURE7:PULSESCONSISTENTLYOBSERVEDWITHMODIFIEDCIRCUITDESIGN:THETRANSMITTEDPULSEISACONSTANTLENGTHREGARDLESS

OFTHERECEIVEDPULSE............................................................................................................................................................................................... 10FIGURE8:TIMELINEOVERVIEW............................................................................................................................................................................................ 18

ListofTables

TABLE1:LISTOFNEWTYPESOFTEXTMESSAGERESPONSESWITHEXAMPLES................................................................................................................5TABLE2:BUDGETOVERVIEW................................................................................................................................................................................................ 17


1

1 Introduction

Throughhardworkandcarefulplanning,ChickadeeTechwasabletobringtheideaofacellphoneoperatedhomemonitoringsystemtorealization.Thechangesnotdocumentedinpreviousspecificationswillbedescribedinthisreport,aswellasimprovementsandfeaturesthisprojectcouldexpandupon.Toconcludethisreport,eachmemberwillreflectontheirexperiencesthroughoutthisproject.


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2 CurrentStatus

Attheconcludingpointintheprototypedevelopment,ChickadeeTechhassuccessfullyimplementedthehomemonitoringsystemproposedinJanuary2009.Usingcellphonetextmessages,weareabletolockandunlockadooraswellasquerythestatusofthreesensorlocations.Thiscommunicationhasbeenimplementedusingaserverrunningonacompanylaptopinconjunctionwithabasestationintheuser’shome.Wehavealsoimplementedaweb‐baseduserinterface,whichallowsuserstoconfiguretheirsystems.TheoverallsystemdesignascurrentlyimplementedisshowninFigure1.

Figure1:SystemOverview

CommunicationfromcellphonesisachievedusingTwitter,whichconvertstextmessagesintoemailsthataretheninturnreadbytheserver.Communicationtothecellphoneisimplementeddirectlyfromtheserver,wherebyemailssentbytheserverareautomaticallyconvertedtotextmessagesbytheuser’sserviceprovider.Thewebinterfaceanddatabasewereconstructedtostoreuserinformationandtoallowtheservertoaccesstheappropriateuserinformationwhenprocessingrequests.


3

Intheuser’shome,thebasestationisconnectedtoanEthernetporttoenablecommunicationwithChickadeeTech’sserver.Itthencoordinatescommunicationwithallsensorsintheuser’shome.RFsignalsforactuatingorqueryingaresenttoeachsensorinturn,usinguniqueaddressbitstoidentifyeachsensor.Thebasestationthencompilesthestatusofallsensorsandrespondstotheserver.

Wehavedemonstratedthatthesensor‐endenclosuresandthesensorsthemselvescanbemountedtowallsandappliancesintheuser’shomewithessentiallynodamagetotheselocations.Thecontactswitchesprovedtobeversatileformountingondoorlocks,ovens,andwindows;andweareconfidentthattheycouldbeusedinawidevarietyofotherlocations.


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3 DeviationfromSpecifications

TheWatchbird™prototypedidnotexactlyfollowthedesignspecificationsinsomeareas.Thesechangesfromthespecificationsareoutlinedinthissection.

3.1 TimingDesign

DuetotheproblemsweexperiencedwiththeRFreceiversandtransmitters,weincreasedthenumberoftriesofthequeryorlockrequestto4.Thisincreasedtheworst‐casetimeforaquery(per‐sensor)from2secondstoapproximately4seconds.Forprototypingpurposes,thisdelaywasnegligiblecomparedtothetextmessagedelays(andthemaximumnumberoftrieswasrarelyused).Thischangeincreasestheworst‐casetimeforaqueryfrom31sto51sandtheworst‐casetimeforalock/unlockrequestfrom35sto59s.

3.2 CellPhone–ServerCommunicationProtocol

Forthecellphonetoservercommunicationprotocol,therehavebeennodeviationsfromthespecificationsfortheusertoservercommunication.Fortheservertouserresponses,however,therehavebeenafewchanges.

Firstly,thelock/unlockconfirmationmessagesandtheincorrectpasswordmessagesarenolongerused.Insteadofsendingalockorunlockconfirmationmessage,theserversimplysendsastatusupdatemessageforanysuccessfuluserrequest.Sincethismessagecontainsthenewstatusofallsensorsanyway,theusercanimmediatelytellthattheirdoorwaslockedorunlockedsuccessfully.Theincorrectpasswordmessageisnolongerusedbecausewiththecurrentdesign,theprototypeisnotabletosupportit.Thisproblemarisesbecausetogenerateatextmessagereply,theserverneedstoknowtheuser’sserviceprovider.Withoutavalidcellphonenumberandpasswordpair,theserverwillnotreadanyuserinformationfromthedatabase.

Finally,therearenowsomeadditionalerrormessagestheservercansendasareplytotheuserrequest.TheseareshowninTable1.


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Table1:Listofnewtypesoftextmessageresponseswithexamples.

MessageType ExampleMessagebasestationdisconnected Basestationnotconnected.

basestationbusy Basestationcurrentlybusywithanotherrequest.Pleasetryagaininaminute.

errorreadingreply Invalidreplyfrombasestation.wrongmessagetype Invalidreplyfrombasestation.invalidsensorname Actuatornamenotfound.

