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ArduinoDevelopmentCookbook

TableofContents


Credits

AbouttheAuthor

AbouttheReviewers

www.PacktPub.com

Supportfiles,eBooks,discountoffers,andmore

WhySubscribe?

FreeAccessforPacktaccountholders

Preface

Whatthisbookcovers

Whatyouneedforthisbook

Whothisbookisfor

Sections

Gettingready

Howtodoit…

Howitworks…

There’smore…

Seealso

Conventions

Readerfeedback

Customersupport

Downloadingtheexamplecode

Downloadingthecolorimagesofthisbook

Errata

Piracy

Questions

1.Poweron–ArduinoBasics

Introduction

DownloadingtheArduinosoftware

Gettingready

Howtodoit…

There’smore

Seealso

ConnectingArduino

Gettingready

Howtodoit…

MacOSX

Windows

Seealso

UploadingcodetoArduino

Gettingready

Howtodoit…

Howitworks…

LearningArduinocodebasics

Gettingready

Howtodoit…

Howitworks…

Seealso

Codebasics–ArduinoC

Gettingready

Howtodoit…

Howitworks…

Seealso

Codebasics–Arduinopins

Gettingready

Howtodoit…

Howitworks…

2.BlinkingLEDs

Introduction

BlinkingLEDwithoutdelay()

Gettingready

Howtodoit…

Howitworks…

Breakingdownthecode

Seealso

ConnectinganexternalLED

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

LEDresistor

MultipleLEDs

Seealso

FadingtheexternalLED

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Seealso

RGBLED

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Commonanode(+)orcommoncathode(-)

WithoutPWM

LEDbargraph

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Commonanode(+)andcommoncathode(-)

Bargraphvariations

Seealso

The7-segmentdisplay

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Commonanode(+)andcommoncathode(-)

Thedot

Variations

3.WorkingwithButtons

Introduction

Connectingabutton

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Pull-upconfiguration

Multiplebuttons

Seealso

Buttonwithnoresistor

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Multiplebuttons

Seealso

Thetoggleswitch

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Seealso

Buttontoserial

Gettingready

Howtodoit…

Code

Howitworks…

Codebreakdown

There’smore…

Buttondebouncing

Gettingready

Howtodoit…

Code

Howitworks…

Codebreakdown

Seealso

1,000buttonsto1pin

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Morebuttons

Findingeachbutton

Pressingmultiplebuttons

Seealso

Buttonmultiplexing

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Morebuttons

Seealso

4.Sensors

Introduction

Simplesensor–potentiometer

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

ArduinoDue

Analogreference(AREF)

Seealso

Temperaturesensor

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Detectingmotion–PIRsensor

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

Measuringdistance–infraredandultrasonic

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Seealso

Noisereduction

Gettingready

Howtodoit…

Code

Howitworks…

Meanfilter

Medianfilter

Mainloop()

Seealso

Accelerometer

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Seealso

Localization–GPS

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Seealso

5.MotorControl

Introduction

Controllingsmallmotors

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

There’smore…

Multiplemotors

Electricalspikes

Seealso

Controllingmotorswithtransistors

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

There’smore…

Pull-downresistor

PNPtransistors

MOSFETs

Differentloads

Seealso

ControllingspeedwithPWM

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Spinningmotorsbothways

Gettingready

Howtodoit…

Code

Howitworks…

Codebreakdown

There’smore…

Controlusingthedirectionpin,PWMpin,andbrakepin

ControlusingInputA,InputB,andPWM

Custom-madeL293Ddriver

Seealso

Servomotor

Gettingready

Howtodoit…

Code

Howitworks…

Codebreakdown

There’smore…

Controllingtheexactpulsetime

Moreservos

Continuousrotationservos

Seealso

Steppermotor

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Transistorunipolarstepperdriver

Identifyingthesteppermotortype

Seealso

Bipolarsteppermotors

Gettingready

Howtodoit…

Code

Howitworks…

Codebreakdown

There’smore…

Brushlessmotors

Gettingready

Howtodoit…

Code

Howitworks…

Codebreakdown

Seealso

6.MoreOutputDevices

Introduction

Creatingsound

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Tonewithnoduration

Toneonmultiplepins

Seealso

Transistordriver

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Seealso

Relaydriver

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Optocouplers/Optoisolators

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Moreoutputs–shiftregisters

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

7.DigitalCommunicationwithArduino

Introduction

Serialoutput

Gettingready

Howtodoit…

Howitworks…

Codebreakdown

Seealso

ControllingtheArduinooverserial

Gettingready

Howtodoit…

Howitworks…

There’smore…

ArduinoMega

TransmittingvaluestoArduino

Seealso

SoftwareserialandUARTbetweenArduinos

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

Usablepins

Moresoftwareserialconnections

Interference

Generalconnectiontips

Seealso

Wirelessserial

Gettingready

Howtodoit…

Schematic

Howitworks…

There’smore…

Seealso

I2CbetweenArduinos

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

ComparingdifferentArduinocategories

MoreaboutI2C

Connectingmoredevices

Seealso

SDcards

Gettingready

Howtodoit…

Code

Howitworks…

Codebreakdown

There’smore…

LCDcharacterdisplays

Gettingready

Howtodoit…

Code

Howitworks…

Codebreakdown

There’smore…

Ethernet

Gettingready

Howtodoit…

Code

Howtotest

Howitworks…

Codebreakdown

There’smore…

Seealso

8.Hacking

Introduction

Moredigitalpins

Gettingready

Howtodoit…

Howitworks…

FasterPWM

Gettingready

Howtodoit…

Howitworks…

Timer0

Timer1

Timer2

There’smore…

Interference

OtherArduinos

Seealso

Storingdatainternally–EEPROM

Gettingready

Howtodoit…

Howitworks…

Codebreakdown

TimingArduinocode

Gettingready

Howtodoit…

Howitworks…

Externalinterrupts

Gettingready

Howtodoit…

Schematic

Code

Howitworks…

Codebreakdown

There’smore…

InterruptsonvariousArduinos

Aboutinterrupt-attachedfunctions

Differenttriggeringmodes

Detachinganinterrupt

A.Electronics–theBasics

Workingofelectriccurrent

Ohm’slaw

Resistorconfigurations

DiodesandLEDs

Diodes

LEDs

Workingwithbreadboards

Index

ArduinoDevelopmentCookbookCopyright©2015PacktPublishing

Allrightsreserved.Nopartofthisbookmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,withoutthepriorwrittenpermissionofthepublisher,exceptinthecaseofbriefquotationsembeddedincriticalarticlesorreviews.

Everyefforthasbeenmadeinthepreparationofthisbooktoensuretheaccuracyoftheinformationpresented.However,theinformationcontainedinthisbookissoldwithoutwarranty,eitherexpressorimplied.Neithertheauthor,norPacktPublishing,anditsdealersanddistributorswillbeheldliableforanydamagescausedorallegedtobecauseddirectlyorindirectlybythisbook.

PacktPublishinghasendeavoredtoprovidetrademarkinformationaboutallofthecompaniesandproductsmentionedinthisbookbytheappropriateuseofcapitals.However,PacktPublishingcannotguaranteetheaccuracyofthisinformation.

Firstpublished:April2015

Productionreference:1170415

PublishedbyPacktPublishingLtd.

LiveryPlace

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BirminghamB32PB,UK.

ISBN978-1-78398-294-3

www.packtpub.com

CoverImagebyCornelAmariei(<[email protected]>)

http://www.packtpub.com

mailto:[email protected]

CreditsAuthor

CornelAmariei

Reviewers

SimoneBianchi

WilsondaRochaFrança

VincentGijsen

FrancisPerea

CommissioningEditor

EdwardGordon

AcquisitionEditor

SamWood

ContentDevelopmentEditor

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TechnicalEditor

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CopyEditors

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ProjectCoordinator

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Proofreaders

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Graphics

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CoverWork

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AbouttheAuthorCornelAmarieiisaRomanianinventorandentrepreneurinthefieldsofRoboticsand3Dprinting.HehasbeenworkingwiththeArduinoplatformsinceitsearlydaysin2007.Hispastexperienceinvolveslargecargogammarayscanningrobotics,ATMsecuritysystems,andblindassistingdevices.Inhissparetime,heisaperformingmusicianplayingmultipleinstruments—predominatelytheguitar.Heisalsoaswimmer,waterpoloplayer,andphotographer.

Overtheyears,hehasbuilthundredsofArduinoprojects,rangingfromflyingQuadcopterstolevitatingmagnetsandunderwaterrobots.Currently,hesplitshistimebetweendoinghisundergraduatestudiesinelectricengineeringandcomputerscienceatJacobsUniversityinBremen,Germany,andhisstart-upsandresearchanddevelopmentjob.

Iwouldliketothankmyparents:mymother,Cristina,andmyfather,Eugen,forbuyingmemyfirsttechnologybook18yearsago.Idon’tknowwhetherthiswastheintendedpaththeyhadinmindforme,butconsideringtheamountofsupporttheyofferedduringthewritingofthisbook,Ibelievenowitis.

Iwouldalsoliketothankmyfriends,colleagues,andbusinesspartnersforacceptingmynewprojectandprovidingmewiththetimerequiredtocompleteit,evenifthismeantmoreworkforthem.

Finally,IwouldliketothankPacktPublishingforofferingmethechancetowritethisbookandforhandlingallthedelaysIbroughttotheproject,asmostofthisbookwaswrittenintransit,shortbreaks,latenights,andearlymornings.

Thankyou.

AbouttheReviewersSimoneBianchilivesinItaly,wherehegotadegreeinelectronicengineering.

NowheworksfulltimeforasoftwarehouseasaJavadeveloper.Inhissparetime,helikestofeedhiscurioussidebyexploringothertopicssothathecandevelopcomponentsfortheTalendplatform,anappfortheAndroidsystem,delighthimselfbybuildingIoTprojectsusingdifferentmicrocontrollers(suchastheArduinoandSparkCore)withthehelpofhis6-year-oldnephew,Leonardo,orsimplylearnnewthingssuchasAngularJSor3Dgraphics.

I’dliketothankPacktPublishingforgivingmetheopportunitytoreviewtheirbookagainafterTalendforBigDataandArduinoAndroidBlueprints,andIhopeIhavecontributedtomakingthisyourfavoritebookcompanionduringyourArduinoprojects.

Leo,hereisyourprojectbook.

WilsondaRochaFrançaisasystemarchitectinaleadingonlineretailcompanyinLatinAmerica.HeisanITprofessional,computersciencepassionate,andanopensourceenthusiast;hegraduatedwithauniversitydegreefromCentroFederaldeEducaçãoTecnológicaCelsoSuckowdaFonseca,RiodeJaneiro,Brazil,in2005andalsoholdsamasterofbusinessadministrationdegreefromUniversidadeFederaldoRiodeJaneiroin2010.

Heispassionateaboute-commerceandtheWeb;hehadtheopportunitytoworknotonlyinonlineretail,butalsoinothermarkets,suchascomparisonshoppingandonlineclassifieds.HehasdedicatedmostofhistimetobeingaJavawebdeveloper.

HeiscurrentlyworkingonaMongoDBbookandhadalsoworkedasarevieweronInstantVarnishCacheHow-to,PacktPublishing.

Firstandforemost,Iwouldliketothankmywife,Christiane,forstandingbyme.IwouldalsoliketoexpressmyspecialgratitudetoPacktPublishingforgivingmesuchattentionandtime.Mythanksandappreciationalsogotomyfamilyandpeoplewhohavehelpedmeoutwiththeirabilities.

VincentGijsenisanall-rounder.Withabachelor’sinembeddedsystemsandamaster’sininformationscience,hehasalsoworkedinabigdatastart-upandiscurrentlyworkingasasecurityofficerandcybersecurityconsultantregardingvitalinfrastructure.HehasbeenarevieweronStormBlueprints:PatternsforDistributedReal-timeComputation,PacktPublishing.

Hehasabroadrangeofinterests.Inhissparetime,helikestofiddlewithlasers,microcontrollers,andotherrelatedelectronics,hencethisreview.Hehopesyoulikethisbookasmuchasheenjoyedreviewingit.

FrancisPereaisaprofessionaleducationprofessoratConsejeríadeEducacióndelaJuntadeAndalucíainSpainwithmorethan14yearsofexperience.

Hespecializesinsystemadministration,webdevelopment,andcontentmanagement

systems.Inhissparetime,heworksasafreelancerandcollaborates,amongothers,withñmultimedia,alittledesignstudioinCórdobaworkingasasystemadministratorandmainwebdeveloper.

HehasalsocollaboratedasatechnicalreviewerforSketchUp2013forArchitecturalVisualization,ArduinoHomeAutomation,andInternetofThingswiththeArduinoYún,byPacktPublishing.

Whennotsittinginfrontofacomputerortinkeringinhisworkshop,hecanbefoundmountainbikingorkitesurfingorasabeekeepertakingcareofhishivesinAxarquíaCounty,wherehelives.

Iwouldliketothankmywife,Salomé,andourthreekids,Paula,Álvaro,andJavi,forallthesupporttheygivemeevenwhenweallarebusy.Therearenowordstoexpressmygratitude.

Iwouldalsoliketothankmycolleaguesinñmultimediaandmystudentsforbeingpatient.Theneedtobeatthelevelyoudemandiswhatkeepsmegoingforward.

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PrefaceTheyearwas2005whenafewguysfromtheInteractionDesignInstituteIvrea,Italywantedtocreateasimplemicrocontrollerboardfortheirstudents—aboardthatwasmoremodern,cheaper,andeasiertousethanthedesignsavailableatthatmoment.AndtheynameditArduino,afterthelocalbar,whichwasnamedafterKingArduino.

Theinitialversionwasbulky,complicatedtoconnect,andlackedUSB,andotherfeaturescommonlyfoundthesedays,buttheboardhadpotential.Now,Arduinoisrenownedforitssimplicityandeaseofuse.ChildrenarebuildingprojectsusingArduinothatonly10yearsagowouldhaverequiredengineers.

Thewholedesignisopensourcedandclonesoftheboardcanbefoundeverywhereintheworld.ThereisnoknownnumberofArduinoboardsbutitisintherangeofhundredsofthousandsorevenmore.Everybodycandesigntheirowncustomimplementationofthestandardinventedin2005.

Today,Arduinohasbeentoeverycorneroftheplanetandevenaboveit.Ithasfueledotherrevolutionssuchasthemaker,theopensourceand3Dprintingmovements.Itiscontinuouslyupgradedtobefasterandhandlemore.ButwhatisArduino?

Arduinoisamicrocontrollerboard,designedtoconnecttoelectronicsandcontrolthem.WecanwritecodefortheArduinothatwillgetdatafromtheenvironment,andmakedecisionsandtakeactionsbasedonthedata.Robots,3Dprinters,toys,eventoastersmayhaveanArduinoinside,poweringupalltheinteraction.

ThisbookcontainsrecipesthatshowhowtoimplementkeytopicsoftheArduino,startingfrombasicinteractionwithbuttonsandLEDs,goinguptointeractionwiththeGlobalPositioningSystem(GPS),makingmusic,orcommunicatingwiththeInternet.Itisintendedforprogrammingorelectronicsenthusiastswhowanttocombinethebestofbothworldstobuildinteractiveprojects.

WhatthisbookcoversChapter1,Poweron–ArduinoBasics,willteachyoutoconnect,install,andtransferthefirstprogramtotheArduinoboard.ThischaptercoversthebasicsofhowtousetheArduinoboard,thetypesofboards,andhowtousetheArduinoIDE.

Chapter2,BlinkingLEDs,coversoneofthebasicusesofArduino,controllingLEDs.Varioustypesandimplementationshavebeencovered,RGBLEDs,blinkingandfadingLEDs,7-segmentdisplays,ormoreadvancedcontroltechniques.

Chapter3,WorkingwithButtons,willshowyouhowtodetectandusebuttonsasakeyinputmethod.Severaltypesofbuttonshavebeencoveredalongwithsolutionstothemostcommonbuttonimplementationissues.Also,waysofconnectingmorebuttonsthanavailabledigitalpinshavebeenshown.

Chapter4,Sensors,coversthemostimportantsensorsthatcanbeconnectedtotheArduino.ProbablythemostimportantthingforArduinoistobeabletoreadasmanyparametersfromtheenvironmentaspossible.Usingsensors,itcanreaddistance,temperature,lightintensity,orevengloballocalization.

Chapter5,MotorControl,willshowyouhowtoconnectandcontrolmultipletypesofmotors.MakingthingsmoveisincrediblyeasyusingmotorsandArduino.Smallandlarge,brushlessandservosmotoralongwithspeedanddirectioncontrol,haveallbeencoveredhere.

Chapter6,MoreOutputDevices,talksaboutgettingmoreoutofArduino.Thischaptercovershowtocontroldifferentloads,howtomakesound,howtoisolateandprotecttheboard,andhowtocommandmoreoutputs.

Chapter7,DigitalCommunicationwithArduino,coversseveralcommunicationprotocolssuchasUART,I2C,Serial,andEthernet,togetthemostoutofthecommunicationinterfacesavailableonArduino.Arduinocancommunicatewithotherboards,computers,andeventheInternet.

Chapter8,Hacking,talksaboutthesmallhacksthatcanhelpanArduinodesigngofurther.ItincludesspeedingupthePWM,reactingtoexternalinterrupts,orevenstoringdatainsidetheArduinoforever.

Appendix,Electronics–theBasics,coversthebasicsofelectronics,suchasbreadboards,Ohm’slaw,andsoon.

WhatyouneedforthisbookIngeneral,fortherecipesinthisbookyouwillneedthefollowingitems:

AnArduinoboardAUSBcabletoconnecttheArduinotothecomputerAbreadboardwithajumperwirekitAgeneralsetofresistorswithvaluesbetween100ohmand10,000ohmAnassortmentofgeneralLEDsAfewpushbuttonsandswitches1N4148and1N4001/1N4007diodes

Someofthemorefocusedrecipesrequirespecifichardwarecomponentsinordertoimplementthem.Thisisalistofspecificcomponentsrequiredperchapter:

Chapter2,BlinkingLEDs:

RGBLED7-segmentdisplaywithatleastonedigitStandardmulti-segmentbargraph

Chapter3,WorkingwithButtons:

4051orequivalentmultiplexerIntegratedCircuit(IC)

Chapter4,Sensors:

10KorotherpotentiometerLM35orTMP36temperaturesensorIntegratedCircuit(IC)PIRmotionsensorGassensorssuchastheMQ-3,MQ-4,MQ-5,andothersintheseriesSharpIRsensorsuchastheGP2Y0A21YKUltrasonicsensorsuchastheMaxSonarEZseriesorsimilarSimpleaccelerometerbreakoutsuchastheADXL335StandardI2CStandardGPSreceiverwithUARTcommunication4051orequivalentmultiplexerIntegratedCircuit(IC)

Chapter5,MotorControl:

SmallvibratingmotorStandardNPNtransistorssuchastheBC547,2N3905,ortheTIP120StandardLogicLevelNChannelMOSFETssuchastheIRF510orIRF520ArduinomotorshieldStandardRCservomotorULN2003orULN2004DarlingtonArrayICSmallbipolarsteppermotorBrushlessmotorwithsuitedESC

Chapter6,MoreOutputDevices:

8-ohmsmallspeakerStandardNPNtransistorssuchastheBC547,2N3905,ortheTIP120General5Vrelay1.5–3.0VbatterywithwireterminalsGeneraloptocoupler/optoisolatorsuchastheTLP621,4N35,orLTV-816A74HC595shiftregister

Chapter7,DigitalCommunicationwithArduino:

AnotherArduinoboardRFLinkTransmitterandReceiver(434/315Mhz)orequivalentArduinocompatbileEthernetShieldLCDcharacterDisplayArduinocompatibleSDshield

Chapter8,Hacking:

ADCmotorAresistorbetween220ohmand4,700ohmAstandardNPNtransistor(BC547,2N3904,N2222A,TIP120)oralogiclevel-compatibleMOSFET(IRF510,IRF520)Astandarddiode(1N4148,1N4001,1N4007)

WhothisbookisforIfyouwanttobuildprogrammingandelectronicsprojectsthatinteractwiththeenvironment,thisbookwillofferyoudozensofrecipestoguideyouthroughallthemajorapplicationsoftheArduinoplatform.Itisintendedforprogrammingorelectronicsenthusiastswhowanttocombinethebestofbothworldstobuildinteractiveprojects.

SectionsThisbookcontainsthefollowingsections:

GettingreadyThissectiontellsuswhattoexpectintherecipe,anddescribeshowtosetupanysoftwareoranypreliminarysettingsneededfortherecipe.

Howtodoit…Thissectioncharacterizesthestepstobefollowedfor“cooking”therecipe.

Howitworks…Thissectionusuallyconsistsofabriefanddetailedexplanationofwhathappenedintheprevioussection.

There’smore…Itconsistsofadditionalinformationabouttherecipeinordertomakethereadermoreanxiousabouttherecipe.

SeealsoThissectionmaycontainreferencestotherecipe.

ConventionsInthisbook,youwillfindanumberofstylesoftextthatdistinguishbetweendifferentkindsofinformation.Herearesomeexamplesofthesestyles,andanexplanationoftheirmeaning.

Codewordsintext,databasetablenames,foldernames,filenames,fileextensions,pathnames,dummyURLs,userinput,andTwitterhandlesareshownasfollows:“Intheloop()function,wefirstprintthehalfChristmastree.”

Ablockofcodeissetasfollows:

if(logFile)

logFile.print(val1);//Writefirstvalue

logFile.print("");//Writeaspace

logFile.println(val2);//Writesecondvalue

logFile.close();//closethefile

Newtermsandimportantwordsareshowninbold.Wordsthatyouseeonthescreen,inmenusordialogboxesforexample,appearinthetextlikethis:”Toeasilyfindinformationaboutacard,runtheArduinoIDEbuilt-inexamplefoundunderFile|Examples|SD|CardInfo.”

NoteWarningsorimportantnotesappearinaboxlikethis.

TipTipsandtricksappearlikethis.

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Tosendusgeneralfeedback,simplysendane-mailto<[email protected]>,andmentionthebooktitleviathesubjectofyourmessage.

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QuestionsIfyouhaveaproblemwithanyaspectofthisbook,youcancontactusat<[email protected]>,andwewilldoourbesttoaddresstheproblem.


Chapter1.Poweron–ArduinoBasicsInthischapter,wewillcoverthefollowingrecipes:

DownloadingtheArduinosoftwareConnectingArduinoUploadingcodetoArduinoLearningArduinocodebasicsCodebasics:ArduinoCCodebasics:ArduinoPins

IntroductionWhenwehaveanidea,wetakeapenandwesketchitdownonapieceofpaper.Imagineifwecouldbuildthingsthatinteractwiththeenvironmentjustaseasily.ThisiswheretheArduinoplatformcomesintoplay.

Arduinoisanopensourcefamilyofelectronicmicroprocessorboardsthatwecaneasilyprogramtounderstandandinteractwiththeenvironment.Overtheyears,Arduinohasbecomethestandardforbuildingelectronicsprojects.Arduinohasbeensentintospacetorunmicrosatellites;ithasbeensenttothebottomoftheoceantocontrolsmallroboticsubmersibles;andnow,Arduinohasarrivedforyou.Let’sexplorethelimitlessworldofArduino.

Ifyouwanttogothroughthebasicsofelectronicsbeforestartingwiththebook,youcanrefertotheAppendix,Electronics–theBasics.

DownloadingtheArduinosoftwareThefirstthingweneedistheArduinoIntegratedDevelopmentEnvironment(IDE).OneofthebestpartsaboutArduinoisthatthesoftwareinwhichweneedtoprogramtheboardsisfreeandopensource.TheArduinoIDEiscompatiblewithWindows,MacOSX,andLinux.

GettingreadyWeonlyneedonethingtocompletethisrecipe—acomputerconnectedtotheInternet.

Howtodoit…Followthesesimplesteps:

1. VisittheArduinowebsiteathttp://arduino.cc/.2. Inthemainmenu,gototheDownloadsection.3. SelectyouroperatingsystemanddownloadthelateststablereleaseoftheArduino

software.Atthetimeofwriting,thelateststableversioncompatiblewithallstandardboardswasversion1.0.5.

4. Afteritdownloads,installtheArduinosoftware.

http://arduino.cc/

There’smoreNowthatwehavetheArduinoIDEinstalled,let’sfamiliarizeourselveswiththeuserinterface.

HereisascreenshotoftheArduinosoftwarerunningonWindows.ItlooksthesameonMacandLinux,sinceit’sallwritteninJava.

First,wewilldiscusstheToolBar.IntheToolBar,wecanfindthemostusedbuttons:

Button Description

TheVerifybuttoncompilesthecodeandchecksitforerrors.

TheUploadbuttoncompilesthecodeand,ifthereisnoerrorinthecode,uploadsittotheArduinoboard.

TheNewbuttonstartsanewprogram.IntheArduinoworld,programsarecalledsketches.

TheOpenbuttonsimplyallowsustoopenasavedsketch.

TheSavebuttonsavesthecurrentsketch.

ThisbuttonopenstheSerialMonitorwindowthatallowsustocommunicatewiththeArduinoboard.Itisextremelyhelpfulwhenwedebugaprogram.MoreinformationcanbefoundintheSerialoutputrecipeinChapter7,DigitalCommunicationwithArduino

IntheSketchtab,wecanseealltheopenedArduinoSketches.Thiscomeshandywhenwewanttoworkonmultipleprogramsatthesametime.

TheCodeSpaceareaiswhereallthemagichappens.That’swherewewritethecodethatpowerssatellitesandcatfooddispensers.It’sacodeeditorwithautomaticsyntaxhighlightingandautoarranging.

TheStatusDisplayareaindicatesallthebadstuff.Wheneverthereareerrorsinthecode,theywillbedisplayedthere.Italsodisplayserrorsintheconnectionwiththeboard.TheonlygoodthingitcandisplayisthatthecodehasbeensuccessfullyuploadedtotheArduinoboard.

Additionalfunctionalitycanbefoundinthemainmenubar.Here,wehavetheclassicFilemenuwherewehaveSave,Open,Close,andalsosomeexamples.Inthefollowingrecipes,morewillbediscussedaboutthemenubarcomponents.AnicetrickworthsharingisintheToolsmenu—theAutoFormattoolwillformatthecodetolookprofessionalandclean.

SeealsoConsiderthefollowingrecipestobetterunderstandhowtousetheArduinosoftwareenvironment:

TheConnectingArduinorecipeTheUploadingcodetoArduinorecipe

ConnectingArduinoBeforewecanstartwritingcodeandmakingthingsmove,wefirstneedtoconnecttheArduinoboardtoourcomputer.TheArduinoboardiscompatiblewithMac,Windows,andLinux.Herewewilldiscusshowtoconnectandinstallthedrivers.

GettingreadyThefollowingaretheingredientsrequiredforthisrecipe:

AnArduinoboardconnectedtothecomputerviaUSBTheArduinoIDEdownloadedandinstalled

Howtodoit…Thisrecipeissplitintwo,asthestepsforMacandWindowsareslightlydifferent.

MacOSXFollowthesestepstoconnectArduinotoMacOSX:

1. ConnecttheArduinotothecomputerusingaUSBcable.Ifeverythingisproperlyconnected,thegreenlightwillturnandstayon.

2. IfyouhaveanArduinoUno,Leonardo,Due,orMega2560,nodriversareneededandtheboardisreadytogo.

3. Ifyou’reusinganolderArduinoboardsuchastheDuemilanove,Diecimila,orProMini,youwillrequireFTDIdrivers.Toobtainthem,youcanvisithttp://www.ftdichip.com/Drivers/VCP.htmanddownloadthelatest.Afterdownloadingthem,clickontheinstallerandfollowtheinstructions.Finally,rebootthecomputerandtheArduinoboardwillbeinstalled.

WindowsThefollowingstepsarerequiredfortheUno,Mega2560,Leonardo,andDueboardswhenconnectingArduinotoWindows:

1. ConnecttheArduinotothecomputerusingaUSBcable.Ifeverythingisproperlyconnected,thegreenlightwillturnonandstayon.

2. Windowswillbeginitsdriverinstallationprocessandfail.ClicktheStartbuttonandopentheControlPanel.There,navigatetoSystemandthenDeviceManager.

3. IntheDeviceManagerwindow,searchforPorts(COM&LPT)andlookforaportwithanamesimilartoyourboard.FortheArduinoUno,theportshouldbenamedArduinoUNO….IfthereisnosuchtitleunderPorts,lookinOtherDevicesforanUnknownDevice.ThatwillbeyourArduinoboard.

4. Right-clickontheArduinoBoardinDeviceManagerandchooseUpdateDriverSoftware.Next,selectBrowsemycomputerfordriversoftware.

5. ThiswillrequirethepathtotheArduinodriver.ThiscanbefoundintheArduinoinstallationfolderinProgramFiles,inthedriversfolder.ItisnamedArduino.inf.SelectthefileandWindowswillfinishinstallingthedriver.

ThesearethestepsfortheolderFTDI-basedDuemilanove,Diecimila,Nano,andMegaboards:

1. ConnecttheArduinotothecomputerusingaUSBcable.Thegreenlightwillturnonifeverythingisconnectedproperly.

2. InWindowsVistaandhigher,thedriverswillinstallautomaticallyandtheboardwillbereadyforuse.

3. Ifthedriverinstallationfails,navigatetoDeviceManagerinasimilarfashionasforthenewerboardsand,underPorts(COM&LPT),searchforaUSBSerialConverterorsimilar.ChooseUpdateDriverSoftware,selectBrowsemy

http://www.ftdichip.com/Drivers/VCP.htm

computerfordriversoftware,andthenselecttheFTDIdriverfolderfromtheArduinoinstallationfolder,inthedriversfolder.Afterselection,clickonNextandWindowswillfinishinstallingtheArduinoboard.

SeealsoTheprocedureforanUbuntuLinuxcomputerisathttp://playground.arduino.cc/Linux/Ubuntu.

http://playground.arduino.cc/Linux/Ubuntu

UploadingcodetoArduinoIt’stimetopowerontheArduinoboardandmakeitdosomething.Inthisrecipe,wewillconnecttheArduinotothecomputeranduploadanexamplesketchfromtheArduinoIDE.

GettingreadyToexecutethisrecipe,thefollowingarethecomponentsrequired:

AcomputerwiththeArduinoIDEinstalledAnArduinoboardconnectedtothecomputerviaUSB

Howtodoit…Followthesesteps:

1. ConnecttheArduinotothecomputerusingaUSBcable.Ifeverythingisproperlyconnected,thegreenLEDlightwillturnon.

2. IfthisisthefirsttimetheArduinohasbeenconnectedtothecomputer,driverinstallationmightberequired.PleasefollowtheConnectingArduinorecipetoproperlysetuptheArduinoboard.

3. StarttheArduinoIDEand,intheMenuBar,gotoFile|Examples|01.BasicsandclickontheBlinkexample.ThiswillloadtheBlinksketch.

4. MakesureyourArduinoboardisselectedintheBoardmenu.ThemenucanbefoundintheMenubarinTools|Board.

5. Weneedtocheckwhetherthecorrectserialportisselected.UnderTools|SerialPort,wecanseeallavailableserialportdevicesconnectedtothecomputer.OnWindows,eachportwillbelabeledasCOMfollowedbyanumber.Usually,ArduinoinstallsonCOM3,butnotalways.AfastwaytocheckwhichserialporttheArduinoisconnectedtoistounplugthecableandseewhichCOMportdisappearsinthemenu.ThatwillbeourArduinoboard.IntheMac,theportshouldbecalledsomethingbeginningwith/dev/tty.usbmodemor/dev/tty.usbserial.

6. ClickontheUploadbuttonontheToolBar.Ifeverythingrunsproperly,theTXRXLEDsontheArduinoboardwillbeginblinkingforashorttimeuntiltheuploadisdone.Afterthis,oneLEDlightontheArduinoBoardshouldslowlyblink.

Howitworks…Whenweuploadasketchtotheboard,theArduinosoftwarefirstcompilesthecode.Ifthereisanerrorinthecode,itwillwriteitintheStatusDisplayareaandwillstoptheupload.Ifnoerrorsarefound,itwillbeginwritingthecompiledcodetotheboard.Errorswillappeariftheboardorserialportisnotproperlyselected.Wheneverythingiscorrectlysetup,theTXRXLEDswillblink,meaningdataisbeingtransferredbetweenthecomputerandtheArduinoboard.Whenthetransferisdone,theboardwillresetandthecodewillimmediatelybeginexecuting.

ThecodeisstoredintheArduinoboarduntilitiserasedorreplacedbyanothercode.Wecantaketheboardandplugitintoabatteryortoanothercomputer,anditwillstillexecutethisblinking.

LearningArduinocodebasicsHerewebeginwiththebasicsofcodingforArduino.WritingcodeforArduinoandotherembeddedplatformsisalittledifferentfromwritingcodeforacomputer.Butdon’tfear—thedifferencesaresmall.

GettingreadyToexecutethisrecipe,weneedjustoneingredient:theArduinoIDErunningonacomputer.

Howtodoit…ThesearethetwomandatoryfunctionsintheArduinocodingenvironment:

voidsetup()

//OnlyexecuteoncewhentheArduinoboots

voidloop()

//Codeexecutestop-downandrepeatscontinuously

Howitworks…EachArduinosketchhastwomandatoryfunctions:thesetup()functionandtheloop()function.Thesetup()functiononlyexecutesonce:eitherwhenweapplypowertotheArduinoorwhenitresets.Usually,weusethisfunctiontoconfigurethepinsoftheArduino,tostartcommunicationprotocols,suchasserialcommunication,ortoperformactionsweonlywanttoperformoncewhentheArduinoboots.

Theloop()functionexecutescontinuously.Codeinthisfunctionisexecutedtop-down;whenitreachestheendofthefunction,itjumpsbacktothestartandrunsagain.ThishappensforeveruntiltheArduinoisswitchedoff.Inhere,wewritethecodewewanttoruncontinuously.

SeealsoContinuetheArduinocodebasicswiththefollowingrecipe,Codebasics:ArduinoC.

Codebasics–ArduinoCTheArduinousesaslightlyreducedC/C++programminglanguage.Inthisrecipe,wewillrememberafewbasicsofC/C++.

GettingreadyEnsurethatyouhavetheArduinoIDErunningonacomputer.

Howtodoit…HereisasimpleexampleofbasicArduinoC/C++manipulatingtwovariables:

//GlobalVariables

intvar1=10;

intvar2=20;

voidsetup()


var2=5;//var2becomes5oncetheArduinoboots

voidloop()

//Codeexecutestop-downandrepeatscontinuously

if(var1>var2)//Ifvar1isgreaterthanvar2

var2++;//Incrementvar2by1

else//Ifvar1isNOTgreaterthanvar2

var2=0;//var2becomes0

Howitworks…Thecodeplayswithtwointegervariables.Herewehaveacodebreakdowntobetterexplaineachstep.

First,wedeclaredtwoglobalvariables—var1andvar2—andwesetthemtothevaluesof10and20respectively.

//GlobalVariables

intvar1=10;

intvar2=20;

WhentheArduinoboots,itfirstallocatestheglobalvariablesintomemory.Inthesetup()function,wechangethevalueofvar2to5:

voidsetup()


var2=5;//var2becomes5oncetheArduinoboots

AftertheArduinoallocatestheglobalvariables,itexecutesthecodeinsidethesetup()functiononce.Followingthis,theloop()functionwillexecuterepeatedly.Inside,wehaveanifconditionthatwillplaywiththevaluesofvar2.Ifvar1isgreaterthanvar2,weincreasevar2byone.Eventually,var1willnotbegreaterthanvar2,andthenwesetvar2to0.Thiswillresultinaninfiniteaddingandequalingofvar2.

ThisisoneexampleonhowtheArduinoexecutesthecodeinitstwomainfunctions.

SeealsoContinuetheArduinocodebasicswiththefollowingrecipe,Codebasics–Arduinopins.

Codebasics–ArduinopinsThemostimportantfeatureoftheArduinoisitscontroloverdigitalinput/output(I/O)pins.Oneachpin,wecansetavoltagevalueof5V,representinglogicHIGH,or0V,representinglogicLOW.Also,wecanreadwhetheravalueof5Vor0Visappliedexternally.Herewewilllearnhow.

GettingreadyForthisrecipe,ensurethatyouhavetheArduinoIDErunningonacomputer.

