Air Quality Sensor (Rev. A) - Texas Instruments

1 SharpDN7C3CA008( Sensor )TI HDC1000(Temp/Humidity)VIM-878 LCDL aunchpad HeaderLaunchpad HeaderDebug HeaderTest HeaderPower HeaderDisplay ButtonMSP430FR4133 StatusLED1 TIDUB68A December2015 RevisedFebruary2016 SubmitDocumentationFeedbackCopyright 2015 2016,TexasInstrumentsIncorporatedAir QualitySensorTI DesignsAir QualitySensorMSP430,LaunchPadare trademarksof ,Cortexare registeredtrademarksof a trademarkof othertrademarksare the propertyof qualityand its effectson healthand vitalityhaverecentlybecomea air pollutionhavebeenlinkedto detrimentalhealtheffectsand adverseimplicationson qualityoflife. The goldenstandardof measuringthe levelof airpollutionis the Air QualityIndex(AQI).

2 In this TIDesign,a simpleair qualitymonitoris createdandimplementedusingthe designusesthe TI MSP430FR4133microcontrollerin tandemwith the sharp ,the AQI is calculatedand displayedusingan8-character, DesignFilesMSP430FR4133 ProductFolderHDC1000 ProductFolderASKOur E2E ExpertsDesignFeatures AirQualityIndexLevels(AQI) CalculatesTemperatureand HumidityLevels Offersan 8-Character,14-SegmentLCDto DisplayCalculationResults Usesan Ultralow-PowerMSP430FR4133 DeviceWithan IntegratedLCDC ontrollerFeaturedApplications Air Purifiers WeatherStations IndustrialSystems Air ConditionerSystemsAn IMPORTANTNOTICEat the end of this TI referencedesignaddressesauthorizeduse, intellectualpropertymattersand otherimportantdisclaimersand December2015 RevisedFebruary2016 SubmitDocumentationFeedbackCopyright 2015 2016.

3 TexasInstrumentsIncorporatedAir QualitySensor1 Key to to 500 g/m3 AQI SensingRange78 to 500 AQI2 SystemDescriptionTI built the systemdesignto be affordableand greateffortwas placedintoselectingthe optimalsensorto calculatethe AQI and measureparticulatematterconcentration,th e SharpDN7C3CA006sensorcan measureto a to calculatedownto the g/m3levelallowsfor an accuratecalculationof a pluggedinto a specializedequationprovidedbythe US EPAand the AQI is additionto AQI,the integratedTI HDC1000is usedto calculatehumidityand humidityreadingsare consideredwhencalculatingthe compliancewith the specificationin the AQI can be usedto gaugethehealthinessof the environmentalair.

4 Figure1 showshow the EPAdefinesvariouslevelsof air EPAAir QualityIndexLevelsThe obviousapplicationsfor this designis use in homeappliancesand industrial-relatedapplicationssuchas air significantlevelof industrialization,measuringairqualityrel iablyand cost effectivelyis air qualityindexexceedsa certainthreshold,manyorganizationssuchas the air qualityindexof China(AQICN)encouragemaskusage( ) to preventhazardousinhalationof pollutedair. A homeconsumersolutionthataccuratelymeasur esand reportsair qualityfactorsprovidesa significantconveniencefor purifierscan also benefitfromincorporatingair an unintelligentand rudimentaryair purificationalgorithm,enhancementscan beaddedto purifyair only if the AQI crossesa presetor levelof intelligencewouldreducethe overallpowerconsumptionof the designby minimizingthe duty cycleof the ( Sensor )TI HDC1000(Temp/Humidity)

5 VIM-878 LCDL aunchpad HeaderLaunchpad HeaderDebug HeaderTest HeaderPower HeaderDisplay December2015 RevisedFebruary2016 SubmitDocumentationFeedbackCopyright 2015 2016,TexasInstrumentsIncorporatedAir chosethe MSP430FR4133 MCUdue to its low-poweroperationand the MSP430 is usedin this designto fostera of the criticaladvantagesof usingthe MSP430is the 8-characterVaritronixVIM-878segmentLCDis used,amicrocontrollerwith 36 LCDI/Os is ,the abilityof the MSP430to pragmaticallyconfigurewhichLCDpins are usedfor SEGlinesand whichpins are usedfor COMlinesmadelayoutofthis showsthe LCDin VaritronixVIM-878 LCDin ActionIn additionto the LCDmodule,the low-powercentricperipheralset of the MSP430FR4133allowsfor alow-powerdesignand 10-bitADCmoduleis a perfectcompanionforthe Sharpsensorcontainsan integratedpoweramplificationsystemthatle ts the sensoroutputintegrateeasilywith the ADCmoduleof the MSP430withoutany intricateand powerfularrayof timersof the MSP430allowsfor a highlyconfigurableand additionto providinga systemtick.