3.3 Server

3.3.1 Hardware

Therewerenodeviationstotheserverhardware.Asintendedinthedesignspecifications,weusedanexistingcompanylaptoptohelpavoidanyunnecessarycostsintheprototype.

3.3.2 Software

Theserversoftwarehasbeensimplifiedbyintegratingtheuserconfigurationintothequeryandlock/unlockrequestsratherthanhavingadditionalconfigurationmessages.Insteadofcontinuallycheckingthedatabaseforanychanges,theserveronlyreadstheuserconfigurationdatawhenitreceivesarequestfromthatuser.

3.4 Server/BaseStationCommunicationProtocol

Duetothechangestotheserverdesign,thesensorconfigurationrequestandsensorconfigurationconfirmationmessagesarenolongerused.Instead,wheneveraqueryorlock/unlockrequestisgeneratedfromtheserver,thatrequestwillincludealistofallcurrentlyconnectedsensors.

3.5 BaseStation

ThePICDEM.net2developmentboardwasusedasourbasestationhardware.Onlyafewminorchangestothehardwareandsoftwareofthesystemoccurred.


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3.5.1 Hardware

TheLinxLRseriesreceiverandtransmitterwereindeedusedatthebasestationend.Theywere,however,connectedtoa3.3Vpowersupplyratherthanthe5Vpowersupplyproposedinthespecifications.Thischangewaseasytoimplementandrequiredlesscomponentsthantheoriginaldesign.Furthermore,adigitalI/Opinwasusedasinputfromthereceiver,insteadoftheanalogoneoutlinedinthedesignspecifications,sotheRSSIpinofthereceiverwasnotusedinthefinalimplementation.Throughtesting,itwasfoundthatthereceiveroutputwassuitablefordigitalinputtothemicrocontroller,whichsimplifiedthedesignofthesystem.TherevisedinterfaceisshowninFigure2.

Figure2:Revisedbasestation‐RFinterface

Additionally,slightlydifferentcircuitrywasusedatthebasestationcomparedtothatpresentedinthedesignspecifications(aresultofthechangeinpowersupplyvoltage).ThiscircuitryisshowninFigure3.


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Figure3:RevisedRFcircuitryatbasestation.

3.5.2 Software

Theonlysignificantchangetothebasestationsoftwarewasthatthereceiverisonlypoweredupaftertransmittinghascompleted.Thiswaschosenbothtohelpconservepoweraswellastoavoidanydamagetothereceiver’ssensitivitythatmightoccurfromhavingfull‐strengthtransmissionoccuratsuchacloseproximity.

3.6 RFTransceivers

Asstatedinthedesignspecifications,weimplementedourdesignusingaLinxLRtransmitterandreceiveratthebasestation,andLinxKH2transmittersandreceiversatthesensorlocations.However,wewerenotabletoattainthefullrangeexpectedfromthesemodules,asisdiscussedfurtherinthesectionforfutureplans.


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3.7 RFTransceiver/Sensor/ActuatorCircuitry

Afewchangesweremadetothedesignofthecircuitryatthesensorlocations.ThemostsignificantwastheeliminationoftheANDgatechipsandinverterfromourdelaycircuit.Weoriginallyunderstoodthatthe555timerchiprequireditsinputtobegenerallyheldhigh,andtriggeredbyashortnegativepulse.Weunderstoodthatitwouldnotworktohavetheinputtothetimergenerallyheldlow,andthatthefallingedgeofashortpositivepulsewouldnotcorrectlytriggerthetimer.Asaresult,werequiredaninverterattheinput,aswellasanANDgateattheoutputtoensuretherewasnooverlapbetweenthereceivedandtransmittedpulses.

However,whiletestingourcircuits,wediscoveredthatitwasactuallypossibletotriggerthetimerwithapositivepulse,andthuseliminatetheANDgatesandinverterinthecircuit.TherevisedcircuitisshowninFigure4.

Figure4:Revisedtimedelaycircuit.

Thischangereducedthesizeandcomplexityofourcircuit,aswellasimprovingitsperformance.Theincreaseinperformanceisattributedtothefactthatnowthetransmitterwillalwaystransmitfortheamountoftimespecifiedbythetimercircuit.Previously,thetransmittertransmittedforthisamountoftime,lessthetimethereceiverwasreceivingdatafor,asshowninFigure5.Inourtestingwenoticedthatevenwhenthebasestationtransmittedforaconstantamountoftime,theamountoftimethereceiver‐decoder’soutputpinsremainedvalidvariedsignificantly,whichweattributetothe

x4 .QuadTimer

trigger output

timing GND

RCtimeconstants

datafromreceiver‐decoder

Vcc

.QuadTimer

trigger output

timing GND

Vcc

Vcc

…8RCpairs…x4

x4

x4

x4

x4

x8

…8… …8…

x8

tosensorinput

pull‐upresistors pull‐upresistors

x8


9

timingwithinthereceiver‐decoderchip.Asaresult,whenthereceiver’soutputpinswerevalidforlongerthanexpected,thetransmitterdidnothaveaslongasitneededtorespondtothebasestation,asshowninFigure6.Withourimproveddesign,theresponsefromsensorlocationsismuchmoreconsistent,asshowninFigure7.