Howtodoit…ThefollowingcodeturnsapinHIGHandLOWrepeatedlywhilereadingtheexternalvoltageappliedtoanother:

voidsetup()

//Setpin2asadigitalOutput

pinMode(2,OUTPUT);

//Setpin3asadigitalInput

pinMode(3,INPUT);

voidloop()

//Setpin2HIGH

digitalWrite(2,HIGH);

//Wait100milliseconds

delay(100);

//Setpin2LOW

digitalWrite(2,LOW);


delay(100);

//Readthevalueofpin3andstoreitinavariable

intpinValue=digitalRead(3);

Howitworks…Thecodesetstwopinsinoutputandinputmodeandthenwritesandreadsfromthem.Hereisthecodebreakdown:

Insetup(),weusethepinMode()functiontosetpinnumber2asanoutput.Whenwesetapinasanoutput,wecansetthatpinaseitherHIGH(5V)orLOW(0V).Also,wesetpinnumber3asaninput.Apinconfiguredasinputcanreadexternalvoltagesappliedtoit.ItcanreadHIGHifthevoltageisaround5VandLOWifthevoltageiscloseorequalto0V:

voidsetup()

//Setpin2asadigitalOutput

pinMode(2,OUTPUT);

//Setpin3asadigitalInput

pinMode(3,INPUT);

Intheloop()function,weusethedigitalWrite()functiontosetpinnumber2toHIGH.Then,wewaitfor100millisecondsusingthedelay()function.Thisfunctionstopstheexecutionofthecodeforthespecifiedtime,inmilliseconds.Thereafter,wesetthepintoLOWandwaitanother100milliseconds.Intheend,wereadthevalueofpin3inavariable:

voidloop()

//Setpin2HIGH

digitalWrite(2,HIGH);


delay(100);

//Setpin2LOW

digitalWrite(2,LOW);


delay(100);

//Readthevalueofpin3andstoreitinavariable

intpinValue=digitalRead(3);

TipDownloadingtheexamplecode

Youcandownloadtheexamplecodefilesfromyouraccountathttp://www.packtpub.comforallthePacktPublishingbooksyouhavepurchased.Ifyoupurchasedthisbookelsewhere,youcanvisithttp://www.packtpub.com/supportandregistertohavethefilese-maileddirectlytoyou.


http://www.packtpub.com/support

Chapter2.BlinkingLEDsInthischapter,wewillcoverthefollowingrecipes:

BlinkingLEDwithoutdelay()ConnectinganexternalLEDFadingtheexternalLEDRGBLEDLEDbargraphThe7-segmentdisplay

IntroductionInthischapter,wewillexploreLEDswiththeArduino.ThefastestwaytogetsomefeedbackfromasystemorfromtheArduinoisviaanLED.Theyaresimpledeviceswhichareeitheronoroff.However,theyformthebasisforadvancedtechnologiessuchasLEDTVs,projectors,orlasers.Inthischapter,wewillalsoseehowtousethemefficientlyandexploresomeinterestingapplicationsforthem.

LEDstandsforLightEmittingDiodeand,initscore,it’sjustadiodethatemitslight.LEDsareincrediblycommonthesedaysandcanbefoundatanycommonelectronicsshop.Radioshack,Digikey,Farnell,Sparkfun,Adafruit,orPololuarejustafewplaceswecanbuyLEDsfrom,online.

BlinkingLEDwithoutdelay()ItiseasytomaketheLEDblinkonanArduino.Weturniton,wait,turnitoff,waitagain,andthenwerepeatthecycle.However,thiswaitstatewillcompletelyhalttheArduinoexecution.WewanttomaketheLEDblinkwhiletheArduinoisperformingotheractions.

GettingreadyForthisrecipeallyouneedisanArduinoboardconnectedtothecomputerviaUSB.

Howtodoit…ThefollowingcodewillmaketheinternalLEDblinkontheArduinowithouteverusingthedelay()function:

//VariableforkeepingthepreviousLEDstate

intpreviousLEDstate=LOW;

unsignedlonglastTime=0;//LasttimetheLEDchangedstate

intinterval=200;//intervalbetweentheblinksinmilliseconds

voidsetup()

//DeclarethepinfortheLEDasOutput

pinMode(LED_BUILTIN,OUTPUT);

voidloop()

//Herewecanwriteanycodewewanttoexecutecontinuously

//Readthecurrenttime

unsignedlongcurrentTime=millis();

//Comparethecurrenttimewiththelasttime

if(currentTime-lastTime>=interval)

//Firstwesettheprevioustimetothecurrenttime

lastTime=currentTime;

//ThenweinversethestateoftheLED

if(previousLEDstate==HIGH)

digitalWrite(LED_BUILTIN,LOW);

previousLEDstate=LOW;

else

digitalWrite(LED_BUILTIN,HIGH);

previousLEDstate=HIGH;

NoteWhilemostArduinoshavetheLEDonpin13,somedon’t.TomakesureweareaddressingthecorrectLEDpin,wecanusetheLED_BUILTINconstant.ThisisalreadydefinedintheArduinolanguageandwillalwaysequaltheLEDpinnumberoftheArduinoboardthathasbeenused.

Howitworks…ThebigdifferencebetweenanormalLEDblinkingprogramandthisoneisthatwedon’tusethedelay()function.Thedelay()functionsimplystopsthecodeexecutionuntilthespecifiedamountoftimepasses.Here,wetracktheinternaltimeoftheArduino;whenenoughtimepasses,wechangestate.TheinternaltimesincethestartoftheArduinoisaccessibleusingthemillis()function,whichwillreturnthetime—inmilliseconds—sincetheprogramstartedworking.

Thisapproachiscallednon-blocking,sinceitdoesn’tblocktheexecutionofourcode.Thedelay()functionisconsideredtobeablockingfunction,asitblockscodeexecution.

BreakingdownthecodeThecodetrackstheamountoftimepassedandchangesthestateoftheLEDifenoughtimehaspassed.

Weneedafewvariables.ThepreviousLEDstatevariablewillstorethelaststateoftheLED.ThelastTimevariablerememberswhentheLEDstatechangedfromHIGHtoLOWorfromLOWtoHIGH.WhenwesetapinasHIGH,itwilloutput5V.WhenwesetitasLOW,itwilljustgoto0V.

TheintervalvariableistheintervalinmillisecondsatwhichwewanttheLEDtochangestate.

//VariableforkeepingthepreviousLEDstate

intpreviousLEDstate=LOW;

unsignedlonglastTime=0;//LasttimetheLEDchangedstate

intinterval=200;//intervalbetweentheblinksinmilliseconds

Inthesetup()function,wesettheLEDpinasanoutput:

voidsetup()


pinMode(LED_BUILTIN,OUTPUT);

Theimportantpartcomesintheloop()function.ThefirststepistorecordthetimesincetheArduinobeganrunningtheprogram.Themillis()functionreturnsverybignumbers;variablesgettingdatafromthisfunctionshouldalwaysbedeclaredaslongorunsignedlong.Unsignedvariablescanonlytakepositivevalues,from0tothemaximumallocatedspace.Forexample,anormallongvariablecantakevaluesfrom-2,147,483,648upto2,147,483,648,whileanunsignedlongcangofrom0upto4,294,967,295.

unsignedlongcurrentTime=millis();

Now,weneedtoseeifenoughtimehaspassedsincethelasttimewechangedthestateoftheLED.Forthis,wecomparewiththeprevioustime.Ifthedifferencebetweenthecurrenttimeandthelastisbiggerthantheintervalwedeclared,wecanproceedtochangethestateoftheLED:

if(currentTime-lastTime>=interval)

Whentheintervalhaspassed,wefirstrecordthenewtimeasbeingtheprevioustime.Bydoingthis,weresetthetimetowhichwewillcomparethenexttime.Then,wecheckwhatthepreviousLEDstatewasandwesettheLEDtotheoppositestate.IfitwasLOWwesetittoHIGHandifitwasHIGH,wesetittoLOW.ThepreviousLEDstatevariableisalsosettothenewLEDstate:

lastTime=currentTime;

//ThenweinversethestateoftheLED

if(previousLEDstate==HIGH)

digitalWrite(LED,LOW);

previousLEDstate=LOW;

else

digitalWrite(LED,HIGH);

previousLEDstate=HIGH;

SeealsoTheButtondebouncingrecipeinChapter3,WorkingwithButtons,forothertopicswhichavoidthedelay()function

ConnectinganexternalLEDLuckily,theArduinoboardscomewithaninternalLEDconnectedtopin13.Itissimpletouseandalwaysthere.ButmosttimeswewantourownLEDsindifferentplacesofoursystem.WemightconnectsomethingontopoftheArduinoboardandcannolongerseetheinternalLED.Here,wewillexplorehowtoconnectanexternalLED.

GettingreadyForthisrecipe,weneedthefollowingingredients:

AnArduinoboardconnectedtothecomputerviaUSBAbreadboardandjumperwiresAregularLED(thetypicalLEDsizeis3mm)Aresistorbetween220–1,000ohm

Howtodoit…FollowthesestepstoconnectanexternalLEDtoanArduinoboard:

1. Mounttheresistoronthebreadboard.ConnectoneendoftheresistortoadigitalpinontheArduinoboardusingajumperwire.

2. MounttheLEDonthebreadboard.Connecttheanode(+)pinoftheLEDtotheavailablepinontheresistor.WecandeterminetheanodeontheLEDintwoways.Usually,thelongerpinistheanode.AnotherwayistolookfortheflatedgeontheoutercasingoftheLED.Thepinnexttotheflatedgeisthecathode(-).

3. ConnecttheLEDcathode(-)totheArduinoGNDusingjumperwires.

SchematicThisisonepossibleimplementationontheseconddigitalpin.Otherdigitalpinscanalsobeused.

HereisasimplewayofwiringtheLED:

CodeThefollowingcodewillmaketheexternalLEDblink:

//DeclaretheLEDpin

intLED=2;

voidsetup()


pinMode(LED,OUTPUT);

voidloop()

//HerewewillturntheLEDONandwait200milliseconds


delay(200);

//HerewewillturntheLEDOFFandwait200milliseconds


delay(200);

TipIftheLEDisconnectedtoadifferentpin,simplychangetheLEDvaluetothevalueofthepinthathasbeenused.

Howitworks…Thisisallsemiconductormagic.WhentheseconddigitalpinissettoHIGH,theArduinoprovides5Vofelectricity,whichtravelsthroughtheresistortotheLEDandGND.Whenenoughvoltageandcurrentispresent,theLEDwilllightup.TheresistorlimitstheamountofcurrentpassingthroughtheLED.Withoutit,itispossiblethattheLED(orworse,theArduinopin)willburn.TrytoavoidusingLEDswithoutresistors;thiscaneasilydestroytheLEDorevenyourArduino.

CodebreakdownThecodesimplyturnstheLEDon,waits,andthenturnsitoffagain.Comparedtothepreviousrecipe,inthisonewewilluseablockingapproachbyusingthedelay()function.HerewedeclaretheLEDpinondigitalpin2:

intLED=2;

Inthesetup()functionwesettheLEDpinasanoutput:

voidsetup()


Intheloop()function,wecontinuouslyturntheLEDon,wait200milliseconds,andthenweturnitoff.Afterturningitoffweneedtowaitanother200milliseconds,otherwiseitwillinstantaneouslyturnonagainandwewillonlyseeapermanentlyonLED.

voidloop()

//HerewewillturntheLEDONandwait200miliseconds


delay(200);

//HerewewillturntheLEDOFFandwait200miliseconds


delay(200);

There’smore…Thereareafewmorethingswecando.Forexample,whatifwewantmoreLEDs?DowereallyneedtomounttheresistorfirstandthentheLED?

LEDresistorWedoneedtheresistorconnectedtotheLED;otherwisethereisachancethattheLEDortheArduinopinwillburn.However,wecanalsomounttheLEDfirstandthentheresistor.ThismeanswewillconnecttheArduinodigitalpintotheanode(+)andtheresistorbetweentheLEDcathode(-)andGND.ChecktheDiodesandLEDsrecipeintheAppendix,Electronics–theBasics,wherewediscusstheneededresistancestopowerupanLED.Or,ifwewantaquickcheat,checkthefollowingSeealsosection.

MultipleLEDsEachLEDwillrequireitsownresistoranddigitalpin.Forexample,wecanmountoneLEDonpin2andoneonpin3andindividuallycontroleach.WhatifwewantmultipleLEDsonthesamepin?DuetothelowvoltageoftheArduino,wecannotreallymountmorethanthreeLEDsonasinglepin.Forthiswerequireasmallresistor,220ohmforexample,andweneedtomounttheLEDsinseries.Thismeansthatthecathode(-)ofthefirstLEDwillbemountedtotheanode(+)ofthesecondLED,andthecathode(-)ofthesecondLEDwillbeconnectedtotheGND.TheresistorcanbeplacedanywhereinthepathfromthedigitalpintotheGND.

SeealsoFormoreinformationonexternalLEDs,takealookatthefollowingrecipesandlinks:

TheFadingtheexternalLEDrecipeTheRGBLEDrecipeFormoredetailsaboutLEDsingeneral,visithttp://electronicsclub.info/leds.htmToconnectmultipleLEDstoasinglepin,readtheinstructableathttp://www.instructables.com/id/How-to-make-a-string-of-LEDs-in-parallel-for-ardu/Becausewearealwayslazyandwedon’twanttocomputetheneededresistorvalues,usethecalculatorathttp://www.evilmadscientist.com/2009/wallet-size-led-resistance-calculator/

http://electronicsclub.info/leds.htm

http://www.instructables.com/id/How-to-make-a-string-of-LEDs-in-parallel-for-ardu/

http://www.evilmadscientist.com/2009/wallet-size-led-resistance-calculator/

FadingtheexternalLEDTheLEDhastwostates:ONandOFF.Butwhatifwewanttoadjustthebrightness?HowcanwedothatifwecanonlyturnitONorOFF?ByturningitONandOFFquickly.

WewilluseatechniquecalledPulseWidthModulation(PWM),whichisbuiltintotheArduino.ItallowsustodimtheLEDwithupto256settings.

GettingreadyWerequirethefollowingingredientsforthisrecipe:

AnArduinoboardconnectedtothecomputerviaUSBAbreadboardandjumperwiresAregularLEDAresistorbetween220–1,000ohm

Howtodoit…ThisrecipeusesthesamecircuitastheConnectinganexternalLEDrecipewithasingledifference,thepinusedtoconnecttheLEDisnotdigitalpin2butPWMpin3.

SchematicThisisonepossibleimplementationonthethirddigitalpin.OtherdigitalpinswithPWMcanbeused.OnthetypicalArduino,suchasUNO,therearesixpinsthatalsohavePWMfunctionality.Thesepinsare3,5,6,9,10,and11.

HereisasimplewayofwiringtheLED:

CodeThefollowingcodewillmaketheexternalLEDfade:

//DeclaretheLEDpinwithPWM

intLED=3;

voidsetup()



voidloop()

//HerewewillfadetheLEDfrom0tomaximum,255

for(inti=0;i<256;i++)

analogWrite(LED,i);

delay(5);

//FadetheLEDfrommaximumto0

for(inti=255;i>=0;i--)

analogWrite(LED,i);

delay(5);

TipIftheLEDisconnectedonadifferentPWMpin,simplychangetheLEDvaluetothevalueofthepinthathasbeenused.

Howitworks…ThisallworkswithPWM,whichworksbyswitchingbetweenLOWandHIGHveryfast.Ifweturnadigitalpinonandoffathousandtimespersecond,wewillobtain,onaverage,avoltagethatishalfoftheHIGHvoltage.IftheratiobetweenHIGHandLOWis2:3,theobtainedvoltagewillbetwo-thirdsoftheHIGHvoltageandsoon.ThefollowingdiagrambetterexplainshowPWMworks:

PWMisquitedifficulttoobtainbut,luckily,Arduinohasanin-builtfunctionthatconfiguresalltheregistersandtimersinordertoobtainPWM.

CodebreakdownThecodefadestheLEDonandoffbychangingthePWM.Here,wedeclaretheLEDpinondigitalpin3:

intLED=3;

Inthesetup()function,wesettheLEDpinasanoutput:

voidsetup()



Intheloop()function,weusetheimportantPWMfunctionanalogWrite().ThisfunctionprovidesananalogsignalonthedigitalPWMpin.Thevaluesforthevoltagecanbebetween0–255,0for0voltsand255for5Vor3.3V,dependingontheArduinoboardused.Here,wefadeintheLEDslowlyusingaforfunctionandthenwefadeitout:

voidloop()

//HerewewillfadetheLEDfrom0tomaximum,255


analogWrite(LED,i);

delay(5);

//FadetheLEDfrommaximumto0


analogWrite(LED,i);

delay(5);

There’smore…ThePWMtechniqueisusedinalmostalldigitalsystems.Soundisdigitallyproducedusingthistechnique;that’showwecanlistentomusiconacomputer.ArduinoonlyhasafewpinsforPWM.Theyareusuallylabeledwitha~sign.TheanalogWrite()functionwillnotworkonnon-PWMpins.

SeealsoFormoreinformationonPWM,takealookatthefollowingrecipesandlinks:

TheRGBLEDrecipehttp://makezine.com/2011/06/01/circuit-skills-pwm-pulse-width-modulation-sponsored-by-jameco-electronics/

http://makezine.com/2011/06/01/circuit-skills-pwm-pulse-width-modulation-sponsored-by-jameco-electronics/

RGBLEDWecangetLEDsinavarietyofcolorsthesedays,butwhataboutanLEDthatcanchangecolor?WeallknowthatacombinationofRed,Green,andBlue(RGB)cangiveusanycolor.UsingtheArduinoPWMfunctionality,wewillseehowwecanobtain16millioncolorcombinationswithanRGBLED.

RGBLEDstandsforRedGreenBlueLED.InsidesuchanLEDwecanfindonered,onegreen,andoneblueLED,mountedtogether.

GettingreadyThefollowingaretheingredientsneededforthisrecipe:

AnArduinoboardconnectedtothecomputerviaUSBAbreadboardandjumperwiresAnRGBLEDThreeequalresistorsbetween220–1,000ohm

Howtodoit…FollowthesestepsinordertoconnectanRGBLEDtoanArduinoboard:

1. MounttheRGBLEDonthebreadboard.2. Weneedtoidentifywhichpinrepresentswhichcolorandwhichpinisthecommon

one.Thefollowinggraphicexplainsjustthat:

3. Connect5Vtothecommonanode(+)oftheRGBLED.Thisisthelongestofthefourpins.

4. Connecteachsmallercathode(-)pintooneindividualresistor.5. ConnecteachremainingpinoneachresistortoanindividualPWMpinonthe

Arduino.

SomeRGBLEDsareacommoncathode(-)configuration.Inthiscase,connectthecathode(-)toGND.

SchematicThisisonepossibleimplementationusingacommonanode(+)RGBLEDonthePWM,pins9,10,and11:

Hereisonewayofwiringeverythingonthebreadboard:

CodeThefollowingcodewillmaketheRGBLEDchangeafewcolors:

//DeclarethePWMLEDpins

intredLED=9;

intgreenLED=10;

intblueLED=11;

voidsetup()

//DeclarethepinsfortheLEDasOutput

pinMode(redLED,OUTPUT);

pinMode(greenLED,OUTPUT);

pinMode(blueLED,OUTPUT);

//Asimplefunctiontosetthelevelforeachcolorfrom0to255

voidsetColor(intredValue,intgreenValue,intblueValue)

analogWrite(redLED,255-redValue);

analogWrite(greenLED,255-greenValue);

analogWrite(blueLED,255-blueValue);

voidloop()

//Changeafewcolors

setColor(255,0,0);//RedColor

delay(500);

setColor(0,255,0);//GreenColor

delay(500);

setColor(0,0,255);//BlueColor

delay(500);

setColor(255,255,0);//Yellow

delay(500);

setColor(0,255,255);//Cyan

delay(500);

setColor(255,0,255);//Magenta

delay(500);

setColor(255,255,255);//White

delay(500);

TipIftheRGBLEDisconnectedtodifferentPWMpins,simplychangethevaluesofredLED,greenLED,andblueLEDtothevaluesofthepinsthathavebeenused.

Howitworks…RGBLEDsaremadeupofthreeLEDs:onered,onegreen,andoneblue.Becausetheyarephysicallyclosetogether,ifwemanipulatethemindividually,thecolorwewillseeistheresultingcombinationofthethreeLEDcolors.

CodebreakdownThecodecontrolsthreeLEDsindividuallyusingthesametechniquefromtheFadingtheExternalLEDrecipe.Here,wedeclarethethreeLEDpinsonthePWMchannels9,10,and11:

intredLED=9;

intgreenLED=10;

intblueLED=11;

Inthesetup()function,wesettheLEDpinsasoutputs:

voidsetup()

//DeclarethepinsfortheLEDasOutput

pinMode(redLED,OUTPUT);

pinMode(greenLED,OUTPUT);

pinMode(blueLED,OUTPUT);

HereisacustomfunctioncalledsetColor()thatmakeseverythingeasier.ThefunctionhasthreeparametersandthepowerforeachR,G,andBLED.Thevaluescanvaryfrom0–255foreachLED,whichmeanswehave16,581,375possiblecolors.Inreality,wewillneverusethatmany.

voidsetColor(intredValue,intgreenValue,intblueValue)

analogWrite(redLED,255-redValue);

analogWrite(greenLED,255-greenValue);

analogWrite(blueLED,255-blueValue);

TipInthisexample,weuseacommonanode(+)RGBLED.ThismeansthatwecontrolthecurrentthatgoesintotheArduinopin—andnotout—asweusuallydo.Code-wiseinthisconfiguration,whenweturnthepintoHIGHorto255,theLEDwillbeOFF.Thisisthereasonforthe255–redValueparameter;itinvertsthevalue.

Weusetheloop()functionwecreatedtoobtainafewcombinations.Here,weonlyuseeitherfullpower(255)or0.Wecanexperimentwithin-betweenvaluestoobtaindifferentcolors.Giveitatrywiththiscode:

voidloop()

setColor(255,255,0);//Yellow

delay(500);

setColor(0,255,255);//Cyan

delay(500);

setColor(255,0,255);//Magenta

delay(500);

There’smore…TherearemanytypesofRGBLEDs.LargedisplaysthatwefindinconcertsoroncommercialboardshavethousandsofRGBLEDstoshowtheimage.Therearealsomanymorewaysofconnectingthem.

Commonanode(+)orcommoncathode(-)AnRGBLEDhasthreeLEDswithin,withonepintiedtogether.Inacommonanode(+)version,wewillhavethreeLEDswiththeiranodes(+)connectedtogether.Thesameholdstrueforacommoncathode(-)configuration,onlythatthecathode(-)istiedtogetheramongsttheLEDs.Commoncathodesareeasiertousebuthardertofind.

Foracommoncathode(-),weconnectthecathodetotheGNDandthethreeindividualanodestoanindividualdigitalpinontheArduinousingresistors.

WithoutPWMWedon’talwaysneed16millioncolors.SimplyusethedigitalWrite()functionsandwecanstillobtainsevencolorsfromtheLED.

LEDbargraphWeallhateprogressbars!Theyarealwaysdelayingusfromdoingsomething.ButintheArduinoworldtheycanbeveryhandy.Here,wewillseehowtobuildonewithLEDs.AnLEDbargraphisjustabunchofLEDsputtogetherinafancycase,buttherearemanyusesforit.Wecandisplaythedatefromasensor,showacriticalcondition,ormakeafunnylightshowwithit.

GettingreadyWewillneedthefollowingingredientstoexecutethisrecipe:

AnArduinoboardconnectedtothecomputerviaUSBAbreadboardandjumperwiresAnLEDbargraphResistorsbetween220–1,000ohm

Howtodoit…Followingarethestepstoconnecta10-segmentbargraphtotheArduino:

1. MounttheLEDbargraphontothebreadboard.2. Ifthebargraphisacommonanode(+)configuration,connectthecommonanode(+)

pintothe5VportontheArduino.Ifthebargraphisacommoncathode(-),connectthepintotheGNDportontheArduino.

3. ConnecteachindividualsegmentpintooneindividualArduinodigitalpin,usingaresistor.Tomakethingssimple,connectallthesegmentpinstosuccessivedigitalpinsontheArduino.

SchematicThisisonepossibleimplementationofacommonanode(+)10-segmentLEDbargraph:

Hereisonepossiblewayofwiringitonabreadboard:

CodeThefollowingcodewillmaketheLEDbargraphfullandthenempty:

//DeclarethefirstandlastPinoftheLEDBar

intpin1=2;

intpin10=11;

voidsetup()

//DeclarethepinsasOutputs

for(inti=pin1;i<=pin10;i++)

pinMode(i,OUTPUT);

//AsimplefunctiontosetthevalueoftheLEDBar

voidsetBarValue(intvalue)

//Firstweturneverythingoff


digitalWrite(i,HIGH);

//Writethevaluewewant

for(inti=pin1;i<=pin1+value;i++)

digitalWrite(i,LOW);

//Incasewehavevalue0

if(value==0)

digitalWrite(pin1,HIGH);

voidloop()

//Playwithafewdisplays

//Ping-Pong

for(inti=0;i<=10;i++)

setBarValue(i);

delay(100);


setBarValue(i);

delay(100);

TipThiswasdesignedforacommonanode(+)configuration.Foracommoncathode(-)configuration,weneedtochangethedigitalWritefunctiontooutputthereverse.IfitisHIGH,itshouldoutputLOW.

Howitworks…AnLEDbargraphisassembledfrommultipleLEDs.WecancontroleachLEDindividuallytoobtainthedesiredeffect.TakealookattheConnectinganexternalLEDrecipeformoredetailsonexternalLEDs.Inthisexample,wewillwriteafunctiontosettheprogressvalueontheLEDbargraph.

CodebreakdownThiscodeloadsandunloadstheLEDbargraphjustlikeaprogressbar.Here,wedeclarethefirstandthelastpinsusedintheLEDbar.Thereisnopointindeclaringallofthemasweknowtheyareconsecutiveinthisimplementation:

intpin1=2;

intpin10=11;

Inthesetup()function,weseteachLEDpinasanoutput.Thissimpletrick,usedhere,helpstosetallthepinsbetweenpin1andpin10asoutputs:

voidsetup()



pinMode(i,OUTPUT);

InthecustomsetBarValue()function,wemakethebarshowacertainprogresslevel.Asthemaximumis10andtheminimumis0,ifwewrite5,halftheLEDsonthebarwillbeonwhiletheotherhalfareoff:

//AsimplefunctiontosetthevalueoftheLEDBar

voidsetBarValue(intvalue)

//Firstweturneverythingoff


digitalWrite(i,HIGH);

//Writethevaluewewant

for(inti=pin1;i<=pin1+value;i++)

digitalWrite(i,LOW);

//Incasewehavevalue0

if(value==0)digitalWrite(pin1,HIGH);

Finally,intheloop()function,weuseourcustomfunctiontoloadthebarandthenunloadit.Inthefollowingcode,weuseaforlooptoincreasethebarvaluetothemaximumandthenwedecreaseitbackto0:

voidloop()


setBarValue(i);

delay(100);


setBarValue(i);

delay(100);

There’smore…LEDbargraphscanbeveryhelpfulinvarioussituations.Usuallytheyareusedtoshowthebatterylevelonasystemorthevalueofasensor.Afewvariationsonthebarcanbeseenasfollows.

Commonanode(+)andcommoncathode(-)EachLEDbariseitheracommonanode(+)oracommoncathode(-).Ifit’sacommonanode(+),weconnecttheanodeto5V,eachotherpintoaresistor,andtheresistorstoindividualdigitalpinsontheArduino.Forthecommoncathode(-),connectthecathodetotheGNDandeachpin,usingaresistor,toindividualArduinodigitalpins.

BargraphvariationsLEDbargraphscomeinmultiplesizesandshapes.Theycanhave5to50LEDs.Therearesomewhichareround.AlotofthemhavefourtofivecolorsofLEDsinonebar.Choosewhatfitsyourdesignortastebest.

SeealsoForothertopicsregardingLEDassemblies,pleasecheckthefollowingrecipe:

The7-segmentdisplayrecipe

The7-segmentdisplaySincethebeginningofelectronics,7-segmentdisplayshavebeenusedtodisplaynumbers.Theyareeasytoconnectandunderstand,andquitefuntouseoncetheyareproperlyimplemented.Wecanusesuchadisplaytoshowthestatusofoursystemortoshowdatafromasensor.

GettingreadyThefollowingingredientsareneededforthisrecipe:

AnArduinoboardconnectedtothecomputerviaUSBAbreadboardandjumperwiresA7-segmentdisplayResistorsbetween220–1,000ohm

Howtodoit…Followthesestepsinordertoconnecta7-segmentdisplaytotheArduino:

1. Mountthe7-segmentdisplayonthebreadboard.2. Ifthedisplayisacommonanode(+)configuration,connectthecommonanode(+)

pintotheVCCportontheArduino.Ifitisacommoncathode(-),connectthecathodetotheGNDportontheArduino.

3. ConnecteachindividualsegmentpintooneindividualArduinodigitalpinusingaresistor.

SchematicHereisonepossibleimplementationofacommonanode(+)7-segmentdisplay:

Hereisonepossiblewayofwiringitonabreadboard:

CodeThefollowingcodewillmakethe7-segmentdisplaycountdownfrom3andrestart:

//DeclarethepinsfortheSegmentdisplay

intpinUP=2;//Uppersegment

intpinUPR=3;//Up-rightsegment

intpinDWR=4;//Down-rightsegment

intpinDW=5;//Downsegment

intpinDWL=6;//Down-leftsegment

intpinUPL=7;//Up-leftsegment

intpinCT=8;//Centersegment

voidsetup()


pinMode(pinUP,OUTPUT);

pinMode(pinUPR,OUTPUT);

pinMode(pinDWR,OUTPUT);

pinMode(pinDW,OUTPUT);

pinMode(pinDWL,OUTPUT);

pinMode(pinUPL,OUTPUT);

pinMode(pinCT,OUTPUT);

voidwriteNumber(intvalue)

//Firstweerasethepreviousvalue

digitalWrite(pinUP,HIGH);

digitalWrite(pinUPR,HIGH);

digitalWrite(pinDWR,HIGH);

digitalWrite(pinDW,HIGH);

digitalWrite(pinDWL,HIGH);

digitalWrite(pinUPL,HIGH);

digitalWrite(pinCT,HIGH);

//Ifwewanttowrite0

if(value==0)

digitalWrite(pinUP,LOW);

digitalWrite(pinUPR,LOW);

digitalWrite(pinDWR,LOW);

digitalWrite(pinDW,LOW);

digitalWrite(pinDWL,LOW);

digitalWrite(pinUPL,LOW);

//Ifwewanttowrite1

if(value==1)



//Ifwewanttowrite2

if(value==2)



digitalWrite(pinCT,LOW);

digitalWrite(pinDWL,LOW);


//Ifwewanttowrite3

if(value==3)



digitalWrite(pinCT,LOW);



voidloop()

//Aresettingcount-down

writeNumber(3);

delay(1000);

writeNumber(2);

delay(1000);

writeNumber(1);

delay(1000);

writeNumber(0);

delay(1000);

TipThiswasdesignedforacommonanode(+)configuration.Foracommoncathode(-)configuration,weneedtochangethedigitalWritefunctionstooutputtheinverse.IfitisHIGHitshouldoutputLOW,forexample.

Howitworks…A7-segmentdisplayismadeupofsevenLEDsconnectedtogetherinacertainphysicalpattern.Ifwecontrolthesevensegmentsindividually,wecanwriteanydigitonthedisplayandsomeletterstoo.Let’slookintothecode.

CodebreakdownThecodemakesthe7-segmentdisplaycountdownfrom3to0andthenreset.Here,wedeclaretheindividualpinsforeachLEDsegmentonthedisplay:

intpinUP=2;//Uppersegment

intpinUPR=3;//Up-rightsegment

intpinDWR=4;//Down-rightsegment

intpinDW=5;//Downsegment

intpinDWL=6;//Down-leftsegment

intpinUPL=7;//Up-leftsegment

intpinCT=8;//Centersegment

Inthesetup()function,weseteachLEDpinasanoutput:

voidsetup()

pinMode(pinUP,OUTPUT);

pinMode(pinUPR,OUTPUT);

pinMode(pinDWR,OUTPUT);

pinMode(pinDW,OUTPUT);

pinMode(pinDWL,OUTPUT);

pinMode(pinUPL,OUTPUT);

pinMode(pinCT,OUTPUT);

ThecustomwriteNumber()functiontakesanumberwewanttoshowonthedisplayastheargument.Afterthat,iterasesthedisplayandlightsupeachindividualsegment,inordertoobtainthewantedpattern:

voidwriteNumber(intvalue)

//Firstweerasethepreviousvalue

digitalWrite(pinUP,HIGH);

digitalWrite(pinUPR,HIGH);

digitalWrite(pinDWR,HIGH);

digitalWrite(pinDW,HIGH);

digitalWrite(pinDWL,HIGH);

digitalWrite(pinUPL,HIGH);

digitalWrite(pinCT,HIGH);

//Ifwewanttowrite1

if(value==1)



Intheloop()function,weuseourcustomfunctiontomakethedisplaycountdown:

voidloop()

writeNumber(2);

delay(1000);

writeNumber(1);

delay(1000);

writeNumber(0);

delay(1000);

There’smore…The7-segmentdisplayscanbeusedinmultipleapplications.Displayingadigitvalueisthemostused,however.Intotal,wecandisplayalldigitsfrom0to9,togetherwiththelettersA,b,c,C,d,E,F,h,andH.Hereareafewthingstoconsider:

Commonanode(+)andcommoncathode(-)Each7-segmentdisplayiseithercommonanode(+)orcommoncathode(-).Ifit’sacommonanode(+),weconnecttheanodeto5VandeachotherpinwithresistorstoindividualdigitalpinsontheArduino.Forthecommoncathode(-),connectthecathodetotheGNDportandtheotherpins,usingresistors,toindividualArduinodigitalpins.

ThedotMost7-segmentdisplaysactuallyhaveaneighthsegment.It’sthesmalldotinthebottomrightcorner.Whenweusemultiple7-segmentsdisplays,wecanusethatdottocorrectlyrepresent,forexample,thenumber3.14.

VariationsThe7-segmentdisplayisjustthemostpopularconfiguration.Thereareothertypes,suchasthe9-segment,the14-segment,andthe16-segment.Onthe16-segment,anyEnglishcharactercanbedisplayed.

Chapter3.WorkingwithButtonsInthischapter,wewillcoverthefollowingrecipes:

ConnectingabuttonButtonwithnoresistorThetoggle.switchButtontoserialButtondebouncing1,000buttons,1pinButtonmultiplexing

IntroductionButtonsarethebasisofhumaninteractionwiththeArduino.Wepressabutton,andsomethinghappens.Theyaresimplecomponents,astheyonlyhavetwostates:openedorclosed.Whenabuttonisclosed,currentcanpassthoughit.Whenit’sopened,nocurrentcanpass.Somebuttonsareclosedwhenwepushthem,somewhentheyarereleased.

Inthischapter,wewillexplorevariousbuttonconfigurationsandseehowtotacklecommonproblemswiththese.Let’sjumpin!

ConnectingabuttonOneofthebasicinteractionsyoucanhavewiththeArduinoispushingabutton,whichcausesanotheraction.Here,wewillseehowtoconnectanduseabutton.

Tokeeptheexamplesimple,wewillconnectabuttontotheArduino,andwheneverwepressandholdit,theinternalArduinoLEDwilllightup.Butfirst,weneedtotalkalittleaboutbuttons.Thereareafewcommonconfigurationsfoundineverydayelectronics.Wecancategorizebuttons/switchesbasedonthreemaincharacteristics:

MomentaryandmaintainedbuttonsOpenorclosedbuttonsPolesandthrows

Momentarybuttonsareactiveaslongastheyarepressed,whilemaintainedbuttonskeepthestateweletthemin.Keyboardshavemomentarybuttonswhilethetypicallightswitchisamaintainedbutton.

Momentarybuttonscaneitherbeopenedorclosed.Thisreflectstheconnectionstatewhennotpressed.Aclosedmomentaryswitchwillconductcurrentwhilenotpressedandinterruptthecurrentwhenpressed.Anopenedbuttonwilldotheopposite.

Lastly,therearepolesandthrows.Thefollowingfigureexplainsthemaintwotypes:

SinglePoleSingleThrow(SPST)switcheshaveaclosedstateinwhichtheyconductcurrent,andanopenedstateinwhichtheydonotconductcurrent.MostmomentarybuttonsareSPST.

SinglePoleDoubleThrow(SPDT)switchesroutethecurrentfromthecommonpintooneofthetwooutputs.Theyaretypicallymaintained;oneexampleofthisisthecommonlightswitch.

Thecommonbuttonwe’llbeusinginthischapterisapushbutton.It’sasmallmomentaryopenedswitch.Ittypicallycomesina4-pincase:

Thepinsinsidethetworedellipsesareshortedtogether.Whenwepressthebutton,allfourpinsareconnected.

GettingreadyThesearetheingredientsneededtoexecutethisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBAbreadboardandjumperwiresApushbutton,whichcanbefoundatanyelectronicsstore,suchastheonlineshopsofSparkfun,Radioshack,Adafruit,andPololuAresistorbetween1K–100Kohm

Howtodoit…Thefollowingarethestepstoconnectabutton:

1. ConnecttheArduinoGNDand5Vtoseparatelongstripsonthebreadboard.2. Mountthepushbuttononthebreadboardandconnectoneterminaltothe5Vlong

stripandtheothertoadigitalpinontheArduino—inthisexample,pin2.3. MounttheresistorbetweenthechosendigitalpinandtheGNDstrip.Thisiscalleda

pull-downsetup.Moreonthislater.

