Download - Basics: Introduction to Circuits - Iowa State Universityclass.ece.iastate.edu/ee185/pdfs/basics/Circuits_Intro.pdfPreparing the Multi-Meter Above your desk, you have a digital multi-meter

EE185Lab

Basics:IntroductiontoCircuitsTheTILaunchpadhasnumerouscapabilities.Let’sstartwiththemostbasicusageandsimplyuseitselectricalpowertomakecircuits.

SetupandPreparation

ItemList• TILaunchPadMSP430G2• Breadboard• M/FJumperWires(2)• M/MJumperWires(2)• 3-5Resistors(Anyvalue)• AnLED • Banana-to-Breadboardcables(2)

Preparingthebreadboard1. ConnecttheTILaunchpadtothecomputerwiththeUSBcable.

a. AnLEDontheLaunchPadshouldilluminatetosignalthatitispowered.2. Usingthe2male-to-femalejumperwires,connectthepositive(VCC)andnegative(GND)pinson

theLaunchPadtothepositive(red)andnegative(blue)railsonthebreadboard.(Figure1)NOTE!-TherearemultipleVCCandGNDpinsontheLaunchPad;usethecorrectones.

Figure1:PoweringthebreadboardwiththeTILaunchPad

PreparingtheMulti-MeterAboveyourdesk,youhaveadigitalmulti-meterwhichcanbeusedtomeasureusefulquantitiesincircuits,likevoltage.Pluginyourbanana-to-breadboardcablesintothetoprightsocketsshowninFigure2.Thelocationofthevoltmeterandohmmetersettingsisalsoshown.

Figure2:Agilent34401ADigitalMulti-meter

TipsonBreadboardingThebreadboardhasapatternofmetallicrailsunderneaththesockets,whichelectricallyconnectwiresinsertedintothebreadboard.Onlycertainsocketsareconnected(Figure3).Noticethatthepowerrailsrunallthewaydownthebreadboard,contrarytotheterminalstripsinthemiddle.

Yourpowerrailsmaynotextendthefulllengthofbreadboard.Examinethered/bluelinestobesure.

Figure3:HiddenConnectionsoftheBreadboard

MeasuringVoltageTutorialIfyouhaven’tusedavoltmeterbefore,openthetutorialMeasuringVoltagewithaVoltmeteronthelabwebsite.Youmayfindthistutorialhelpfulasyouprogressthroughthislabmaterial.

Circuit1:LED

Createandtestthefollowingcircuit(Figure4)withasmallvalue(around100Ω)ofR1.

Figure4:AnLEDcircuit

ThingstoConsider• NotethatthewirescomingoutoftheLEDhavedifferentlengths.Thisisdeliberate.• Tryusingthemulti-metertomeasurethevoltagedropacrosstheLED.Thenacrosstheresistor.

o Comparetothevoltagedropacrossallthecomponents(fromVCCtoGND).• YoucandeterminethecurrentflowingthroughthecircuitusingOhm’sLaw.• Anarticleaboutvoltage,current,resistance,andOhm’slawcanbefoundatthefollowinglink:

o https://learn.sparkfun.com/tutorials/voltage-current-resistance-and-ohms-law

Circuit2:TwoResistors

Createandtestthiscircuit(Figure5)withdifferentvaluesforR1andR2.

Figure5:Tworesistorsinseries

ThingstoConsider• Thecolorsontheresistorsrepresentthevalueoftheresistance.• Whenaresistorisnotinthecircuit,youcanmeasureitsvalueofresistancebyconnectingthe

ohmmeterleadstobothendsoftheresistor.(Thebreadboardcouldhelpwiththis).• Oncethecircuitisassembled,thevoltagedropacrossaresistorcanbefoundbyconnectingthe

voltmeterleadstobothendsoftheresistor.• YoucandeterminethecurrentthrougheachresistorbyusingOhm’sLaw.

Circuit3:ThreeResistors

Createandtestthiscircuit(Figure6)withdifferentvaluesforR1,R2,andR3.

Figure6:Threeresistorsinseries

ThingstoConsider• Considerthevoltagedropacrosseachresistor,andcompareitwiththevoltagedropacrossall

theresistorsatonce(therailvoltage).• YoucancalculatethecurrentsthrougheachresistorusingOhm’sLaw,andthencomparethe

currents.

Circuit4:Button

Createandtestthiscircuit(Figure7)usingalargevalueforR1.

Figure7:ButtonwithPull-downResistor

Thingstoconsider• Youcanuseamulti-metertoobservethevoltageatdifferentpointswhenthebuttonisused.• Youcandeterminehowthe4pinsofthepushbuttonareconnectedwithacontinuitytest.

Review

Afterthislab,youshouldhaveagoodunderstandingofthefollowingtopics.Ifyou’renotsureaboutsomeofthem,gobackthroughthelabandtrytoafindagoodplacetoexplorethetopic.

Youshouldbeabletodothefollowing• Powertherailsofabreadboard,anddesigncircuitsbetweentherails• Readandmeasuretheresistanceofaresistorwithanohmmeter• Measurethevoltagedropacrosstwopointsinacircuitwithavoltmeter• DeterminethecurrentflowingthroughacircuitwithresistorsusingOhm’sLaw• Designacircuit,suchthatadesiredvoltageappearsatsomepointinthecircuit

o Example:Usingonlyresistors,designacircuitsuchthat2.5VappearsonthevoltmeterwhenmeasuringthevoltagefromGNDtosomepoint(severaldesignscouldwork)

• LightupanLEDinacircuit

Application

Tryapplyingtheskillsyoulearnedfromthislab.Youcancomeupwithyourownprojectideaortryonefromtheflowchart.