Figure5:Originallyexpectedpulseswithoriginalcircuitdesign.

KH2receiverdatapin

inverteddatapin(input)

timeroutput

timeroutputANDinput

expectedreceivedpulse

expectedtransmitted

pulse


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Figure6:Pulsessometimesobservedwithoriginalcircuitdesign:thetransmittedpulseisnolongerlongenough.

Figure7:Pulsesconsistentlyobservedwithmodifiedcircuitdesign:thetransmittedpulseisaconstantlengthregardlessofthereceivedpulse.

Secondly,wehadintendedtopowerdownthemajorityofthecircuitforthemajorityofthetime,andleaveonlythereceiverturnedon.Ourintentwasthatwhenthereceivergotamessageintendedforthesensor,itwouldactivatetherestofthecircuit.However,thisgoalprovedtobemoredifficultthanexpected,becausealargeportionofthecircuithadtobeactivatedtoprocesstheoriginallyreceivedpulsecorrectly.WhenthisproblemwaspresentedtoJasonLee,hesuggestedthatourcurrentconsumptionof15mAwasquiteacceptableforprototypingpurposes,andsowedidnotmakefurtherattemptsinthisregard.

KH2receiverdatapin

inverteddatapin(input)

timeroutput

timeroutputANDinput

possiblereceivedpulse

possibletransmitted

pulse

KH2receiverdatapin

timeroutput

possiblereceivedpulse

consistenttransmitted

pulse


11

Alsopertainingtothepowerofthecircuit,weaddedavoltageregulatortothesystem.WehadoriginallyplannedtorunthecircuitusingtwoAAbatteries,whichwouldprovide3Vtothesystem.However,wediscoveredthatwhenthebatteriesslightlydegraded,theynolongerprovidedenoughvoltageforthereceivertooperatecorrectly.ThereforeweusedfourAAbatteries,andtheir6Vwassteppeddownto3.5Vusingavoltageregulator.Wefoundthatthischangemadethesystemfarlesssensitivetodecreasesinbatteryvoltage.

Inourdesignspecification,wehadindicatedthatwewouldusethevalidtransmissionlinefromthereceiver,andpropagateitthroughourcircuittothetransmitenablelineatthetransmitter.However,werealizedthatwehaddesignedourcommunicationcodessuchthatthefirstdataline,D0,wasalways1.Asaresult,itwasredundanttoalsousethevalidtransmissionline.Byeliminatingtheuseofthevalidtransmissionsignal,wewereabletoeliminateathirdofthenecessarychipsfromthetimingdelayportionofthecircuit.(Althoughweonlyreducedthenumberofdatalinesfrom9to8,eachchipwasabletoservice4datalines,meaningweonlyneeded2ofeachchipratherthan3.)

3.8 SensorModulesThesensormodulesworkedverywellwiththeinitialdesignasproposedinthedesignspecification,andlittletonochangeswereappliedtothedesign.

3.9 LockActuator

Thelock‐unlockactuatorwaslargelyimplementedasoutlinedinthedesignspecifications.Onechangewastheadditionofalevelshifter,whichwasnecessarybecausewhilemostofourcircuitwasrunningat3.5V,thelockrequired6Vtooperate.Wealsoneededtoaddasecondsetoffourbatteriesexclusivelyforlockingorunlockingthedoor.Wediscoveredthatwhenthedoorlockwasactuated,itdrewsomuchpowerfromthebatteriesthattherewasnotenoughpowertoactivatetheremainderofthecircuit,andthusthesensorlocationwasunabletorespondproperlytothebasestation.Ideally,thissecondsetofbatterieswouldhavebeenthefourbatteriesalreadyincludedwiththekeypaddoorlock.However,itwouldhavebeendifficulttoconnectwirestotheexistingbatterycase,andsowefeltthatusinganothersetwasthebestsolutionfortheprototype.

Theotherchangewasthatweoriginallyintendedthesensorcircuittoonlyrespondtothebasestationonceitdetermined(atthecomparators)thatithadreceivedaquery,lockorunlockrequest.However,wedecidedthatthekeyfactorwasthatthesensorlocationacknowledgedithadreceivedthebasestation’srequest.Therefore,weeliminatedacomparatorforthequerycode,aswellasanORgate.Thesensorlocationnowalwayssendsbackaresponse,regardlessofthemessagetype.Ifthemessagewasaquery,thereturnmessagewillbethesensor’sstatus.However,ifitisalockorunlockrequest,thereturnmessagewillsimplybeanacknowledgementofthereceivedmessage.


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Basedonthecontentsofthemessage,thebasestationwillbeabletodetermineifthesensorlocationcorrectlyinterpretedalockorunlockrequest.