SchematicThisisonepossibleimplementationontheseconddigitalpin.Otherdigitalpinscanalsobeused.

Hereisanexampleofwiringitonabreadboard:

CodeThefollowingcodewillreadifthebuttonhasbeenpressedandwillcontrolthebuilt-inLED:

//DeclarethepinsfortheButtonandtheLED

intbuttonPin=2;

intLED=13;

voidsetup()

//Definepin#2asinput

pinMode(buttonPin,INPUT);

//Definepin#13asoutput,fortheLED


voidloop()

//Readthevalueoftheinput.Itcaneitherbe1or0.

intbuttonValue=digitalRead(buttonPin);

if(buttonValue==HIGH)

//Ifbuttonpushed,turnLEDon


else

//Otherwise,turntheLEDoff


TipIfthebuttonisconnectedtoadifferentpin,simplychangethebuttonPinvaluetothevalueofthepinthathasbeenused.

Howitworks…Thepurposeofthebuttonistodrivethedigitalpintowhichit’sconnectedtoeitherHIGHorLOW.Intheory,thisshouldbeverysimple:justconnectoneendofthebuttontothepinandtheotherto5V.Whennotpressed,thevoltagewillbeLOW;otherwiseitwillbe5V,HIGH.However,thereisaproblem.Whenthebuttonisnotpressed,theinputwillnotbeLOWbutinsteadadifferentstatecalledfloating.Inthisstate,thepincanbeeitherLOWorHIGHdependingoninterferencewithothercomponents,pins,andevenatmosphericconditions!

That’swheretheresistorcomesin.Itiscalledapull-downresistorasitpullsthevoltagedowntoGNDwhenthebuttonisnotpressed.Thisisaverysafemethodwhentheresistorvalueishighenough.Anyvalueover1Kwillworkjustfine,but10Kohmisrecommended.

CodebreakdownThecodetakesthevaluefromthebutton.Ifthebuttonispressed,itwillstartthebuilt-inLED.Otherwise,itwillturnitoff.

Here,wedeclarethepintowhichthebuttonisconnectedaspin2,andthebuilt-inLEDonpin13:

intbuttonPin=2;

intLED=13;

Inthesetup()function,wesetthebuttonpinasadigitalinputandtheLEDpinasanoutput:

voidsetup()

pinMode(buttonPin,INPUT);


Theimportantpartcomesintheloop()function.Thefirststepistodeclareavariablethatwillequalthevalueofthebuttonstate.ThisisobtainedusingthedigitalRead()function:


Lastly,dependingonthebuttonstate,weinitiateanotheraction.Inthiscase,wejustlightuptheLEDorturnitoff:

if(buttonValue==HIGH)


else



There’smore…Inthisexample,we’veseenhowtoconnectthebuttonwithapull-downresistor.However,thisisnottheonlyway.Itcanalsobeconnectedusingapull-upresistor.

Pull-upconfigurationInapull-upconfiguration,theresistorwillpullupthevoltageto5Vwhenthebuttonisnotpressed.Toimplementit,connectoneterminalofthebuttontothedigitalpinandtheotheronetoGND.Now,connecttheresistorbetweenthedigitalpinand5V.

Thisconfigurationwillreturninvertedvalues.Whenpressed,thebuttonwillgiveLOW,notHIGH,asitwilldrawthepindowntoGND,0V.However,itbringsnoadvantagesoverthepull-downconfiguration.

MultiplebuttonsWhatifwewanttoimplementmultiplebuttons?Weonlyneedtouseonedigitalpinconfiguredasinputforeachbuttonweuse.Also,eachbuttonneedsitsindependentpull-downorpull-upresistor.

SeealsoForothertopicsregardingbuttons,checkthefollowingimportantrecipesinthischapter:

TheButtonwithnoresistorrecipeTheButtontoserialrecipeTheButtondebouncingrecipe

ButtonwithnoresistorItissimpletoconnectabuttontotheArduino.Youneedthebutton,somewires,andaresistor.Butwhatifwenolongerneedtheresistorandwanttostillbeabletousethebuttonwithnofalsereadings?

Theresistorismandatoryforproperoperationofabutton,andeverybodywillinsistonusingit.However,thereisalittlesecretembeddedineachArduinopin.Eachpinalreadyhasapull-upresistorthatwecanenablewithjustonesmallchangeinourcode.

GettingreadyForthisrecipe,youwillneedjusttwocomponents:

AnArduinoboardconnectedtoacomputerviaUSBApushbutton

Howtodoit…Thereisjustonesimplestepinthisrecipe:

1. ConnecttheArduinoGNDtoaterminalonthebuttonandconnectthechosendigitalpintotheotherterminal.

SchematicHereisoneimplementationonthe12thdigitalpin.Otherdigitalpinscanalsobeused.

Hereisasimplewayofwiringthebutton:

Formostbuttonswithstandardthrough-holeterminals,wecandirectlyinputthepinsintotheterminalsontheArduino.

CodeThefollowingcodewillreadifthebuttonhasbeenpressedandwillcontrolthebuilt-inLED:

//DeclarethepinsfortheButtonandtheLED

intbuttonPin=12;

intLED=13;

voidsetup()

//Definepin#12asinputandactivatetheinternalpull-upresistor

pinMode(buttonPin,INPUT_PULLUP);

//Definepin#13asoutput,fortheLED


voidloop()

//Readthevalueoftheinput.Itcaneitherbe1or0


if(buttonValue==LOW)



else



Tip

Ifthebuttonisconnectedtoadifferentpin,changethebuttonPinvaluetothevalueofthepinthathasbeenused.

Howitworks…Whenwepressthebutton,thevalueoftheArduinopinshouldbeeitherLOWorHIGH.Inthisconfiguration,whenwepressthebutton,thepinisconnecteddirectlytoGND,resultinginLOW.However,whenitisnotpressed,thepinwillhavenovalue;itwillbeinafloatingstate.

Toavoidthis,aninternalpull-upresistorisconnectedbetweeneachpinand5V.Whenweactivatetheresistor,itwillkeepthepinatHIGHuntilwepressthebutton,thusconnectingthepintoGND.

CodebreakdownThecodetakesthevaluefromthebutton.Ifthebuttonispressed,itwillstartthebuilt-inLED.Otherwiseitwillturnitoff.

Here,wedeclarethepintowhichthebuttonisconnectedaspin12,andthebuilt-inLEDaspin13:

intbuttonPin=12;

intLED=13;

Inthesetup()function,wesetthebuttonpinasadigitalinputandweactivatetheinternalpull-upresistorusingtheINPUT_PULLUPmacro.TheLEDpinisdeclaredasanoutput:

voidsetup()



Intheloop()function,wecontinuouslyreadthevalueofthebuttonusingthedigitalRead()function,andwestoreitinanewlydeclaredvariablecalledbuttonValue:


Lastly,dependingonthebuttonstate,weinitiateanotheraction.Inthiscase,wejustlightuptheLEDorturnitoff:

if(buttonValue==LOW)



else



There’smore…ItiseasytoconnectabuttontotheArduinowithoutanyresistors.Whatifweneedmorebuttons?

MultiplebuttonsEachbuttonrequiresitsowndigitalpinandresistor.TheArduinoalreadyhasonepull-upresistorineachdigitalandanalogpin,sointheend,allthatisneededisonepinforeachindividualbutton.TheotherterminalofthebuttonsistiedtogethertoGND.

SeealsoForothertopicsregardingbuttons,checkthefollowingimportantrecipesinthischapter:

TheButtontoserialrecipeTheButtondebouncingrecipe

ThetoggleswitchAtoggleswitchcanbeveryusefulforvariousprojects.Itcanholdoneormoreconstantstates.Forexample,wecanhaveafewofthemandconfigureacertainsystemtoworkacertainwaybasedontheconfiguration.Thisisdoneallthetimeoncomputermotherboardsandotherelectronicdevices.

Atwo-statetoggleswitchisjustlikeastandardpushbutton;only,itremainsinthestateweputitin.Anon-offswitchisatwo-statetoggleswitch.Itbecomesmoreusefulwhenwehaveathree-statetoggleswitchasinthisrecipe.Ithastwousablestatesandanoffstate.

Inthisrecipe,wewilluseabasictoggleswitchtolightuptwoLEDs.Whenthetoggleswitchisinoneendposition,onlyoneLEDwillbeswitchedon.Ifitisintheotherendposition,theotherLEDwillbeswitchedon.Finally,ifthetoggleswitchisinthecenter,bothLEDswillbeswitchedoff.

GettingreadyThefollowingaretheingredientsrequiredtoexecutethisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBAbreadboardandjumperwiresAtleastonetoggleswitch,whichwecanalwaystakeoutofanoldelectrictoyorbuyfromSparkfun,Digikey,andsoonTwoLEDsandtworesistorsbetween220–1,000ohm

Howtodoit…FollowthesestepsinordertoconnectthetoggleswitchtotheLEDs:

1. ConnecttheArduinoGNDtoalongstriponthebreadboard.2. MountthetoggleswitchandconnectthemiddleterminaltothelongGNDstripon

thebreadboard.3. Connecttheothertwoterminalsofthetoggleswitchtodigitalpins2and3onthe

Arduinoboard.4. MountthetwoLEDsandconnecttheirgroundterminaltothelongGNDstriponthe

breadboard.5. Connectpin5tooneoftheLEDsusingaresistorbetweenpin5andtheinputofthe

LED.Dothesameforpin6andtheotherLED.

SchematicThisisonepossibleimplementation.Otherdigitalpinscanalsobeused.

Hereisapossiblebreadboardimplementation:

CodeThefollowingcodewillcheckthestatusofthetoggleswitchandwilldrivetheLEDsaccordingly:

intbuttonPin1=2;

intbuttonPin2=3;

intLED1=5;

intLED2=6;

voidsetup()

//DefinethetwoLEDpinsasoutputs

pinMode(LED1,OUTPUT);


//Definethetwobuttonsasinputswiththeinternalpull-upresistor

activated

pinMode(buttonPin1,INPUT_PULLUP);


voidloop()

//Readthevalueoftheinputs.Itcanbeeither0or1

//0iftoggledinthatdirectionand1otherwise

intbuttonValue1=digitalRead(buttonPin1);


if(buttonValue1==HIGH&&buttonValue2==HIGH)

//Switchtoggledtothemiddle.TurnLEDsoff

digitalWrite(LED1,LOW);


elseif(buttonValue1==LOW)

//Buttonistoggledtothesecondpin


digitalWrite(LED2,HIGH);

else

//Buttonistoggledtothethirdpin

digitalWrite(LED1,HIGH);


TipIfthetoggleswitchisconnectedtootherpins,simplychangethebuttonPin1andbuttonPin2variables.ThesamegoesfortheLEDpins.

Howitworks…Whenthetoggleswitchistoggledtooneofthetwoendpositions,itwillconnectoneoftheArduinopinstoGND.ThepinthatisnotconnectedtoGNDwillstayHIGHduetotheinternalpull-upresistorintheArduinopin.Ifthetoggleswitchisinthecentralposition,nopinwillbeconnectedtoGNDandbothwillbeHIGH.

CodebreakdownThecodetakesthevaluefromthetwopinsconnectedtothetoggleswitch.IfoneofthemgoesLOW,itwillturnononeoftheLEDs.

Here,wedeclarethepinstowhichthetoggleswitchisconnectedaspins2and3.TheLEDsaredefinedonpins5and6:

intbuttonPin1=2;

intbuttonPin2=3;

intLED1=5;

intLED2=6;

Inthesetup()function,wesetthepinsfortheLEDsasoutputsandthetwopinsgoingtothetoggleswitchasinputs.Also,weactivatetheinternalpull-upresistorsothatitdoesnotneedanexternalone:

voidsetup()

//DefinethetwoLEDpinsasoutputs



//Definethetwobuttonsasinputswiththeinternalpull-upresistor

activated



Intheloop()function,wecontinuouslyreadthevaluesofthetwopinsgoingtothetoggleswitch,andwestoretheminthevariablesbuttonValue1andbuttonValue2:



Lastly,dependingonthetoggleswitchstate,weinitiateanotheraction:

if(buttonValue1==HIGH&&buttonValue2==HIGH)

//Switchtoggledtothemiddle.TurnLEDsoff

elseif(buttonValue1==LOW)

//Buttonistoggledtothesecondpin,oneLEDON

else

//Buttonistoggledtothethirdpin,theotherLEDON

There’smore…Toggleswitchescanbeveryusefulwhenusedtogether.ADIPswitchisveryinteresting,asitusuallyhasmultiplesmalltoggleswitches.Eachtimeweaddatoggleswitch,wedoublethenumberofconfigurations.Withfourtwo-stateswitches,wecanhaveupto16configurations.

Thisisusefulwhenwehaveasystemthatneedsalotofconfigurations.Ratherthanuploadingcodeagainandagain,wecanusethetoggleswitchestochoosewhattodo.

SeealsoUsethefollowinglinkstofindsomecommonswitchesyoucanbuy:

https://www.sparkfun.com/products/9276https://www.sparkfun.com/products/8034

https://www.sparkfun.com/products/9276


ButtontoserialIfwewanttoeasilytrackhowabuttonacts,serialcommunicationisthebestandsimplestway.Allweneedtodoistoreadthestatusofthebuttonandprintittotheserialconnection.

TestingwhetherabuttonisworkingcanbesolvedbyusinganLED.However,ifweneedtochecktwobuttonsorbetterunderstandwhat’shappeningwhenthebuttonispressed,serialcommunicationismuchsaferandmayevenbesimpler.


AnArduinoboardconnectedtoacomputerviaUSBAbutton

Howtodoit…ThisrecipeusestheButtonwithnoresistorrecipe’shardwareimplementation.Pleaseimplementthesameschematicasinthatrecipe.Wewillhavedifferentcodehere,whichwilloutputthevaluesontheserialconnection.

CodeThefollowingcodewillprintthebuttonstatusontheserialconnection:

intbuttonPin=2;

voidsetup()

//Definepin#2asinput


//EstablishtheSerialconnectionwithabaudrateof9600

Serial.begin(9600);

voidloop()

//Readthevalueoftheinput.Itcaneitherbe1or0.


//Sendthebuttonvaluetotheserialconnection

Serial.println(buttonValue);

//Delaystheexecutiontoallowtimefortheserialtransmission

delay(25);

TipIfthebuttonisconnectedtoanotherdigitalpin,simplychangethevalueofbuttonPintothedigitalpinthathasbeenused.

Howitworks…Whenthebuttonispressed,itcaneitherreturnavalueof1or0.Becauseweactivatedtheinternalpull-upresistorinsidetheArduinopin,thevalueswillbesafe,andnofloatingconditionwillbeobtained.Afterwereadthevalueofthepin,wesendittotheserialconnection.

CodebreakdownThecodetakesthevaluefromthebuttonconnectedtodigitalpin2andwritesittotheserial.

Inthesetup()function,wesetthebuttonpinasaninputandactivatetheinternalpull-upresistor.Then,westarttheSerialconnectionwithaspeedof9,600bitspersecond:

voidsetup()


Serial.begin(9600);

Intheloop()function,wecontinuouslyreadthevalueoftheconnectedbutton:


Then,weprintthevalueusingtheSerial.println()command.WecanalsouseSerial.print();however,printlnwillwritethevalueandgotoanewlineafterwards.Thislooksmuchbetteranditiseasiertounderstand:


Attheend,weneedadelaytoallowthedatatobetransmitted.Thedelaycanbeshortsinceweonlysendonevalue;however,itismandatorytohaveit.Otherwise,theserialwillconstantlyoverflowandnogoodvalueswillreachthecomputer:

delay(25);

There’smore…Toprintmorethanonebutton,wecanusetheSerial.print()functiontowriteeachbuttonstateinlineandthenusetheSerial.println()functiontogotothenextline.Hereisasimpleimplementation:

Serial.print(buttonValue1);//Printfirstvalue

Serial.print("");//Leaveanemptyspacebetween

Serial.println(buttonValue2);//Printthesecondvalue

ButtondebouncingAbuttonisasimpledevice;whenwepushit,itgivesavalue,otherwiseitgivesanothervalue.Unfortunately,itisnotalwayslikethat.Whenwepushorreleaseabutton,foraverysmallamountoftimethebuttonbouncesbetweenpushedornot.Thisisduetomechanicalerrorsandwearandtearinthebutton.

Evenifitisasmallamountoftime,theArduinoisquick,andwhenwepressthebutton,itmayreadvaluesthatarequicklybouncingbetweenpressedandnotpressed.Inmostcases,thisisnotaproblem;butinmanycases,thishappensanditcantakehourstodetectwhatisgoingwrong.Betterbesafethansorry!

Anotherveryimportantapplicationofthisisreadingabuttononlyonce.Whenwepressthebutton,wekeepitpressedforafewmilliseconds.Inthistime,theArduinocanreadithundreds,eventhousandsoftimes.Itdetectsafewhundredtimesinsteadofoncethatwepushedthebutton.ThisistheprimaryuseofdebouncingintheArduinoworld.


AnArduinoboardconnectedtoacomputerviaUSBAbutton

Howtodoit…ThisrecipeusesthehardwareimplementationintheButtonwithnoresistorrecipe.Pleaseimplementthesameschematicasinthatrecipe.Wewillhaveadifferentcodehere,whichwilloutputthedebouncedvaluesontheserialconnection.

CodeThefollowingcodewillreadthestatusofthebuttonandprintitovertheserialconnection:

//Declarethepinforthebutton

intbuttonPin=2;

//Variableforkeepingthepreviousbuttonstate

intpreviousButtonValue=HIGH;

longlastDebounce=0;//Lasttimethebuttonwaspressed

longdebounceTime=50;//Debouncedelay

voidsetup()

//Definepin#2asinputandactivatetheinternalpull-upresistor



Serial.begin(115200);

voidloop()

//Readthevalueoftheinput.Itcaneitherbe1or0


if(buttonValue!=previousButtonValue&&millis()-lastDebounce>=

debounceTime)

//Readingisuseable,printit


//Resetthedebouncingtimer

lastDebounce=millis();

//Changetothelatestbuttonstate

previousButtonValue=buttonValue;

//AllowsomedelayfortheSerialdatatobetransmitted

delay(10);

TipIfthebuttonisconnectedtoanotherdigitalpin,changethevalueofbuttonPintothevalueofthedigitalpinthathasbeenused.

Howitworks…Toavoidreadingthebuttonmultipletimesanddetectingfalsereadings,therearetwoimportantsteps.First,weonlyreadchangesinthebuttonstate.Ifthebuttonhasthesamevalueasatthelastreading,weignoreit.Second—andhereistheimportantstep—ifthebuttonhasbeenpressedorreleased,wedon’tevaluateitsvalueforthefollowingfewmilliseconds.Thiswillmakesurethatnorapidoscillationsinthebuttonstateareread.

Itispossibletoimplementthiswithasimpledelay()function;however,delay()stopstheArduinoboardfromexecutinganythingelse.

CodebreakdownThecodetakesthevaluefromthebuttonconnectedondigitalpin2andusesdebouncinglogictoassureproperoutput.

Weneedtodeclareafewvariables.ThepreviousButtonValuevariablekeepstrackofthepreviousstateofthebutton.ThelastDebouncevariableisimportant;itstorestheparticulartimeatwhichthebuttonwaspressedearlier.ThedebounceTimevariableistheamountoftimeinmillisecondsbetweeneachreading.Itisimportantforthesetwovariablestobedeclaredaslongtype,becausethenumbersgetprettybigquitefast.

intpreviousButtonValue=HIGH;

longlastDebounce=0;//Lasttimethebuttonwaspressed

intdebounceTime=50;//Debouncedelay

NoteTheArduinokeepsaninternalcountoftimepassedsincetheprogrambeganrunning.Toaccessthistime,wecanusethemillis()function,whichreturnsthetimeinmilliseconds.

Inthesetup()function,wesetthebuttonpinasaninputandweactivatetheinternalpull-upresistor.Then,westarttheserialconnectionwithaspeedof115,200bitspersecond:

voidsetup()


Serial.begin(115200);

Intheloop()function,wecontinuouslyreadthevalueoftheconnectedbutton:


Nowweneedtoapplythedebouncingpartofthecode.ItconsistsofanIFclausewithtwoconditions:

Thefirstconditioncheckswhetherthenewreadingisdifferentfromthelastone.Wedon’twanttodetectabuttonpushahundredtimeswhenwepressonce.Thesecondconditioncheckswhetherenoughtimehaspassedsincethelastreading.Thismakessurethevaluedoesn’tbouncebetweenstates.

ThetimeisdeclaredinthedebounceTimevariable.Agoodvalueisaround50

milliseconds.Itcanbelower,butwewillonlyneedittobelowerifwewanttopressthebuttonmorethan20timesasecond.

if(buttonValue!=previousButtonValue&&millis()–lastDebounce>=

debounceTime)

Then,weprintthevalueusingtheSerial.println()command:


ItisveryimportantoneachusablereadingtoupdatethelastDebounceandpreviousButtonValuevariables.Thesewillbethenewvaluesthatthedebouncingfilterwillcompare.

lastDebounce=millis();

previousButtonValue=buttonValue;

Attheend,weneedashortdelaytoallowthedatatobetransmitted:

delay(10);

SeealsoToclearlyunderstandwhatcontactbouncingis,visithttp://en.wikipedia.org/wiki/Debounce#Contact_bounce.

http://en.wikipedia.org/wiki/Debounce#Contact_bounce

1,000buttonsto1pinOnebutton,onepin—thatisthewaythingsareusuallydoneonArduinoboards.Butitissolimiting.Therearesometricksthatletyouconnectmorethanonebuttontoapin.Actually,itisevenpossibletoconnect1,000buttonstojust1pin.Wewillexplorethispossibilityinthisrecipe.


AnArduinoboardconnectedtoacomputerviaUSBAbreadboardandjumperwiresThreebuttonsFourresistorsofequalvalue:1Kohmworkswell

Howtodoit…Weimplementasimpleconfigurationusingonlythreebuttonsonthesamepin.Herearethesteps:

1. ConnecttheArduinoGNDtoalongstriponthebreadboard.AlsoconnecttheArduino5Vtoalongstrip.

2. ConnectoneoftheresistorsfromtheGNDstriptoananalogpin—here,pinA0—ontheArduino.

3. Connectthreeresistorsinseriesstartingatthe5Vstrip.4. Ateachjunctionoftworesistors,connectonebutton.Alsoconnectthethirdbuttonat

theendoftheresistorseries.5. ConnecttheotherterminalsofthebuttonstogetherandtotheA0analogpinonthe

Arduino.

SchematicThisisonepossibleimplementation.Otheranalogpinscanalsobeused.

Thisisapossiblebreadboardimplementation:

CodeThefollowingcodewillreadtheanalogpinontheArduinoboardanddetectwhichbuttonispressed:

//DeclaretheAnalogpinontheArduinoboard

intbuttonPin=A0;

voidsetup()


Serial.begin(9600);

voidloop()

//Readthevalueoftheinput.Itcanvaryfrom0-1023

intbuttonValue=analogRead(buttonPin);

if(buttonValue<200)

//Avalueunder200representsnobuttonpushed

Serial.println("0");

elseif(buttonValue>=200&&buttonValue<300)

//Avaluebetween200-300representsthethirdbutton

Serial.println("S3");


//Avaluebetween300-400representsthesecondbutton


elseif(buttonValue>=400)

//Avaluegreaterthan400representsthefirstbutton


//DelaystheexecutiontoallowtimefortheSerialtransmission

delay(25);

Tip

Ifthebuttonsareconnectedtoanotheranalogpin,simplychangethebuttonPinvariabletotheanalogpinthathasbeenused.

Howitworks…Thisisallpossibleduetoanelectriccircuitcalledthevoltagedivider.Eachtimeabuttonispressed,adifferentvoltagedivideriscreated.EachbuttonbringsadifferentvoltagetotheanalogpinontheArduino.Wecanreadthisanalogvoltageandattributeaspecificvaluetoeachbutton.

CodebreakdownThecodetakesthevaluefromtheanalogpinandcheckstowhichbuttonitcorresponds.Itprintsoutontheserialwhichbuttonhasbeenpushed.

Here,wedeclaretheanalogpinthathasbeenused:

intbuttonPin=A0;

Inthesetupfunction,westarttheserialconnectionwithaspeedof9,600bitspersecond:

voidsetup()

Serial.begin(9600);

Intheloop()function,wecontinuouslyreadthevalueoftheanalogpin,whichcanbefrom0–1023:

intbuttonValue=analogRead(buttonPin);

Then,wecheckwhichbuttonispressed.Weshouldbeabletoattributeoneexactvaluetoeachbutton.However,duetocomponenttolerancesanderrors,it’smuchsafertouseaninterval.Iftheexpectedvalueis250andthebuttonreturns251,thecodewillnotdetectthebutton.Inthisexample,theintervalsareextreme:0–200fornobutton,200–300forthethirdbutton,300–400forthesecondbutton,andover400forthefirst.Thebestwaytofindoutthevaluesistomakeasimpleprogramprinttheanalogvalueofthepinontheserial:

if(buttonValue<200)

//Avalueunder200representsnobuttonpushed

Serial.println("0");


//Avaluebetween200-300representsthethirdbutton



//Avaluebetween300-400representsthesecondbutton


elseif(buttonValue>=400)

//Avaluegreaterthan400representsthefirstbutton


Intheend,alwayshavesomedelaywhenworkingwithserialcommunicationtoavoidoverflow:

delay(25);

There’smore…Thisisaveryusefulsolutionwhenweneedmultiplebuttonsbuthaveonlyafewpinsleft.Anotheradvantageisthetimeneededtoreadtheanalogpin.Ittakesaround0.1millisecondtoreadtheanalogpin,whichsolvessomeproblemswithdebouncing.

Hereareafewtipsonhowtoeasilydomorewiththisconfiguration.

MorebuttonsThetitlesays1,000butthereareonlythreebuttonshere.However,theprincipleisthesame.Wecanconnectasmanybuttonsaswehavetoatheoreticalmaximumof1023.Eachbuttonneedsaresistor,soforaconfigurationof100buttons,wewilluse100resistorsinseriesandateachjunctionoftworesistors,wewillmountabutton.Again,wewillmountthehundredthbuttonattheend.TheRdresistorthatconnectsthepintoGNDisalsomandatory.

Thevaluesoftheresistorsarealsoveryimportant.ItisrecommendedtohaveahighvaluefortheRdresistor:somewherebetween100K–1Mohm.Theotherresistorsshouldbeequaltomakethingseasier:somewherebetween1K–10Kohm.

FindingeachbuttonThesimplestwaytofindthevalueofeverybuttonconnectedistoprintthevalueoftheanalogpinrepeatedlywhilepressingthebuttonsoneatatime.Eachoneshouldgiveauniquevalueandavaluecloseto0whennobuttonispressed.HereisthecodetoprintpinA0:

Serial.println(analogRead(A0));

delay(10);

PressingmultiplebuttonsIfwedon’tusetoomanybuttons,wecanactuallydetectmultiplebuttonpresses.Whenwepresstwobuttons,theresistorswillbeconnectedinparallelandtheoverallresistancewilldrop.Thiswillcausetheanalogreadingtobehigher.Usetheserialoutputtocheckwhathappensinyourconfiguration.

SeealsoTounderstandhowavoltagedividerworks,visithttp://en.wikipedia.org/wiki/Voltage_divider.

http://en.wikipedia.org/wiki/Voltage_divider

ButtonmultiplexingUsingamultiplexer,itispossibletomaketheArduinoreadoverahundredbuttonseasily.Amultiplexer/demultiplexerisanintegratedcircuitthatselectsoneofseveralinputsandforwardsthemtotheoutput.Itrequiresafewcontrolpinstodeterminewhichinputtoforwardtotheoutput.

GettingreadyFollowingaretheingredientsrequiredforthisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBAbreadboardandjumperwiresFourbuttonsA4051multiplexerorsimilar,whichwecanfindatanyelectronicsstoreandonlineatDigikey,Sparkfun,Adafruit,andsoon

Howtodoit…Weimplementasimpleconfigurationusingonlyfourbuttons.Herearethesteps:

1. ConnecttheArduinoGNDtoalongstriponthebreadboard.AlsoconnecttheArduino5Vtoalongstrip.

2. MountthefourbuttonsandconnectoneoftheirterminalstothelongGNDstrip.3. Connecttheotherterminalofeachbuttontoanindividualinput/outputpinonthe

4051—inthiscase,pinsy0,y1,y2,andy3.4. ConnecttheE,VEE,andGNDpinsofthe4051multiplexertothelongGNDstrip.5. ConnecttheVccpinonthe4051tothe5Vstriponthebreadboard.6. ConnectS0,S1,andS2tothreedigitalpinsontheArduino—inthisexample,8,9,

and10.

SchematicThisisonepossibleimplementation.Otherpinscanalsobeused.

Thisisapossiblebreadboardimplementation:

CodeThefollowingcodewillreadthefourbuttonsconnectedtothemultiplexerbyswitchingtheactivepinonit:

//DefinetheinputpinontheArduinoandthe3selectionpinsconnected

tothe4051

intbuttonPin=2;

intA=10;

intB=9;

intC=8;

voidsetup()

//Definepin#2asinputwiththepullupresistoron


//DefinetheoutputpinsgoingtothecontrollinesoftheMultiplexer

pinMode(A,OUTPUT);

pinMode(B,OUTPUT);

pinMode(C,OUTPUT);


Serial.begin(9600);

voidloop()

//WefirstreadportIO0

digitalWrite(A,LOW);

digitalWrite(B,LOW);

digitalWrite(C,LOW);

intbuttonIO0=digitalRead(buttonPin);

//ThenwereadportIO1

digitalWrite(A,HIGH);




//ThenwereadportIO2

digitalWrite(A,LOW);

digitalWrite(B,HIGH);



//ThenwereadportIO3


digitalWrite(B,HIGH);



//ThenweprinttoSerialthevalues

//Weprintthemin-lineseparatedbyaspace

Serial.print(buttonIO0);

Serial.print("");


Serial.print("");


Serial.print("");

Serial.println(buttonIO3);

//Delaystheexecutiontoallowtimefortheserial

delay(25);

Howitworks…Themultiplexer/demultiplexerisausefulcomponent,but,alittletrickytounderstand.

Hereweusedademultiplexerconfiguration.Eachdemultiplexerhasoneoutputandanumberofinputs—inourcase,eight.Also,ithascontrollines—inourexample,three.Eachcontrollinerepresentsanumber:powerof2minus1.Forthe4051,A=1,B=2andC=4.IfwewanttoreadinputIO5,wesetAandCtoHIGHandS1toLOW.ThismeanstheoutputwillbeconnectedtoA+C=5input;therefore,pinIO5.

Basically,amultiplexergivesthepowertoconnectoneArduinopintooneI/Opinonthemultiplexer.Onlyonepincanbeconnectedatanyparticulartime.

CodebreakdownThecodecommandstheconnectiononthemultiplexerusingthethreecommandlines.Itusesoneinputdigitalpintogetthevaluefromthebuttonsandprintsitontheserialconnection.

Here,wedeclaretheusedpins:

intbuttonPin=2;

intA=10;

intB=9;

intC=8;

Intheloop()function,wesetthemultiplexertoeachpinwewanttoreadandwereadit.InordertoreadpinIO0,wesetA,B,andCtolow,sotheirsumis0.Whenwewanttoreadpin1,wesetAto1.IO3willresultAandBtoHIGH:





Wedothisforeachbuttonwewanttoreadandthenweprinttheoutputvaluesontheserial.

There’smore…Herewehaveonlyfourbuttonsonfourpins—notaverygoodratioofpinstobuttons.However,forthesamenumberofpinswecangeteightbuttons,astherearefourfreepinsonthemultiplexer.

MorebuttonsEveneightbuttonsonfourpinsisnottoomuch.Thereare16-channelmultiplexers,suchasthe4067thatrequirefourcontrollines,totalingsixteenbuttonsonfivepins.Wecangoevenfurther!Wecanusemoremultiplexers,andweonlyneedonenewlineforeachmultiplexertoconnecttoitsoutputwhilesharingthecontrollines.Usinga4067andallthepins,except0and1,ontheArduinoUno,wecanread224buttons.OntheArduinoMega,thiswillresultin800buttons.Theskyisthelimitwithmultiplexers.

SeealsoForanin-depthexplanationonmultiplexers,visithttp://en.wikipedia.org/wiki/Multiplexer.

http://en.wikipedia.org/wiki/Multiplexer

Chapter4.SensorsInthischapter,wewillcoverthefollowingtopics:

Simplesensor–potentiometerTemperaturesensorDetectingmotion–PIRSensorMeasuringdistance–infraredandultrasonicNoisereductionAccelerometerLocalization–GPS

IntroductionAcquiringdatafromtheenvironmentisthefundamentalfunctionofanyautonomoussystem.AndontheArduino,thisfeatureissosimpleandpowerful.Wecanfindsensorsforanythingthesedays,fromhighradiationtosound.Mostofthemevensharethesameinterface,soconnectingandusingthemiseasyonceweunderstandthesimplelogicunderneath.Inthischapter,wewilldiveintothemostcommongroupsofsensorsandwewillseehoweasyitistousethem.

WecanacquireinterestingandusefulsensorsfromDIYelectronicsandroboticsshops.Online,ThesecouldbeSparkfun,Pololu,Adafruit,andTechnobots,justtonameafew.

Simplesensor–potentiometerApotentiometer,alsocalledavariableresistor,isabasiccomponentthatallowsustomodifyitsinternalresistance.Wecanuseittoadjustsettingsinourprogramatanytime.Or,wecanusethemtocontrolthings,suchasarobotichandortheintensityofaparticularlight.Here,wewillmakethebuilt-inLEDblinkwithafrequencythatwewillcontrolviathepotentiometer.Wewillalsoprintthevaluesoverserial.


AnArduinoboardconnectedtoacomputerviaUSBJumperwiresA10K–1Mohmpotentiometer/variableresistor

Howtodoit…Hookingupapotentiometeriseasy,andherearethesteps:

1. Thepotentiometerhasthreeterminals.Connecttheterminalinthecentertoananalogpin;here,wewillconnectittoA2.

2. ConnectoneoftheotherterminalstoGND.3. Connectthethirdterminalto5V.

SchematicThisisonepossibleimplementationusingpinA2astheanaloginput:

Hereisanexampleofhowtowireit:

CodeThefollowingcodewillreadthevalueofthepotentiometer,printitontheserialconnection,andvarytheLEDpulsingfrequencyaccordingly:

intLED=13;//Declarethebuilt-inLED

intsensorPin=A2;//Declaretheanalogportweconnected

voidsetup()

//StarttheSerialconnection

Serial.begin(9600);

//SetthebuiltinLEDpinasOUTPUT


voidloop()

//Readthevalueofthesensor

intval=analogRead(sensorPin);

//PrintittotheSerial

Serial.println(val);

//BlinktheLEDwithadelayofaforthofthesensorvalue


delay(val/4);


delay(val/4);

TipIfthesensorisconnectedtoanotheranaloginput,justchangethesensorPinvaluetomatchthevalueoftheinput.

RotatethepotentiometerheadandobservehowtheLEDchangesitspulsingfrequency.

Howitworks…InsideeachArduinothereisanAnalog-to-DigitalConverter(ADC).Thiscomponentcanconvertananalogsignalvaluetoadigitalrepresentation.ADCscomeinavarietyofranges,accuracies,andresolutions.TheintegratedmodelsfromtheUno,Leonardo,andothernormalArduinoshavea10-bitresolution.Thismeansthatavoltagebetween0and5Von5VArduinoswillberepresentedbyacorrespondingvaluebetween0and1023.Avoltageof2.5Vwillbeequalto512,whichishalfoftherange.

Weshouldneverexceedthemaximumvoltageoftheboardontheanaloginputs.Inmostboards,thisis5V,butontheDueandafewothers,thevoltagecanbe3.3V.Let’sseehowthecodeworksinthecodebreakdown.

Apotentiometerworksbyadjustingtheconductorlengthbetweenthecentralandsideterminals.Itisrecommendedtouseahigh-resistancepotentiometer;otherwise,alotofcurrentwillpassthrough,heatingitup.Anyvalueover10Kohmshouldbegood.

CodebreakdownFirst,wedeclaretwovariablesforthebuilt-inLEDandfortheusedanalogport,towhichweconnectedthepotentiometer:

intLED=13;

intsensorPin=A2;

Inthesetup()function,westarttheserialconnectionandwedeclaretheLEDpinasanoutput:

voidsetup()

Serial.begin(9600);


Thedealbreakeristhefollowingfunction.Itreadstheanalogvalueofthespecifiedanaloginputanditreturnsitasanumberbetween0and1023.Rememberthatthisconversiontakesaround100microsecondsonmostArduinoboards.


