From: noel shelley (noel@shelley1722.freeserve.co.uk)
Date: Fri Oct 22 2004 - 13:34:34 PDT
Good Evening Gentlemen ,
May not answer the question but
might be helpful , if only for warning
lights ! I have seen rear light assemblies that use LEDs
There are some very bright LEDs available , in various colours , red green,
yellow, blue, clear Etc . If put straight across 24V they would draw too
much current and go POP , so a limiting resistor of the right value to suit
the voltage must be used . From the data sheet take the current drawn ,shown
as" If Typ " &" If Max " ,Typically 10-30 , normally 20Ma {0.020 }and
divide into the voltage you
want to use eg 24 V.
24 /0.02 = 1200 or 1.2K Ohms.
The power rating should be 24x .02 = .48 , so 1/2 Watt .
SO a LED with one leg wired through a 1.2K 1/2 Watt resistor will draw 20Ma
.The longer leg is normally +{anode } , if reversed it won`t work .
They come in many sizes 3-5-8-10 mm Dia but all use the same power , except
the ultra brights . { roughly }
Since they are reasonably bright even at 10 Ma , a setup for 24V will still
work on 12V .
At a few cents each , and resistors even less , there is the potential for
some experimentation here , but don`t exceed the If max figure . To test the
current drain wire a multi meter in series on the Ma scale .
When using several together you must have a resistor for each , that way if
one fails the rest still work ! { paralleled } [ they can be seriesed but ,
one goes, all gone ]
A clear lens rather than diffused on the LED will be better .
Right fellas , round to radio shack , Look forward to hearing how you used
this information .
NOW it`s my turn to ask a question , where or how do I get the divide symbol
, and also the Ohms sign , plus many others not on my keyboard , someone
said ASCII codes , what are they and where are they.
Have fun Noel
PS for 12V use 680 Ohm 1/4 Watt resistor .
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