In tutorials I've seen, people connect every LED of a RGB LED to a resistance. I understand the purpose, but could we simply put the same resitance once, if we connect it to the common cathode or annode?
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It won't cause any damage, but it has some negative sideeffects like BartmanEH explained. Why not try it out youself, and see what happens if you e.g. connect both red and blue at the same time. You'll learn more by trying.– GerbenFeb 8, 2016 at 10:38
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1For a detailed explanation see Why exactly can't a single resistor be used for many parallel LEDs?– GreenonlineFeb 8, 2016 at 11:18
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1 Answer
The problem with one resistor in common anode/cathode is that when you activate more than one colour of the RGB LED, you will have additional current flowing through the one resistor which will cause increased voltage drop across the one resistor due to ohms law which will cause less forward voltage across the LED and likely extinguish it or at least make it much less bright.
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2Yes, if you only need one colour activated at a time, then it would be ok to have just one resistor. Feb 8, 2016 at 0:47
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See Why exactly can't a single resistor be used for many parallel LEDs?. However if you only ever turn one on at a time, it should be OK as the answer says.– Nick Gammon ♦Feb 8, 2016 at 4:25