Andnowwedotwothings.Weprintthevalueontheserialconnection,andthenwemaketheLEDblinkwithanin-betweendelayofthereadvaluedividedbyfour,tomakeitblinkfast:



delay(val/4);


delay(val/4);

There’smore…TheanalogRead()functionisoneofthemostimportantfunctionsontheArduinoplatform.Almosteverysensorusesthiskindofinterfacing.Thereareafewmorethingstoknow.

ArduinoDueTheArduinoDuehasafewgreatfeaturesontheanalogside.Firstofall,ithasanintegrated12-bitADC,soitcanreturnmoreprecisevaluesbetween0and4095.However,itcomespreconfiguredtoonlyoutput10bit.WecanchangethatusingtheanalogReadResolution(bits)function.

Forexample,analogReadResolution(12)willmaketheanalogRead()functionoutput12-bitvalues.

NoteRememberthattheDueisdesignedforamaximumof3.3V,not5V;applyingmorethan3.3Vwilldamagetheboard.

Analogreference(AREF)MostArduinoshaveanAREFpinthatenablesustogivethevoltagerangeonwhichtheADCwillreturn.Soifweinput2VtotheAREFpinandconfigurethecode,itwilloutput1023for2Vand0for0V.Thisfeatureisusefulifwehavesensorsthatoutputlessthan5Vandweneedmoreprecision.

TotelltheArduinoweareusinganexternalreferenceonAREF,weneedtousetheanalogReference(type)function.Thetypeargumentcantakethefollowingvalues:

DEFAULT:Thisisthestandardconfigurationwitharangefrom0Vto5VEXTERNAL:ThiswillusethevalueonAREFforreference

AnotherimportantthingtorememberistousetheanalogReference()functionfirst,beforeusingtheanalogRead()function.IfthereferencetypeisnotsettoEXTERNAL,butwedoapplyavoltagetoAREF,whenweusetheanalogRead()functionwewillbasicallyshortthemicrocontroller.Thiscandamagetheboard.

Formoredetailsaboutothertypesofanalogreferences,checktheSeealsosection.

SeealsoFormoreinformationontheArduinoDueanalogReadResolution()functionandmoreanalogreferences,visitthefollowinglinks:

http://arduino.cc/en/Reference/AnalogReadResolutionhttp://arduino.cc/en/Reference/AnalogReference

http://arduino.cc/en/Reference/AnalogReadResolution

http://arduino.cc/en/Reference/AnalogReference

TemperaturesensorAlmostallsensorsusethesameanaloginterface.Here,weexploreaveryusefulandfunsensorthatusesthesame.Temperaturesensorsareusefulforobtainingdatafromtheenvironment.Theycomeinavarietyofshapes,sizes,andspecifications.Wecanmountoneattheendofarobotichandandmeasurethetemperatureindangerousliquids.Orwecanjustbuildathermometer.

Here,wewillbuildasmallthermometerusingtheclassicLM35andabunchofLEDs.


AnArduinoboardconnectedtoacomputerviaUSBALM35temperaturesensorAbreadboardandjumperwiresAbunchofLEDs,differentcolorsforabettereffectSomeresistorsbetween220–1,000ohm

Howtodoit…Thefollowingarethestepstoconnectabuttonwithoutaresistor:

1. ConnecttheLEDsnexttoeachotheronthebreadboard.2. ConnectallLEDnegativeterminals—thecathodes—togetherandthenconnectthem

totheArduinoGND.3. ConnectaresistortoeachpositiveterminaloftheLED.Then,connecteachofthe

remainingresistorterminalstoadigitalpinontheArduino.Here,weusedpins2to6.

4. PlugtheLM35inthebreadboardandconnectitsgroundtotheGNDline.TheGNDpinistheoneontheright,whenlookingattheflatface.

5. ConnecttheleftmostpinontheLM35to5VontheArduino.6. Lastly,useajumperwiretoconnectthecenterLM35pintoananaloginputonthe

Arduino.HereweusedtheA0analogpin.

SchematicThisisonepossibleimplementationusingthepinA0foranaloginputandpins2to6fortheLEDs:


CodeThefollowingcodewillreadthetemperaturefromtheLM35sensor,writeitontheserial,andlightuptheLEDstocreateathermometereffect:

//DeclaretheLEDsinanarray

intLED[5]=2,3,4,5,6;

intsensorPin=A0;//Declaretheusedsensorpin

voidsetup()


Serial.begin(9600);

//SetallLEDsasOUTPUTS

for(inti=0;i<5;i++)

pinMode(LED[i],OUTPUT);

voidloop()

//Readthevalueofthesensor


Serial.println(val);//PrintittotheSerial

//OntheLM35eachdegreeCelsiusequals10mV

//20Cisrepresentedby200mVwhichmeans0.2V/5V*1023=41

//Eachdegreeisrepresentedbyananaloguevaluechangeof

approximately2

//SetallLEDsoff

for(inti=0;i<5;i++)

digitalWrite(LED[i],LOW);

if(val>40&&val<45)//20-22C

digitalWrite(LED[0],HIGH);

elseif(val>45&&val<49)//22-24C












elseif(val>57)//Over28C






delay(100);//SmalldelayfortheSerialtosend

Blowintothetemperaturesensortoobservehowthetemperaturegoesupordown.

Howitworks…TheLM35isaverysimpleandreliablesensor.Itoutputsananalogvoltageonthecenterpinthatisproportionaltothetemperature.Moreexactly,itoutputs10mVforeachdegreeCelsius.Foracommonvalueof25degrees,itwilloutput250mV,or0.25V.WeusetheADCinsidetheArduinotoreadthatvoltageandlightupLEDsaccordingly.

Ifit’shot,welightupmoreofthem,ifnot,less.IftheLEDsareinorder,wewillgetanicethermometereffect.

CodebreakdownFirst,wedeclaretheusedLEDpinsandtheanaloginputtowhichweconnectedthesensor.WehavefiveLEDstodeclareso,ratherthandefiningfivevariables,wecanstoreallfivepinnumbersinanarraywith5elements:

intLED[5]=2,3,4,5,6;

intsensorPin=A0;

Weusethesamearraytricktosimplifysettingeachpinasanoutputinthesetup()function.RatherthanusingthepinMode()functionfivetimes,wehaveaforloopthatwilldoitforus.ItwilliteratethrougheachvalueintheLED[i]arrayandseteachpinasoutput:

voidsetup()

Serial.begin(9600);

for(inti=0;i<5;i++)

pinMode(LED[i],OUTPUT);

Intheloop()function,wecontinuouslyreadthevalueofthesensorusingtheanalogRead()function;thenweprintitontheserial:



Atlast,wecreateourthermometereffect.ForeachdegreeCelsius,theLM35returns10mVmore.WecanconvertthistoouranalogRead()valueinthisway:5Vreturns1023,soavalueof0.20V,correspondingto20degreesCelsius,willreturn0.20V/5V*1023,whichwillbeequaltoaround41.

Wehavefivedifferenttemperatureareas;we’llusestandardifandelsecasualstodeterminewhichregionwearein.ThenwelighttherequiredLEDs.

There’smore…Almostallanalogsensorsusethismethodtoreturnavalue.TheybringaproportionalvoltagetothevaluetheyreadthatwecanreadusingtheanalogRead()function.

Herearejustafewofthesensortypeswecanusewiththisinterface:

Temperature Humidity Pressure Altitude Depth Liquidlevel

Distance Radiation Interference Current Voltage Inductance

Resistance Capacitance Acceleration Orientation Angularvelocity Magnetism

Compass Infrared Flexing Weight Force Alcohol

Methaneandothergases Light Sound Pulse UniqueIDsuchasfingerprint Ghost!

Detectingmotion–PIRsensorEverwonderedhowthosemotionsensorswork?Usually,wefindtheminlightsthatturnupwhenwemove.AlmostallofthemuseasimpleandcommonsensorcalledaPassiveInfrared(PIR)sensor.

Here,wewillbuildoneofthoseannoyingmovement-sensitivelights,usinganArduino,itsbuilt-inLED,andaPIRsensor.

GettingreadyThefollowingaretheingredientsneededtoexecutethisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBJumperwiresAPIRsensor

Howtodoit…HookingupaPIRsensoriseasy:

1. Ithasthreeterminals.Oneisthevoltageinput,oneistheground,andthelastoneisthedatapin.

2. ConnectthegroundonthePIRtooneoftheGNDpinsontheArduino.Connectthevoltageinputto5V,andfinally,connectthedatapintoonedigitalpin.Hereweusedpin2.

SchematicThisisonepossibleimplementationusingpinD2astheinput:


CodeThefollowingcodewillreadthevalueofthedigitalpinonwhichthePIRsensorisconnected.Ifitdetectsmotion,itwillmaketheLEDblink:

intLED=13;//Declarethebuilt-inLED

intsensorPin=2;//Declaretheusedsensorpin

voidsetup()

//SettheLEDpinasOUTPUT


//Setthesensorpinasdigitalinputandactivatetheinternalpull-up

resistor

pinMode(sensorPin,INPUT_PULLUP);

//Waitforthesensortotakeasnapshotoftheroom

//Approximately1-2seconds

delay(3000);//Wearewaiting3

voidloop()

//Readthesensor,ifitgoeslow,weblindtheLEDfor1second

if(digitalRead(sensorPin)==LOW)


delay(1000);


Howitworks…ThePIRsensorusestheradiatedtemperatureofeveryobjectitseesintheinfraredspectrum.Thefirsttimeitpowersup,itrecordshowtheareainfrontlooksandthenitcompareseverythingtothat.Ifitseesasignificantdifference,suchasahumanpassingby,itwillpullitsdatapintoLOW,thusalertingustothemovement.

CodebreakdownFirstly,wedeclarethedigitalpinandthebuilt-inLEDwehaveused:

intLED=13;

intsensorPin=2;

ThePIRinitiallytakesasnapshotoftheenvironmentitisin.Thisprocesstakesaroundoneortwosecondssowecanwaitforaroundthreeseconds,inthesetup()function,tomakesurethesensorisupandready.Also,wedeclarethepinweusedasINPUT_PULLUP.

Thesensorwillpulldownthevoltageonceitdetectsmotion,butforthatitneedssomevoltagetopulldown.Byconfiguringtheinputasapullup,weactivatethebuilt-inresistoronthepinthatwillbringthevoltageupto5V:

voidsetup()


pinMode(sensorPin,INPUT_PULLUP);

delay(3000);

Intheloop()function,wecontinuouslycheckwhetherthesensordetectsmotionbypullingdownthevoltage.ThiswillreturntheLOWvoltageforwhichwearelooking.Oncewedetectmotion,wesimplygettheLEDtoblink,tomakealessannoyingmotion-activatedlight:

if(digitalRead(sensorPin)==LOW)


delay(1000);


Measuringdistance–infraredandultrasonicAdistancesensoristhemostimportantsensorforanyrobot.It’susuallyreferredtoasthe“eyes”ofarobot.Distancesensorsareveryusefulaswecanmakesystemsthatreactbasedonhowclosewearetothemorbasedonthepresenceofvariousobstacles.

Therearetwocommontechnologiesusedinamateurdistancesensing:infraredsensors,suchastheclassicSharpIR,andultrasonicsensors,usuallycalledsonars.Now,let’sbuildadistance-controlledLED!

GettingreadyTobuildadistance-controlledLED,wewillneedthefollowingingredients:

AnArduinoboardconnectedtoacomputerviaUSBOneLEDASharpinfraredproximitysensorsuchastheGP2Y0A21YKortheGP2Y0A02YK0F

Howtodoit…ConnectingaSharpIRiseasy.Maybethisiswhyit’ssopopular.Followthesesimplestepstoconnectone:

1. EachSharpIRhasthreepins.Oneisthepowerinput,whichweconnectto5V.AnotheristhegroundthatwewillconnecttooneGNDpin.Lastly,thereistheanalogoutputpinthatneedstobeconnectedtoananaloginput.Here,weusedpinA0.

2. Wewillmakeasmallillegalconnectionhere.WewilldirectlyconnecttheLEDtotheArduinowithoutanyresistor.Forlow-powerLEDs,thereisnoproblem,andneithertheArduinonortheLEDwillbeaffected.PlugthenegativeterminaltoGNDandtheotherterminaltooneofthepinscloseby.Here,weusedpin11foritsPWMfunctionality.

TipButpleasedon’texceeda3mm,10–20mALED.Nohigh-powerLEDshere!ItcouldeasilyfrytheLEDortheArduino.Ifwedon’tknowhowpowerfulourLEDis,weshouldjustmounta220-ohmresistorinseries.

SchematicThisisonepossibleimplementationusingpinA0astheanaloginputandpin11astheLEDoutput:

CodeThefollowingcodewillreadthevalueofthesensor,printitontheserialconnection,andvarytheLEDintensityusingPWM,tomatchthedistance:


intLED=11;//DeclaretheconnectedLED

voidsetup()

Serial.begin(9600);//StarttheSerialconnection

voidloop()

//Readtheanalogvalueofthesensor

intval=analogRead(A0);

//PrintthevalueoverSerial


//WritethevaluetotheLEDusingPWM

analogWrite(LED,val/4);

//Waitalittleforthedatatoprint

delay(100);

Howitworks…SharpIRsensorsmeasuredistanceusinganinfraredbeamthatreflectsontheobjectbeforeit.Theinfraredbeamisprojectedatasmallangle.Whenithitsanobject,itisreflectedatadifferentangle,dependingonthedistancetotheobject.Thesensordetectsthisangleandoutputsthedistance.

CodebreakdownFirst,wedeclaretwovariablesforthebuilt-inLEDandfortheusedanalogporttowhichweconnectedtheSharpIRsensor:

intsensorPin=A0;

intLED=11;

Inthesetup()function,weonlystarttheserialconnection.Wedon’tneedtodeclaretheLEDpinasoutputbecauseweusetheanalogWrite()function,whichdoesn’trequireadeclaration.

Intheloop()function,wereadthesensor,writethevalueoverserial,andthensettheintensityoftheLEDusingPWM.SincePWMtakesvaluesfrom0to255andtheanalogRead()functionreturnsvaluesfrom0to1023,wedividethevalueofanalogRead()by4whenweuseitinanalogWrite().

There’smore…Distancesensorshaveahugemarketwithhundredsuponhundredsofdifferentmodels.Generally,inthecheap,hobbyistsection,wecaneitherfindinfraredsensors—suchastheSharpIR—orultrasonicsensors.

Aninfraredsensorhasaverynarrowsensingbeam.Thismeansitcandetectobjectsintightplaceswithoutinterferingwithotherobjects.However,ifanobjectistoothinorhasholesinitsbody,thesensorbeammightgothroughitandgivefalsereadings.

Anultrasonicsensor,typicallycalledsonar,usessoundabovethenormalhearingfrequencytodetectdistance.Itdoessobyemittingashortsoundpulseandwaitingforittoreturn.Itmeasuresthetimeittakesforthesoundtotravel,bounceonobjects,andthentravelbacktothesensor.

Becausethespeedofsoundisknown,thetotaltimeittakesforthesoundtoreturnisdependentonthedistancetotheobjects.Thiscreatesaverywidesensingbeam.Itisusefulinmanyapplications,especiallywhenweneedtodetectlarge,complexobjects.However,thewidebeamwillcreateinterferenceifwehavetwoobjectsinrange.Itwillalwaysdetectthecloserone.

Animportantthingtorememberisthatinfraredsensorsaredependentonthecolorofthemeasuredobjectswhilesonarisgenerallynotaffectedbyparametersexcepttheshapeanddistanceoftheobject.

SeealsoHereareafewreferencesabouthowsensorswork:

http://www.societyofrobots.com/sensors_sonar.shtmlTheNoisereductionrecipeforthebetterhandlingofsensordata

http://www.societyofrobots.com/sensors_sonar.shtml

NoisereductionNoiseiseverywhere.Thisworldismadeofnoise.Thisiswhateverybodyrelatedtosensorswillconstantlyrepeat.Butwhatisnoise?It’sunexpecteddatageneratedbysensorsorsignalsources.Itcancompletelyruinthebehaviorofanautonomoussystemifnottreatedproperly.

Here,wewillusetheimplementationfromtheMeasuringdistance–infraredandultrasonicrecipe.TheSharpIRisknownforitsinterferencewithbasicallyanything,andherewewillexploretwostandardmethodsoffilteringthedatageneratedbythesensor.


AnArduinoboardconnectedtoacomputerviaUSBASharpinfraredproximitysensorsuchastheGP2Y0A21YKortheGP2Y0A02YK0F

Howtodoit…ThisrecipeusestheimplementationfromtheMeasuringdistance–infraredandultrasonicrecipe.Pleaseimplementthesamecircuitasyoudidthere.

CodeThefollowingcodewillreadtheoutputoftheSharpIRsensorandwillusetwofilteringmethodstofilteritandthenprintitovertheserialconnection:


//Functionthatreadsasensorwithspecifiednumberofsamples

//Returnsthemeanfilteredvalue

intreadMean(intpin,intsamples)

//Variabletostorethesumofreadings

intsum=0;

//Readthesamplesandaddthemall

for(inti=0;i<samples;i++)

sum=sum+analogRead(pin);

//Dividethesumbythenumberofsamples

sum=sum/samples;

//Returnthesum

returnsum;

//Functionthatreadsasensorwithspecifiednumberofsamples

//Returnsthemedianfilteredvalue

intreadMedian(intpin,intsamples)

//Variabletostorethereadings

intraw[samples];

//Readthesampleseachasavalueinthevector


raw[i]=analogRead(pin);

//Sortthevalues

//Lazybubblesort

inttemp=0;//tempvalue


for(intj=i;j<samples-1;j++)

//Checkifvaluesoutoforder

if(raw[j]>raw[j+1])

//Ifso,swapthem

temp=raw[j];

raw[j]=raw[j+1];

raw[j+1]=temp;

//Returnthemiddlevalue

returnraw[samples/2];

voidsetup()


Serial.begin(9600);

voidloop()

//Printthenormalvalueandthenaspace

Serial.print(analogRead(sensorPin));

Serial.print("");

//Printthemeanfilteredvalueandthenaspace

Serial.print(readMean(sensorPin,15));

Serial.print("");

//Printthemedianfilteredvalue

Serial.println(readMedian(sensorPin,15));

//ShortdelayfortheSerial

delay(100);

Howitworks…Therearehundredsofnoisereductionfilters,eachwiththeirownadvantagesanddisadvantages.Here,weexploretwoverycommonandusefulones:themeanfilterandthemedianfilter.Afiltertakessomevaluesandusestherelationbetweenthemtofigureoutwhichoneisclosertoreality.

NoiseforaSharpIR,forexample,canbearandomreadingof80cmwhentheobjectisat25cm.Thesensormightcontinuouslyoutput25cmandthensuddenly,justforonereading,outputaglitchof80cm.Thiscancausecatastrophiceffectsonanyautonomoussystemthatiscriticallydependentonthedistance.

Let’slookateachofthetwoalgorithmsindividually.

MeanfilterThemeanfiltertakesafewreadingsandthenaveragesthem.Thisgenerallyreducesnoise,butattheexpenseofalowerresponserate.Becausewehavetoreadmultiplesamplesandaveragethem,weincreasetherequiredtimeanddecreasetheoverallresponsefrequency.Mostofthetime,thisisnotaluxuryanditisrequired.Goodandslowvaluesaremuchbetterthanbadvalues.

1. Wedeclareafunctionwithtwoparameters:onewillbethepintowhichthesensorisconnected,andthesecondonewillbethenumberofsamples:

intreadMean(intpin,intsamples)

2. Thenwecontinuouslyreadtheanaloginputusingaforloopwhileaddingthevaluestoasumvariable:

intsum=0;


sum=sum+analogRead(pin);

3. Andherecomestheaveraging.Wedividethesumofallsamplesbythenumberofsamples,thusobtainingtheaveragevalue:

sum=sum/samples;

Intheend,wejustreturnthisaveragedsumvalueusingreturnsum.

MedianfilterThemedianfilterisabitmorecomplicatedbutverypowerful.Itismuchmoreresponsivethanthemeanfilter,asitdoesn’tmanipulatethevaluesinanyway.Itworksontheassumptionthatnoisewillbebothovershootingandundershooting.Overshootingmeansthatthereturnedvalueisgreaterthantheactualvaluewhileundershootingistheopposite.

Thefilterworksbytakinganumberofsamples,sortingtheminascendingorder,andthenreturningthecentralvalue.Usually,ifthenoiseisroughlyequalinbothdirections,the

filteredvaluewillbetheexpectedvalue.

1. Aswiththemeanfilter,wedeclareafunctionwithapinandasampleparameter:

intreadMedian(intpin,intsamples)

2. Thenwedeclareanarraytoholdallthevaluesthatwealsoreadinaforloop:

intraw[samples];


raw[i]=analogRead(pin);

Herecomestheimportantpart—sortingthearray.Hereweuseabubblesort,thelaziestofallsortingalgorithms,butalsotheeasiesttounderstandandimplement.TakealookattheSeealsosectionformoreinformationaboutit.Thealgorithmwillreturnasortedvectorwiththesmallestsamplesatthebeginningandthelargestonesattheendofit.

Lastly,wereturnthevalueinthecenter,whichshouldbeveryclosetotheexpectedvalue:

returnraw[samples/2];

Mainloop()Intheloop()functionwejustprintthenormalvalue,themeanfilteredvalue,andthemedianfilteredvalue,allusingaserialconnection:

Serial.print(analogRead(sensorPin));

Serial.print("");

Serial.print(readMean(sensorPin,15));

Serial.print("");

Serial.println(readMedian(sensorPin,15));

delay(100);

Totest,setasamplesizeof15andrunthecode.Moveanobjectinfrontofthesensorandthencopythedataandputitinchart-generatingsoftwaresuchasMicrosoftOfficeExcel.Varythesamplesizeuntilitfitsyourapplication.

SeealsoFormoreaboutthebubblesortalgorithm,visithttp://en.wikipedia.org/wiki/Bubble_sort.

http://en.wikipedia.org/wiki/Bubble_sort

AccelerometerAccelerometersareadvancedcomponentsthatcanmeasureacceleration.Initially,theyweredesignedforairplanesandrockets,butnowwecanfindtheminanyphone,laptop,harddrive,andawholebunchoftoys.

Bymeasuringacceleration,wecandetermineifanobjectismoving,howrapidlyitischangingdirection,andbenefitfromitsmostpopularuse—determiningtheorientationoftheobject.Accelerometerscomeinvarioustypesandthenumberofaxestheycansenseisthebasisoftheircategorization.Now,almostallaccelerometerscansensethreeaxes—meaningtheycansenseaccelerationinanydirectionithappens.

Inthisexample,wewillreadthedatafromtheaccelerometerandprintitoveraserialconnection.

GettingreadyToexecutethisrecipe,youwillneedthefollowingingredients:

AnArduinoboardconnectedtoacomputerviaUSBAnanalogaccelerometerboard;inthiscase,weusedSparkfunADXL335Abreadboardandjumperwires

Howtodoit…Analogaccelerometersarenotdifficulttoconnect.Thesestepsshouldmakeitallwork:

1. Identifythevoltagesupplyontheaccelerometerboard.It’stypicallylabeledwithVCCor5V.ConnectittotheArduino5V.AlsoconnecttheaccelerometerGNDtotheArduinoGND.

2. Eachaxisshouldhaveananalogoutputpin.ConnecteachanalogoutputtoananaloginputontheArduino.HereweusedanaloginputsA0,A1,andA2ontheArduino.

SchematicThefollowingisapossibleimplementationusinganADXL335accelerometerbreakoutboardfromSparkfun:


CodeThefollowingcodewillreadthevaluesfromtheaccelerometerandprintthemtotheserialconnection.Ifitdetectsmovement,itwillalsoblinkthebuilt-inLED:

//Declarebuilt-inLEDpin

intLED=13;

//DeclaretheX,Y,Zanalogpins

intxPin=A0;

intyPin=A1;

intzPin=A2;

voidsetup()

Serial.begin(9600);


voidloop()

//Readthe3values

intxVal=analogRead(xPin);

intyVal=analogRead(yPin);

intzVal=analogRead(zPin);

//Printthe3valuesontheSerial

Serial.print(xVal);

Serial.print("");

Serial.print(yVal);

Serial.print("");

Serial.println(zVal);

//Checkformovement

//Valuesatrest:

//X~330

//Y~330

//Z~400

//Ifmovement,blinkthebuilt-inLED

if(xVal<310||xVal>350||yVal<310||yVal>350||zVal<380||

zVal>420)


delay(300);


//SmalldelayfortheSerial

delay(50);

Howitworks…Accelerometershavedifferenttechnologiestomakethemreadacceleration.ThemostusedoneinembeddedelectronicsisMEMS.Insidethesensor,wecanfindsomepartsthatarefreelymoving.Whenthisishappening,theychangetheirinternalresistance,andsooutputadifferentvoltagebasedontheamountofmovement.TakealookattheSeealsosectionforamoredetailedexplanation.

CodebreakdownAfterwedeclaretheusedpinsinindividualvariables,wedeclaretheLEDpinasanoutputinthesetup()function.There,wealsoinitiatetheserialconnection.

Intheloop()function,wefirstreadthevaluesofthethreeaccelerometeroutputs:

intxVal=analogRead(xPin);

intyVal=analogRead(yPin);

intzVal=analogRead(zPin);

Thenweprintthemovertheserial,onenexttotheother.Whenthesensorisstandingstillonaflatsurface,itreturnsvaluesofaround330,330,and400onthex,y,andzaxesrespectively.However,ifwemoveorinclineit,thevalueswillrapidlychange.Thefollowinglongifclausechecksforeachanalogpin,ifmovementwasdetected,bycheckingagainstaninterval.Ifanyofthepinsexceedthespecifiedinterval,theArduinowillblinktheinternalLED:

if(xVal<310||xVal>350||yVal<310||yVal>350||zVal<380||

zVal>420)


delay(300);


There’smore…Accelerometersareveryhandyformeasuringmovementandorientation.Ifweintegratetheaccelerationovertime,wecanfindouthowmuchanobjectmoved.Theproblemisthattheyareverysusceptibletovibrations,whichcancompletelyruinthereadings.Inmostmobilephones,anInertialMeasurementUnit(IMU),whichcombinesanaccelerometerandagyroscope,isusedtoobtainbetterorientationreadings.

SeealsoTounderstandhowanaccelerometerworks,visithttp://www.explainthatstuff.com/accelerometers.html.

http://www.explainthatstuff.com/accelerometers.html

Localization–GPSTheGlobalPositioningSystem(GPS)usesanarrayofsatellitesorbitingaroundtheEarthandsendingtimeinformation.AGPSreceiverpicksupthesignaltransmittedfromthesatellites,calculatesthetimeittookforthesignaltoarrive,andbyidentifyingthepositionofthesatellites,triangulatesthepositiononthesurfaceoftheglobe.

GPSisveryusefulinautonomouscars,RCplanesordrones,anddataloggingapplications.Here,wewilllearnhowtoreadthedatafromaGPS,whichissurprisinglyeasy.Inthisrecipe,wewillusetheSoftwareSeriallibrarythatisbetterdetailedintheCommunicationchapter.

GettingreadyFollowingaretheingredientsneededforthisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBJumperwiresandabreadboardAUART-compatible5VGPSreceiversuchastheCopernicus

Howtodoit…Hookingupapotentiometeriseasyandherearethesteps:

1. PlugtheGPSreceiverintothebreadboard.2. ConnectthegroundandpowerontheGPStotheGNDand5VlinesontheArduino.3. ConnecttheTXoftheGPStoadigitalpinontheArduino.Hereweusedpin8.4. ConnecttheRXoftheGPStoanotherdigitalpinontheArduino.Hereweusedpin

9.

SchematicThisisonepossibleimplementationusingpins8and9forasoftserial:


CodeThefollowingcodewillreadtheoutputoftheGPSusingasoftserialconnectionandwriteittothecomputerusingtherealserialport:

//IncludetheSoftwareSeriallibrary

#include<SoftwareSerial.h>

//DefineaSoftwareSerialobjectandtheusedpins

//ConnectGPSTXtoSoftSerialRXandGPSRXtoSoftSerialTX

SoftwareSerialsoftSerial(8,9);//RX,TX

voidsetup()

Serial.begin(9600);//NormalSerial

softSerial.begin(9600);//SoftSerial

voidloop()

//CheckforreceivedcharactersfromtheGPS

if(softSerial.available())

//Writewhatisreceivedtotherealserial

Serial.write(softSerial.read());

Howitworks…AGPSsensorconstantlyoutputsastringfullofinformationviaaserialport.Generally,itoutputslocation,thesatellitesavailable,andthesignalstrength,butmoredatacanbeusuallyfound.Here,wejustreadthedataandprintittothecomputer.

CodebreakdownFirst,weincludetherequiredSoftwareSerial.hlibrary:


ThenwedeclareaSoftwareSerialport:


Webeginbothserialconnectionsinthesetup()function:

voidsetup()



Intheloop()function,wecheckwhetherthereisanycharacteravailableonthesoftserial.Ifthereis,wedirectlysendittotherealserialport,whichisconnectedtothecomputer.ThisbasicallymakesArduinoawirethattransfersallthedatafromtheGPStothecomputer:


Serial.write(softSerial.read());

Ifwerunthecodenow,withtheGPSconnected,wewillseequiteabitofdataintheserialmonitor.TheGPSwillprintthelongitude,latitude,numberofsatellitesfound,andthesignalstrength.MoredetailsmaybeprintedifavailableanddependingontheGPSmodule.

UsingtheCopernicusmoduleinsideathickbuilding,theArduinocontinuouslyprinted:

$GPGGA,,5316.82829,N,08650.76721,W,7,03,,,,,,,*4E

Thisrepresents53.1682829latitudewith8.65207672longitude,whichcorrespondstoNorthBremen,Germany.Italsoshowsthatthreesatellitesareavailableandthesignalqualityisaround7.

There’smore…TheArduinocanactuallyusethedatafromtheGPS.Withsomestringmanipulation,wecanextractthelongitudeandlatitudeanduseitforlocalizationornavigationpurposes.Forexample,wecanbuildanautonomousboatintowhichweinputtheGPScoordinatesofalargelake,andtheboatcantraveltherebycheckingthedifferencebetweenthecurrentlocationandthedestination.ChecktheSeealsosectionforfurtherreferencesaboutstringmanipulation.

SeealsoTolearnhowGPStriangulationworks,visithttp://electronics.howstuffworks.com/gadgets/travel/gps.htmFormoredetailsaboutArduinostringmanipulation,visithttp://arduino.cc/en/Reference/StrsingObject

http://electronics.howstuffworks.com/gadgets/travel/gps.htm

http://arduino.cc/en/Reference/StrsingObject

Chapter5.MotorControlInthischapter,wewillcoverthefollowingtopics:

ControllingsmallmotorsControllingmotorswithtransistorsControllingspeedwithPWMSpinningmotorsbothwaysServomotorSteppermotorBipolarsteppermotorBrushlessmotor

IntroductionThischapterdealswithcommontypesofmotorsandhowtheycanbeoperatedwithArduino.WhilemakinganLEDblinkorshowingsometextonascreencanbecool,nothingismorepowerfulthanmakingsomethingmove.Here,wewilltacklemostofthetypesofmotorthatwecanfindthesedays.

Therearemanythingsthatcanbedoneusingmotors.Usingasimpleservomotor,wecanpositionthingsprecisely.Forexample,arobotichandisusuallyjustabunchofservomotorsgluedtogether.ByusingafewstandardDCmotors,wecanmakeacarmove,makearobotturn,ormakeaboatmoveforward.

WewillexplorestandardDCmotors,servomotors,steppermotors,andbrushlessmotorsinthischapter.

ControllingsmallmotorsControllingasmallmotorcanbeverysimple.Ifthemotorissmallenough,itcanbedirectlyconnectedtotheArduinopin,andsimplyturningthepintoHIGHorLOWwillcontrolthemotor.

Thisrecipewillteachyouthebasiclogicofhowtocontrolamotor;however,thisisnotatypicalwayofconnectingamotortotheArduino.Itisrecommendedthatyoufirstunderstandthisrecipeandthenapplythefollowingone,Controllingmotorswithtransistors.

GettingreadyFollowingaretheingredientsrequiredtoexecutethisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBA220-ohmresistorAverysmallDCmotor—usuallyavibrationmotorwillwork—thatcanbefoundinold(andnew)mobilephonesorcantypicallybebroughtfromwebsitessuchasSparkfunorAdafruit

Howtodoit…Thefollowingarethestepstoconnectthemotor:

1. Justlikeothersmallmotors,avibrationmotorhastwowires.ConnectonewiretotheArduinoGNDpin.Itdoesn’tmatterwhichone,asaDCmotorhasnopolarity;itcanbeconnectedbothways.

2. Mounttheresistorbetweenthechosendigitalpinandtheremainingwireonthemotor.TheresistorwilllimitthecurrentandensurethattheArduinowillnotburn.Arduinoisnotreallydesignedtodrivemotorsthisway.

SchematicThisisonepossibleimplementationontheseconddigitalpin.Otherdigitalpinscanbealsobeused.

Hereisanexampleofhowtowireitonabreadboard:

CodeThefollowingcodewillstartthemotorfor1secondandthenstopitforanother:

//Declarethepinforthemotor

intmotorPin=2;

voidsetup()

//Definepin#2asoutput

pinMode(motorPin,OUTPUT);

voidloop()

//Turnmotoron

digitalWrite(motorPin,HIGH);

//Wait1000ms

delay(1000);

//Turnmotoroff

digitalWrite(motorPin,LOW);

//Waitanother1000ms

delay(1000);

TipIfthemotorisconnectedonadifferentpin,simplychangethemotorPinvaluetothevalueofthepinthathasbeenused.

Howitworks…WheneverwesetthepinatHIGH,currentwillflowfromthedigitalpinthroughtheresistor,throughthemotor,andtoground.Ifthemotorissmallenough,itwillstartspinningifit’sastandardDCmotor;elseitwillstartvibrating,ifitisavibrationmotor.

Theresistorisveryimportantinthiscircuit.EachArduinodigitalpincanonlyhandleupto40mA,with20mAastherecommendedmaximum.Thechosen220-ohmvaluewilllimitthecurrentto22mA,andbecausethemotorisinserieswithanotherresistor,thecurrentwillbeless.Ifthetotalresistanceofthemotorishigherthan200Ohmsthenit’ssafetoomittheresistoranddirectlyconnectthemotortothedigitalpinandGND.

There’smore…Inthisexample,we’veseenhowtoconnectonemotordirectlytoadigitalpin.Butwecanalsoconnectmorethanone.

MultiplemotorsMultiplemotorscanbeconnectedusingdifferentdigitalpinsontheArduinoboard.Forexample,pins2,3,and4canindependentlycontroldifferentmotors.EachdigitalpinontheArduinocancontrolonemotor.However,it’sgenerallyadvisednottodothis,asitwillincreasethecurrentpassingthroughtheArduinountilitburns.Let’slimitourselvestoonemotoronlywiththisimplementation.

ElectricalspikesEveryDCmotorisalsoaninductor.Whenwestopsupplyingthemotorwithcurrent,orwhenwespinthemotorbyhand,itwillgeneratehigh-voltageelectricspikes.Thiscaneasilyburnelectroniccomponents.Toavoidthis,weshouldconnectadiodefromthedigitalpinto5V,withthediodepointingto5V.Wheneverthemotorgeneratesaspike,thediodewillpassittothe5Vline,whichcantolerateit.Luckily,theArduinohasabuilt-inprotectiondiodeoneachpin.

SeealsoTheControllingmotorswithtransistorsrecipeTheControllingspeedwithPWMrecipeTheSpinningmotorsbothwaysrecipeTofindoutmoreaboutthedigitalpinsoftheArduino,takealookattheI/O-PortssectionintheATMega328Pmicrocontroller,foundinArduinoUnoathttp://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdfTolearnindetailhowaDCmotorworks,visithttp://electronics.howstuffworks.com/motor.htm

http://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdf

http://electronics.howstuffworks.com/motor.htm

ControllingmotorswithtransistorsWecancontrolamotorbydirectlyconnectingittotheArduinodigitalpin;however,anymotorbiggerthanacoinwouldkillthedigitalpinandmostprobablyburnArduino.Thesolutionistouseasimpleamplificationdevice,thetransistor,toaidincontrollingmotorsofanysize.

Here,wewillexplorehowtocontrollargermotorsusingbothNPNandPNPtransistors.

GettingreadyToexecutethisrecipe,youwillrequirethefollowingingredients:

AnArduinoboardconnectedtoacomputerviaUSBADCmotorAresistorbetween220ohmand10KohmAstandardNPNtransistor(BC547,2N3904,N2222A,TIP120)Astandarddiode(1N4148,1N4001,1N4007)

AllthesecomponentscanbefoundonwebsitessuchasAdafruit,Pololu,andSparkfun,orinanygeneralelectronicsstore.

