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led resistor?


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miles&Jules
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led resistor?

Hi guys

I dont know anything about resistors, but what does it mean when you connect up a resistor/led and it starts out really bright but then fades down to pretty dull in a few seconds...is it burning out? I tried soldering 2 resistors on but that didn't help either.....what is a good strength resistor for a white led running at 12v 20amp?
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Post Thu Jan 24, 2013 11:18 am 
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marto
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A 12V 20A LED?

Ahh yes something is burning out by the sounds of it. Need more details to help.

Steve
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Post Thu Jan 24, 2013 11:23 am 
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Jaemus
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Definately burning it out.

A fairly safe guide with no other information would be to use a 1kohm resistor. This is safe for most superbright LEDS @ 12v. The amps the supply power is capable of is irrelevant, but you can choose how much current to drive the LED with by selecting the right resistor.
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Post Thu Jan 24, 2013 11:29 am 
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Valen
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If you put enough voltage up em they change colour before they die.
(greens go yellow)

though thinking about it, that may just have been the inside glowing thermally....

try something like this
http://led.linear1.org/1led.wiz
and add a bit to what it says to use
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Post Thu Jan 24, 2013 11:34 am 
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miles&Jules
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Thanks guys i'll give the 1kohm a go!

Val, that calculator looks cool to! Very Happy
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Post Thu Jan 24, 2013 1:34 pm 
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