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Article #170Re: Best way to power array of LEDs?
From: Nucharin W. Jansen
Date: Tue, 05 Nov 2002 22:19
Date: Tue, 05 Nov 2002 22:19
34 lines
3127 bytes
3127 bytes
What's happen when voltage drop across LEDs are not same ? I have problem with white LEDs in series. I can't control the current. I have to adjust in real work one by one in each branch. Ban wrote: > > "Jerry G." <jerryg50@hotmail.com> schrieb im Newsbeitrag > news:Rsan9.14070$qh1.1622310@news.ca.inter.net... > > Each LED must have its own series resistor. Most of these LED's work > > at about 30 to 40 ma with about 1.6 VDC across them. You should be able > > to use a 320 ohm 1/2 watt resistor in series with each LED if these are > > in the spec range that I used as an example. > > > > LED's cannot be wired in parallel to each other being fed from one > > resistor. They can not also be wired in series with each other. > > > > Nope, of cause they can be wired in series if the available voltage allows > it. > Check the datasheet for the typical forward voltage. Red leds have around > 1.7V, yellow/green ones are 1.9-2.3V, blue/white ones even higher 3.2-3.8V. > If you use just a resistor in series with each chain, you should calculate > it for the max. supply voltage which I would suggest is 14.0V. > Now if you put 6 red leds in series with 20mA current rating, you get > 6*1.7V=10.2V; 14V-10.2V= 3.8V; 3.8V/20mA=190 ohms; take 180 or 200 ohms. The > resistor can be a normal 1/4W 0207 type. > > -- > ciao Ban > electronic hardware designer > http://thinkamove.com/
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 112d1e,4ef4c9d4aea85e1f X-Google-Attributes: gid112d1e,public X-Google-Thread: 10d137,4ef4c9d4aea85e1f X-Google-Attributes: gid10d137,public X-Google-Thread: 1118be,4ef4c9d4aea85e1f X-Google-Attributes: gid1118be,public X-Google-Thread: 103407,4ef4c9d4aea85e1f X-Google-Attributes: gid103407,public X-Google-Thread: 1131b0,4ef4c9d4aea85e1f X-Google-Attributes: gid1131b0,public X-Google-ArrivalTime: 2002-11-05 14:30:11 PST Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!newsfeed.stanford.edu!canoe.uoregon.edu!arclight.uoregon.edu!wn13feed!worldnet.att.net!208.49.253.98!newsfeed.news2me.com!yellow.newsread.com!bad-news.newsread.com!netaxs.com!newsread.com!teleglobe.net!news.cscoms.com!not-for-mail From: "Nucharin W. Jansen" <tong@fanwap.com> 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: Wed, 06 Nov 2002 05:19:42 +0700 Organization: C.S. Communications Co. Ltd. Lines: 34 Message-ID: <3DC843FE.4A25FFF3@fanwap.com> References: <0001HW.B9C26E7400A7161B165FEAC0@news.covad.net> <Rsan9.14070$qh1.1622310@news.ca.inter.net> <2Qan9.3129$cS4.107732@news2.tin.it> NNTP-Posting-Host: dial-12.ras-31.bkk.c.cscoms.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: news.cscoms.com 1036534787 63355 202.183.254.107 (5 Nov 2002 22:19:47 GMT) X-Complaints-To: abuse@cscoms.com NNTP-Posting-Date: Tue, 5 Nov 2002 22:19:47 +0000 (UTC) To: Ban <bansuri@masterweb.it> X-Mailer: Mozilla 4.8 [en] (Windows NT 5.0; U) X-Accept-Language: en