Howtodoit…Thefollowingarethestepstoconnectamotorusingatransistor:

1. ConnecttheArduinoGNDtothelongstriponthebreadboard.2. ConnectoneofthemotorterminalstoVINor5VontheArduino.Weuse5Vifwe

powertheboardfromtheUSBport.Ifwewanthighervoltages,wecoulduseanexternalpowersource,suchasabattery,andconnectittothepowerjackonArduino.However,eventhepowerjackhasaninputvoltagerangeof7V–12V.Don’texceedtheselimitations.

3. ConnecttheotherterminalofthemotortothecollectorpinontheNPNtransistor.Checkthedatasheettoidentifywhichterminalonthetransistoristhecollector.

4. ConnecttheemitterpinoftheNPNtransistortotheGNDusingthelongstriporalongconnection.

5. MountaresistorbetweenthebasepinoftheNPNtransistorandonedigitalpinontheArduinoboard.

6. Mountaprotectiondiodeinparallelwiththemotor.Thediodeshouldpointto5Vifthemotorispoweredby5V,orshouldpointtoVINifweuseanexternalpowersupply.

SchematicThisisonepossibleimplementationontheninthdigitalpin.TheArduinohastobepoweredbyanexternalsupply.Ifnot,wecanconnectthemotorto5Vanditwillbepoweredwith5volts.

Hereisonewayofhookingupthemotorandthetransistoronabreadboard:

CodeForthecodingpart,nothingchangesifwecompareitwithasmallmotordirectlymountedonthepin.Thecodewillstartthemotorfor1secondandthenstopitforanotherone:


intmotorPin=2;

voidsetup()

//Definepin#2asoutput

pinMode(motorPin,OUTPUT);

voidloop()

//Turnmotoron

digitalWrite(motorPin,HIGH);

//Wait1000ms

delay(1000);

//Turnmotoroff

digitalWrite(motorPin,LOW);

//Waitanother1000ms

delay(1000);

TipIfthemotorisconnectedtoadifferentpin,simplychangethemotorPinvaluetothevalueofthepinthathasbeenused.

Howitworks…Transistorsareveryneatcomponentsthatareunfortunatelyhardtounderstand.Weshouldthinkofatransistorasanelectricvalve:themorecurrentweputintothevalve,themorewateritwillallowtoflow.Thesamehappenswithatransistor;onlyhere,currentflows.Ifweapplyacurrentonthebaseofthetransistor,aproportionalcurrentwillbeallowedtopassfromthecollectortotheemitter,inthecaseofanNPNtransistor.Themorecurrentweputonthebase,themoretheflowofcurrentwillbebetweentheothertwoterminals.

WhenwesetthedigitalpinatHIGHontheArduino,currentpassesfromthepintothebaseoftheNPNtransistor,thusallowingcurrenttopassthroughtheothertwoterminals.WhenwesetthepinatLOW,nocurrentgoestothebaseandso,nocurrentwillpassthroughtheothertwoterminals.Anotheranalogywouldbeadigitalswitchthatallowscurrenttopassfromthecollectortotheemitteronlywhenwe‘push’thebasewithcurrent.

Transistorsareveryusefulbecause,withaverysmallcurrentonthebase,wecancontrolaverylargecurrentfromthecollectortotheemitter.Atypicalamplificationfactorcalledbforatransistoris200.Thismeansthat,forabasecurrentof1mA,thetransistorwillallowamaximumof200mAtopassfromthecollectortotheemitter.

Animportantcomponentisthediode,whichshouldneverbeomitted.Amotorisalsoaninductor;wheneveraninductoriscutfrompoweritmaygeneratelargevoltagespikes,whichcouldeasilydestroyatransistor.Thediodemakessurethatallcurrentcomingout

ofthemotorgoesbacktothepowersupplyandnottothemotor.

There’smore…Transistorsarehandydevices;hereareafewmorethingsthatcanbedonewiththem.

Pull-downresistorThebaseofatransistorisverysensitive.Eventouchingitwithafingermightmakethemotorturn.Asolutiontoavoidunwantednoiseandstartingthemotoristouseapull-downresistoronthebasepin,asshowninthefollowingfigure.Avalueofaround10Kisrecommended,anditwillsafeguardthetransistorfromaccidentallystarting.

PNPtransistorsAPNPtransistorisevenhardertounderstand.Itusesthesameprinciple,butinreverse.CurrentflowsfromthebasetothedigitalpinontheArduino;ifweallowthatcurrenttoflow,thetransistorwillallowcurrenttopassfromitsemittertoitscollector(yes,theoppositeofwhathappenswithanNPNtransistor).AnotherimportantpointisthatthePNPismountedbetweenthepowersourceandtheloadwewanttopowerup.Theload,inthiscaseamotor,willbeconnectedbetweenthecollectoronthePNPandtheground.

AkeypointtorememberwhileusingPNPtransistorswithArduinoisthatthemaximumvoltageontheemitteris5V,sothemotorwillneverreceivemorethan5V.Ifweuseanexternalpowersupplyforthemotor,thebasewillhaveavoltagehigherthan5VandwillburntheArduino.Onepossiblesolution,whichisquitecomplicated,hasbeenshownhere:

MOSFETsLet’sfaceit;NPNandPNPtransistorsareold.Therearebetterthingsthesedaysthatcanprovidemuchbetterperformance.TheyarecalledMetal-oxide-semiconductorfield-effecttransistors.NormalpeoplejustcallthemMOSFETsandtheyworkmostlythesame.Thethreepinsonanormaltransistorarecalledcollector,base,andemitter.OntheMOSFET,theyarecalleddrain,gate,andsource.Operation-wise,wecanusethemexactlythesamewayaswithnormaltransistors.Whenvoltageisappliedatthegate,currentwillpassfromthedraintothesourceinthecaseofanN-channelMOSFET.AP-channelistheequivalentofaPNPtransistor.

However,therearesomeimportantdifferencesinthewayaMOSFETworkscomparedwithanormaltransistor.NotallMOSFETscanbeproperlypoweredonbytheArduino.Usuallylogic-levelMOSFETswillwork.SomeofthefamousN-channelMOSFETsaretheFQP30N06,theIRF510,andtheIRF520.Thefirstonecanhandleupto30Aand60Vwhilethefollowingtwocanhandle5.6Aand10A,respectively,at100V.

Hereisoneimplementationofthepreviouscircuit,thistimeusinganN-channelMOSFET:

Wecanalsousethefollowingbreadboardarrangement:

DifferentloadsAmotorisnottheonlythingwecancontrolwithatransistor.AnykindofDCloadcanbecontrolled.AnLED,alightorothertools,evenanotherArduinocanbepoweredupbyanArduinoandaPNPorNPNtransistor.Arduinoception!

SeealsoTheControllingspeedwithPWMrecipe.Forgeneralandeasytousemotors,Solarboticsisquitenice.Visitthesiteathttps://solarbotics.com/catalog/motors-servos/.Forhigher-endmotorsthatpackquitesomepower,Pololuhasmadeanameforitself.Visitthesiteathttps://www.pololu.com/category/51/pololu-metal-gearmotors.

https://solarbotics.com/catalog/motors-servos/

https://www.pololu.com/category/51/pololu-metal-gearmotors

ControllingspeedwithPWMAmotorthatcanonlybeonoroffisnotthatuseful.Weneedtocontrolthespeedofamotorusingcode.Sometimes,wewantthemotorathalfspeed;sometimeswewantitfasterandsometimesslower.However,themotorisconnectedtoadigitalpin,whosevaluecaneitherbemaximumornothing.Howcanwemakethisclear1and0intosomethingin-between?WithPulseWidthModulationorPWM.


ADCmotorAresistorbetween220ohmand4,700ohmAstandardNPNtransistor(BC547,2N3904,N2222A,TIP120)oralogic-levelcompatibleMOSFET(IRF510,IRF520)Astandarddiode(1N4148,1N4001,1N4007)

Howtodoit…ThefollowingarethestepstocontrolthespeedofamotorusingPWM:

1. ConnecttheArduinoGNDtothelongstriponthebreadboard.2. ConnectoneofthemotorterminalstoVINor5VontheArduino.Weuse5Vifwe

powertheboardfromtheUSBportor,ifwewanthighervoltages,wecoulduseanexternalpowersource,suchasabattery,andconnectittothepowerjackontheArduino.

3. ConnecttheotherterminalofthemotortothecollectorpinontheNPNtransistorortothedrainpinontheMOSFET.CheckthedatasheettoidentifywhichterminalonthetransistoristhecollectororwhichterminalontheMOSFETisthedrain.

4. ConnecttheemitterpinoftheNPNtransistororthesourcepinoftheMOSFETtotheGNDusingthelongstriporalongconnection.

5. MountaresistorbetweenthebaseorgatepinofthetransistorandonePWMpinontheArduino.Thesepinsaregenerallymarkedwith~nexttothepinnumberontheboard.TheArduinoUnohaspins3,5,6,9,10,and11asPWMpins.

6. Mountaprotectiondiodeinparallelwiththemotorterminals,pointingtoeitherVINor5V,dependingonwhetheranexternalpowersupplyhasbeenusedornot.

SchematicThisisonepossibleimplementation.OtherdigitalpinswithPWMfunctionalitycanbeused;inthisexample,theninthdigitalpinhasbeenused:


CodeThefollowingcodewillstartthemotoratmaximumspeedandthengraduallyreduceitsspeeduntilitstopsit:


intmotorPin=9;

voidsetup()

//PWMpinsdon'trequirethepinMode()function

voidloop()

//Turnmotorontomaximum

analogWrite(motorPin,255);

//Wait1000ms

delay(1000);

//Turnmotorto1/2power


//Wait1000ms

delay(1000);

//Turnmotoroff


//Wait1000ms

delay(1000);

TipIfthemotorisconnectedtoadifferentpin,simplychangethemotorPinvaluetothevalueofthepinthathasbeenused.However,ithastobeaPWM-enabledpin.

Howitworks…PWMisaclevertrickthatallowsadigitalpin,whichcanonlyoutput1or0,tosimulatevaluesin-between.Itworksbyswitchingthedigitalpinonandoffveryfast.Forexample,ifweswitchadigitalpinonfor1millisecondandoffforanothermillisecond,wewillbedoingthison-offcycle500timesasecond.Ifwehaveamotorconnectedtothepin,themotorwillspinathalfspeed.Why?Because,firstofall,weareactuallygivingitpowerhalfofthetime,sincethepinisofffor1millisecondevery2milliseconds.

Inpractice,thismeansweareturningitonandoff,butduetothehighfrequencyatwhichwearedoingit,theresultwillbeamotorwithhalfpower.This,ofcourse,doesn’tworkatlowfrequencies.Ifweturnthemotoronforasecondandoffforanotherone,theresultwillbeamotorthatistrulystartingandstopping;so,thehigherthefrequency,thebetter.

Thisdoesn’tmeanthatwecanonlyhavehalf-speed.Byvaryingthetimethatitisonandthetimeitisoff,wecanobtainmanyspeedvariations.AndthebestpartisthattheArduinohasaninbuiltlibrarytohandlethis.Thefollowingdiagramshowshowallofthisworksinamoregraphicway:

WecanseeinthefirstpartofthegraphicthatwearemostlykeepingthepinLOW,to0V,andthustheaveragevoltageoutputisquitelow.Inthemiddleofthegraphic,weareroughlykeepingthepinHIGHandLOWforanequalamountoftime,andtheresultingvoltageishalf.Inthelastpart,weseethatthetimethepinisHIGHiscalledPulseWidth.ThetotaltimebetweenthebeginningofeachpulseiscalledtheperiodofthePWMsignal.

AfewpinsontheArduinoarePWM-enabledandcanbeusedtogeneratethisPWMsignal.OnalmostallArduinos,thePWMpinsare3,5,6,9,10,and11.TheexceptionsaretheArduinoDueandMega,whichhavemorePWMsonpins2to13.

AlmostallArduinoscanoutput8-bitPWMsignalsatafrequencyof490HzExceptionsarethenewerboardssuchastheUnothat,forpins5and6,output980Hz.An8-bitPWM

meansthatwecanoutputalevelbetween0,whichistheequivalentofLOW,upto255,whichistheequivalentofHIGH.Themiddleisroughlyat127.

CodebreakdownThecodeusestheanalogWrite()function,whichoutputsaPWMsignalonaPWM-enabledpin,atthespecifiedlevel:


ThisfunctionwilloutputthePWMsignalatthevalueof127,whichisroughlyhalfofthe0–255range.Othervaluescanbeprovided,suchas85forone-thirdand170fortwo-thirds.

AverygoodthingtorememberisthattheanalogWrite()functionusedonPWM-compatiblepinswillnotusetheprocessorcontinuously.OncewecallanalogWrite()ataspecificlevel,thecodeexecutionwillcontinueandthePWMsignalwillbegeneratedcontinuously,untilstopped.ThisisaverygoodthingbecausewecanleaveallPWMatthelevelswewantandthenexecutetherestofthecodewithnointerruption.

There’smore…ThePWMpinsareveryuseful.Anyloadcanbecontrolledwiththem;forexample,LEDintensity,motors,orspeakers.InordertousemultiplePWMpins,intheanalogWrite()pinvalue,wejustneedtomodifythepinargumenttothepinwewanttochange.

SpinningmotorsbothwaysIt’sverysimpletocontrolamotorwithatransistor.However,spinningthemotorinjustonedirectionisnotalwaysthatuseful.It’sjusthalfofwhatispossible.MostDCmotorscanspinbothways.Whenweapplythevoltageinonedirection,themotorwillspinononeside.Ifwereversethevoltageontheterminals,themotorwillspintheoppositeway.ButhowcanwedothatwiththeArduino?WeneedtouseanH-Bridge.


AnArduinoboardconnectedtoacomputerviaUSBAnArduino-compatiblemotorshield;thereisanofficialArduinomotorshieldandafewotheroptionsfromdifferentcompaniessuchasSparkfun,Pololu,orAdafruitADCmotor

Howtodoit…ArduinoshieldsareveryusefulbecausetheycansimplybepluggedintotheArduinoandeverythingisalreadymade.Wedon’tneedtospendalotoftimeroutingwirestobreadboardsandtesting.Everythingjustworks.

Thefollowingarethestepstoconnectamotorusingamotorshield:

1. PlugthemotorshieldintotheArduino.2. Connectthetwowireterminalsofthemotortooneofthemotorterminalports.

HereisaschematicofthelogicalconnectionsneededbetweentheArduinoandtheshield.Inthisexample,weareonlyusingtwoofthesixpinstocontrolonemotor.

Thisisaviewoftheshieldconnectedtothemotorandthemotorconnectedtotheshield:

CodeThefollowingcodewilldefineamotorcontrolfunctionandwilluseittospinthemotorforwardathalfspeed,fullspeed,andthenstop;themotorwillthenreverseathalfspeed,reverseatfullspeed,andstopagain:

//Declaretheusedpins

intdirectionPin=12;

intpwmPin=3;

voidsetup()

//SetthedirectionPinasOUTPUT

pinMode(directionPin,OUTPUT);


//Customfunctionwhichcontrolsthespeedanddirectionusingone

variable.

voidsetMotor(intval)

//Ifvalisfrom0to255themotorwillspinforwards

if(val>=0)

//Setthedirection

digitalWrite(directionPin,HIGH);

//Setthespeed

analogWrite(pwmPin,val);

//Ifthevalueisfrom-255to0themotorwillspinbackwards

if(val<0)

//Setthedirection

digitalWrite(directionPin,LOW);

//Setthespeed,-valbecausethevalueisnegativeandpositiveis

requried

analogWrite(pwmPin,-val);

voidloop()

//Turnmotoronhalfspeedforwards

setMotor(127);

delay(1000);

//Motorfullspeedforwards

setMotor(255);

delay(1000);

//Motorstop

setMotor(0);

delay(1000);

//Motorhalfspeedbackwards

setMotor(-127);

delay(1000);

//Motorfullspeedbackwards

setMotor(-255);

delay(1000);

//Motorstop

setMotor(0);

delay(1000);

TipTherearemultipletypesofmotorshieldsfortheArduino.ThepresentedcodewillonlycontrolonemotorontheofficialArduinoMotorShield.VariationshavebeenprovidedintheThere’smore…sectionofthisrecipe.

Howitworks…Inordertospinamotortwoways,weneedacircuitcalledtheH-bridge.Itiscomposedoffourtransistorsthatcontrolthecurrentdirectionthroughthemotor.However,thiscircuitisquitecomplicatedandit’sveryeasytoaccidentallyburnit.ThegoodnewsisthatthereareintegratedcircuitsthatalreadyimplementthisH-bridgeconceptandaddsafetyfeaturessuchasshortprotection,over-currentprotection,andover-temperatureshutdown.

Forthepurposeofthisrecipe,wewillnotdiscussindepthhowtheH-bridgeworks;thatwillbecoveredinafurtherrecipe.Infact,therearesomanymotorshieldsandmotordriversouttherethatmostprobablywewillneverneedtoimplementafullH-bridgebyourselves.

However,therearesomevariationsevenintheshieldsthatarecommonlyused.Someuseonlyonepintocontrolthedirectionandspeedofamotor,someusetwo,somethreeandsomeevenfour.Somedriverscanhandleonemotor;somecanhandletwomotors.Next,wewillbreakdownthecodetocontrolonemotorontheArduinoMotorDriverShield.

CodebreakdownThecodedefinesthetwopinsrequiredtocontrolonemotor.Oneisthedirectionpin,whichsetsthedirectionofthemotor.WhenitisHIGH,themotorwillspinoneway,andwhenitisLOW,theotherway.TheotherpinisthePWMpinthatcontrolsthespeedofthemotor.If,forexample,wesetthedirectionpintoHIGHandspeedto127,themotorwillturnonedirectionwithroughlyhalfthespeed.IfwethenchangethedirectionpintoLOW,itwillreverseitsdirectionandmaintainroughlyhalfthespeed.

Inthesetup()function,wedeclaredirectionPinasanoutput.PWMpinsdon’tneedtobedeclared:

voidsetup()

//SetthedirectionPinasOUTPUT

pinMode(directionPin,OUTPUT);


ThecustomsetMotor()functiontakesoneargument:thespeedofthemotor.Ifthespeedisbetween0and255,themotorwillspinforwardwiththerespectivespeed.For0,itwillnotmoveofcourse.Ifthevalueisfrom-1to-255,themotorwillspinbackwardswithapowerof1to255.

Wedothisusingasimpleifstatement.Ifthevalueisover0,wesetthedirectionpinasHIGHandsetthespeeddirectly:

//Customfunctionwhichcontrolsthespeedanddirectionusingone

variable



if(val>=0)

//Setthedirection


//Setthespeed


Butifthespeedisnegative,wesetthedirectionpinasLOWandthenweuseasimpletrickfortheanalogWrite()function.Itdoesn’tacceptnegativevalues,butbyputtingaminussignbeforethevalue,wereversethesign.Thisway,-valwillequalthepositivepartofvalwhenvalisnegative:


if(val<0)

//Setthedirection



requried


Then,intheloop()function,wejusttestourcustomfunctionbyturningthemotorindifferentdirections.Thecommentsexplainbestwhatishappening.

There’smore…TheArduinoMotorShieldcancontroltwomotorsatthesametime.Also,itisnottheonlyshieldonthemarketthatcancontrolmotors.Actually,therearehundredsofmotorshieldsandmotordrivers.TheyallsharethesameH-Bridgeprincipleandsotheyareallcontrolledinsimilarways.Here,wewillexploreafewtypicalconfigurationsandunderstandhowtoadjustoursetMotor()functiontobecompatiblewithothermotors.

Controlusingthedirectionpin,PWMpin,andbrakepinTheArduinoMotorShieldusesonedirectionandonePWMpin.Anditisnottheonlyonetodoso;theSparkfunArdumotoshieldhasidenticalpinmappings.Thepinsareasfollows:

Function PinforMotorA PinforMotorB

Directionpin 12 13

PWMpin 3 11

Brakepin 9 8

Now,whatisthebrakepin?TheArduinoMotorShieldhasthispinthat,whenturnedHIGH,willstopthemotor.WecanadjustoursetMotor()functionwiththisnewfeatureasfollows:


//Ifvalis0brakingwillbeapplied

if(val==0)

//Startbraking

digitalWrite(brakePin,HIGH);


if(val>0)

//Setthedirection


//Setthespeed


//Stopthebraking

digitalWrite(brakePin,LOW);


if(val<0)

//Setthedirection



requried


//Stopthebraking

digitalWrite(brakePin,LOW);

NowwecanusethesetMotor()function,andwhenwewanttobrake,wesimplyneedtopass0asthemotorspeed.

ControlusingInputA,InputB,andPWMTherearesomanyvariations,butthisisapopularone.ItusestwodigitalpinsfordirectionandoneforPWM.ThisonlyusesonePWMpinwhiletheothertwocanbedigital.

Buthowdowemakethedrivergoforward,backward,orevenbrake?Hereisareferencetable:

InputA InputB Result

0 0 Lowbrake

0 1 Forward

1 0 Backward

1 1 Highbrake

Highsideandlowsidebrakingareinterestingconcepts.Inhighsidebraking,bothmotorterminalsareconnectedtothepowersupply,whileinlowsidebraking,bothareconnectedtoground.Thiswillmakethemotorbrake.

Howdowecontrolthespeed?WecanusethePWMinput.WithInputAandB,wesetthedirection,andwithPWM,thespeed.Nowwecanstopthemotorbyeithersendinga0or11ontheABpins,orbyjustwriting0tothePWM.HereisoursetMotor()functionforthisconfiguration:


//Ifvalis0brakingwillbeapplied

if(val==0)

//Startbraking

digitalWrite(pinA,LOW);

digitalWrite(pinB,LOW);


if(val>0)

//Setthedirection

digitalWrite(pinA,LOW);

digitalWrite(pinB,HIGH);

//Setthespeed


//Ifvalueisfrom-255to-1themotorwillspinback

if(val<0)

//Setthedirection

digitalWrite(pinA,HIGH);

digitalWrite(pinB,LOW);

//Setthespeed


SomedriversalsohaveanenablepinwhichweneedtoeithersetasHIGHorLOWinordertoenablethemotor.Sometimes,thesedriversareactuallymissingthePWMpinbuthaveanenablepin.ByapplyingPWMtoit,wecanobtainthesameresult.

Custom-madeL293DdriverThisoneisforthebrave!WecanbuildourownH-bridgedriverusingthefamousL293DH-bridgedriver.Whenwedon’treallyhavespace,wecanmakeourcustomelectronicsboardwiththefollowingschematic,whichcontrolstwomotors:

Butifwewanttoimplementitonthebreadboard,thisisonepossibleway:

ThereisanotherIntegratedCircuit(IC)thatfunctionsidenticaltoL293D;heck,itevenlooksthesame—allthepinsarethesame.It’salittlecheaper,andit’scalledSN754410.

SeealsoWheneverweareusinganIC,weshouldcheckitsdatasheet.YoucanfindthedatasheetforL293Dathttp://www.ti.com/lit/ds/symlink/l293d.pdf

http://www.ti.com/lit/ds/symlink/l293d.pdf

ServomotorServomotorsaregreatdevicesthatcanturntoaspecifiedposition.Usually,theyhaveaservoarmthatcanturn180degrees.UsingtheArduino,wecantellaservotogotoaspecifiedpositionanditwillgothere.Assimpleasthat!

ServomotorswerefirstusedintheRemoteControl(RC)world,usuallytocontrolthesteeringofRCcarsortheflapsonaRCplane.Withtime,theyfoundtheirusesinrobotics,automation,andofcourse,theArduinoworld.

Herewewillseehowtoconnectaservomotor26andthenhowtoturnittodifferentpositions.

ThefirstmotorIeverconnectedtoanArduino,sevenyearsago,wasaServomotor.Nostalgicmomentover,backtowork!

GettingreadyForthisrecipe,youwillneedthefollowingingredients:

AnArduinoboardconnectedtoacomputerviaUSBAservomotorJumperwires

Therearefewbignamesintheservomotorworld.HitehandFutabaaretheleadingRCservomanufacturers.GoodplacestobuythemareServocity,Sparkfun,andHobbyking.

Howtodoit…Aservomotorhaseverythingbuiltin:amotor,afeedbackcircuit,andmostimportant,amotordriver.Itjustneedsonepowerline,oneground,andonecontrolpin.

FollowingarethestepstoconnectaservomotortotheArduino:

1. Theservomotorhasafemaleconnectorwiththreepins.Thedarkestorevenblackoneisusuallytheground.ConnectthistotheArduinoGND.

2. Connectthepowercablethatinallstandardsshouldberedto5VontheArduino.3. ConnecttheremaininglineontheservoconnectortoadigitalpinontheArduino.

ThisisaviewoftheservomotorconnectedtotheArduino:

CodeThefollowingcodewillturnaservomotorto0degrees,wait1second,thenturnitto90,waitonemoresecond,turnitto180,andthengoback.

//IncludetheServolibrary

#include<Servo.h>

//DeclaretheServopin

intservoPin=3;

//Createaservoobject

ServoServo1;

voidsetup()

//Weneedtoattachtheservototheusedpinnumber

Servo1.attach(servoPin);

voidloop()

//Makeservogoto0degrees

Servo1.write(0);

delay(1000);


Servo1.write(90);

delay(1000);


Servo1.write(180);

delay(1000);

TipIftheservomotorisconnectedonanotherdigitalpin,simplychangethevalueofservoPintothevalueofthedigitalpinthathasbeenused.

Howitworks…Servosarecleverdevices.Usingjustoneinputpin,theyreceivethepositionfromtheArduinoandtheygothere.Internally,theyhaveamotordriverandafeedbackcircuitthatmakessurethattheservoarmreachesthedesiredposition.Butwhatkindofsignaldotheyreceiveontheinputpin?

ItisasquarewavesimilartoPWM.Eachcycleinthesignallastsfor20millisecondsandformostofthetime,thevalueisLOW.Atthebeginningofeachcycle,thesignalisHIGHforatimebetween1and2milliseconds.At1milliseconditrepresents0degreesandat2millisecondsitrepresents180degrees.Inbetween,itrepresentsthevaluefrom0–180.Thisisaverygoodandreliablemethod.Thefollowinggraphicmakesitalittleeasiertounderstand:

RememberthatusingtheServolibraryautomaticallydisablesPWMfunctionalityonPWMpins9and10ontheArduinoUNOandsimilarboards.

CodebreakdownThecodesimplydeclarestheservoobjectandtheninitializestheservobyusingtheservo.attach()function.Weshouldn’tforgettoincludetheservolibrary.Intheloop(),wesettheservoto0degrees,wait,thensetitto90,andlaterto180degrees.

There’smore…Controllingservosiseasy,andhereareafewmoretrickswecanuse.

ControllingtheexactpulsetimeArduinohasabuilt-infunctionservo.write(degrees)thatsimplifiesthecontrolofservos.However,notallservosrespectthesametimingsforallpositions.Usually,1millisecondmeans0degrees,1.5millisecondsmean90degrees,and,ofcourse,2millisecondsmean180degrees.Someservoshavesmallerorlargerranges.

Forbettercontrol,wecanusetheservo.writeMicroseconds(us)function,whichtakestheexactnumberofmicrosecondsasaparameter.Remember,1millisecondequals1,000microseconds.

MoreservosInordertousemorethanoneservo,weneedtodeclaremultipleservoobjects,attachdifferentpinstoeachone,andaddresseachservoindividually.

First,weneedtodeclaretheservoobjects—asmanyasweneed:

//Createservoobjects

ServoServo1,Servo2,Servo3;

Thenweneedtoattacheachobjecttooneservomotor.Remember,everyservomotorusesanindividualpin:

Servo1.attach(servoPin1);



Intheend,wejusthavetoaddresseachservoobjectindividually:

Servo1.write(0);//SetServo1to0degrees

Servo2.write(90);//SetServo2to90degrees

Connection-wise,thegroundsfromtheservosgotoGNDontheArduino,theservopowerto5VorVIN(dependingonthepowerinput),andintheend,eachsignallinehastobeconnectedtoadifferentdigitalpin.Contrarytopopularbelief,servosdon’tneedtobecontrolledbyPWMpins—anydigitalpinwillwork.

ContinuousrotationservosThereisaspecialbreedofservoslabelledascontinuousrotationservos.Whileanormalservogoestoaspecificpositiondependingontheinputsignal,acontinuousrotationservoeitherrotatesclockwiseorcounter-clockwiseataspeedproportionaltothesignal.Forexample,theServo1.write(0)functionwillmaketheservomotorspincounter-clockwiseatfullspeed.TheServo1.write(90)functionwillstopthemotorandServo1.write(180)willturnthemotorclockwiseatfullspeed.

Therearemultipleusesforsuchservos;however,theyarereallyslow.Ifyouarebuildingamicrowaveandneedamotortoturnthefood,thisisyourchoice.Butbecareful,

microwavesaredangerous!

SeealsoAservomotorofferseaseofusewithhighprecisionandpower.However,thereareothermotortypesofferingthesameandtheyevenhavefullcontinuousrotation.TheSteppermotorrecipetalksaboutthemindetail.

SteppermotorWhenweneedprecisionandrepeatability,asteppermotorisalwaysthesolution.Withthewayitisdesigned,asteppercanonlymovefromonesteptothenextandfixinthatposition.Atypicalmotorhas200stepsperrevolution;ifwetellthemotortogo100stepsinonedirection,itwillturnexactly180degrees.Itgetsinterestingwhenweonlytellittogoonestepanditturnsexactly1.8degrees.

Steppermotorsarefoundinprinters,scanners,industrialrobotarms,3Dprinters,andprettymuchineveryprecisionmotiondevice.

Therearetwotypesofsteppermotors:unipolarandbipolar.Unipolarmotorsareeasiertocontrolwhilebipolarmotorsaremorepowerful.

Inthisrecipe,wewillseehowtoconnectaunipolarsteppermotorusingacommonintegratedcircuit.


AnArduinoboardconnectedtoacomputerviaUSB.AbreadboardandjumperwiresAunipolarsteppermotor.AULN2003AorULN2004DarlingtonArrayIntegratedCircuit.JustrememberULN2003AorULN2004;theyarebasicallyseventransistorsstackedtogetherinaconvenientpackage.

WecantypicallybuySteppermotorsfromSparkfun,Pololu,Adafruit,commonelectronicsstores,oreventakethemoutfromoldprinters.

Howtodoit…WeimplementasimplecircuitinwhichweonlyneedtheArduino,theULNIConabreadboard,andtheUnipolarsteppermotor,inthefollowingmanner:

1. ConnecttheArduinoGNDtoalongstriponthebreadboard.2. ConnecttheULN2003ortheULN2004tothecenterofthebreadboard.3. Connectpins1to4—thefirstfourpinsontheleftoftheIC—tofourdigitalpinson

theArduino.4. Thesteppermotorhassixwires.Twoarethecenterofeachwinding.Weneedto

identifythesecenters.Thesimplestwayistotakeamultimeterandusetheresistancemode.Sincethecenterpinisbetweentwoidenticalwindings,ithastogiveanequalresistancewitheitherone.Soifwetestallcablecombinations,whenwefindawirewithequalresistancetotheothertwo,wehavefoundacenter.Whenwefindboth,weconnectthemtogethertopin9ontheIC.

5. WeconnecttheotherfourcablesonthestepperdirectlytotheoutputoftheIC;inthiscase,pins13to16.

6. Nowweneedtoconnectthepowersupply.Ifwepowerthestepperfromthebuilt-in5V,weconnect5Vtothecommonpin—pin9ontheIC.Ifweuseanexternalpowersupply,wecanconnectthepositiveterminalthereorconnectpin9totheVIN,iftheArduinoispoweredfromanexternalpowersupply.

7. Lastly,weconnectgroundtotheIC.Connectthe0Vpin,pin8totheGNDstripwemadeearlierinstep1.

SchematicThisisonepossibleimplementation.Otherpinscanalsobeused.TheCOMpincanbeconnectedto5Voranexternalpowersupply.


CodeThefollowingcodewillspinaunipolarstepper180degreesinonedirectionandthenback:

//IncludetheStepperlibrary

#include<Stepper.h>

//DeclareaSteppermotorwith200steps

//connectedonpins2,3,4,5

//Syntax:stepper1(stepsPerRevolution,pin1,pin2,pin3,pin4)

Stepperstepper1(200,2,3,4,5);

voidsetup()

//SetthespeedofthestepperinRPM

stepper1.setSpeed(60);

voidloop()

//Turnthestepper100stepswhichmeans180degrees

stepper1.step(100);

//Waithalfsecond

delay(500);

//Turnthestepper100stepsback

stepper1.step(-100);

//Waithalfsecond

delay(500);

TipOtherdigitalpinscanbeusedwhendeclaringthesteppermotor.Also,otherspeedscanbetried.However,keepinmindthatsteppermotorsarenotverygoodwithspeed.

Howitworks…SteppermotorsdifferfromnormalDCmotorsinthat,ratherthanjustspinninginonedirectionoranother,theymoveinsmallincrementsinagivendirection.Thesesmallincrementsarecalledsteps.Wecantellasteppertogooneormorestepsinoneparticulardirection.Theyarenotnecessarilyfast,buttheyhavehighprecisionandquitesometorque.Forexample,thepaperfeederonaprinterusesasteppermotor.3DprintersandCNCmachinesusethemforveryhighprecisionandrepeatability.

Luckily,theArduinohasabuilt-inlibrarytocontrolunipolarsteppermotors.Andtheyareveryeasytocontrolindeed.

CodebreakdownThecodedeclaresasteppermotor,selectsaspeed,andmakesitturninbothdirections.

Here,wedeclarethesteppermotor.Thesyntaxrequiresthenumberofstepsofthemotorasthefirstparameterandthenthefourpinstowhichweconnectedthemotor:

Stepperstepper1(200,2,3,4,5);

Anotherimportantstepisdeclaringthespeedatwhichwewantthemotortoturn.If,forexample,wesetaspeedof60RPMasinthiscase,andthemotorhas200steps,itwilltakearound5millisecondstoincrementonestep.Thespeedofthemotorcanbechangedatanytime.


Lastly,tomakethemotormove,weneedtoorderthenumberofstepstoincrement.Ifwefeedanegativenumberofsteps,itwillmoveintheoppositedirection.Notethatthestep()functionwillpausetheexecutionoftheprogramuntilthemotorspinscompletely.If,forexample,weset200stepsataspeedof1RPM,itwilltakeonefullminuteuntiltheArduinowillcontinueexecution.


NoteArduinoassumesthesteppermoveswhileitordersittomove.Thestepperhasnofeedbackcircuit,soifweholdtheshaftofthemotor,theArduinowillbelieveitismovingthoughthesteppermightnotbemoving.

There’smore…TheULN2003AandULN2004integratedcircuitsareveryusefullittledevices,especiallywhenwecontrolunipolarsteppermotors,astheyhaveeverythingbuiltin—thetransistor,thediode,andeverythingelse.However,ifit’sreallyneeded,wecanjustusefourtransistors,fourdiodes,andfourresistorstospinaunipolarmotor.

TransistorunipolarstepperdriverHereisonepossibleimplementationofacustomunipolarstepperdriver.WecanuseanystandardNPNtransistor.Darlingtonpairsarepreferred,suchastheTIP120,TIP121,or2N6045.Rememberthatsteppermotorsusequitealotofcurrent,usuallyintherangeof2–5A,sothechosentransistorhastobeabletohandleit.Hereisonerecommendedimplementation:

IdentifyingthesteppermotortypeTherearemultiplesteppermotortechnologies.Thisisasimpleguideonidentifyingthetype.Afour-cablesteppermotorisusuallybipolar.Withsixcables,itismostprobablyunipolarwherethetwocentercoilcableshavetobeconnectedtogether.Therearesomeversionswithonlyfivecablesthatarealsounipolarandalreadyhavethetwocentercoilsconnectedtogetherinternally.Also,therearesteppermotorswitheightcables,buttheyareincrediblyrare.Theyarealsounipolarandthefourcentercableshavetobeconnectedtogether.

SeealsoFindacomprehensivetutorialonsteppermotorsathttps://learn.adafruit.com/all-about-stepper-motors/what-is-a-stepper-motor

https://learn.adafruit.com/all-about-stepper-motors/what-is-a-stepper-motor

BipolarsteppermotorsUnipolarsteppermotorsareeasytocontrolatthecostoflowefficiencyandpower.Bipolarsteppermotorshavemuchhigherefficiencyandtorque;howevertheyaremuchhardertocontrol.Tofullycontrolone,twoH-bridgesarerequired.LuckilytherearemultipleArduino-compatiblebipolarstepperdriversoutthere.Herewewillexploreafewoptions.

GettingreadyWecancontrolabipolarsteppermotorusingtheArduinoMotorShield.Herearetheingredientsneededforthisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBAnArduinoMotorShieldAbipolarsteppermotor

Howtodoit…Weconnectthesteppermotortotheshieldusingthefollowingsteps:

1. CarefullymounttheArduinoMotorShieldontopoftheArduino.Becarefulnottobendanypins.

2. Identifythetwocoils.Useamultimetertomeasuretheresistancebetweenallthewires.Theoneswithalowresistanceinbetweenarethecoils.

