Bottom line: don't put LEDs in parallel as they will not evenly share current. If the forward voltages are different, then only the LED with the lowest forward voltage will light up as it will turn on and steal all of the current before the other LEDs will exit cutoff. If the forward voltages are the same, then the LEDs will split the current and light up at half brightness, approximately (not exactly because the current will never quite split exactly). However, if you try to turn on more than one, then the LEDs will be in parallel and they will behave in an unexpected manner. If you only try to turn on one element at a time, it will work correctly. However, if you a stick one resistor pin on the common terminal, you will have some issues.
If you wire the common terminal directly to a power rail and put 3 resistors on the other side, it will work as expected. However, an RGB LED is a rather different animal since one side of all of the elements are tied together. But if I connect the anodes to +5V through their separate 220ohm resistors(according to the instruction), the colours will combine.įor a single LED you are correct - which side you put it on does not matter. When I bridge all three anodes together, only the red LED lights up. However, when I bridge the G and B pins together, only the green LED lights up. When I touched any one of the R, G or B anode legs with a jumper wire connected to +5V, the respective colour lights up alright. I tried that by plugging the LED into the breadboard and connecting the cathode through a 220ohm resistor to the ground of Arduino UNO. But I thought, why can't I put the resistor on just the cathode of the LED? In the project book, the instructions for the colour mixing lamp is to use separate 220ohm resistor for each of the RGB legs. Recently I bought the official Arduino starter kit and played around with the common cathode RGB LED that came with this kit. Different from the best answer of this one: Why does a resistor need to be on the anode of an LED?īut well, I'm also an electronics noob ^.^
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