3.10 SetupandUserInterface

Theuserinterfaceimplementationdeviatedfromthedesignspecificationduetochangesinthebasestationsoftwareandserverprogram.Becausethelistofsensorsisnolongerstoredonthebasestationandisonlyobtainedwhentheusersendsaquery,andthesensorslotsarealwaysafixednumber,addingandremovingsensorsbecameunnecessary.Instead,theuserwillalwayshaveafulllistofavailablesensorslots,andtheuserwillmarkactivesensornumberdesignationsasavailablebyplacingacheckmarkonthecorrespondingcheckbox.Additionally,thenumberofsensorslotswaschangedfrom10to5intheprototypesothesensorlistreflectedtotalavailablesensorsforthedemo.

4 FuturePlansChickadeeTechhasdevisedsomeideasforprojectexpansionandfuturework.Theseideasarepresentedinthissection.

4.1 FullSystem

Fortheproductionlevelfullsystem,wewouldliketoincreasethenumberoflocationsinthehomethatmaybemonitored.Todothis,wewilladdothertypesofsensors,suchasHallEffectproximitysensors,temperaturesensors,watersensors,andpowerusagesensors.Toaddinsomeofthesesensorsinausefulfashion,wealsoplanonaddingfunctionalitytothesystemsothattheusermaybealertedifaneventoccurs(suchasflooding).Addingthisfunctionalitywillhelpensurepeace‐of‐mindfortheuseraswellasdecreasepotentialdamagethatmayoccurfromaccidentsinthehome.

4.2 CellPhone–ServerCommunicationProtocol

Fortheproductionlevel,wewillphaseoutthecurrentuseofTwitterbyincludingfunctionalityintheservertosendandreceivetextmessagesdirectly.Thiswillalsomeanthattheuserdoesnotneedtoindicatetheirserviceprovider.Finally,sincetheserverwillnowbeabletosendreplytextmessageswithonlytheknowledgeoftheincomingcellphonenumberandwillnotrequireuserconfigurationinformationtodoso,wewilladdtheincorrectpassworderrormessagebackintothesystem.


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4.3 Server

4.3.1 Hardware

Intheproductionlevelsystem,ratherthanusinganexistingcompanylaptoptoruntheserver,wewillpurchaseadedicatedservermachineoptimizedforrunningcontinuously,anditwillbeconnectedtoaphonelinetoallowforsendingandreceivingtextmessagesdirectly.

4.3.2 Software

Onceadedicatedphonelineisconnected,theserversoftwarewillbemodifiedtosendandreceivetextmessagesdirectlyratherthanconnectingviaemail.Thiswillrequiresomenewcodetobewritten,butitwillalsoallowfortheremovalofthecodethathandlessendingandreceivingemails.

Theserversoftwarewillalsoneedtobemodifiedsothattheusermaybealertedifanemergencysuchasfireorfloodingoccursintheirhome,orifalowbatterystateoccursinoneormoreoftheirsensors.Thiswillrequireaddingfunctionalitythatallowsthebasestationtocontacttheserveriftheseeventsoccur,aswellasnewmessageformatsforthesealerts.

4.4 Server/BaseStationCommunicationProtocol

Tohelpminimizebandwidthusage,theactualformatofthemessagesbetweentheserverandbasestationwillberevisedfortheproductionlevel.Currently,themessageconsistsof1bytetoindicatemessagetype,2bytestoindicatelength,and1bytepersensorlisted.However,thesensorlist,forexample,canberevisedtouseeachbittorepresentwhetheraparticularsensorisconnectedornot,allowingupto8sensorsperbyte.Throughsimplificationslikethis,themessagesizecanbereducedbyasignificantfraction.

4.5 BaseStation

4.5.1 Hardware

Fortheproductionlevelhardware,wewilluseonlythemicrocontrolleritselfwithaccompanyingcircuitryonaWatchbird™basestationboardratherthanthedevelopmentboard.Toaccomplishthis,anewboardforthebasestationwillneedtobedesigned.


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4.5.2 Software

Fortheproductionlevel,thebasestationsoftwarewillneedtobemodifiedtosupporttheencrypteddatatransfertoboththeserverandthelockactuatorunit.

Additionally,someoftheserver’sfunctionality(suchasthesetupwebinterface)maybemovedtothebasestationtoreduceloadontheserver.Thebasestationshouldbeabletosupportthisfunctionality.

Finally,thebasestationsoftwarewillneedtobemodifiedtosupportthealertmessagesdiscussedabove.Forthesemessages,thebasestationwillneedtoreceivethealertfromthesensorinquestionandcontacttheservertonotifytheuser.

4.6 RFTransceivers

WestillplantousetheLinxLRtransmittersandreceiversatthebasestation,andtheLinxKH2transmittersandreceiversatthesensorlocations.However,wewouldliketotakefulladvantageoftherangeofferedbythesemodules.Inordertodoso,wewouldplacetheRCpowersupplyfiltersdirectlynexttothepowerconnectionsonthemodule,whichwedidnotdoinouroriginalPCBdesign.Weanticipatethatthischangewouldmakethereceiveddataconsiderablycleaner,andthereforeimprovethereceptionrange.

Indoorlocklocations,weplantouseamicrocontrollertoimprovedatatransmissionsecurity.Asaresult,theencoderanddecodercapabilitiesoftheKH2serieschipswouldnolongerbenecessary,andwecouldswitchtothecheaperandsmallerLRchipsthatwearecurrentlyusingatthebasestation.

