From: "Nucharin W. Jansen"
Subject: Re: Best way to power array of LEDs?
Date: Thu, 07 Nov 2002 05:42:28 +0700
Organization: C.S. Communications Co. Ltd.
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NNTP-Posting-Date: Wed, 6 Nov 2002 22:42:32 +0000 (UTC)
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Yes, I mean in series.
But two strings can not use the same R values.
So sad it very hards to calculate the current and R.
the forward voltage drop does not identical in each LED.
and it changes when current change too.
strings 1 : ( 12 volt - ( 3.453 + 3.6324 + 3.833 ) ) / 40 ohm = 27 mA
Now I want 20 mA , How to calculate the resistor ?
Since forward voltage change when the current change too.
Lizard Blizzard wrote:
> Nucharin W. Jansen wrote:
> > 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.
> You say the LEDs are in series, so the current is identical in each one.
> All you have to do is put a current limiting resistor in series with
> those, and use a value that will give you the right current thru all.
> If you made a mistake and meant parallel, then yes, you should not
> connect LEDs in parallel without a resistor in series with each LED to
> limit and equalize the current.
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