EE 459 Team 1 Final Report.pdfAppendix APage 1 of 6Page 2 of 6Page 3 of 6Page 4 of 6Page 5 of 6Page 6 of 6Appendix BAppendix B Source CodeAppendix CMicrosoft Word - Appendix C Parts List and Cost AnalysisEE459SeniorDesignProjectDURACELLDURASAVERByTEAM1SaraAdkinsPaulVanWierenRobertWhitleyIntroductionMostmodernelectronicdevicesconsumesmallamountsofelectricalpowerevenwhentheyhavebeenturnedoff.Thisstandbypower,or“vampirepower”,canbeasignificantportionofelectricalpowerusageinatypicalhome.Ourpowercontrollerisdesignedtominimizethiswastefulpowerconsumptionbyprovidingtheuserwithuser-programmablepoweroutletsthatvirtually“unplug”devicesduringnon-usagetimes.Astandardapplication,forexample,wouldbetoprogramatelevisiontovirtuallyunplugduringthetypicaleight-hourworkday,therebyeliminatingitsstandbypowerconsumptionduringtheportionofthedaythatitisunused.SectionI:HardwareDesignInordertodescribethelayoutofourprojectinthemostsystematicwaypossible,wehavechosentobreakourhardwarereportintotwoparts:oneforeachofthetwocomponentboards(themainmoduleandtheRFremotecontrol).Eachofthesecomponentboards,inturn,isanalyzedusingasimpleblockdiagram,whosedescriptionisbrokenintosectionsoutliningeachoftheimportantorinterestingcomponents.Inordertosavespace,simple,widely-usedcomponentssuchasLED’sandthelikewillnotbeexplainedindetail. Ourdescriptionbeginswiththemainmoduleboard:MainModule:BlockDiagram: Thefollowingisablockdiagramofthehardwarelayoutofthemainmodule:Userinputconsistsofsixpush-buttons,whileuserfeedbackisaccomplishedusinga24characterx2lineLCD.Theprimaryfunctionaloutputsofthedevicearefouroutletplugswhichallowvirtualunpluggingofdevicesaspertheprojectdescription.Themicrocontrollercommunicateswiththereal-timeclockthroughanI2Cinterface,requiringtwobidirectionalhardwarelines.ThereisalsoatestLEDforrunningtestprogramsontheprototypeboard.Inaddition,themicrocontrollerreceivesinputsfroma10MHzclockanda315MHzRFreceiver.UserInputButtons: Userinputtothedeviceisachievedusingsixbuttonstonavigatemenus,makeselections,andresetthedevice.Thelayoutofthebuttonsinshownbelow.Thefourwhitedirectionalbuttonsallowtheusertoprogressthroughthemenus.Ingeneral,theleftandrightbuttonsmovebetweenmenus,whiletheupanddownbuttonsallowchangingthecurrentoptionwithinagivenmenu.Theblackselectbuttonallowstheusertoselectthemenuoptioncurrentlybeingdisplayed.Aresetbuttonallowstheusertoforceahardwareresetofthedevice. Theinputbuttons,withtheexceptionoftheresetbutton(whichhasnoneedforde-bouncing)arede-bouncedusingthefollowingRCcircuitnetwork:Thisdesignisanimprovedversionofawell-acceptedSPSTbuttonde-bouncingscheme.Theinitialdesigndidnotincludethe4.7uFcapacitor(valuesfortheresistorsandtheothercapacitorwerenotgivenbytheinitialdesign,whichwasmeantasadesigntemplateratherthanacompletecircuit).However,thisinitialdesignhasacriticalweakness.Inordertobeabletoeffectively“pulldown”thesignaltoanappropriateTTLlogic0,thevalueofthefirstresistor(470Ohminourcircuit)mustbekeptverysmallinrelationtothesecondresistor(10kOhminourcircuit).Usingthevaluesgiveninourcircuit,intheabsenceofthelargercapacitor,theRCtimeconstantofthecircuituponclosingtheswitchisroughly20timessmallerthanthetimeconstantuponopeningtheswitch(duetothetworesistorsactinginparallel,thusdramaticallydecreasingtheresistancetoACground).Wefoundinexperimentsthatthebouncedurationofthebuttonsignalwas~2msregardlessoftheswitchbeingopenedorclosed.Thus,useoftheinitialcircuitwouldrequireaclosed-switchtimeconstantofatleast2ms,therebynecessitatingahugeopen-switchtimeconstant(ontheorderof40msorso).Thiswouldgreatlyreducethepulsedurationofthebutton-press,andpossiblyeveneliminateitcompletely.
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