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Article #271Re: Best way to power array of LEDs?
From: budgie
Date: Fri, 04 Oct 2002 08:16
Date: Fri, 04 Oct 2002 08:16
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On Fri, 04 Oct 2002 08:19:10 +0200, Tilmann Reh <tilmann.reh@autometer.de> wrote: >DaveC schrieb: >> = > >> Have assembled an array of LEDs for use as a 3rd brake light in my car,= > >> configured as 4 rows of 9 jumbo LEDs, as of yet unwired. Of course the = >power >> supply will be 12 volts nominal (13.8 volts, maximum). >> = > >> My options, as I see them, are: >> 1) Wire individual resistors to each LED based on its operating current= > >> 2) Wire each row in parallel and connect one resistor based on operatin= >g >> current for 9 LEDs >> 3) Install voltage regulator to output voltage (ie, 1.3 volts?) to oper= >ate >> all LEDs in parallel. >> = > >> What is the best method to power these from an intermittent (whenever I= > press >> the brake pedal) power source? > >Better use many LEDs in series to avoid unnecessary power loss. >With 12V supply, you can use about 5 LEDs in series and a smaller >resistor for each chain. These chains are then connected in parallel. The problem with that approach is that, as you put more in series, the volt drop across the resistor reduces but the voltage variation due to system volts looms up large. As a result, the brightness varies more with system volts than single LED/resistor strings. As for power saving, that's like not using your parachute because it will cause wear. I'm sure he isn't planning on driving around with the anchors on all the time.
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 112d1e,4ef4c9d4aea85e1f X-Google-Attributes: gid112d1e,public X-Google-Thread: 1131b0,4ef4c9d4aea85e1f X-Google-Attributes: gid1131b0,public X-Google-Thread: 10d137,4ef4c9d4aea85e1f X-Google-Attributes: gid10d137,public X-Google-Thread: 103407,4ef4c9d4aea85e1f X-Google-Attributes: gid103407,public X-Google-Thread: 1118be,4ef4c9d4aea85e1f X-Google-Attributes: gid1118be,public X-Google-ArrivalTime: 2002-10-04 01:20:25 PST Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!newsfeed.stanford.edu!bloom-beacon.mit.edu!news-out.cwix.com!newsfeed.cwix.com!news1.optus.net.au!optus!news.uwa.edu.au!nntp.waia.asn.au!nnrp.waia.asn.au!not-for-mail From: budgie@nowhere.cantech.net.au (budgie) Newsgroups: sci.electronics.components,sci.electronics.design,alt.engineering.electrical,aus.electronics,sci.electronics.repair Subject: Re: Best way to power array of LEDs? Date: Fri, 04 Oct 2002 08:16:31 GMT Organization: CanTech Online Lines: 40 Message-ID: <3d9d4dbc.3648371@news.cantech.net.au> References: <0001HW.B9C26E7400A7161B165FEAC0@news.covad.net> <3D9D32DE.93168158@autometer.de> NNTP-Posting-Host: proteus.cantech.net.au X-Trace: nnrp.waia.asn.au 1033719299 2169 203.26.6.6 (4 Oct 2002 08:14:59 GMT) X-Complaints-To: usenet@nnrp.waia.asn.au NNTP-Posting-Date: Fri, 4 Oct 2002 08:14:59 +0000 (UTC) X-Newsreader: Forte Free Agent 1.21/32.243 Cache-Post-Path: proteus.cantech.net.au!unknown@ra125.cantech.net.au X-Cache: nntpcache 2.3.3 (see http://www.nntpcache.org/)