3. ConnectthefourstepperwirestothemainterminaloutputoftheShield.Onecoilgoestoonemotoroutputandtheotheronetotheotheroutput.

Here’showitshouldlook:

CodeThefollowingcodewillspinthesteppermotor100stepsinonedirectionand100stepsintheother:

//IncludetheStepperlibrary

#include<Stepper.h>

//Declaretheusedpins

intdirA=12;

intdirB=13;

intpwmA=3;

intpwmB=11;

//DeclareaSteppermotorwith200steps

Stepperstepper1(200,dirA,dirB);

voidsetup()

//PWMpinsrequiredeclarationwhenusedasDigital

pinMode(pwmA,OUTPUT);

pinMode(pwmB,OUTPUT);

//SetPWMpinsasalwaysHIGH

digitalWrite(pwmA,HIGH);

digitalWrite(pwmB,HIGH);

//Setsteppermotorspeed


voidloop()

//Turnthestepper100stepswhichmeans180degrees

stepper1.step(100);

//Waithalfsecond

delay(500);

//Turnthestepper100stepsback


//Waithalfsecond

delay(500);

Howitworks…Abipolarsteppermotoronlyhastwocoilswithnocentertap,incontrasttoaunipolardesign.Thismeansthatthecoilshavetobeturnedoninbothdirectionsatdifferenttimes.Asacomparison,abipolarstepperisexactlyliketwoDCmotorswhichalwayshavetobecontrolledintheoppositedirectionatthesametime.Whenonecoilisexcitedinonedirection,theotheronehastobereversed.Byshiftingthis,wegenerateapulsewhichmakesthestepperspin.

CodebreakdownOnlythedifferencesfromthepreviousunipolarstepperrecipewillbeexplainedhere.Thecodewilldothesame—itwillturnthemotor100stepsinonedirectionandtheninreverse.

WeonlyneedtodeclarethetwodirectionpinsoftheArduinoMotorShield.AsexplainedintheSpinningmotorsbothwaysrecipe,thedirectionpinsetswhichdirectionthecoilwillbeexcitedin.

Stepperstepper1(200,dirA,dirB);

ThetwoPWMpinsselecthowmuchpowerweattributetothecoils.However,asthisisastepper,wealwayswantfullpower;sowewillsimplifyanddirectlysetthePWMpinsalwaysasHIGH:

//PWMpinsrequiredeclarationwhenusedasDigital

pinMode(pwmA,OUTPUT);

pinMode(pwmB,OUTPUT);

//SetPWMpinsasalwaysHIGH

digitalWrite(pwmA,HIGH);

digitalWrite(pwmB,HIGH);

There’smore…Bipolarsteppersarethemostcommonbreed.Theyarehighlyefficientandpowerfulatthepriceofhavingcomplexdrivers.Andtherearealotofdriversforthem,waytoomanytobecovered.Eachonehasadifferentinputtype.Thebestadviceistocheckafewwell-knownstepperdriverproducerssuchasSparkfun,Pololu,orAdafruit.Theyofferguidesforeachoftheirstepperdrivers,andtheseareusuallyveryeasytouse.

BrushlessmotorsLet’stalkalittleabouttheedgeofelectricmotors.Atypicalelectricmotorhasarotor,astator,andbrushes.Thebrushestransmittheelectricalcurrenttotherotor,thusspinningthemotor.Thedrawbackofthebrushesisthattheycontinuouslyrubonthecommutator.Asananalogy,imaginedrivingacarwiththebreakspartiallypressed.That’swhatthebrushesdotothemotor.However,thereisasolution!

Brushlessmotors,asthenameimplies,donothaveanybrushes.Thismeanstheyaremuchmoreefficient,theylastlonger,andtheyaremorepowerful.Butofcoursethereisadrawback;theyrequirecomplicatedcontrol.Luckily,brushlessmotorshavefoundtheirwayintotheremote-controlledworldandwecannowfindcheapandusefulbrushlessmotorsandbrushlessmotorcontrollersorElectronicSpeedControl(ESC).

GettingreadyTomakethisrecipework,wewillneedafewbasicthings:

AnArduinoboardconnectedtoacomputerviaUSB.AnRCbrushlessmotor,whichisavailableintwotypes—inrunnersandoutrunners.InrunnerslooksimilartoanormalDCmotorbuttheyrunatveryhighspeeds,whileoutrunnersarewiderandshorter,and—waitforit—theircaserotates,notthecenterofthemotor.Isn’tthatstrange?WecanfindbrushlessmotorsinanyRCmodelstore.SomefamousstorestheyaresoldinareConradforEuropeandHobbykingforUSAandworldwide.AbrushlessmotordriverorESC,Careful!ThereareESCsforstandardDCmotors—notmany—butthereare.AquickwaytodetermineifanESCisforbrushlessmotors(otherthanreadingthedescription)istocheckhowmanyoutputcablesithas.Ifithasthreecables,itisforbrushlessmotors.Otherwise,keepsearching.Theycanbefoundatanystorethatsellsbrushlessmotors.

Howtodoit…AbrushlessmotordriverusesthesamestandardconnectorandsignalasanRCservo.Herearethestepstoconnecteverything:

1. ConnectthethreewiresofthemotortothethreeoutputwiresoftheESC.2. TheESCneedspower,andbrushlessmotorsareveryhungry!Itisrecommendedto

usealithium-ionorlithiumpolymerbattery,designedforhighloads,inordertocontrolsuchmotors.Don’tbemisledbythe9Vbatteryinthegraphic.

3. Lastly,connectthecontrolwiretotheArduino.Remember,ESCsusethesamestandardconnectorandsignalasanyRCservo.Wemayomitthered,5Vconnection,asESCsarepoweredbythebattery.AneatthingtorememberisthatmostESCshaveinternal5Vregulators,calledBatteryEliminationCircuit(BEC).ThismeanswecanpowerupArduinofromtheESC,byconnectingthe5VoutputoftheESCtothe5VlineontheArduino.

Here’showitshouldlook:

CodeThefollowingcodewillarmtheESCandthenstartthemotorfor5seconds,stopitforanotherfive,anddothatagainandagainandagain:

//IncludetheServolibrary

#include<Servo.h>

//DeclaretheServopinfortheESC

intservoPin=3;

//Createaservoobject

ServoServo1;

voidsetup()

//Weneedtoattachtheservototheusedpinnumber


//ArmtheESC,apulsebetween0.7-1msusuallywilldo

Servo1.writeMicroseconds(700);

delay(3000);//LeavesometimetoarmtheESC

voidloop()

//Startthemotoraquarterspeed

Servo1.write(64);

delay(5000);//Wait5seconds

//Stopthemotorfor5seconds

Servo1.write(0);

delay(5000);

Howitworks…Brushlessmotorsandbrushlessmotorcontrolarequiteadvancedtopics.TakealookattheSeealsosectionformoredetailsonthese.However,wedon’treallyneedtounderstandhowtheyworkinordertousethem.That’swhatArduino’sallabout:makingthingssimple.

BrushlessmotorcontrollersorESCsusethesamestandardasanRCservo.Ifweapplyapulsewithadurationof1millisecond,or0degrees,intheServo.write()function,thecontrollerwillstopthemotor.Apulseof2milliseconds,or180degrees,willresultinmaximumpower.Valuesinbetweenwillresultinmotorspeedsinbetween.

Becausebrushlessmotorsarequitepowerful,everyESChastobefirstarmedinordertoallowthemotortodoanything.Todothis,wesendapulsewithaverylowduration,somewherebetween0.7–1millisecondforaround3seconds.Whenthecontrollerarmsthemotor,itwillstartbuzzingafewtimes.Afterthat,allthepowercanbeunleashed.

CodebreakdownThecodeisverysimilartotheservomotorcode,asbothusethesamestandard.Onedifferenceisinthearming,asshownhere:

voidsetup()


//ArmtheESC

Servo1.writeMicroseconds(700);

delay(3000);//LeavesometimetoarmtheESC

Weneedtooutputashortpulseforaround3secondsinordertoarmthemotor.WedothisusingtheServo1.writeMicroseconds(700)function,whichoutputsa700-microsecondpulse.

Oncethemotorisarmed,wecancontrolitusingstandardServo1.write()commands.

SeealsoTounderstandhowabrushlessmotorworks,finedagreatexplanationinthisvideoathttps://www.youtube.com/watch?v=bCEiOnuODac

https://www.youtube.com/watch?v=bCEiOnuODac

Chapter6.MoreOutputDevicesInthischapter,wewillcoverthefollowingtopics:

CreatingsoundTransistordriverRelaydriverOptocouplers/OptoisolatorsMoreoutputs–shiftregisters

IntroductionInthischapter,wewilllookoversomemoregeneralapplicationsofArduinooutputs.Sometimes,wedon’thaveenoughdigitalpinsforourproject,butwecanextendthatusingshiftregisters!Also,wecantrymakingsomemusicbyjustaddingaspeaker.ButwhatifweneedtoconnectanACcircuittotheArduino?Alltheanswers,andmore,canbefoundinthischapter.

CreatingsoundSoundisaverypowerfuloutputthatisusuallytakenforgranted.WeseethingssuchasLEDs,wefeelthingssuchasmotors,butwealsohear.ArduinohasanicelittlelibrarycalledTonethataidsingeneratingsoundsatspecificfrequencies.Forpeoplepassionateaboutmusic,wecanactuallyplaymonophonicsongsforthemostgeekishsoundpossible.

GettingreadyFollowingaretheingredientsrequiredtoexecutethisrecipe:

AnArduinoboardconnectedtoacomputerviaUSB.Asmall8-ohmspeaker.A120-ohmresistor;largervaluesalsowork,butthesoundwillbelesspowerful.Don’tuseresistorsunder100ohms.

Howtodoit…FollowthesestepstoconnectaspeakertotheArduino:

1. ConnectoneterminalofthespeakerdirectlyintotheGNDoftheArduino.2. Usinga120-ohmresistorinseries,connecttheotherterminaltoanavailabledigital

pin;inthisexample,pin12.

SchematicThisisonepossibleimplementationonthe13thdigitalpin.Otherdigitalpinscanalsobeused.

Hereisanexampleofhowtowireitintheair.Nobreadboardneededhere:

CodeThefollowingcodewillplaythefamousSolfeggio—DoReMiFaSolLaTi:

//Definingthe8frequenciesthatmakethe7notesandonerepetitionin

theSolfeggio

#defineDo131

#defineRe147

#defineMi165

#defineFa175

#defineSol196

#defineLa220

#defineTi247

#defineDo2262

//Definingthepinconnectedtothespeaker

inttonePin=13;

voidsetup()

//Tonepinsdon'tneedtobedeclared

voidloop()

//Do

tone(tonePin,Do,125);

delay(125);

//Re

tone(tonePin,Re,125);

delay(125);

//Mi

tone(tonePin,Mi,125);

delay(125);

//Fa

tone(tonePin,Fa,125);

delay(125);

//Sol

tone(tonePin,Sol,125);

delay(125);

//La

tone(tonePin,La,125);

delay(125);

//Ti

tone(tonePin,Ti,125);

delay(125);

//HigherDo

tone(tonePin,Do2,125);

delay(125);

TipIfthespeakerisconnectedtoadifferentpin,simplychangethetonePinvaluetothevalueofthepinthathasbeenused.

Howitworks…Thetone()functionisveryeasytouse.Itgeneratesasquarewaveof50%dutycycleatthespecifiedfrequency.Whatdoesthatmean?ItmeansthattheusedpinwillbeHIGHhalfthetimeandLOWhalfthetime.Itwillchangebetweenthesetwostatesatthespecifiedfrequency.

Everymusicalnotehasaspecificfrequency;inourcase,Do,whichisaC3,hasthefrequencyof131Hz.Thiswavewillmakethespeakervibrateandgeneratesound.ArduinocanonlysupportmonophonicsoundusingtheTonefunction.Thismeansitcanonlygenerateonenoteatatime.Still,itisquiteusefulandfun.Nowontothecodebreakdown!

CodebreakdownThecodesimplyusesthebuilt-intonefunction,whichhasthefollowingparameters:

tone(pin,frequency,duration)

First,wedeclaretheusedpin:

inttonePin=13;

Then,inloop(),wesimplyusetheTonefunctionforeachnote,oneaftertheother,withadurationof125millisecondsonthedeclaredtonePin:

voidloop()

//Do

tone(tonePin,Do,125);

delay(125);

…

TipWeneedtomakesurewearenotcallingthetone()functionagaininthefollowing125milliseconds,asitwillchangethefrequency.

Itwouldbeeasiertodeclareanarraycontainingallthenotesanduseaforlooptoplaythemall:

//Arrayapproach

intsolfege[]=Do,Re,Mi,Fa,Sol,La,Ti,Do2;

for(inti=0;i<8;i++)

tone(tonePin,solfege[i],125);

delay(125);

TipThetone()functioncannotplaysoundsunder31Hz,andonboardsotherthantheMega,itwillinterferewithPWMpins3and11.

There’smore…ThereisalittlemorefunctionalityintheTonefunction.Hereareafewmorethingswecando:

TonewithnodurationToneonmultiplepins

Let’sseewhattheyare.

TonewithnodurationThetone()functionhastwovariants.Theoneweusedplaysthenoteuntilthetimeexpiresoruntilweusethetone()functionagain,whichevercomesfirst.However,thereisasimplervariantthatdoesn’thavethedurationparameter;itonlycontainsthepinandthefrequency.Whenweusethatfunction,thenotewillstartplayingcontinuously.Inordertostopthenote,weneedtousethenoTone(tonepin)function.Hereisanexample:

tone(tonePin,Do);

delay(100);

noTone(tonePin);

ThenoTone()functionhasonlyoneparameter:thepinnumber.Weneedtousethesamepinnumberastheoneusedinourtone()function;otherwise,itwillnotstopthesoundanditmightinterferewithourcode.

ToneonmultiplepinsTheTonefunctioncanonlyplayonenoteononepinatatime.However,wecanstopplayingonapinandbeginplayingonanotherone.Inthefollowingexample,weplayDoonthe12thpinandthenReonthe13thpin.This,ofcourse,requirestwospeakers:

//Doonpin12

tone(12,Do,125);

delay(125);

noTone(12);

//Reonpin13

tone(13,Re,125);

delay(125);

noTone(13);

SeealsoForareferenceforthefrequenciesofeachnote,visithttp://www.phy.mtu.edu/~suits/notefreqs.html.RememberthatArduinocannotplayfrequenciesunder31Hz(C1isthefirstnoteitcanplay).Wonderingwhyitcannotplaylessthan31Hz?Findoutathttp://forum.arduino.cc/index.php?topic=28055.0.Ifwewanttouseamorepowerfulspeaker,weshouldamplifythelimitedpowerontheArduinodigitalpinsusingatransistordriver.MoredetailscanbefoundintheTransistordriverrecipe.

http://www.phy.mtu.edu/~suits/notefreqs.html

http://forum.arduino.cc/index.php?topic=28055.0

TransistordriverEachArduinodigitalpincanoutputalimitedamountofcurrent,anabsolutemaximumof40mA.ThisisenoughtopoweranLED,asmallbuzzerspeaker,ormaybeasmallvibratingmotor.However,weneedmorecurrentforourapplicationsmostofthetime.

Usingatransistordriver,wecaneasilypowerupmoredemandingloads.Here,wewillquicklyexplorehowtobuildageneraltransistordriver.

GettingreadyFollowingaretheingredientsforthisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBAresistorbetween220and4,700ohmAstandardNPNtransistor(BC547,2N3904,N2222A,TIP120)Astandarddiode(1N4148,1N4001,1N4007)

Howtodoit…FollowthesestepstoconnectanexternalloadtotheArduinousinganNPNtransistor:

1. Connectoneoftheterminalsoftheloadto5VorVIN.Ifweareusingaloadthatrequiresavoltagehigherthan5VorhighercurrentthantheArduino5Vcanprovide(around500mA),wecanusetheVINpinandconnectanexternalpowersupplyorbatterytotheArduinopowerconnector.

2. Checkthedatasheetofthetransistor.Weneedtocorrectlyidentifythebase,collector,andemitterpins.

3. ConnecttheemitterpintoGND.4. ConnectthebasepinofthetransistortoonedigitalpinoftheArduino,usinga

resistorbetween220and4,700ohm.5. Connecttheotherfreeterminaloftheloadtothecollector.6. Forsecurityreasons,connectadiodeacrosstheloadresistor.Thediodehastopoint

fromthecollectortothepowersupply.Thiswillprotectthetransistorfromspikesgeneratedbyanyinductiveloadssuchasamotororarelay.

SchematicThisisonepossibleimplementationonthe9thdigitalpin.Otherdigitalpinscanalsobeused.

Tip

Iftheusedloadispolarized(itcontainsapositiveandanegativeterminal),connectthenegativeterminaltothecollectorontheNPNtransistorandthepositiveterminaltothepowersupplythathasbeenused(5VorVIN).

CodeThefollowingcodewillturntheloadonandoffatanintervalof500milliseconds:

//Declaretheusedpin

intloadPin=9;

voidsetup()

//Declaretheusedpinasoutput

pinMode(loadPin,OUTPUT);

voidloop()

//TurnontheLoad

digitalWrite(loadPin,HIGH);

delay(500);

//500mslater,turnofftheLoad

digitalWrite(loadPin,LOW);

delay(500);

TipIftheloadisconnectedtoadifferentpin,simplychangetheloadPinvaluetothevalueofthepinthathasbeenused.

Howitworks…WhenwesetthedigitalpinasHIGH,usingthedigitalWrite()command,thetransistorwillgetcurrentinthebase.WhenanNPNtransistorreceivesenoughcurrentinthebase,itwillallowcurrenttopassfromthecollectortotheemitter,actinglikeaclosedswitch.Whenthereisnocurrentatthebase,thecollectorandemitterpinswillactlikeopenedswitches.Thisisasimplejelly-beamexplanationofhowatransistorworks.Thefollowinggraphicfurtherexplainstheconcept.Asmallcurrentfromthebasetotheemitterwillallowalargecurrenttopassfromthecollectortotheemitter.

SeealsoThiswasaverysimpleintroductiontohowtouseNPNtransistorsforgeneralpurposes.Formoredetails,takealookatthefollowingrecipes:

TheControllingmotorswithtransistorsrecipeinChapter5,MotorControlTheControllingspeedwithPWMrecipeinChapter5,MotorControl

RelaydriverSometimeswejustneedtoeasilyswitchonandoffanexternalload.MaybetheloadispoweredbyACcurrent;maybeit’sveryhighvoltagethattheArduinocan’thandle.Atransistorisusuallyusedtopoweronsuchthings;however,transistorsarequitecomplicated.Thereisasimplerdevicethatcanjustswitchonoroff,atslowspeeds,anexternalload.Thisdeviceisknownasarelay.

GettingreadyToexecutethisrecipe,wewillneedthefollowingingredients:

AnArduinoboardconnectedtoacomputerviaUSBAgeneral5VrelayAresistorbetween220ohmand4700ohmAstandardNPNtransistor(BC547,2N3904,N2222A,TIP120)Astandarddiode(1N4148,1N4001,1N4007)

Howtodoit…Therelaycoilunfortunatelyusesquitealotofcurrent.TopreventthisfromburningtheArduinopins,wewilluseatransistordrivertostarttherelay:

1. Connectoneoftheterminalsoftherelaycoiltothe5VpinontheArduino.2. Checkthedatasheetofthetransistor.Weneedtocorrectlyidentifythebase,

collector,andemitterpins.3. ConnecttheemitterpintoGND.4. ConnectthebasepinofthetransistortoonedigitalpinoftheArduinousinga

resistorbetween220and4,700ohm.5. Connecttheotherfreeterminaloftherelaycoiltothecollector.6. Therelayisaninductiveload.Whenweturnitoff,itcancreatehighvoltagespikes

thatmightburnthetransistor.Toprotectagainstthis,connectadiodefromthecollectorto5V,pointingtothe5Vpin.

SchematicThisisonepossibleimplementation.Otherdigitalpinscanalsobeused.

CodeInthisrecipe,weusethesamecodefromthepreviousrecipe,Transistordriver,whichsimplyturnstherelayonandoffevery500milliseconds:

//Declaretheusedpin

intrelayPin=9;

voidsetup()


pinMode(relayPin,OUTPUT);

voidloop()

//TurnontheRelay

digitalWrite(relayPin,HIGH);

delay(3000);

//3secondslater,turnofftheRelay

digitalWrite(relayPin,LOW);

delay(3000);

TipIfthetransistorisconnectedtoadifferentpin,simplychangetherelayPinvaluetothevalueofthepinthathasbeenused.

Howitworks…Arelayisnothingmorethanasimpleswitchoperatedbycurrent.Whenweapplyenoughcurrenttothecoilpins,itwillgenerateanelectromagneticfieldthatwillclosetheswitch.Whenwestopapplyingthecurrent,therelaywillreleasetheswitchbacktotheopenposition.

EachtimewewriteaHIGHtothedigitalpin,thetransistorswitchesthecoilonandtheinternalswitchintherelaycloses.Now,electricitywillpassbetweenthetwoconnectedoutputterminalsoftherelay,andourloadwillreceivecurrent.

RelaysareverygoodforswitchingACcurrents.Also,theloadcircuitandtheArduinocontrolcircuitsarecompletelyindependent,whichisverysafe.Anotherveryimportantfeatureofanyrelayisthatitcanhandlecurrentinanydirection;thisiswhatmakesithandleACcurrents.

TipThisrecipeusesatransistordriverinordertostarttherelaycoil.Formoredetailsonhowthetransistorworks,pleasechecktheTransistordriverrecipeinthischapter.

Optocouplers/OptoisolatorsTherearetimeswhenwewanttocompletelyinsulatetwocircuits,butstillpasssignalsbetweenthem.Wecandothatwitharelay.However,arelayisveryslow.Ittakesaround10–30millisecondstoswitchonoroff.Wecan’tdoPWMorcommunicationsatthispace.However,thereisacleverIntegratedCircuit(IC),calledeithertheoptocouplerortheoptoisolator,whichdoesexactlythat.

Inthisrecipe,wewilluseanoptocouplertoswitchonanLEDwithacompletelydifferentcircuitthathasitsownindependentpowersupply.


AnArduinoboardconnectedtoacomputerviaUSBTwogeneral220-ohmto1,000-ohmresistorsAbreadboardA1.5–3.0Vbattery,preferablywithwireterminalsAgeneralLEDAgeneraloptocoupler/optoisolatorsuchastheTLP621,4N35,orLTV-816

Howtodoit…FollowingarethegeneralstepstoconnectanoptocouplertotheArduinoandthentoconnectanothercircuitcontaininganLED,resistor,andpowersupplytotheoptocoupleroutput:

1. Connecttheanode(positiveterminaloftheLED)oftheoptocouplertoadigitalpinontheArduino,usingastandard220–1,000ohmresistor.

2. Connectthecathode(LEDnegativeterminal)oftheoptocouplertoGND.3. Nowtheoptocouplerisconnected.Weneedtoconnectsomethingtoitsoutput.In

thiscase,wewillconnectanLEDusingaresistorandexternalpowersupply.4. ConnectthecathodeoftheLED(negativeterminal)tothecollectoroutputonthe

optocoupler.5. Connecttheemitteroutputoftheoptocouplertothenegativeterminalofthebattery.6. Useastandard220–1,000ohmresistortoconnecttheanodetothepositiveterminal

ofthebattery.

SchematicThisisatypicalimplementationusingdigitalpin9:

Andonthebreadboard,thisworksjustfine:

CodeWeareusingthesamecodefromthepreviousrecipe,Transistordriver,whichsimplyturnstheLEDonandoffusingtheoptocouplerevery500milliseconds:

//Declaretheusedpin

intoptoPin=9;

voidsetup()


pinMode(optoPin,OUTPUT);

voidloop()

//Turnontheoptocoupler

digitalWrite(optoPin,HIGH);

delay(500);

//500mslater,turnofftheoptocoupler

digitalWrite(optoPin,LOW);

delay(500);

TipIftheoptocouplerisconnectedtoanotherdigitalpin,simplychangethevalueofoptoPintothevalueofthedigitalpinthathasbeenused.

Howitworks…AnoptocouplerismadeofanLEDandaphototransistor.Itisacleverlittledevice.WhenweturnontheLED,itlightsupthetransistor.Thedifferencebetweenthisphototransistorandatypicaltransistoristhatthebaseislight-sensitive.Whenlighthitsit,itallowscurrenttopassfromthecollectortotheemitter.Thismakestheinputandtheoutputcompletelyindependent.Operation-wise,itworksjustlikeatransistorwithanextracathodepinfortheLEDinput,whichmustbeconnectedtothesamegroundastheArduino.

Moreoutputs–shiftregistersArduinohasalimitednumberofdigitalpins.Sometimes,wewanttobuildprojectsthatrequiremorepinsthanwehaveavailableonourboards.Thisisactuallyacommonprobleminelectronics,whichledtotheinventionoftheshiftregister.

Ashiftregistertransformsserialdatatoparalleloutput.Basically,wetelltheregisterwhatvaluetosetforeachoutputpinithas.If,forexample,ithaseightoutputpins,wewillfirstsaythevalueofthe8thpinandthenthe7thpinuntilwegettothefirstone.TheadvantageisthatweareusingaroundthreeArduinopinstogeteightorevensixteen,whichisveryconvenient.

Therearealotofshiftregistersavailableandtheymostlyworkthesame.Forsimplicity,wewillonlyaddressthecommonlyavailable74HC595tocontroleightLEDswithjustthreepins.

GettingreadyForthisrecipe,wewillrequirethefollowingingredients:

AnArduinoboardconnectedtoacomputerviaUSBA74HC595shiftregisterAbreadboardalongwithjumperwires8LEDs8commonresistorsbetween220–1,000ohm

Howtodoit…Thisisquiteabigcircuit,andputtingittogetherrequiressomepatience:

1. Pluginthe74HC595inthecenterofthebreadboardsothatitspinsgooneachside.Beconsideratewithspace;alotwillbeused.It’sbettertomountitononesideofthebreadboard.

2. MounttheeightLEDsandconnecta220–1,000ohmseriesresistortoeach.3. Connectthecathode(negativeterminal)ofeachLEDtoacommonpointandconnect

thatpointtotheArduinoGND.4. ConnecttheGNDoftheshiftregistertotheArduinoGND.AlsoconnectVCCand

MRtogethertotheArduino5Vpin.5. ConnecteachindividualresistortooneoftheoutputQ0,Q1,Q2,uptoQ7pins.

SchematicThisisonepossibleimplementationofthecircuit.Otherpinscanbechosentocommunicatewiththeshiftregister:

Hereisanexampleofhowtowireitonabreadboard:

CodeThefollowingcodewillmakeaflowillusionpatternontheLEDs:

//Declaringthe3usedpinstoconnecttotheRegister

intDS=8;

intST_CP=10;

intSH_CP=11;

//WemakeanArraywiththevaluesofeachpinoutputonthe

//ShiftRegister

booleanout[8];

voidsetup()

//Setthepinsasoutputs

pinMode(DS,OUTPUT);//Pinfortheactualdata

pinMode(ST_CP,OUTPUT);//Clockpin

pinMode(SH_CP,OUTPUT);//Latchpin

voidwritePins()

//WefirstsettheLatchPinLOW

digitalWrite(SH_CP,LOW);

//Thenwewriteeachbitindividually


digitalWrite(ST_CP,LOW);

digitalWrite(DS,out[i]);

digitalWrite(ST_CP,HIGH);

//Latchthepinback

digitalWrite(SH_CP,HIGH);

voidloop()

//WewillmanuallymakeeachEVENoutputHIGH

out[0]=HIGH;out[1]=LOW;




//WritetotheShiftRegister

writePins();

delay(300);

//AndtheneachODDoutputHIGH

out[0]=LOW;out[1]=HIGH;




writePins();

delay(300);

Howitworks…Theshiftregisterhasaninputpintowhichwesendthevaluesoftheoutputs.Forexample,onashiftregisterwithfouroutputpins—Q0,Q1,Q2,andQ3—ifwesendonthedatapininsuccession:1,0,1,0,itwillmakeQ0high,Q1low,Q2high,andQ3low.

However,wewanttobeabletowritewithoutaffectingthecurrentoutputoftheshiftregister,andafterwefinishwritingeveryoutput,wewanttomaketheregisterapplythenewvaluestoitsoutputpins.Forthisweusethelatchpin.WhenwegetthepinatLOW,inourcase,itwillnotchangethecurrentoutputvaluesuntilweputthepinatHIGHagain.Also,itneedsawayofknowingwhenwesenda1ora0;itneedsaclocktomakesureitreadseachbitattherightinterval.Forthat,weusetheclockpin.

CodebreakdownFirst,wehavetodeclarethethreepinsthathavebeenused:

intDS=8;

intST_CP=10;

intSH_CP=11;

ThenwemakeanarraycontainingtheoutputvaluesLOWorHIGHofeachshiftregisterpin:

booleanout[8];

Now,weneedtomakeasimplefunctionthatwritesthevaluestotheshiftregister.Insideit,wefirstlatchthepin:

digitalWrite(SH_CP,LOW);

Followingthis,weneedtogivetheclocktotheregisterandinputonebitatatime.Wedothisinaforloop.Weneedtogotheoppositewayinthearray,astheregistertakesthevaluesinreverse:


digitalWrite(ST_CP,LOW);

digitalWrite(DS,out[i]);

digitalWrite(ST_CP,HIGH);

Attheend,wesimplylatchbacktheSH_CPpin:

digitalWrite(SH_CP,HIGH);

Inloop(),weassignHIGHandLOWvaluestoeachoutputandthenweuseourWritePins()functiontowritethosevalues:





//WritetotheShiftRegister

writePins(

Chapter7.DigitalCommunicationwithArduinoInthischapter,wewillcoverthefollowingrecipes:

SerialoutputControllingtheArduinooverserialSoftwareserialandUARTbetweenArduinosWirelessserialI2CbetweenArduinosSDcardsLCDcharacterdisplaysEthernet

IntroductionArduinoisnotaloneintheuniverse;itcanusedifferentdigitalcommunicationprotocolstotalkwithquiteafewothersystems.It’soneofthegreatfeaturesoftheplatform;ithasallofthestandardprotocolsbuiltin,allowingittocommunicatewiththousandsofdifferentdevices.

Digitalcommunicationhasnumerousadvantages.Itislesssusceptibletonoisethananalogcommunication,anditusuallyonlyrequirestwolinestocommunicatetohundredsofdevices.Thisallowscommunicationwiththecomputer,withothermicrocontrollerssuchastheArduino,withtheInternet,andevenpagestostoredata.

SerialoutputThisisthedefaultfordebuggingandcommunicationintheArduinoworld.WheneverwewanttodeterminewhatishappeninginArduino,howasensorisperformingorjustgeneralcodedebugging,wecanusetheserialoutputfunctionstowriteamessagetothecomputer.

Here,wewillexplorethebasicsfollowedbyafewtipsandtricksonhowtowritedifferenttypesofdata.AnimportantthingaboutserialcommunicationonArduinoisthatitcanonlybedonebetweentwodevices.Itisnotpossibletohavethreeormoredevicesonthesameserialconnection.

GettingreadyJustoneingredientisneededforthisrecipe—anArduinoboardconnectedtoacomputerviaUSB.

Howtodoit…WejustneedtoconnecttheArduinotothecomputerandbeginprogramming.

ThefollowingcodewillprinthalfaChristmastreeintheserialmonitorandthenthevaluesoftwoanalogports,providingthemostcommontypesofserialoutputencounteredonArduino:

voidsetup()

//InitializetheSerialcommunicationwitha9600baudrate

Serial.begin(9600);

voidloop()

//PrintahalfChristmastree


for(intj=0;j<i;j++)

Serial.print("*");

Serial.println();

//Printthetrunkofthehalftree

Serial.println("=");

//Leaveanemptyspace

Serial.println("");

//ReadthevalueofA0andprintit



//Simplerwayofprintingavalue


//Leaveanemptyspace

Serial.println("");

//Adelaytonotoverflowthebufferandkeeptheterminalclean

delay(500);

Ifeverythingworksout,weshouldgetthefollowingoutputintheserialmonitor:

*

**

***

****

*****

******

*******

********

=

299

296

Howitworks…Wheneverwewanttowritesomethingtothecomputer,weusethebuilt-inUSBconnection.However,themicrocontrollerinsidetheArduinousesaUARTconnection,whichispassedthroughaUART-USBconverter.ThiscreatestheconnectionbetweenthecomputerandArduino.Wewillseehowthisworksinthefollowingsubsection.

CodebreakdownThefirstthingweneedtodoisopenaserialconnection.Weusuallydothisinthesetup()functionaswekeepitopenforever.TheSerial.begin(val)functionstartstheconnection.Thevalargumentisthespeedoftheconnection.Bothdevicesneedtobesettothesamespeed,whichiscalledthebaudrate.TosettherateonthePCside,usetheboxontheserialmonitorwindowinArduino.

Intheloop()function,wefirstprintthehalfChristmastree.WeusetheSerial.print("*")functiontoprintoneasteriskcharacter.Whenwefinisharow,wecreateanewoneusingprintln();.

Afterthis,wereadavaluefromtheanalogportandprintitontheserialport:



WereadthevalueoftheA0portinthevalvariableandprintit,goingtoanewlineeachtime.Inthenextline,weuseamoreelegantwayofprintingoutthevalueontheanalogportA1:


Asapractice,trytomakethefullChristmastreeusingforloops.Onlythencanyoucallyourselfamasterintheserialterminal.

SeealsoItishighlyrecommendedtocheckthefollowingrecipesforpropermotorcontrol:

TheControllingtheArduinooverserialrecipe

ControllingtheArduinooverserialIntheSerialoutputrecipe,we’veseenhoweasyitistoprintsomedatafromArduinotothecomputer.However,thiscanworktheotherway.IntheserialmonitorwindowintheArduinoIDE,wecanwriteastringandsendittoArduino.

Here,youwilllearnwhattodowiththatstringandhowyoucanuseittocontrolthings.

GettingreadyThereisjustoneingredientneededtoimplementthisrecipe—anArduinoboardconnectedtoacomputerviaUSB.

Howtodoit…ConnectArduinotothecomputersothatwecanstartprogrammingit.Thefollowingcodewillstartthebuilt-inLEDwhenitreceivesan'a'.ItwillstoptheLEDwhenitreceivesan'x',andwillblinkitforaspecifiedamountoftimewhenitreceives'b'followedbyanumberfrom1to9,suchas'b4':

intled=13;

voidsetup()

pinMode(led,OUTPUT);

Serial.begin(9600);

voidloop()

if(Serial.available())

charcom=Serial.read();

//Actaccordingtothevaluereceived

if(com=='x')

//StoptheLED

digitalWrite(led,LOW);

elseif(com=='a')

//StarttheLED

digitalWrite(led,HIGH);

elseif(com=='b')

//Blinkwithadelaycorrespondingtothevaluereceivedafter'b'

if(Serial.peek()>'0'&&Serial.peek()<='9')

digitalWrite(led,HIGH);

delay((Serial.read()-48)*100);//48isASCIIfor'0'


Howitworks…Let’sgothrougheachsection.Firstofall,weneedtosetuptheLEDpinasoutputandbegintheserialconnectionwithabaudrateof9,600bitspersecond:

voidsetup()

pinMode(led,OUTPUT);

Serial.begin(9600);

Intheloop()function,wewanttoreceivethecommandsfromthecomputer.Arduinohasaserialbufferinwhichallreceivedcharactersarestored.Thisisindependentofthecodewehaverunning.First,let’scheckifthereisanythinginthatbuffer,otherwisethere’snopointindoinganything:


Nowweneedtoreadonecharacterfromthebuffer.EachtimeweusetheSerial.read()function,weerasethecharacterfromthebuffer.So,thebestthingwillbetostoreitinatemporaryvariable.Sincewearereadingcharacters,wewillusethecharvariablethatonlytakes8bitsofmemory:

charcom=Serial.read();

Everythinggetssimplefromthispointon;therearejustafewthingstoremember.Wecancomparecharacters,allofthembeingpartoftheASCIIcode.TakealookattheSeealsosectionofthisrecipeforaguideonASCII.Thefollowingifclausewilltriggerwhenthereceivedcharacterisan'x'andwillstoptheLED:

if(com=='x')


It’simportanttorememberthat,justlikeanyothercommunicationmethod,serialcommunicationissusceptibletonoise.Thisshouldalwaysbetakenintoaccountwhenprogramming.Cascadingifclausesisagoodstrategy.Wheneverwedesignsuchaninterpreterforthereceivedcharacters,weshouldalwaysmakesureweonlytriggerforthecharacterswewant;otherwise,somenoisecancorruptthingsatanytime.

Finally,wemaketheLEDblinkforatimeequalto100millisecondsmultipliedbythecharacterreceivedafter'b'.The(Serial.read()-48)*100)formulareadsacharacterandsubtracts48.TheSerial.read()functionreturnstheASCIIequivalent,andinASCII,0correspondsto48,1correspondsto49,andsoon.Basically,thisconvertsthecharactertoadecimalvalueandthenmultiplesitto100.