4.7 RFTransceiver/Sensor/ActuatorCircuitry

AsdiscussedinSection3.7,thenumberofchipsusedinthesensorcircuitryhasalreadybeendecreasedfromouroriginaldesign.Foraproductionlevelmodel,wewouldplantousesurfacemountcomponentsfortheentirecircuit,andwewouldhaveallcomponentsonaPCB.Manysurfacemountcomponentsareconsiderablysmallerthanthecomponentsweusedduringprototyping,andaPCBwouldalsomakeitmorefeasibletoplacecomponentsclosertogether.Asaresult,weareconfidentthatourproductionleveldesignwouldbesignificantlysmallerthantheprototype.

Wealsohopetoimprovethepowerconsumptionofourproductionlevelmodel,increasingthetimebetweenbatterychangesfromapproximately5daystoacoupleofmonths.Thisratherdrasticimprovementwouldbepossibleifmostofthecircuitwaspowereddownforthevastmajorityofthe


15

time.Weunderstandthatitisevenpossibletopowerdownthereceiverbyusingthereceivedsignalstrengthindicator(RSSI).Thereceivercontinuestomonitorreceiveddatainalowpowerstate,whichmeansitsRSSIpinwillcontinuetobeactive.AdditionalcircuitrycouldbedesignedsuchthatwhentheRSSIpinpassedacertainthreshold(indicativeofavalidtransmission),thereceiverandtherestofthecircuitwouldturnon.

Wewouldalsoimplementabatterymonitoringfeatureinthesensorendcircuitry,sothattheuserwouldbenotifiedwhenthebatteriesinaunitwerealmostdead.Thisimprovementwouldmeanauserwouldnotencounter“sensornonresponsive”replieswhenthebatteriesonaunitdied.Instead,theywouldbeabletoactaheadoftime,andthusmaintainconstantsensorfunctionality.

4.8 SensorModulesThetypesofsensordesigncouldbeexpandedtoaccommodatedifferentneedsthatapressswitchcouldnotaccommodateinahousehold: ProximityHallEffectsensortodetectobjectdistancewhereactualcontactisnotpossible; Temperaturesensortodetermineifroomtemperatureisaboveorbelowdesiredlevel; Watersensortodeterminewaterlevelinawatertank,orfloodingorleakagefromaroofor

tank; Powersensortodetermineifadigitallyoperatedapplianceisconsumingabovedesiredpower

level.

Inallabovecases,acontactswitchcannotmonitorthesituationandthenewsensordesignsareneededtoaccomplishthetasks.Inordertoachievethisimprovedflexibility,thesensorcircuitrycouldadoptsocketstoswitchbetweensensorssouserscouldeasilybuyanewtypeofsensoranduseitrightawayafterthenewsensorispluggedin.

4.9 LockActuator

Forthelockactuator,ourprimaryfuturegoalistoconsolidateitspowersupplyintoasinglesetoffourAAbatteries.AproductionlevelmodelwouldintegratethekeypadlockcircuitrywiththeRFcircuitrywedesigned,whichwouldmakeitmorepracticalforallpowertocomefromonesetofbatteries.Furthermore,wesuspectthatfurthervoltageregulation,and/ormodificationstothetimingcircuitrywouldpreventthehighpowerrequiredbythedoorlockfrominterferingwiththetransmitter’soperation.

Wewouldalsoliketoimprovethesecurityofdatatransfertothedoorlock.Whilethisisnotapriorityatsimplesensorlocations(wheretheinformationaboutone’sovenisnotofparticularinteresttothieves,andthestatusofawindowbeingopenisfairlyobvioustosomeonewhocansee


16

thehouse),securityatadoorlockiscritical.Thereforewewouldinvestigatetheuseofamicrocontrolleratthelockactuatorlocationstoimplementsometypeofencryptedwirelessdatatransfer.Thismicrocontrollerwouldalsobeusedforthekeypadfunctions,sotwomicrocontrollerswouldnotbenecessary.

Lastly,althoughnotrelatedtoalockactuatordirectly,wewouldliketopursuetheimplementationofactuatorsinotherlocations.Therewouldbeagreatincreaseinutilityifwecoulddesignunobtrusiveactuatorstoperformtaskssuchasclosingwindows,turningoffovens,oradjustingthermostats.

4.10 SetupandUserInterface

Therearemanypossibleareaswheretheuserinterfacecouldbeexpanded.Securedatatransferanddataencryptionaredefinitelyessentialelementsintheproductionleveluserinterfacedesign.SecureSocketsLayermustbeappliedtouserloginanduserregistrationmenus,aswellastheWatchbirdTMconfigurationmenu.ThewebsitewillalsoneedtoencryptallthedatastoredonSQLdatabasesoifthedatabasewasbreached,thedatacouldnotbedecipheredeasily.