6 The timerof the MSP430alsocontrolsthe timingpulsesfor boththe Sharpsensorand attachedfan. The Sharpsensorhas a stricttimingrequirementof the pulserequiredto initiatea Timer_Amoduleof the MSP430containsa precisionPWMfeaturethat makesgeneratingsucha pulseeasyand HDC1000humidityand temperaturesensorperfectlypair with the Sharpsensorrequiresa humidityreadingfor propercalculationof AQI,the low cost and ease-of-useof the HDC1000madeit an idealcomponentfor the HDC1000usesI2C communicationtoreportthe 14-bittemperatureand humidityreadingbackto the the MSP430side,theI2C linesconnectto the EUSCI linesand a low-poweroptimizedsoftwaredriverprocesse sthe additionto displayingair qualityreadingson the LCDdisplay.

7 The usercan displaytemperatureand showsthe December2015 RevisedFebruary2016 SubmitDocumentationFeedbackCopyright 2015 2016,TexasInstrumentsIncorporatedAir followingare producthighlightsof the MSP430FR4133device: Embeddedmicrocontroller 16-bitRISC architectureup to 16 MHz to V Optimizedlow-powermodes(at 3 V) Activemode:126 A/MHz Standbymode:greaterthan1 A with real-timeclock(RTC)counterand liquidcrystaldisplay(LCD) Shutdown( ):15 nA Low-powerferroelectricRAM(FRAM) Up to nonvolatilememory Built-inerrorcorrectioncode(ECC) Configurablewriteprotection Unifiedmemoryof program,constants,and storage 1015writecycleendurance Radiationresistantand nonmagnetic EachLCDpin software-configurableas SEGor COM to V by followingare producthighlightsof the HDC1000device: Relativehumidity(RH)operatingrange0 to 100% 14-bitmeasurement Relativehumidityaccuracy 3% Temperatureaccuracy C 200-nAsleepmodecurrent Averagesupplycurrent.

8 820 nA at 1sps,11-bitRH measurement A at 1sps,11-bitRH and temperature Supplyvoltage3 to 5 V 2-mm I2C December2015 RevisedFebruary2016 SubmitDocumentationFeedbackCopyright 2015 2016,TexasInstrumentsIncorporatedAir hardwaredesignof the SharpDN7C3CA006sensorallowsfor a methodofself-calibration. housedin a plasticenclosurewith an externalfan appliedtothe fan, an air sampleis drawninto the samplingpulseis appliedto the ILEDpin ofthe sensorand an analogsampleis readthroughthe ADCmoduleof the powercompensationof the analogsignaloccursinternallyon the SharpDN7C3CA006sensor,eliminatingthe needfor any externalamplificationor Air Chamberof SharpDN7C3CA006 The externalenclosureallowsfor self-calibrationbecausea readingcan be madewithoutpowerto thefan.

9 Withoutpowerto the fan, the air samplein the chamberis consideredcleanand can be usedas areferenceor recommendationis consistentwith thecontrolsamplingmethodfromthe achievepowercontrolof the fan, a MOSFET switchwas addedto the 5-Vinputto the fan. showsthis systemin (CBP) IBPBP-=-+ December2015 RevisedFebruary2016 SubmitDocumentationFeedbackCopyright 2015 2016,TexasInstrumentsIncorporatedAir FrequencyTo obtainthe mostaccurateresults,the algorithmto sampleand recordthe default,the firmwareof this TI Designcollects50 samplesof a mathematicmeanis calculatedfromthese50 AQI,eachmeasurementoccursevery30 temperatureand humidity,the measurementsoccurevery30 differencein samplingtime is becausethereis likelyless variationin airqualityovera shortperiodof time,but the temperaturecan AQIsample.

10 Humidityand temperaturesamplesare also takenbecausethe Sharpsensorrequiresa humiditysampleto accuratelycalculatethe sensoradoptsa light scatteringmethodforcalculation,any environmentalhumidityin the air mustbe measuredand CalculationWhenthe beenmeasuredfromthe ,the AQI is thencalculatedby manydifferentvariationsof air qualitymetrics,this designusesthe onedefinedby the EnvironmentalProtectionAgency(EPA).Figur e5 showsthe equationto calculatethe AQIfromthe the indexfor pollutantpCPis the roundedconcentrationof pollutantpBPHiis the breakpointthat is greaterthanor equalto CPBPLois the breakpointthat is less thanor equalto CPBPHiis the breakpointthat is greaterthanor equalto CPIHiis the AQI valuecorrespondingto BPHiILois the AQI valuecorrespondingto BPLoFigure5.