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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
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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
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6.4 ANDRAST.QUINTIN........................................................................................................................................................................ 227 CONCLUSION ...................................................................................................................................................................23
TheWatchbirdTMRemotePeaceofMindSystem:PostMortem
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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
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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.
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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
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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
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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
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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
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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.