Inadditiontosecurityenhancements,aninternetqueryimplementationhasalsobeenconsideredforuserconvenience.ThecurrentsystemdesignonlyallowstheusertoquerytheWatchbirdTMsystemthroughcellphonetextmessages,whichareusuallychargedpertextmessage.Thiscostcouldbecomeaburdentotheuserifthesystemisqueriedfrequently.Toofferusersanalternativemethodtoquerytheirsystem,wewillimplementtheabilitytoquerytheWatchbirdTMsystemthroughtheuserinterface.Withthisfunctionality,theinternetbecomesanotheroptiontoobtainthestatusoforissuecommandstotheWatchbirdTMsystem.


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5 BudgetandTimelineOverview

5.1 Budget

OurbudgetoverviewispresentedinTable2.

Table2:BudgetOverview

Item EstimateCost

ActualCost

AmountOverBudget

EmbeddedPCorMicrocontroller $200 $213.68 $13.68PC/MicrocontrollerComponents(RAM,PowerSupply/Programmer)

$100 $238.27 $138.27

Display $60 $0.00 $0.00Keypad $4 $0.00 ‐$4.00RFTransmitters/Receivers $11 $303.64 $292.64RF/KeypadDoorLock $150 $110.88 ‐$39.12SensorEnd/DoorLockCircuitry,PCBs $0 $269.47 $269.47Sensors $30 $12.60 ‐$17.40IntegrationComponents $100 $101.64 $1.64Cases $0 $94.77 $94.77MiscellaneousCosts(sockets,protoboard,cables,batterycasesetc.)

$100 $21.16 ‐$78.84

DemoMaterials(mountingmaterials,door,window,batteries)

$0 $108.93 $108.93

TotalCosts $755 $1,475.04 $720.04

ItisevidentthatweweresignificantlyoverbudgetinthedevelopmentoftheWatchbird™prototype.Thiswasmostlyduetothefactthatwehadnotdecidedonafinalimplementationatthetimethatthebudgetwasestimated.Weendedupspendingmoremoneythanexpectedonamicrocontrollerprogrammer(nearly$200),andmuchmorethanexpectedontheRFandsensorendcircuitry.Additionally,afewofourreceiversandtransmittersweredamagedinthecourseofdevelopmentandneededtobereplaced.Finally,wedidnotbudgetforprofessionalcases,andthisaswelladdedsignificantlytoouractualcost.

However,wedidsecure$700infundingfromtheESSEF,whichmadetheremainingcostsacceptablewhensplitbetweenthefourgroupmembers.


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5.2 TimelineOverview

OurtimelineoverviewispresentedinFigure8.

Figure8:TimelineOverview

Theredbarsindicatetheamountthateachcomponentwentovertime.Therewereseveralreasonsforthedevelopmentbeingbehindschedule.

Firstly,wespentasignificantamountoftimeatthebeginningofthesemestertryingtodecidethebestwaytoimplementtheproduct.Weconsideredmicrocontrollersvs.embeddedPCs,ZigBeevs.Bluetoothvs.simpleRFtransmission,microcontrollersatallsensorlocations,andmanyotheroptions.Thisputusbehindschedulefortheremainderofdevelopment.

Additionally,weencounteredmanyissueswiththeRFsectionwhichrequiredsignificanttroubleshooting,whichagainputusbehindschedule.Weintegrated,debugged,andtestedthesystemasdevelopmentprogressed,however,sodevelopmentwasonlysloweddownbythisproblemratherthancompletelyheldup.


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6 GroupReflections

6.1 SamanthaGrist

Ifeelthatcarryingoutthisprojecthasallowedmetogrowimmenselyasbothanengineerandaleader.

Asanindividualengineer,Iwasveryluckytohavebeenabletoworkonseveral,diverseareasofthesystem.IreallyenjoyedintegratingthemicrocontrollersoftwarewiththeRFchips,aswellasdesigningandfabricatingcircuitsandhelpingtointegratethedoorlockactuatorintooursystem.Theprojectgavemetheopportunitytoimplementsomelow‐levelsoftware,whichIfoundveryinterestingbecauseitblurredthelinebetweenwhatIhadpreviouslyconsideredsoftwareandhardware;Ihadpreviouslyhadverylittleexperiencewithusingsoftwaretocontrolindividualpinsatsuchalowlevel.IalsogainedexperienceindesigningPCBsandorderingparts,whichreallyemphasizedgoodplanninganddouble‐checking.Finally,fabricatinganddebuggingcircuitsallowedmetoreallytakeprideinmywork,doitcarefully(butquickly!),andlearnthestepsnecessarytofixthingsifsomethingwentwrong.Bytheendofthesemester,IfeltthatIhadgainedasignificantamountoftechnicalknowledgeandproblemsolvingskills.Furthermore,Ireallycametoappreciatetheindividualtalentsthateachofmyothergroupmembersbroughttotheproject,andlearnedfromthemaswell.

