Tutorial

7/27/2015 UnregulatedPowerSupplyTutorialSparkFunElectronics
https://www.sparkfun.com/tutorials/103 6/9
20Ohmsisaboutthevaluefortheidealloadthatwillleavethesupplyoperatingclosetoitsratedpeak
currentoutput.Theoscilloscopeoutputofthepeakvoltageagreeswiththecalculation.
R=V/I,whereV=6VandI=300mA,R=20Ohms
Witha20Ohmloadyouwillseeclosetotheratedoutput.However,thesignalisanythingbutpureDC!
There's2Vofripple!Aregulatororanadditionalfiltercircuitmustbeusedtoflattenoutthiswaveforuse
inmostdigitalelectronics.
Therearesomewallsuppliesthatarecalledswitchedmodeandprovideamoresufficientlyregulated
outputthanthesupplyinthistutorial.Thismeanswhenyoumeasuretheopencircuitoutput,youwillsee
closetothevoltagethatisspecified.SparkFuncurrentlysellsonlyswitchedmodesupplies.
Tosumitup,theoutputlistedontheboxofyourpowersupplysays6V300mADC.Inmost
circumstances,youwillnotsee6V,300mA,oragoodDCsignal.Itseemsthatthereshouldbe
somethingonthesupplythatsays'RatedOutput'insteadofjust'Output'oratleastalittlemoreinfoon
thequalityoftheoutputsignal,butthatmightbetoomuchtoaskforapieceofelectronicsthatcostsa
fewdollars.
PopQuiz:Whyistheoscilloscopesignalabout120HzwhentheACfromthewalloutletis60Hz?
Conclusion
Ifyouhaveanycomments,questions,ortyposfeelfreetoemail:[e-mail].
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TheTrustedOne / about7yearsago / 12
Lovethesite,hatetoburstyourbubble,TheUnitedStatesisnottheonlycountryusing120Vac60Hz
power,lookuphigheronthemap,thelargercountryaboveyoudoestoo.:D
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