I'm asking this because it's a pain to place one resistor for each anode. Is this the only solution?
Also, I'm intrigued by the fact that a lot of tutorials about LEDs talk about using a 220 ohm resistor. Why? Even for a red LED consuming 25 mA, the required resistor for running it on a 5V line(that's what Arduino provides, right?) is only 120 Ohms.
what happens if I put the resistor on the cathode instead of using 3 resistors for each color anode?
Then it won't work. Once you put the red LED on then the others won't come on because the red LED clamps the voltage at a lower value than is needed to turn on the other colours.
Why? Even for a red LED consuming 25 mA, the required resistor for running it on a 5V line(that's what Arduino provides, right?) is only 120 Ohms.
Most LEDs work at 20mA not 25mA. Yes you can use a lower resistor but most LEDs are good enough at between 10 to 15mA
what happens if I put the resistor on the cathode instead of using 3 resistors for each color anode?
Then it won't work. Once you put the red LED on then the others won't come on because the red LED clamps the voltage at a lower value than is needed to turn on the other colours.
Well, that makes sense. Thanks for the response. It's a pain to work with so many resistors :(.
. Yes you can use a lower resistor but most LEDs are good enough at between 10 to 15mA
That's quite some news to me, I always calculated resistors for the 20mA-30mA range. Isn't 10 mA too low though? Won't the LED be too dim?