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From: sasrer@unx.sas.com (Rodney Radford)
Subject: Re: Need LCD wiring - 16 wires
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Date: Thu, 17 Nov 1994 14:47:36 GMT
References: <NAHSHON.94Nov13120343@dan.haifa.ibm.com>  <3a6f7m$da4@wumpus.cc.uow.edu.au> <NAHSHON.94Nov14170123@dan.haifa.ibm.com>  <CzCABG.5Ms@news.Hawaii.Edu> <94320.201332LEEK@QUCDN.QueensU.CA>
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>>The LCD screens I have that have LED backlighting have a limit of 100ma
>>for the backligting.  If you hook it up to +5, it will draw more and
>>damage the screen.
>The Optrex 40x4 LED backlight takes about 350mA.  Always use a current
>limiting resistor or source, do not connect it directly to +5V.

What size limiting resistor is necessary to keep the LED backlight current
to the 350mA (or 100mA) values specified above?  This requires knowledge of
the voltage drop across the LED backlight - is it the traditional 1.5-2v
drop across a standard LED? If so, then I would need about 100 ohm resistor
for 350mA if I use a 5v supply - does this sound correct?

Thanx.

BTW - I purchased some 16x2 LCD displays with LED backlight surplus, so I
   don't have any specs on the backlight.  

--
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Rodney Radford,     Senior Systems Developer,  Image Technology Group
sasrer@unx.sas.com  SAS Institute, Inc, Cary, NC 27513  (919) 677-8000 x7703
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