WeusetheSerial.peek()functiontoreadacharacterfromthebufferwithoutremovingit.Ifwewanttoremoveit,weusetheSerial.read()function.RememberthatSerial.peek()willalwaysreturnthesamecharacterifnoSerial.read()functionisused.

There’smore…Serialcommunicationisahugesubjectingeneral.Hereareafewmoretipsthatshouldbeuseful.

ArduinoMegaThereareafewArduinoplatformsthathavemorethanoneserial/UARTconnection.Inthosecases,wewon’tbeaddressingusingSerial.read(),Serial.print(),andsoon.Forthem,wewillbeusingSerial1insteadofjustSerial.

Forexample,Serial1.begin(9600)willstartthefirstserialportwiththebaudrateof9600.OnanArduinoplatformwithmultipleserialconnections,Serial1isusuallytheoneconnectedtotheUSBport.OntheArduinoYùn,however,wecanuseSerial.begin()foraUSBconnection.

TransmittingvaluestoArduinoTherearetimeswhenwewanttosendavaluefromthecomputertotheArduino.Let’sdesignasmallsystemthatsupportssendingvaluesfrom0to999.Inordertomakeeverythingsimple,wewilluseacharacterthatindicatesthatanumberfollows.Thenumberwillalwayshavethreecharacters.Thus,0willberepresentedby'n000'and12willberepresentedby'n012'.Hereisthesimplealgorithm:

if(com=='n')

intval=(Serial.read()-48)*100+

(Serial.read()-48)*10+

(Serial.read()-48);

ThefirstSerial.read()functionwillreturnthehundreds,thesecondonewillreturnthetens,andthethirdonewillreturntheunities.

SeealsoYoucanfindanASCIItableathttp://www.asciitable.com/.ThistableisaveryimportantconceptforArduinoserialcommunication.

http://www.asciitable.com/

SoftwareserialandUARTbetweenArduinosTheserialport,professionallycalledUniversalAsynchronousReceiver/Transmitter(UART)communication,isgenerallyusedtoprogramanddebugtheArduinoviatheUSBport.TherearemultiplesensorsandsystemsthatuseUARTasthemaincommunicationmethod,andsometimesweneedtodiscussbetweentwoArduinostoshareinformation,workload,andsoon.

However,mostArduinosonlyhaveoneserialport,whichisusedbytheUSBconnection.Serialcommunicationcanonlyhappenbetweentwodevices.Whatcanwedonow?Withabitofluck,we’llhaveanArduinoMegaorsimilarthathasuptofourserialports,butifwedon’t,therestillisasolution.AspeciallibraryhasbeenwrittenthatsimulatesanUARTportonotherdigitalpins.Thereareafewdrawbacks,butitgenerallyworks.


2ArduinosJumpercables

Howtodoit…FollowstepstoconnecttwoArduinoUNOsusingsoftwareserial:

1. Assumingweusepins8and9forRXandTXonbothArduinos,connectpin8ononeArduinowithpin9ontheotherone,andpin9onthefirstArduinotopin8onthesecondone.

2. ConnecttheGNDofbothArduinostogether.3. Ifwedon’tpowerupbothArduinosviaUSB,thenweneedtopowerupatleastone

andconnect5Voneachtogether.

SchematicHereisanimplementationusingpins8and9forRXandTX:


CodeThefollowingcodeissplitintwoparts.ThemasterArduinowillreceivecommandsfromthecomputerandwritethemoverthesoftserial.TakealookattheControllingtheArduinooverserialrecipeinthischapterformoredetailsaboutserial.Here’sthefirstpartofthecode:




SoftwareSerialsoftSerial(8,9);//RX,TX>

voidsetup()



voidloop()

//Checkforreceivedcharactersfromthecomputer


//Writewhatisreceivedtothesoftserial

softSerial.write(Serial.read());

Andhereistheslavecodethatinterpretsthecharacterssentfromthemaster.Ifthecharacteris'a',itwillstartthebuilt-inLED.Ifthecharacteris'x',itwillstopit:




SoftwareSerialsoftSerial(8,9);

//RX,TX

//LEDPin

intLED=13;

voidsetup()


pinMode(LED,OUTPUT);//DefineLEDpinmode

voidloop()

//CheckifthereisanythinginthesoftSerialBuffer


//Readonevaluefromthesoftserialbufferandstoreitinthe

variablecom

intcom=softSerial.read();

//Actaccordingtothevaluereceived

if(com=='x')

//StoptheLED


elseif(com=='a')

//StarttheLED


Howitworks…SoftwareserialsimulatesastandardserialportondifferentdigitalpinsontheArduino.Itisveryhandyingeneral;however,itissimulated,soitdoesn’thavededicatedhardware.Thismeansitwilltakeresources,particularlyexecutiontimeandmemory.Otherwise,itworksjustlikeanormalserialconnection.Allthefunctionspresentinthenormalserialportarealsopresentinsoftwareserial.

CodebreakdownFirst,wewilllookinthemaster,whichtakescharactersreceivedonthenormalserialportandwritesthemtooursimulatedserialconnection.Inthebeginning,weincludetheSoftwareSerial.hlibrary:


Then,weneedtodeclareaserialobject.Wedosousingthefollowingsyntax:


Theserialconnectionwillbecalled,inthiscase,softSerial.Itwillusepin8forRXandpin9forTX.TakealookattheThere’smore…sectionforsomeinformationonwhichpinswecanuse.

UsingthesoftSerialobject,wecanuseallfunctionsfoundinanormalserialconnection,suchassoftSerial.read(),softSerial.write(),andsoon.Inthiscode,wecheckifthereisanythingintherealserialbuffer.Ifthereis,wereaditfromthatbufferandwewriteittothesoftwareserial:


softSerial.write(Serial.read());

Intheslavecode,werunasimplifiedversionofthecodefromtheControllingtheArduinooverserialrecipe,exceptthatweuseasoftwareserial.ThisonlychangesthedeclarationandinsteadofwritingSerial.read(),Serial.available(),andsoon,wewritesoftSerial.read()andsoftSerial.available().

There’smore…Softwareserialhassomeimportantconsiderationsanddrawbacks.Herewetackleafewofthem.

UsablepinsWecan’tuseeverypinontheArduinoforsoftwareserial.ForTX,generally,anythingcanbeused,butfortheRXpin,onlyinterrupt-enabledpinscan.OntheArduinoLeonardoandMicro,onlypins8,9,10,11,14,15,and16canbeused,whileontheMegaorMega2560only10,11,12,13,50,51,52,53,62,63,64,65,66,67,68,and69canbeused.

MoresoftwareserialconnectionsItispossibletohavemorethanonesoftwareserialconnection;however,onlyonecanreceivedataatatime.Thiswillgenerallycausedataloss.ThereisanalternativesoftwareseriallibrarywrittenbyPaulStoffregen,whichtacklesexactlythisproblem.ThelinkcanbefoundintheSeealsosectionofthisrecipe.

InterferenceThesoftwareseriallibraryusesthesametimerasafewotherlibraries.Thismeansthatotherfunctionsmightbeaffectedbytheuseofasimulatedserialport.ThebestknowninterferenceiswiththeServolibrary.ThebestwaytoovercomethisistousetheArduinoMega,orsomethingsimilar,whichhasfourhardwareserialports—enoughforanyproject.

GeneralconnectiontipsUARTconnectionsareverysimple;however,therearethreekeyaspectstoremember.Wheneverconnectingtwoserialdevices,theTXpinononedevicegoestotheRXpinontheotherdevice.Ifwedothattheoppositeway,wemightkillthedevice!Also,thedevicesneedtoatleastsharethesameGround(GND).Lastly,thedeviceshavetobesetatthesamespeed,typicallyreferredtoasthebaudrate.

SeealsoFindanalternativetothesoftwareseriallibrarywrittenbyPaulStoffregenathttp://www.pjrc.com/teensy/td_libs_AltSoftSerial.html

http://www.pjrc.com/teensy/td_libs_AltSoftSerial.html

WirelessserialSometimeswejustwanttocutthewiresandsenddataoverair.Believeitornot,it’snotthatdifficult.Wecanquicklytransformaserialorsoftwareserialportintoawirelessoneifwehaveawirelesstransmitterandreceiverpair.Thesewirelesscomponentsarequitecheapandeasytofind.Theyareavailableinafewdifferentfrequencies,andtheyareveryeasytosetup.

Wewillusethecodefromthepreviousrecipe,SoftwareserialandUARTbetweenArduinos;exceptthatwewillimplementtheserialoverair.Thereisacatch;wecanonlysenddatainonedirection.

GettingreadyToexecutethisrecipe,weneedthefollowingingredients:

2ArduinosJumpercablesOneRFlinktransmitterandRFlinkreceiverpair

Howtodoit…ThefollowingarethestepstoconnecttwoArduinoUNOsusingSoftwareSerialoverwireless:

1. Assumingweusepins8and9forRXandTXonbothArduinos,connectpin9onthemasterArduinototheDATApinonthetransmitter.

2. Connectpin8ontheslaveArduinototheDATApinofthereceiver.3. ConnecttheGNDandthe5VofthetransmittertothemasterArduino.4. ConnecttheGNDandthe5VofthereceivertotheslaveArduino.5. Usethesamecodeasthepreviousrecipe,SoftwareserialandUARTbetweenArduinos.

SchematicHereisanimplementationusingpins8and9forRXandTXwiththetransmitteronthemasterArduinoandthereceiverontheslave:


Howitworks…TheRFLinkTransmitterReceiverpairissimpletosetupanduse.Basically,thetransmitteroutputsaradiosignalcorrespondingtoanythingitgetsontheDATApin.Inthesameway,thereceiveroutputsanythingitreceives.Theydon’tcareaboutthebaudrateaslongasitisslowenough.

Thiskindofwirelesscommunicationisverysusceptibletonoise.Itisrecommendedtouseverylowbaudrates—9,600oreven4,800aregoodcandidates.Also,thegreaterthedistance,themorenoiseweget.Inordertocombatthiswecan,again,lowerthebaudrate.

There’smore…Wecanimplementatwo-waysystemifweusetwoRFLinkpairsofdifferentfrequencies.Iftheyarenotofdifferentfrequencies,theywillcompletelyinterferewithoneanotherandboththemasterandtheslaveArduinoswillreceivewhateverisbeingtransmittedbyeither.

SeealsoThereare,however,someprofessionalmodulesdesignedtofacilitatetwo-wayserialcommunication.TheyarecalledXbeeandcomeinallkindsofflavors.Moreaboutthesecanbefoundathttps://www.sparkfun.com/pages/xbee_guide.

https://www.sparkfun.com/pages/xbee_guide

I2CbetweenArduinosMaybesometimeswewanttosharetheworkloadofoneArduinowithanother.Ormaybewewantmoredigitaloranalogpins.Inter-IntegratedCircuitorI2C(pronouncedIsquaredC)isthebestsolution.

I2Cisaninterestingprotocol.It’susuallyusedtocommunicatebetweencomponentsonmotherboardsincamerasandinanyembeddedelectronicsystem.

Here,wewillmakeanI2CbususingtwoArduinos.WewillprogramonemasterArduinotocommandtheotherslaveArduinotoblinkitsbuilt-inLEDonceortwicedependingonthereceivedvalue.


2ArduinosJumpercables

Howtodoit…FollowthesestepstoconnecttwoArduinoUNOsusingI2C:

1. ConnectpinsA4andA5ononeArduinotothesamepinsontheotherone.2. TheGNDlinehastobecommonforbothArduinos.Connectitwithajumper.

SchematicHereisasimpleimplementation.Thereisnoneedforabreadboard.


NoteRemembernevertoconnect5Vand3.3VArduinostogether.Itwon’thurtthe5VArduino,butitwillcertainlyannoyits3.3Vbrother.

CodeThefollowingcodeissplitintwoparts:themastercodeandtheslavecode,whichrunontwodifferentArduinos.First,let’stakealookatthemastercode:

//IncludethestandardWirelibraryforI2C

#include<Wire.h>

intx=0;

voidsetup()

//StarttheI2CBusasMaster

Wire.begin();

voidloop()

Wire.beginTransmission(9);//transmittodevice#9

Wire.write(x);//sendsx

Wire.endTransmission();//stoptransmitting

x++;//Incrementx

if(x>5)x=0;//resetxonceitgets6

delay(500);

Andhereistheslavecodethatinterpretsthecharacterssentfromthemaster:

#include<Wire.h>

intLED=13;

intx=0;

voidsetup()


//StarttheI2CBusasSlaveonaddress9

Wire.begin(9);

//Attachafunctiontotriggerwhensomethingisreceived.

Wire.onReceive(receiveEvent);

voidreceiveEvent(intbytes)

x=Wire.read();//readonecharacterfromtheI2C

voidloop()

//Ifvaluereceivedis0blinkLEDfor200ms

if(x=='0')


delay(200);


delay(200);

//Ifvaluereceivedis3blinkLEDfor400ms

if(x=='3')


delay(400);


delay(400);

Howitworks…Tobrieflygothroughthetheory,I2Crequirestwodigitallines:SerialDataline(SDA)totransferdataandSerialClockLine(SCL)tokeeptheclock.EachI2Cconnectioncanhaveonemasterandmultipleslaves.Amastercanwritetoslavesandrequesttheslavestogivedata,butnoslavecandirectlywritetothemasterortoanotherslave.Everyslavehasauniqueaddressonthebus,andthemasterneedstoknowtheaddressesofeachslaveitwantstoaccess.Nowlet’sgothroughthecode.

CodebreakdownFirst,let’slookatthemaster.WeneedtoincludetherequiredWire.hlibrary:

#include<Wire.h>

Then,inthesetupfunction,webegintheI2CbususingtheWire.begin()function.Ifnoargumentisprovidedinthefunction,Arduinowillstartasamaster.

Lastly,wesendacharacterx,whichisbetween0and5.Weusethefollowingfunctionstobeginatransmissiontothedevicewiththeaddress9,writethecharacter,andthenstopthetransmission:

Wire.beginTransmission(9);//transmittodevice#9

Wire.write(x);//sendsx

Wire.endTransmission();//stoptransmitting

Nowlet’sexploretheslaveArduinocode.WealsoincludetheWire.hlibraryhere,butnowwestarttheI2CbususingWire.begin(9).ThenumberintheargumentistheaddresswewanttousefortheArduino.Alldeviceswithaddress9willreceivethetransmission.

NowweneedtoreactsomehowwhenwereceiveanI2Ctransmission.Thefollowingfunctionappendsatriggerfunctionwheneveracharacterisreceived.Bettersaid,whenevertheArduinoreceivesacharacteronI2C,itwillrunthefunctionwetellittorun:

Wire.onReceive(receiveEvent);

Andthisisthefunction.Here,wesimplystorethevalueofthereceivedcharacter:

voidreceiveEvent(intbytes)

x=Wire.read();

Inloop(),wesimplyinterpretthatcharactertoblinkthebuilt-inLEDatdifferentspeedsdependingonthereceivedcharacter.

There’smore…I2Cisacomplicatedtransmissionprotocol,butit’sveryuseful.AllArduinosimplementit,withafewdifferencesinpinmappings.

ComparingdifferentArduinocategoriesThepinsforI2CaredifferentindifferentArduinocategories.Herearethemostcommon:

Board I2Cpins

Uno,ProMini A4(SDA),A5(SCL)

Mega,Due 20(SDA),21(SCL)

Leonardo,Yún 2(SDA),3(SCL)

MoreaboutI2CEachI2Cbuscansupportupto112devices.AlldevicesneedtoshareGND.Thespeedisaround100kb/s—notveryfastbutstillrespectableandquiteuseable.Itispossibletohavemorethanonemasteronabus,butit’sreallycomplicatedandgenerallyavoided.

AlotofsensorsuseI2Ctocommunicate,typicallyInertialMeasurementUnits,barometers,temperaturesensors,andsomeSonars.RememberthatI2Cisnotdesignedforlongcablelengths.Dependingonthecabletypeused,2mmightalreadycauseproblems.

ConnectingmoredevicesIfweneedtoconnectmorethantwodevicesonanI2Cbus,wejusthavetoconnectallSDAandSCLlinestogether.WewillneedtheaddressofeveryslavetobeaddressedfromthemasterArduino.

SeealsoYoucanfindagoodexplanationonhowamastershouldrequestinformationtoaslaveathttp://arduino.cc/en/Tutorial/MasterReader.Thisisanexampleclosertoreallife,asthisisthewayweusuallyrequestinformationfromsensors.

http://arduino.cc/en/Tutorial/MasterReader

SDcardsSDcardsaregreattostoredatainthelongterm.Arduinohasalibraryspecificallydesignedtotalktothem.Withthislibrary,wecancreate,write,read,anddestroyfiles.Thisisveryhandy,especiallyindataloggingapplications.WecanhaveanArduinorunningformonths,recordingdata,andwritingittotheSDcard.

Inthisexample,wewillreadthedatafromtwoanalogportsandwriteittotheSDcard.


AnArduinoboardconnectedtoacomputerviaUSB.AformattedSDcard;ArduinoacceptsonlyFAT16orFAT32formatting.AnEthernetshieldoranyotherArduino-compatibleSDshield.Optionally,twoanalogsensors.WewillstoretheirvaluesontheSDcard.Itworkswithoutthem,butwewillonlyrecordrandomvaluesontheanalogports.

Howtodoit…FollowthesestepstopreparetouseanSDcard:

1. PlugtheArduino-compatibleSDshieldintotheArduino.2. FormattheSDcardtoeitherFAT16orFAT32.3. InserttheSDcardintotheSDcardslotontheshield.

CodeThefollowingcodewillreadtheanalogvaluesfromA0andA1andwritethemtothelog.txtfileontheSDcard:

#include<SD.h>

//DeclaretheselectSPIpin.Pin4fortheEthernetshield

intselectSPI=4;

voidsetup()

Serial.begin(9600);//Serialfordebugging

//DeclarethestandardselectSPIpinasOUPTUT.Pin53forMega-like

boards

pinMode(10,OUTPUT);

//CheckifthereisanySDcardpresent

if(!SD.begin(selectSPI))

Serial.println("Cardnotfound");

return;//stopexecution

Serial.println("Cardfound");

voidloop()

//ReadA0andA1

intval1=analogRead(A0);

intval2=analogRead(A1);

//Openthefile

FilelogFile=SD.open("log.txt",FILE_WRITE);

//Checkifthefileisavailable

if(logFile)





else

//ifthefilecan'tbeopened,alert

Serial.println("erroropeningfile");

Howitworks…SDcardsuseatechnologycalledSerialProtocolInterface(SPI)tocommunicate.ArduinohasoneSPIconnectionembeddedintoit.Inthecodebreakdown,wewillexplorehowitallworks.

CodebreakdownThefirstthingwedoisincludetheSD.hlibrary.Afterthat,weinitializeavariablethatwillrepresenttheselectpinforSPI.SPIcanhandlecommunicationbetweenmultipledevices.Inordertoknowwhichdeviceweareaddressing,aselectpinisimplemented.InthecaseoftheEthernetshield,whichembedsanSDcardadapter,thisispinnumber4.

Followingthis,andduetothewaySPIisimplementedintheArduinomicrocontroller,weneedtoselectthestandardselectpinasOutput,regardlessofwhetherweareusingit.ForstandardArduinos,thatispin10andforMega,it’spin53:

pinMode(10,OUTPUT);

Nowwecanstarttheconnectionandcheckifanycardispresent.Ifnot,wewillstoptheprogramcompletely.WeneedtotelltheSDlibrarytheselectpinonwhichitcanfindtheSDcard:

if(!SD.begin(selectSPI))

Serial.println("Cardnotfound");

return;//stopexecution

Intheloop()function,wereadthevalueofthetwoanalogports.Afterthat,weopenthefileusingthefollowingfunction:

FilelogFile=SD.open("log.txt",FILE_WRITE);

Ifthefiledoesn’texist,itwillbecreated.Weshouldcheckifthefileisavailableforwriting.WeuseanifclauseonthelogFilefile.Ifitisavailable,wewillsimplywritetoit:

if(logFile)





Otherwise,wejustalertusingtheserialconnectionthatwestartedfordebugging.

There’smore…SDcardsandSPIsarequitecomplexingeneral.Hereareafewthingstoknow:

Notallcardswork:Therearecaseswhenfastcardswillnotwork.Generally,cardsofclass4workwell,whilecardsofclass6andfasterpresentproblems.Toeasilyfindinformationaboutacard,runtheArduinoIDEbuilt-inexamplefoundunderFile|Examples|SD|CardInfo.ItwillprintoutallthedetailsitcanacquireabouttheSDcard.ReadingfromSDcards:Readingisofcoursepossible.Itusesthesameprotocolastheserialconnection.TheArduinoIDEexampleReadWritefoundunderFile|Examples|SDgivesagoodexplanation.Noteonelectronicconnections:MostArduinosworkon5VwhilethestandardforSDcardsis3.3V.TheEthernetshieldandotherArduino-compatibleSDshieldsallhaveabuilt-inlogiclevelshifterthatshiftsthevoltagesfrom5Vto3.3Vandviceversa.IfweareimplementingacustomSDcardconnector,weshouldatleastuseavoltagedividerfortheoutputsignalsfromtheArduinototheSD;otherwise,wewillburntheSDcard.SparkfunsellsaveryhandyLogicLevelShifter,whichwillworkperfectlyinthisapplication.

LCDcharacterdisplaysThereisnothingbetterthanwritinganyinformationfromtheArduinotoasmallLCDcharacterdisplay.Theyareincrediblyhandyandjustlookplaincool.Evenbetter,Arduinohasabuilt-inlibrarytodothis.Let’sexplorehowwecanimplementit.

GettingreadyWewillneedthefollowingingredientsforthisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBAnLCDcharacterdisplayofanydimension—16x2isthestandardsizeA10K-ohmpotentiometerJumperwires

Howtodoit…First,weneedtoconnectthemonitortotheArduino.Thisgenerallyrequiresaminimumof6digitalpinsasshowninthefollowingdiagram:

Thisisonepossiblebreadboardimplementation:

FollowthesestepstoconnectanLCDtotheArduino:

1. ConnectGNDtotheVSSandR/Wpins.2. Connect5VtotheVcc/Vddinput.3. Connect6digitalpinstoE(enable),RS,andDB4-DB7.Thisisthe4-bitwayof

connectingHD44780-baseddisplays,suchasthecommonLCDcharacterdisplays.4. Lastly,connecta10K-potentiometerwiththecentral,movingtaptopinVo,onepin

to5V,andonetoGND.Byadjustingthispotentiometer,weareadjustingthecontrastofthedisplay.

CodeThefollowingcodewillprint"HelloArduino"onthefirstline,andonthesecondlineitwillprintthenumberofsecondspassed:

//IncludetherequiredLCDlibrary

#include<LiquidCrystal.h>

//InitializeaLCDandpassthepinsintheorderrs,enable,d4,d5,d6,

d7

LiquidCrystallcd(3,5,10,11,12,13);

voidsetup()

//BegintheLCDwiththenumberofcolumnsandrows

lcd.begin(16,2);

voidloop()

//Setcursoratbeginningcolumnandrow:

lcd.setCursor(0,0);//lcd.home()doesthesame

lcd.print("HelloArduino!");

//Setcursoratbeginningofsecondrow

lcd.setCursor(0,1);

lcd.print(millis()/1000);

TipAnydigitalpinscanbeusedtoconnectanLCDaslongastheyarenotusedbyanythingelse.

Howitworks…AlmostallLCDcharacterdisplaysusetheHitachiHD44780driverstandard,whichisimplementedasalibraryintheArduinoenvironment.EachLCDhasanumberofcolumnsandrows,withthemosttypicalconfigurationsbeing8x2,16x2,and20x4.Werequireatleastsixdigitalpinstocontrolthesedisplays.

CodebreakdownInitially,wejustincludetheLiquidCrystal.hlibrary.ThenwecreateaLiquidCrystalobjectcalledLCDinwhichwewritethepinnumbersused:

LiquidCrystallcd(3,5,10,11,12,13);

Afterwards,inthesetup()function,weinitializethedisplayusinglcd.begin(columns,rows).Intheend,wecansimplyjumptoanylocationandwriteanythingwewant:

lcd.setCursor(0,0);

lcd.print("HelloArduino!");

lcd.setCursor(0,1);

lcd.print(millis()/1000);

There’smore…ThereareafewmorethingswecandowithLCDs:

Morewaysofconnecting:Inthisexample,weimplementedthesimplestofallversions.Itrequirestheminimumamountofcables;however,therearefourtypesintotal:

LiquidCrystal(rs,enable,d4,d5,d6,d7)

LiquidCrystal(rs,rw,enable,d4,d5,d6,d7)

LiquidCrystal(rs,enable,d0,d1,d2,d3,d4,d5,d6,d7)

LiquidCrystal(rs,rw,enable,d0,d1,d2,d3,d4,d5,d6,d7)

HavingaccesstotheRWpinwillallowustoreadfromthemonitor,whichisnotreallyusefulaswearetheoneswhoalsowriteonit.Usually,thispinisjustconnectedtoGNDtomakeitstayinreceivemode.Usingalleightdatalinesisnotnecessarybutistwiceasfastasonlyusingfour.

TherearealsosomeI2C-basedLCDdisplaysthatonlyrequirethetwoI2Cpins.Ifwearetightonpins,thatisthesolution.

Noimage:Whenwesetupthecircuitforthefirsttime,therearealotofchancesofnotextshowingup.Weshouldplaywiththecontrastpotentiometertomakesureit’snotkillingorsupersaturatingthecontrast.Backlight:SomeLCDdisplaysalsohaveabuilt-inbacklight.Checkthedatasheetforthescreenusedtofindouthowtoenableit.Mostrequireanexternalresistorthatisalwaysspecifiedinthedatasheet.

EthernetUsinganEthernetshield,wecanconnectanArduinototheInternet.AllthepowerandawesomenessoftheInternetcancometothissmallblueboardweareprogramming.Thisisahugetopic;however,theArduinoEthernetlibrarymakesitallsimple.

Here,wewillcreateaninterestingapplicationforthisfunctionality.WewillmaketheArduinoalocalwebservertowhichwecanconnecttofindoutthereadingsofthefirstthreeanaloginputs,usingourbrowser.


AnArduinoAnArduinoEthernetshieldArouterorjustanEthernetcable

Howtodoit…Followthesestepstobuildtheserver:

1. CarefullyplugtheEthernetshieldintotheArduino.2. ConnectanEthernetcabletotheshield.3. ConnecttheotherendoftheEthernetcabletothesameroutertowhichyour

computerisconnected.

CodeThefollowingcodeattemptstoconnecttoarouterusingDHCP.Onceitdoes,itwilloutputtheIPviaserialandthenitwillwaitforincomingconnections.Whenaconnectionisset,itwilloutputthevaluesofthefirstthreeanaloginputsviaanHTMLpage.Thecodeisasfollows:

//IncludetherequiredSPIandEthernetLibraries

#include<SPI.h>

#include<Ethernet.h>

//MACAddressfortheEthernetShield

bytemac[]=0x00,0xAA,0xBB,0xCC,0xDD,0x01;

//CreateanEthernetServerobjectonport80

EthernetServerserver(80);

voidsetup()

Serial.begin(9600);//StartSerial

//StarttheEthernetconnectionandcheckifsucceeded

while(Ethernet.begin(mac)==0)

Serial.println("FailedtoconfigureEthernetusingDHCP");

delay(500);

Serial.println("ConnectionEstablished");

//PrinttheIPAddress

Serial.print("ServerIPaddress:");

Serial.println(Ethernet.localIP());

voidloop()

//Checkforclients

EthernetClientclient=server.available();

//Whenthereisaclient

if(client)

while(client.connected())

if(client.available())

//GETrequestsfromclientsendinanemptynewline

//Ifanewlinecharacterisfoundandthesecondcharacterisa

newline

if(client.read()=='/n'&&client.read()=='/n')

//SendaHTTPresponse

//HTTPheader:

client.println("HTTP/1.1200OK");

client.println("Content-Type:text/html");

client.println("Connection:close");//Connection

closesafterresponse

client.println("Refresh:3");//Refreshpageevery3seconds

client.println();

//HTMLPage:

client.println("<!DOCTYPEHTML>");

client.println("<html><body>");

//Writethevaluesofthefirst3AnalogInputsinparagraphs

for(intanIn=0;anIn<3;anIn++)

client.print("<p>");//Beginparagraph

client.print("AnalogInput");

client.print(anIn);//Printtheanaloginputnumber

client.print("=");

client.print(analogRead(anIn));//Printchannelvalue

client.println("</p>");//Endparagraph

client.println("</body></html>");

//Allowmessagetobeprocessedbybrowser

delay(10);

//Closeconnectiontoclient

client.stop();

Serial.println("ClientDisconnected");

HowtotestIftheEthernetshieldispluggedintothesamerouterasyourcomputer,checkfortheIPtheArduinogivesoverserial.Then,inyourbrowseraddressbar,writethatIPandhitEnter.Itwilltakeyoutothecustompage.

Howitworks…TheEthernetshieldhasapowerfulprocessorinside,designedjusttotacklealltheprotocolsofEthernet,TCP,UDP,andsoon.Itisaveryadvancedcomponent.TheshieldusestheSPIcommunicationprotocolforhigh-speedcommunicationwiththeArduino.Thankfully,Arduinohasalibrarytosimplifyeverything,aswecanseeinthecodebreakdown.

CodebreakdownBothSPIandEthernetlibrarieshavetobeincludedforthisbadboytowork:

#include<SPI.h>

#include<Ethernet.h>

AnythingconnectedtotheInternetoranylocalnetworkrequiresauniqueMACaddress.Here,wewillwritearandomoneinabytearrayandhopenootherdevicehasit:

bytemac[]=0x00,0xAA,0xBB,0xCC,0xDD,0x01;

WeneedtocreateanEthernetServerobjecttotackleallthecomplexconnectionprotocols.Theargumentofthefunctionistheportonwhichtheserverwilllistenforconnections.Port80isthestandard:


Here,weattempttostarttheEthernetconnectionwiththespecifiedMACaddress.Ifitfailsandreturns0,itwillattemptagain.However,therearefewchancesifitdoesn’tworkfromthefirstattempt.Thisistherequiredcode:

while(Ethernet.begin(mac)==0)

Serial.println("FailedtoconfigureEthernetusingDHCP");

delay(500);

OncetheDHCPhasbeenset,weneedtoknowtheIPoftheserver.ThefollowingfunctionwillprinttheIPaddressovertheserial:

Serial.print("ServerIPaddress:");

Serial.println(Ethernet.localIP());

Intheloop()function,wefirstdeclareavariableoftypeEthernetClient,whichwilltakethevalueoftheavailabilityofaclient:

EthernetClientclient=server.available();

Oncewehaveaclient,whileitisconnected,wecheckifitisavailable,usingthefollowingsyntax:

if(client)

while(client.connected())

if(client.available())

NowweneedtolistentoGETcommandsfromtheclient.Thesecommandsrequest

informationtobesentbacktotheclient.AttheendofeachGETrequest,wehaveanemptylinethatwecanfindusingthefollowingsyntax:

if(client.read()=='/n'&&client.read()=='/n')

Ifwedetectsuchacommand,werespondwithawebsite.EachwebsitestartswithaHTTPanswerheader,whichincludessomebasicdetailsabouttheconnectionandthewebsite.Inourcase,wetellthebrowsertorefresheverythreesecondstoseetheupdatesinthevalues:

client.println("HTTP/1.1200OK");

client.println("Content-Type:text/html");

client.println("Connection:close");

client.println("Refresh:3");

client.println();

AndthenwewritetheactualwebsiteHTMLcode.FormoredetailsaboutHTML,takealookattheSeealsosectionofthisrecipe.

Intheend,weclosetheconnectionandloopbacktowaitforotherconnections.

There’smore…WecanactuallymakethisdataavailableacrosstheInternet,butforthisweneedtohaveaprivateIPaddress.Ifindeedwehaveoneofthese,wecanchangetheconnectioncodetothefollowing:

bytemac[]=0xDE,0xAD,0xBE,0xEF,0xFE,0xED;

IPAddressip(192,168,1,177);//YourprivateIP


ThiswillsetuptheserverusingthespecifiedIP.IfindeedwehaveaprivateIPandwestarttheserveronthatIP,wecanaccessitfromanywhereintheworldbyjusttypingthatIPaddressintoourbrowseraddressbar.

SeealsoTheEthernetshieldcandoatonofthings.Formoreinformationaboutit,visithttp://arduino.cc/en/Reference/Ethernet.ForanHTMLprimer,visithttp://www.w3schools.com/html/.

http://arduino.cc/en/Reference/Ethernet

http://www.w3schools.com/html/

Chapter8.HackingInthischapter,wewillcoverthefollowingtopics:

MoredigitalpinsFasterPWMStoringdatainternally–EEPROMTimingArduinocodeExternalinterrupts

IntroductionThischapterisfortherebels!It’saboutthetipsandtricksthatpushtheArduinosdevelopmentalittletotheedge.Sometimes,wemaywanttoexecutesomecodeatpreciselythetimesomethinghappens,evenwhenwearedoingsomethingcompletelydifferent.OrwemaywanttostoredatawithinArduinoevenifwepoweritoff.Allofthatandmorecanbelearnedinthischapter,folks!

MoredigitalpinsTherearetimeswhenweneedmoredigitalpinsontheArduinowithoutanyotherexternalcomponents.AnArduinoUnohas14digitalpins,from0to14,right?Wrong!Itactuallyhas20.Theanaloginportscanatalltimesbeusedasdigitalports,andtheyhaveallthefunctionalityofnormaldigitalports.

TipAwordofcaution:pins0and1aretheUARTportsusedforprogrammingneedtotakeextracareaboutwhatweconnectthere,becausewhenweareprogrammingtheboard,thosepinswillswitchfromHIGHtoLOWthousandsoftimes.

GettingreadyJustoneingredientisneededforthisrecipe—anArduinoBoardconnectedtoacomputerviaUSB.

Howtodoit…ThefollowingcodeshowshowtousepinsA0andA1asnormaldigitalpins:

voidsetup()

pinMode(A0,OUTPUT);

pinMode(A1,OUTPUT);

voidloop()

digitalWrite(A0,HIGH);

digitalWrite(A1,LOW);

delay(500);


digitalWrite(A1,HIGH);

delay(500);

Howitworks…Internally,allpinsonArduinoboardshavedifferentfunctions.Theonlyfunctiontheyallshareisthebasicdigitalinputandoutput.AllofthemcanoutputeitherHIGHorLOWandallofthemcanreadeitherHIGHorLOW.

Inotherwords,allofthefollowingfunctionswillworkthesamewayasonanyrandomdigitalport:

pinMode(A0,OUTPUT);

pinMode(A1,INPUT);

pinMode(A2,INPUT_PULLUP);//SetasaninputwithPULLUPresistor


digitalRead(A1);

FasterPWMThisisanexoticprocedure!ThestandardPWMfrequencyontheArduinoisaround490Hz.Whileitcangetmostjobsdone,itisnotreallythatfast.However,wecanchangethat.

FasterPWMisespeciallyusefulwhencontrollingmotors.AtlowPWM,thetorqueisgreatlyaffected,anditcanalsocreateaudiblenoise.ThebestwaytotestthisistoimplementtheControllingspeedwithPWMrecipefromChapter5,MotorControl,andincreasethePWMfrequency.

NoteAnotetoremember:thismightinterferewithotherfunctions,suchasdelay().Wehavetobeextracarefulwhenthishappens.

GettingreadyFollowingaretheingredientsrequiredtoimplementthisrecipe:

AnArduinoboardconnectedtoacomputerviaUSBADCmotorAresistorbetween220ohmand4,700ohmAstandardNPNtransistor(BC547,2N3904,N2222A,TIP120)oralogiclevel-compatibleMOSFET(IRF510,IRF520)Astandarddiode(1N4148,1N4001,1N4007)

Howtodoit…AfterweimplementthesamecircuitasintheControllingspeedwithPWMrecipefromChapter5,MotorControl,whichstartsamotoronpin9,wejusthavetoaddonelinetothesetup()function:


intmotorPin=9;

voidsetup()

//ChangeTimer1dividerwhichwillmakethePWMfaster

//InthisSettingitwillhaveafrequencyof31372.55Hz

TCCR1B=TCCR1B&0b11111000|0x01;

voidloop()

//Fadethemotorin


analogWrite(motorPin,i);

delay(20);

//Stopthemotor


delay(2000);

Howitworks…InternaltimersinsidetheATMegachipdrivePWMpinsoneachArduino.Atimerisacomponentthatkeepstime;shocking,isn’tit?TheArduinoUNOhasthreesuchtimers:

Timer0Timer1Timer2

TwoPWMpinsareassignedtoeachofthesetimers.Pins9and10areassignedtoTimer1,pins11and3totimer2,andpins5and6toTimer0.Timers1and2sharethesamePWMfrequencyof490HzwhileTimer0istherebelwithawhopping976Hz.