Asaleader,thisprojectwasveryinterestingformeasitwasthefirsttimeIhadactedasaleaderinaproject.Iamgenerallyaquietorshyindividualingroups,sothiswasreallyabigstepforme.Itwaseasedbythefactthatwerotatedthechairofeachmeeting,andallatsometimecontributedsomesortofleadershiptothegroup,butIreallyfeelthatithelpedmegrowasaleader.OneproblemthatIencounteredstemmedfromthefactthatIsometimeshaveveryhighstandardswithregardstomywork,andattimesduringthesemester,IfoundthatIhadtocatchmyselfbeforeItriedtoforcethesestandardsontomygroupmembers.Irealizedthatthereneedstobeacompromisebetweenqualityandtimeandsotriednottoforcemypersonalstandardsontoothers,butattimesitwasalittlebitfrustratingformewhenothersdidnotseemtotakeasmuchprideintheirworkasItryto(andI’msureothersprobablyfeltasimilarfrustrationtowardsme!).Ireallylearnedthatwhenworkingingroupsitisnecessarytocompromisebetweenwhateachmemberfeelsisacceptablequalityandjusttrytoworktogethertogetthingsdone.

Onthewhole,however,Ithinkthatwedivideduptheworkwellandworkedeffectivelyasateam.Westartedoffbyeachtakingapartoftheproject,andeachcontributedwherevernecessaryafterourpartshadbeencompleted.Ithinkthatthecontributiontopartsoftheprojectwhichwehadnotoriginallychosenwasveryimportantinthistime‐limitedproject,andallowedustoworktogetherandsolveproblemsasquicklyaspossibleastheyappeared.

Aboveeverythingelse,Ireallybelievethateachofushascontributedalottothisproject,andhasaccomplishedsomethingincredible.Iamamazedatbothwhateachgroupmemberhascompletedandatwhatwewereabletoachievebyworkingtogether.


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6.2 EricShen

ThisprojectexposedmetovariousareaofanengineeringprojectandIlearnedalotinthelast4months.Sincethefirstweekofthesemesterwehavebeenmeetingfrequentlytodiscusstheprojectdesignsanddocumentations.Ifoundsplittingupthesectionsofthespecificationsandthencompilingandeditingbyeachgroupmemberisextremelyefficient.Allofusnotonlygivesfinishingtouchonthedocumentbutalsolearnmoreabouteachother'sdesignthroughediting.TheweeklygroupmeetingwithrotatingchairmanisarefreshingexperienceformebecauseIexperiencedholdingameetingforthefirsttime.Itforcedmeoutoftheroleofafollowerandputsmeincharge,androtatingchairmanalsoallowsmetoobservedifferentmeetingformatsfromdifferentpersoneachweek.

Whenthegroupfirstsplitthedesignintosections,Ichose2sections,asectionthatIhadsomeexperiencewith,andasectionthatIhaveneverdonebefore.Iwasabletoquicklycomeupwithasensordesignthatiseasytouse,easytoimplement,flexibleandlowcostwithinashortperiodoftime.TheinitialdesignwastestedandworkedverywellandIwasabletodeliveracomponentthatcanbeattachedtotheoverallsensorendcircuitryeasily.However,myprocessofdesigningtheuserinterfaceandthedatastoragecouldbedescribedasventuringintotheunknown.IhadageneralideaofhowIwantedtoapproachtheproblem,butIwasmissingtheknowledgetocarryoutthedesign.HadInotstumbledintoafriendwhosuggestedmetouseASP.NET,Iwouldnothavebeenabletobuildtheuserinterfacehostedonaserver.Inotonlygainedvaluableknowledgeonbuildingdynamicwebsite,butalsoondatabaseaswell.BecauseIwasabletofinishmytasksearly,Iwasabletohelpoutwiththemakingofthe3rdsensorendcircuitandthemakingthedemomaterials.Ienjoyedthehandsonlonghourdoingsolderinganddrillinginmachineshop;itwasalotmorefunthanlonghoursofdebuggingstaringatthecomputerscreen.

Forgroupdynamics,wewereabletocommunicateefficientlythroughemailsandmsnmessenger.Meetingswereheldregularlyandeveryattended.Eachofuscontributedtotheprojectandcompletedindividualassignedparts.Inshort,wewereabletocompletetheprojectasateam.

Startingaprojectofthisscaleandbuildingfromthegroundupisahugeamountofworkthatcanbarelysqueezedintoa4monthperiod.IfIamtodoasimilarprojectinacourselikeENSC440,Iwouldwanttomakesurethesystemfunctionsaredefinedandsystemdesignsareready,aswellassomeactualcircuitbuiltandworking.


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6.3 DerekLowes

Thissemesterhasbeenanexcellentexperienceforme.Developingaprojectofthisscalefrombarewispsofideastoaworkingprototypehasbeenalotofstressattimes,butIhavedefinitelylearnedalot.IgainedexperienceinareasI’dneverworkedwithbefore,likeTCP/IPcommunicationprotocols,orIMAPandSMTPprotocolsforworkingwithemails.

IfIweretodothisagain,themainthingIwoulddodifferentlyistotakeintoaccountjusthowmuchtimeandeffortsomethinglikethistakes.Forexample,trytobedecisivewithdesigndecisionstomaximizethetimeforactuallyputtingtheprojecttogether,andwhenscheduling,nomatterhowmuchcontingencytimeyouallowfor,itprobablyisn’tenough.

