Re: Best way to power array of LEDs?

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#282

From: John Woodgate
Date: Fri, 04 Oct 2002 12:56

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I read in sci.electronics.design that Ban <bansuri@masterweb.it> wrote
(in <2Qan9.3129$cS4.107732@news2.tin.it>) about 'Best way to power array
of LEDs?', on Fri, 4 Oct 2002:
>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.

But the current drops to around 10 mA when the battery voltage is 12 V,
which may or may not matter in terms of reduced brightness. With a
string of 3 LEDs in series, and 470 ohms, the current at 14 V is 19 mA
and at 12 V it is around 15 mA. A good guide is that the string should
not take up more than half the lowest supply voltage.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
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From: John Woodgate <jmw@jmwa.demon.contraspam.yuk>
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, 4 Oct 2002 13:56:01 +0100
Organization: JMWA Electronics Consultancy
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