23.04.2010 ©Vellemannv
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3)Selectthecolour
TherearebasicallytwotypesofLEDstripswhencolourisconcerned:
Singlecolourtypes
TheseLEDstripsonlyhaveonecolour.Mostoftenthiscolourisblueorwhite(coldwhite‐CW:resembles
daylight,warmwhite‐WW:resemblesincandescentlight),butothercoloursarealsoavailablee.g.red,
green,amber…
Thesestripscanbeeasilyidentifiedastheyhaveonly2wires(plusandminus)forpowersupply.
Bycontrollingthepowerthestripcanbedimmed(preferablyusingPulseWidthModulationorPWM).
RGBLEDstrips
Withthesestripsitispossibletoprodu ceanycolourbyusingadditivecolourmixing.Thesestripscontain
red,greenandblueLEDs;eithercombinedinasingleRGBLEDorasseparateLEDs(resultinginmoreLEDs
permeter,see§2).
Typicallythesestripshave4
wires,acommonwireand3otherwires:onepercolour(red,greenandblue).
Bycontrollingthepowertoeachseparatecolour,theintensityoftheindividualcolourscanbeadjustedand
thusanycolour(includingwhite)canbecreated.
Notes:
• WithRGBstripsthecommonwireisusuallyconnectedtotheanodesoftheLEDs(positive)oftenthiswireis
colouredblack;thewiresforcontrollingR,GandBareconnectedtothecathodes(negative)oftheLEDs,
oftencolouredred,greenandblue.Inthiscase
redandblackwirearenot+and–supplyvoltages!
• Theratedpowerismostoftengivenforeachsinglecolour,notforthewholestrip.Keepthisinmindwhen
choosingthepowersupplyorcontroller.Addupthecurrent/powerofthethreecolourstodeterminethetotal
current/powerconsumption.
• SpecialRGBstripsareavailablewhereeverysingleRGBLEDisseparatelycontrollableandmagnificentcolour
andanimationeffectscanbecreated.Thesestripscanonlybeusedwithaspecialdedicatedcontroller.
4)Selectionofthepowersupply
TherequiredpowersupplydependsofthechoiceofLEDstripandtheirtotallength.
Both12Vdcand24VdcLEDstripsareavailable.Themainadvantageof24VdcLEDstripsisthatyouhave
doublethequantity ofLEDsforthesamecurrentandpowerconsumptionthanwitha12VdcLED
strip.
Obviously‐sincetheLEDquantityisdoubled‐thelightoutputisalsotwiceasstrong.
Thesecondcriterionisthetotallengthwhichdetermineshowmuchoutputpower(Watts)yoursupplymust
becapableofdelivering.ThecurrentsorpowerratingsareastandardspecificationforeachLEDstrip
and
canbefoundinthedatasheets.
ForinterconnectionofLEDstripssee§2
Example:
Weassumethesameexampleof§2forcalculationofthepowersupply(20mVellemanCHLS3B).
In§2wecalculatedthatonly2stripsmaybeinterconnectedwhichtotalsto10m.Sinceweneed
20m
wemuststillconnect2oftheselengthsinparalleltothepowersupply.
Aswealreadycalculatedweneed4x18W=72W.Whatwearelookingforisaprotected12Vdc
supplywhichiscapableofdeliveringapowerofatleast72W.