Astogroupdynamics,Ifeelourgroupworkedverywelltogether.Forthedocumentation,wedivideditintoindividualparts,didourwrite‐ups,andthenputittogetheranddidmultipleroundsofediting.Ifeelthisdidanexcellentjobofgettingtheinitialcopyofthedocumenttogetherpromptly,andthenhavingplentyoftimetopolishitupintoagoodfinishedproduct.Astotheprojectitself,weagaindivideditintosectionsandworkedonitseparatelyatfirst,andthenstartedworkingtogethermoreandmoreasthevarioussectionsbegantomerge.

OnethingIthinkwedidwellwasbybasicallytreatingtheconnectionsbetweenthedifferentsectionsascomponentsthemselves.Forexample,whiledevelopingtheserverandbasestation,weweresimultaneouslydevelopingthemethodfortheserverandbasestationtocommunicatewitheachother.Thismadeintegrationanongoingprocessrightfromthebeginning,andhelpedusavoidhavingtorevampanysectionsduetoincompatibilities.

Allinall,whilethiswasabigproject,andtookalotoftimeandeffort,itwasanexcellentlearningexperience,andthesenseofaccomplishmentaftercompletingsomethingthismajorisgreat.Ilearnedalot,anditwasdefinitelyworthdoing.


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6.4 AndraSt.Quintin

Fromatechnicalperspective,Ihavelearnedagreatdealintheprocessofdesigningandimplementingthesensor‐endcircuitryofourdevices.Withregardstoradio‐frequency(RF)communications,Ilearnedabouttheintricaciesanddetailsthistechnologyrequires:acleanpowersupply,careinantennachoiceandpositioning,static‐safehandingofcomponents,andprecisionintimingthesignals.DesigningtheprintedcircuitboardfortheRFdevicesfamiliarizedmewiththestepsrequiredtogofromanideatoasoftwaredepictiontoaphysicalrealization.AlthoughIhadbeenintroducedtoPCBsoftwareinENSC204,theneedtoproduceaphysicallycorrectboardwithouthavingtopayforasecondattemptwasavaluableexperience!Layingoutthecircuitontheprototypingboardtaughtmetheimportanceofcarefulplanninganddouble‐checking;itcertainlywasbettertomeasuretwiceandcut(orsolder)once,ratherthantryingtodiscoverandcorrectaproblemlater.Ialsosignificantlyimprovedmysolderingskillsandmycircuitdebuggingskillsthroughouttheimplementationprocess.Troubleshootingcircuitproblemsattheendofthesemesterwasdefinitelyeasierthanatthebeginning!

Intermsofgroupdynamics,Iexperiencedandlearnedfromthedifferentapproachespeoplehavetocompletingaproject.Whatmayseemtobeaperfectlyacceptablejobtoonepersonmayappeartobelackingissomeregardbyanother.Similarly,somethingthatmightseemlikeawasteoftimeinthepursuitofperfectionbyonepersonmayseemtobeanessentialcomponenttoanother.Havingexperiencedbothsidesofthissituationthroughoutthesemester,Ihavecometorealizethattherecannotbeone“right”opinioninthisregard.Inagroupsituation,Ifoundthatstrategiesfordealingwiththesedifferencesincludedfocusingonthegoalsthatweultimatelyintendtoachieve;objectivelyassessinghowtheworkathanddidordidnotaccomplishtothesegoals;deliveringandreceivingcriticisminafair,calm,andprofessionalmanner;helpingeachotherouttominimizeindividualweaknessesandmaximizeindividualstrengths;andrespectingthefactthateachmembershaddifferentopinionsonthedetailsofimplementingourproject.

Ialsolearnedthatwhileitisoftendifficult,itisimportanttofindtherightbalancebetweenthetwoimportantadagesof“divideandconquer”and“twoheadsarebetterthanone.”Inalargeprojectlikethiswithmultiplecomponents,itwassensibletomakeeffectiveuseoftimebyhavingeachpersonworkingonsomethingdifferent,andattimesIwisheditwaspossibletotakefurtheradvantageofthisdivisionoflabour.Butatthesametime,itwasvaluabletohavemultiplethoughtsonhowtoimplementanidea,orhowtotroubleshootaproblem.

Throughoutthisproject,Icametofullyrealizetheimportanceofself‐initiativeonbehalfofallgroupmembers.Itwasimmenselyhelpfulwhensomeonewasabletosay“Ithinkweneedtogettask‘X’done,andIamgoingtotackleit,”ratherthansaying“Whatneedsdoingnext?”AsIwasnotdirectlyinvolvedinthesoftwaresideofoursystem,allIreallysawwasthatthesoftwareworkedverywell.SoeventhoughIdidnotwitnessit,Iwasveryimpressedwiththeamountofself‐initiative,attentiontodetail,coordination,andtroubleshootingthatittookforthesystemtorunflawlessly.

Allinall,Igainedvaluabletechnicalknowledgeandimportantgroupworkexperience.IamproudofwhatIlearnedasanindividual,andproudofwhatwewereabletoaccomplishasateam.


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7 Conclusion

TheWatchbirdTMsystemwasacomplexandchallengingproject.Overthepast4monthswedevelopedaviable,lowcost,textmessagebasedhome‐monitoringsystem.Weareconfidentitthatcanbeusedforawidevarietyofhome‐monitoringapplications,andthatitisamarketableproductthatwillprovidepeace‐of‐mindforuserseveryday.