Eachtimerhasaninternalprescalerthatdividestheclockrate,whichistypicallygivenbythe16MHzquartzoscillator.Ifwechangetheprescalervalue,allfunctionsallocatedtothattimerwillchangethefrequency.PWMisoneofthosefunctions.Thereisjustonelineofcodethatchangesthedividerofonetimer:


Nowthatlooksfunky.Itactuallyisverysimple.AllweneedtoknowisthatTCCRxBrepresentstimerx.Sotimer0isTCCR0B,timer1isTCCR1B,andsoon.Thefullsyntaxisasfollows:

TCCRxB=TCCRxB&0b11111000|setting;

Herexisthetimernumberandsettingisthesettingweareusingtochangethedivider.Thefollowingtableswillelucidateeverything.

Timer0ThistimercontrolsthePWMpins5and6.PleasereadtheThere’smore…sectionofthisrecipeaboutinterferencewiththedelay()function.

Setting Divider Frequency

0x01 1 62,500Hz

0x02 8 7,812.5Hz

0x03 64 976.5625Hz(Default)

0x04 256 244.14Hz

0x05 1024 61.035Hz

SoifwewanttomakeTimer0runat62500Hz,wehavetoimplementinthesetup()function:


Timer1

ThisisresponsibleforPWMpins9and10.


0x01 1 31,372.55Hz

0x02 8 3,921.16Hz

0x03 64 490.20Hz(Default)

0x04 256 122.55Hz

0x05 1024 30.64Hz

Timer2ThisisresponsibleforPWMpins11and3.


0x01 1 31,372.55Hz

0x02 8 3,921.16Hz

0x03 32 980.39Hz

0x04 64 490.20Hz(Default)

0x05 128 245.10Hz

0x06 256 122.55Hz

0x07 1024 30.64Hz

Wecanmodifythesettingofallthreetimersifwewant,bywritingthethreemodifiersinthesetup()function.

AllofthiscanbefoundundertheTimer/Counter0andTimer/Counter1PrescalerssectionintheATmega328Pdatasheet.TakealookattheSeealsosectionofthisrecipe.

There’smore…Thereareafewmorethingstoknowaboutthisexoticprocedure.

InterferenceTimersareveryimportantintheArduinoworld.Alotoffunctionsandlibrariesusethem.Whenwechangethefrequencyofthetimer,itaffectsthefrequencyofalllibrariesthatuseit.TheServo,Stepper,SoftwareSerial,orevenbasicfunctionssuchasdelay()willbeaffected.Herewewilltalkaboutthedelay()function.

Thedelay()functionusesTimer0torecordthetimepassed.Ifwechangethedivideronthetimer,itwilldirectlyaffectthefunction.Forexample,ifwechangethesettingfromthedefault0x03to0x02,itwillchangethedividerfrom64to8;wewillthusmakethefunctioneighttimesfaster.Thismeansthatdelay(1000)willnotlast1,000millisecondsbut125milliseconds.Tocorrectthis,wecannowwritedelay(8000),whichwillrunforafullsecond.

NotePaygreatattentiontothefunctionalitythetimerdivisionchangeaffects.Evencommoneverydaythingscanbeaffected.Thebestwaytofindoutisthroughexperimentation.Ifsomethingnolongerworksafteratimerdivisionchange,youhavetheculprit.

OtherArduinosAllArduinoshaveinternaltimers.Inordertochangethem,wehavetocheckthedatasheetoftheATMegainsidetheusedArduinoandseewhatsettingswecanchange.Forexample,theArduinoMegaandMega2560havethefollowingtimerslinkedtothefollowingpins:

Timer PWMpins

Timer0 4,13

Timer1 11,12

Timer2 9,10

Timer3 2,3,5

Timer4 6,7,8

SeealsoFormoreinformationaboutTimerandPWMhacking,readthisarticlebyKenShirriffathttp://arduino.cc/en/Tutorial/SecretsOfArduinoPWM.AbetterwaytohavemorecontroloverPWMistousespecializedICsthatdojustthat.HereisaverynicePWMShieldfromSparkfun,whichyoucanfindathttps://www.sparkfun.com/products/10615.ThebiblicaldatasheetoftheATMega328P,thebrainoftheArduinoUnocanbefoundathttp://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdf.

http://arduino.cc/en/Tutorial/SecretsOfArduinoPWM


http://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdf

Storingdatainternally–EEPROMSometimeswewanttostoresomevaluesinsidetheArduinoevenwhenweturnitoff.Luckily,eachArduinohasaninternalElectricallyErasableProgrammableRead-OnlyMemory(EEPROM)justforthat.

AnoteforusingEEPROM–—theEEPROMsinsidetheArduinoshavealifecycleof100,000reads/writes.Itmayseemalot,butitisn’t.OnlyusetheEEPROMwhenstrictlyneeded.

HerewewillprogramArduinotorecordhowmanytimeswepressedabutton.Ifthepoweriscut,itwillstillrememberthelastcountusingtheEEPROM.

GettingreadyFollowingaretheingredientsneededtoexecutethisrecipe:

AnArduinoBoardconnectedtothecomputerviaUSBApushbutton

Howtodoit…ThisrecipeisbasedontheButtonwithnoresistorrecipefromChapter3,WorkingwithButtons.Itusesthesamehardwareimplementationwithadifferentcode.

ThefollowingcodewillreadthelastknownbuttonpresscountfromtheEEPROMandthen,ateachbuttonpress,willaddonetothatvalueandwriteitbacktotheEEPROM:

//IncludetherequiredEEPROMlibrary

#include<EEPROM.h>

intcount=0;//Countervariable

intaddress=9;//AddresswerewestorethedataintheEEPROM

intbuttonPin=12;

voidsetup()

//Readthelaststoredvalueofthebutton

count=EEPROM.read(address);


Serial.begin(9600);

//PrinttheinitialvalueintheEEPROM

Serial.print("Initialvalue:");

Serial.println(count);

voidloop()

//Whenbuttonpressisdetected

if(digitalRead(buttonPin)==LOW)

count++;//incrementcounter

//Writethecountvariabletothespecifiedaddress.

EEPROM.write(address,count%256);

Serial.println(count);

delay(500);//Somedebouncingdelay.

Howitworks…ThemicrocontrolleroneachArduinohasasmallinternalEEPROMdesignedtoholddataevenwhennopowerisapplied.Thesizeavailablevariesdependingonthemicrocontrollerused.Forexample,theArduinoUnothatusestheATMega328has1KB,whiletheATMega2560foundintheArduinoMega2560has4KB.ThismeansthatanArduinoUnohas1,024addresseswith1byteeach.Inthecodebreakdown,wewillexplorehowtousetheEEPROMandtheEEPROMlibrary.

CodebreakdownAsalways,weneedtoincludetheEEPROM.hlibrary:

#include<EEPROM.h>

ThefirstfunctionweuseintheEEPROMlibraryisthefollowing:

count=EEPROM.read(address);

Here,wereadthevaluefoundintheEEPROMatthatspecifiedaddress,andstoreitinourcountvariable.Wedothisinthesetup()functionsothatwecanbegincountingatthelastsavedvalue.

Followingthis,wedetecteachtimethebuttonispressed.Whenwedetectthat,weincrementthecounterandwritethelatestvaluetothesameaddressontheEEPROM:

EEPROM.write(address,count%256);

TheEEPROMismadeoutof1-bytecells,sowecannotwriteanumbergreaterthan255withoutoverflowing.Wecanusemultiplebytestostorelargervalues,butinthiscase,asit’sjustasimpledemonstration,weusecount%256tosafelystartfrom0when255ispassed.

TimingArduinocodeThisisaquickandveryhelpfulrecipe.Thereareseveraltime-sensitiveapplicationsontheArduino,andsometimesweneedtofindthespeedatwhichtheArduinoexecutesvariouscommands.HerewehaveasimpleimplementationthatwilltellushowmuchtimeittakestosetadigitalpinatHIGHandLOW10,000times.

GettingreadyForthisrecipe,werequireanArduinoboardconnectedtoacomputerviaUSB.

Howtodoit…Wejustneedtowritethefollowingcode:

//Variabletoholdthepassedtime

unsignedlongtime=0;

intpin=3;//Declareapin

voidsetup()

Serial.begin(115200);//HighspeedSerial

pinMode(pin,OUTPUT);

voidloop()

//Getcurrenttime

time=micros();

//Codetobetestedforexecutiontime

for(inti=0;i<10000;i++)

digitalWrite(pin,HIGH);

digitalWrite(pin,LOW);

//Findthepassedtimeandprintit

Serial.println(micros()-time);

Howitworks…Themicros()functionreturnsthenumberofmicrosecondspassedsincetheArduinowasturnedon.Remember,thereare1,000microsecondsinamillisecondand1,000,000microsecondsinonesecond.

Thecodesimplyworksbyrecordingthetimebeforethefunctionwewanttotimeandafter.Then,itsubtractsthetwoandobtainsthetimepassed.Indeed,wewillalsorecordthetimeittakestomakethesubtraction,sothemethodisnotperfect.However,wecandeterminehowlongittakestomakethatsubtractionbyrepeatingit10,000timesandrecordingthetime.

ExternalinterruptsInterruptsareweirdthingsintheArduinoworld;however,theyareimmenselyuseful.Sowhatarethey?Interruptssignaltothemicrocontrollerthatsomethinghashappenedanditneedstotakesomeaction.Basicallytheyworklikethis:wecanattachaninterrupttoadigitalpin.Wheneveritdetectsachange,itwillpauseanythingthemicrocontrollerisdoing,executeafunctionwetellittoexecute,andthenresumenormaloperation.

Inthisexample,wewillfadetwoLEDsusingPWMandwhilethatishappening,wewillbeabletoselectwhichLEDisfadingusingthebuttonconnectedtoaninterrupt.


AnArduinoboardconnectedtoacomputerviaUSBJumpercablesandabreadboardTwostandardLEDsTworesistorsbetween220–1,000ohmApushbutton

Howtodoit…ThefollowingarethestepstoconnectthetwoLEDsandthebutton:

1. ConnectthetwoLEDstothebreadboardandconnecttheirnegativeterminalstogetherandtoGND.

2. ConnecttoeachpositiveLEDterminaloneresistorandconnecttheotherterminaltopin5andpin6.

3. ConnectoneterminalofthepushbuttontoGNDandtheotheronetopin3,whichisinternallyconnectedtointerrupt1.

SchematicHereisonepossibleimplementationusingpins3,5,and6:


CodeThefollowingcodewillfadeoneexternalLED.Whenwepressthebutton,itwillchangewhichLEDisfading:

//IncludetherequiredWirelibraryforI2C

intLED1=5;

intLED2=6;

//Setavariablewhichwecanchangeintheinterruptfunction

volatileintcurrentLED=LED1;

voidsetup()

//SetthebuttonpinasaninputwithPULLUPresistor

pinMode(3,INPUT_PULLUP);

//Attachaninterrupttothatpinwhichcorrespondstointerrupt1

//ItwilltriggerwhentheinputsignalsisFALLING

attachInterrupt(1,changeLED,FALLING);

//Functionthatisbeingtriggeredbytheinterrupt

voidchangeLED()

if(currentLED==LED1)currentLED=LED2;

elsecurrentLED=LED1;

voidloop()

//FadeIn


analogWrite(currentLED,i);

delay(10);

//FadeIn

for(inti=255;i>0;i--)

analogWrite(currentLED,i);

delay(10);

NoteDuetobouncingofthebuttonwhenwepressit,theinterruptmighttriggerseveraltimesandunexpectedbehaviormightoccur.

Howitworks…Whenachangeisdetectedonaninterruptpin,thecodeispaused,thespecifiedfunctionisrun,andthecodeexecutionisresumed.Thechangecanbeafallingorrisingedge,andafewmorethings.TakealookattheThere’smore…sectionofthisrecipe.

Let’slookinthecodebreakdown.

CodebreakdownThefirstimportantdifferenceweseeisthevolatilevariabletype:

volatileintcurrentLED=LED1;

Thevolatilevariabletypeisadirectivetothecompiler.IttellstostorethevariableineasilyaccessibleRAMasitwillbeaccessedduringexecution.Anyvariablewechangeduringaninterrupt-attachedfunctionhastobevolatile,otherwiseweirdthingswillhappen.

Inthesetup()function,weattachafunctiontointerrupt1.WecallthechangeLED()functionanditwilltriggerwhenthereisafallingedgeinthesignalontheinterruptpin.Formoreabouttriggertypes,takealookattheThere’smore…sectionofthisrecipe.

attachInterrupt(1,changeLED,FALLING);

Nowlet’sexplorethechangeLEDfunction.Anyfunctionattachedtoaninterruptcannotreturnanything(ithastobeavoidfunction)andcannothaveanyarguments.Anyvariablemodifiedinsideanattachedfunctionhastobevolatile.

voidchangeLED()

if(currentLED==LED1)currentLED=LED2;

elsecurrentLED=LED1;

Inthisfunction,weinvertthecurrentvalueofthecurrentLEDvariable.Ifit’sLED1itbecomesLED2andsoon.ThisfunctioncanexecuteatanytimeaFALLINGedgeisdetectedontheinterruptpin.

There’smore…Herewewilllookalittlemoredeeplyintothedifferentthingsinterruptscando.

InterruptsonvariousArduinosDifferentArduinoshaveadifferentamountofexternalinterrupts.Remember,intheattachInterrupt()function,thefirstparameteristhenumberoftheinterrupt,notthedigitalpinonwhichitcanbefound.Thefollowingtableisagoodreference:

Board Interrupt0 Interrupt1 Interrupt2 Interrupt3 Interrupt4 Interrupt5

Uno,ProMini 2 3 - - - -

Mega2560 2 3 21 20 19 18

Leonardo 3 2 0 1 7 -

Yún 3 2 0 1 7

OntheYún,pins0and1arealsousedforserialcommunication,sotrytoavoidthem.

TheArduinoDue,however,isanexception.Wecanassignaninterrupttoanydigitalpin.IntheattachInterruptfunction,thefirstargumentwillactuallybedigitalPinwewanttouse.

Aboutinterrupt-attachedfunctionsRememberthatthecodepauseswhenaninterruptisdetectedandourfunctionisexecuted.Becauseoftimerinterference,thedelay()functionwillnotwork.Also,charactersreceivedbytheserialduringtheexecutionofourinterruptfunctionmightbedropped.However,thedelayMicrosecond()functionshouldworkjustfine.

Ingeneral,functionstriggeredbyinterruptshouldbeasshortaspossiblewithminimumimpactandexecutiontime.Otherwise,theymightjustdoverystrangethings.

DifferenttriggeringmodesThelastargumentoftheattachInterrupt()functionisthetriggeringmode.TherearefourdifferentmodeswithafifthcustommodefortheArduinoDue:

LOW:ThistriggersthefunctionwheneverthevalueontheinterruptpinisLOW.IfthefunctionfinishesexecutionandthepinisstillLOW,itwillexecuteagainandagainuntilthepinisHIGH.CHANGE:Thistriggersthefunctionwheneverachangeisdetectedontheinterruptpin.ChangemeansthateitherthepinswitchesfromLOWtoHIGHorfromHIGHtoLOW.RISING:ThiswilltriggerthefunctionwheneverthesignalontheinterruptpinchangesfromLOWtoHIGH.FALLING:ThiswilltriggerthefunctionwheneverthesignalontheinterruptpinchangesfromHIGHtoLOW.

HIGH:ThisisaDueexclusiveandworksexactlylikeLOWmode,exceptthatittriggerswhenthesignalisHIGH.

DetachinganinterruptThereisalsoafunctionthatdetachesinterrupts:

detachInterrupt(interrupt);

Itrequirestheinterruptnumberastheargument.OntheDue,itrequiresthepinnumbertowhichtheinterruptwasattached.

OncethedetachInterrupt()functionisused,adifferentfunctioncanbeattachedusingtheattachInterrupt()function.

AppendixA.Electronics–theBasicsTheArduinoisanelectronicplatform.Inordertouseitproperly,weneedtoknowatleastsomebasicsaboutelectronics,suchas:

WorkingofelectriccurrentOhm’slawDiodesandLEDsWorkingwithbreadboards

WorkingofelectriccurrentHere,wewillexplorehowelectriccurrentworks.Electriccurrentrepresentstheflowofelectricalchargeinaconductorandit’smeasuredinamperes,symbolizedbyA.Voltagerepresentsthedifferenceinelectricalpotentialbetweentwopointsofacircuit.Itismeasuredinvolts,symbolizedbyV.Let’sthinkofabattery.Eachbatterycanbeconsideredavoltagesource,andithastwoterminals,apositive(+)andanegative(-).Followingisoneofthestandardizedsymbolsforvoltagesources:

Inthediagram,weseeavoltagesourcethatproduces9volts.Thismeansthatthepositiveterminalhasa9Vdifferenceoverthenegativeterminal.Thenegativeterminalisusuallyreferredtoasground,GNDforshort.Animportantconventionwhendealingwithcurrentisthedirectionofcurrentflow—fromhigherpotential(voltage)tolower.Thefollowingdiagramshowshowthecurrentflowsfromthepositiveterminal,througharesistor,backtothenegativeterminal:

Resistanceisthemeasureofthepropertyofamaterialtoopposecurrentflow.It’smeasuredinohms,symbolizedbytheGreekletterΩ.Theresistoristhecomponentthatusesitsinternalresistancetorestrictcurrentflow.Thisistheschematicsymbol,andnexttoit,anormalresistor:

Inthefollowingsection,wewillseehowresistorsfunctioninacircuit.

Ohm’slawElectronicsisallrelatedtoOhm’slaw.Thisprovidestherelationbetweenvoltage,current,andresistanceinacircuit.Thelawstatesthatthecurrentpassingthrougharesistorisdirectlyproportionaltotheappliedvoltageacrossit.Inmathematicalforms,itlookslikethis:

Asimplewaytorememberandapplyitaccordingtoeitherofthevariablesisthefollowingtriangle:

Ifwewanttofindthecurrent,wecoverIandwegetVdividedbyR.ThesamegoesforR:wecoveritandweobtainVdividedbyI.Lastly,VwillequalImultipliedwithR.Let’snowapplythisknowledgetothefollowingcircuit:

Here,wehaveone5-voltvoltagesourceinserieswithoneresistorR1witharesistanceof100Ω.Becausewehaveonlyoneresistor,thetotalvoltageacrossitwillbeequaltothevoltageofthesource,5V.WecannowapplyOhm’slawtofindthecurrentinthecircuit:

Rememberthat1ampereequals1,000milliamperes,representedbytheunitmA.

ResistorconfigurationsIfwehavemorethanoneresistorinseries,wecanusetheruleofseriesresistance.Itstatesthatanynumberofresistorsinseriescanbereplacedbyonlyone,withtheresistanceequaltothesumofallreplacedresistances.Mathematically,itisdepictedasseenhere:

ThefollowingdiagramshowsthetworesistorsontheleftinseriesR1andR2.Ontheright,itshowsthesamecircuit,butnowwithanequivalentresistorR3,whichequalsR1+R2.

Thereisalsotheparallelresistorconfiguration.Whenwemounttwoormoreresistorsinparallel,thecurrentissplitamongthem.Thisresultsinaloweroverallresistance.Fortworesistors,theformulalookslikethis:

Thefollowingdiagramprovesjustthat.Ontheleftwehavethenormalcircuitwithtworesistorsinparallel,andontherightwehavetheequivalentresistorvalue:

Wecanbuyresistorswithavarietyofinternalresistances.Toeasilydeterminewhatresistancearesistorhas,acolorcodehasbeencreated.Wecanfindthecolorstripesoneveryresistor.Thisisahelperdiagram,whichshowshowtoreadtheresistorcolorcode:

Youcanfindanonlineequivalentresistancecalculatorathttp://calculator.tutorvista.com/equivalent-resistance-calculator.html.

http://calculator.tutorvista.com/equivalent-resistance-calculator.html

DiodesandLEDsTherearetwomorecomponentsweshoulddiscuss:diodesandLEDs.

DiodesAdiodeisacomponentthatonlyallowscurrenttopassinonedirection.Thearrowinthecircuitsymbolindicatesthisdirection:

Nexttothecircuitsymbolontheleft,wehavearealdiode.Thestriperepresentsthestripeinthecircuitsymbol,andthedirectionwherethecurrentgoesoutofthediode.

Ifwelookatthefollowingcircuits,theoneontheleftwillconductcurrentwhiletheoneontherightwillnot:

However,evenwhenadiodeallowscurrenttopass,itdropsthevoltage.Foratypicalvalue,itdropsthevoltageby0.7V.Let’stryandapplyOhm’slawtotheleftcircuitagain.Ifthediodedropsthevoltageby0.7V,itmeanswehave4.3Vacrosstheresistor.Thiswillresultin:

LEDsThereisavariationofthenormaldiode,calledLightEmittingDiodeorLED.It’sbasicallyaverysmallandefficientlightbulb.WecanfindLEDsineverythingthesedays:displays,phones,computers,toys,andsoon.Theyhavethesamefunctionasadiode,exceptthattheyalsoemitlightwhencurrentpassesthroughthem.Theelectricalsymbolisalmostthesame,butitlookscompletelydifferentinreallife:

Theycomeinavarietyofcolorsandpowerratings.Atypical3-mmgreenLEDwillconsumearound20mAandwillcausea1.9Vdropacrossit.Adiodedoesn’trestricttheamountofcurrentthroughit,soweshouldalwaysconnectaresistorinserieswithadiodeorLED.Inthefollowingschematic,wehavea20mALEDthatcausesa1.9Vdrop.Let’strytocalculatetheperfectresistanceforit:

Duetothe1.9-voltdropacrosstheLED,weonlyhave3.1Vacrosstheresistor.NowwecanapplyOhm’slawtofindtheresistance:

YoucanfindanonlineLEDresistancecalculatorathttp://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator.

http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator

WorkingwithbreadboardsWhenweneedtotestaschematic,wecanquicklyassembleelectroniccomponentsonabreadboard.Itisasimpleandverypowerfulinventionthatmakeselectronicsprototypingeasy.

Lookatthebreadboardandcorrelatewiththefollowingdiagram.Breadboardsdifferinsize,shape,andcolorbuttheyallsharethesameprinciple:

Ontheleftwehaveasimplebreadboard;ontheright,wehavethesamebreadboardwiththeinternalconnectionsshown.Atthebottomandthetopoftheboardwecanseeletters.Ifwefollow,wecanseethat,oneachrow,thelettersA,B,C,D,andEareinterconnected,asshownbytheyellowwire.

Thismeansthat,ifweplugapininA,wewillhaveaconnectiontoB,C,DandEonthesamerow.Rowsarenotinterconnected.Asseeninthediagram,eachrowisindividual.Also,onthesamerow,A,B,C,D,andEarenotconnectedinanywaytoF,G,H,I,andJ.

Somebreadboardsalsohavelongpowerconnectorsonthesides.Wecanseetheminthisexamplebytheredandblackcable.TheselongstripsareveryusefulforsupplyingpowerandGNDtodifferentpartsoftheboardeasily.

IndexA

accelerometerabout/Accelerometerusing/Gettingreadyconnecting/Howtodoit…,Schematic,Codeworking/Howitworks…URL/Seealso

ADCabout/Howitworks…

analogReadResolution()functionreferences/Seealso

Analogreference(AREF)about/Analogreference(AREF)

analogWrite()function/CodebreakdownArduino

about/IntroductionURL/Howtodoit…connecting/ConnectingArduinoconnecting,toMacOSX/MacOSXconnecting,toWindows/Windowscode,uploading/UploadingcodetoArduino,Howtodoit…,Howitworks…codebasics/LearningArduinocodebasicsbutton/Introductionspeaker,connectingto/Code,Howitworks…,Tonewithnoduration,SeealsoNPNtransistor,usedforconnectingexternalload/Howtodoit…,Schematic,Howitworks…,Seealsooptocouplers/optoisolators,connectingto/Howtodoit…,Schematic,Codecontrolling,overserial/ControllingtheArduinooverserial,Howitworks…values,transmittingto/TransmittingvaluestoArduinotutorial,URL/Seealso

ArduinoC/Codebasics–ArduinoC,Howitworks…Arduinocode

timing/TimingArduinocode,Howitworks…ArduinoDue

about/ArduinoDuereferences/Seealso

ArduinoMega/ArduinoMegaArduinopins/Codebasics–Arduinopins,Howitworks…Arduinosoftware

downloading/DownloadingtheArduinosoftware,There’smoreASCIItable

URL/SeealsoATMega328P

URL/SeealsoattachInterrupt()function/InterruptsonvariousArduinos

BBatteryEliminationCircuit(BEC)/Howtodoit…bipolarsteppermotor

about/Bipolarsteppermotors,Gettingreadyconnecting/Howtodoit…,Code,Howitworks…

breadboardsworkingwith/Workingwithbreadboards

brushlessmotorsabout/Brushlessmotorsconnecting/Howtodoit…,Codeworking/Howitworks…URL/Seealso

bubblesortalgorithmURL/Seealso

buttonabout/Introductionconnecting/Connectingabutton,Gettingready,Schematic,Code,Howitworks…momentarybuttons/Connectingabuttonmaintainedbuttons/Connectingabuttonpull-upconfiguration/Pull-upconfigurationmultiplebuttons/Multiplebuttonsconnecting,toserial/Buttontoserial,Howtodoit…,Codebreakdowndebouncing/Buttondebouncing,Howtodoit…,Howitworks…,Codebreakdownmultiplebuttons,connectingtosinglepin/1,000buttonsto1pin,Schematic,Code,Codebreakdown,There’smore…value,finding/Findingeachbuttonmultiplebuttons,pressing/Pressingmultiplebuttonsmultiplexing/Buttonmultiplexing,Schematic,Howitworks…,There’smore…

button,withnoresistorconnecting/Buttonwithnoresistor,Howtodoit…,Schematic,Code,Howitworks…,Seealsomultiplebuttons/Multiplebuttons

Ccode

uploading,toArduino/UploadingcodetoArduino,Howtodoit…,Howitworks…

codebasics,Arduinoabout/GettingreadyArduinoC/Gettingready,Howitworks…Arduinopins/Codebasics–Arduinopins,Howitworks…

contactbouncingURL/Seealso

continuousrotationservos/Continuousrotationservos

Ddatasheet,forL293D

URL/SeealsoDCmotor

URL/Seealsodelay()function/Howitworks…,Howitworks…,Interferencedemultiplexer

using/Buttonmultiplexing,Schematic,Code,Howitworks…,There’smore…digitalcommunication

advantages/Introductiondigitalpins

URL/Seealsoabout/Moredigitalpinsusing/Gettingready

digitalWrite()function/Howitworks…diodes

about/Diodesdistance-controlledLED

building/Gettingready,Schematic,Code,Howitworks…,There’smore…distancesensor

about/Measuringdistance–infraredandultrasonic

EEEPROM

about/Storingdatainternally–EEPROMusing/Howtodoit…,Howitworks…,Codebreakdown

electriccurrentworking/Workingofelectriccurrent

ElectronicSpeedControl(ESC)/BrushlessmotorsEthernetshield

about/Ethernetbuilding/Howtodoit…testing/Howtotestworking/Howitworks…,Codebreakdownreferences/Seealso

externalinterruptsabout/Externalinterruptsattaching,todigitalpins/Externalinterrupts,Howtodoit…,Code,Howitworks…,CodebreakdownonvariousArduinos/InterruptsonvariousArduinosattachedfunctions/Aboutinterrupt-attachedfunctionstriggeringmodes/Differenttriggeringmodesdetaching/Detachinganinterrupt

externalLEDconnecting,toArduinoboard/ConnectinganexternalLED,Howtodoit…,Schematic,Code,There’smore…working/Howitworks…,There’smore…LEDresistor/LEDresistormultipleLEDs/MultipleLEDsreferences/Seealsofading/FadingtheexternalLED,Schematic,Code,Howitworks…,There’smore…

Ffrequencies,musicnote

URL/Seealso

GGNDport/Commonanode(+)andcommoncathode(-)GPS

about/Localization–GPSusing/Howtodoit…,Schematic,Codeworking/Howitworks…,Codebreakdownreferences/Seealso

Ground(GND)/Generalconnectiontips

II2C

about/I2CbetweenArduinos,MoreaboutI2Cused,forconnectingtwoArduinoUNOs/Code,Howitworks…,Codebreakdowncomparing,indifferentArduinocategories/ComparingdifferentArduinocategoriesdevices,connecting/Connectingmoredevices

IDEabout/DownloadingtheArduinosoftware

InertialMeasurementUnit(IMU)/There’smore…input/output(I/O)pins/Codebasics–ArduinopinsIntegratedCircuit(IC)/Custom-madeL293Ddriver,Optocouplers/Optoisolators

LLCDcharacterdisplays

about/LCDcharacterdisplays,There’smore…using/Howtodoit…connecting,toArduino/Howtodoit…,Codeworking/Howitworks…,There’smore…backlight/There’smore…

LEDabout/Introduction,LEDsblinking,withoutdelay/BlinkingLEDwithoutdelay(),Howtodoit…,Howitworks…,Breakingdownthecodecode,breakingdown/BreakingdownthecodeURL/LEDs

LEDbargraphabout/LEDbargraphconnecting,toArduino/Howtodoit…,Schematic,Howitworks…,Codebreakdownworking/Howitworks…commonanode(+)/Commonanode(+)andcommoncathode(-)commoncathode(-)/Commonanode(+)andcommoncathode(-)variations/Bargraphvariations

loop()function/Howitworks…

MMacOSX

Arduino,connectingto/MacOSXmaintainedbuttons/Connectingabuttonmillis()function/Howitworks…momentarybuttons/ConnectingabuttonMOSFETs/MOSFETsmotors

about/Introductionsmallmotors/Controllingsmallmotorscontrolling,withtransistors/Controllingmotorswithtransistors,Gettingready,Schematic,Code,Howitworks…spinning,inbothdirection/Spinningmotorsbothways,Howtodoit…,Code,Howitworks…,Codebreakdowndirectionpin,using/Controlusingthedirectionpin,PWMpin,andbrakepinPWMpin,using/Controlusingthedirectionpin,PWMpin,andbrakepinbrakepin,using/Controlusingthedirectionpin,PWMpin,andbrakepinInputA,using/ControlusingInputA,InputB,andPWMInputB,using/ControlusingInputA,InputB,andPWMPWM,using/ControlusingInputA,InputB,andPWMcustom-madeL293Ddriver/Custom-madeL293Ddriverservomotors/Servomotorsteppermotor/Steppermotorbipolarsteppermotor/Bipolarsteppermotorsbrushlessmotors/Brushlessmotors

multiplexerusing/Buttonmultiplexing,Schematic,Code,Howitworks…,CodebreakdownURL/Seealso

Nnoisereduction

about/Noisereductionrequisites/Gettingreadysteps/Howtodoit…,Howitworks…filters/Howitworks…

noisereductionfiltersmeanfilter/Meanfiltermedianfilter/MedianfilterMainloop()/Mainloop()

NPNtransistorused,forconnectingexternalloadtoArduino/Howtodoit…,Code,Howitworks…,Seealso

OOhm’slaw

about/Ohm’slawresistorconfigurations/Resistorconfigurations

Ohm’slawabout/Ohm’slaw

optocouplers/optoisolatorsabout/Optocouplers/Optoisolatorsconnecting,toArduino/Howtodoit…,Howitworks…

PpinMode()function/Howitworks…PIRsensor

about/Detectingmotion–PIRsensorhookingup/Howtodoit…,Schematic,Code,Howitworks…

PNPtransistor/PNPtransistorspotentiometer

about/Simplesensor–potentiometerrequisites/Gettingreadyhookingup/Howtodoit…,Schematic,Code,Howitworks…,There’smore…ArduinoDue/ArduinoDueAnalogreference(AREF)/Analogreference(AREF)

pull-downresistor/Pull-downresistorPWM

about/FadingtheexternalLED,FasterPWM,Gettingreadyreferences/Seealsoused,forcontrollingspeed/ControllingspeedwithPWM,Howtodoit…,Schematic,Code,Howitworks…,Codebreakdownworking/Howitworks…,Timer2interference/Interference

PWMhackingURL/Seealso

PWMShieldURL/Seealso

Rrelaydriver

about/Relaydriver,Gettingreadyusing/Howtodoit…,Code,Howitworks…working/Howitworks…

RemoteControl(RC)/Servomotorresistancecalculator

URL/ResistorconfigurationsRGBLED

about/RGBLEDconnecting,toArduinoboard/Howtodoit…,Schematic,Code,Codebreakdown,There’smore…commonanode(+)/Commonanode(+)orcommoncathode(-)commoncathode(-)/Commonanode(+)orcommoncathode(-)PWM,avoiding/WithoutPWM

S7-segmentdisplay

about/The7-segmentdisplayconnecting,toArduino/Howtodoit…,Schematic,Code,Howitworks…,Codebreakdowncommonanode(+)/Commonanode(+)andcommoncathode(-)commoncathode(-)/Commonanode(+)andcommoncathode(-)dot/Thedotvariations/Variations

SDcardsabout/SDcards,Gettingreadyusing,preparationsteps/Howtodoit…,Howitworks…,Codebreakdownlimitations/There’smore…

sensorspotentiometer/Simplesensor–potentiometertemperaturesensors/TemperaturesensorPIRsensor/Detectingmotion–PIRsensordistancesensors/Measuringdistance–infraredandultrasonicdistance-controlledLED/Gettingreadyreferences/Seealsoaccelerometer/Accelerometer

Serial.peek()function/Howitworks…Serial.print()function/There’smore…Serial.println()command/CodebreakdownSerial.read()function/TransmittingvaluestoArduinoSerialClockLine(SCL)/Howitworks…SerialDataline(SDA)/Howitworks…serialoutput

obtaining/Serialoutput,Howitworks…,CodebreakdownSerialProtocolInterface(SPI)/Howitworks…servomotors

about/Servomotorconnecting,toArduino/Howtodoit…,Code,Howitworks…,Codebreakdownexactpulsetime,controlling/Controllingtheexactpulsetimeservos/Moreservoscontinuousrotationservos/Continuousrotationservos

setMotor()function/There’smore…setup()function/Howitworks…,Codebreakdownshiftregisters

about/Moreoutputs–shiftregistersconnecting/Howtodoit…working/Howitworks…,Codebreakdown

SinglePoleDoubleThrow(SPDT)/ConnectingabuttonSinglePoleSingleThrow(SPST)/Connectingabuttonsmallmotors

about/Controllingsmallmotorscontrolling/Gettingready,Schematic,Howitworks…multiplemotors/Multiplemotorselectricalspikes/Electricalspikesreferences/Seealso

softwareserialandUARTbetweenArduinos/SoftwareserialandUARTbetweenArduinos,Gettingreadyused,forconnectingArduinoUNOs/Howtodoit…,Schematic,Codeworking/Howitworks…,Codebreakdownusablepins/Usablepinsmultipleconnections/Moresoftwareserialconnectionsinterference/Interferenceconnectiontips/Generalconnectiontipslibrary,URL/Seealso

sonars/Measuringdistance–infraredandultrasonicsound

creating/Creatingsound,Howtodoit…,Schematic,Code,Howitworks…,There’smore…,Seealso

speakerconnecting,toArduino/Howtodoit…,Code,Tonewithnoduration,Seealso

steppermotorabout/Steppermotor,Gettingreadyunipolar/Steppermotorbipolar/Steppermotorconnecting,commonintegratedcircuitused/Steppermotor,Gettingready,Code,Howitworks…,Codebreakdowntransistorunipolarstepperdriver/Transistorunipolarstepperdrivertype,identifying/IdentifyingthesteppermotortypeURLs/Seealso

Ttemperaturesensors

about/Temperaturesensor,Howtodoit…,Codeworking/Howitworks…,Codebreakdown

TimerURL/Seealso

toggleswitchabout/Thetoggleswitchtwo-statetoggleswitch/Thetoggleswitchusing/Thetoggleswitch,Gettingready,Schematic,Code,Howitworks…,There’smore…connecting,toLEDs/Howtodoit…references/Seealso

tone()functionusing/Howitworks…about/Codebreakdownwithnoduration/Tonewithnodurationonmultiplepins/Toneonmultiplepins

ToolBarVerifybutton/There’smoreUploadbutton/There’smoreNewbutton/There’smoreOpenbutton/There’smoreSavebutton/There’smore

transistordriverabout/Transistordriver

transistorsused,forcontrollingmotors/Controllingmotorswithtransistors,Howtodoit…,Schematic,Code,Howitworks…pull-downresistor/Pull-downresistorPNPtransistor/PNPtransistorsMOSFETs/MOSFETsdifferentloads/Differentloadsreferences/Seealso

UUART

betweenArduinos,andsoftwareserial/SoftwareserialandUARTbetweenArduinos,Schematic,Code

UbuntuLinuxcomputerURL/Seealso

Vvariableresistor/Simplesensor–potentiometervoltagedivider

URL/Seealso

WWindows

Arduino,connectingto/Windowswirelessserial

using/Wirelessserial,Howitworks…

XXbe

URL/Seealso

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