basics: introduction to circuits - iowa state...
TRANSCRIPT
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.