The RGB LED I bought is a cheap one. It seems that even though it has 3 colour components (R,G,B), It cannot really reproduce such colours as I see on a PC monitor. For example, setting the same low value to all three components does not give me a dark grey colour as I see on a computer monitor, but just a small white colour (not even actually white, some red or blue colours are glistening if I stare at it).

Is this because this is a cheap module or an RGB LED cannot produce PC-monitor colours? If the answer is the latter, is there some type of small lamp hardware that can reproduce real RGB colours?

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  • Try pigpio. sudo pigpiod then pigs p 17 100 p 27 50 p 22 25. The colour should be stable. 17/27/22 are the GPIO connected to pins 11/13/15. The values 100/50/25 are out of 255 (e.g. 0 off, 128 half on, 255 full on).
    – joan
    Jul 17, 2020 at 17:55
  • Could you please tell me the number on the smd resistors? Jul 17, 2020 at 19:50
  • your eyes do not see absolute color very well, but can see relative color well .... if you put two slightly different colors side by side, then you can see the difference between them ... if you look at the two colors individually, then you cannot see any difference .... that is why the LED may look the same when set to various colors
    – jsotola
    Jul 18, 2020 at 20:35

1 Answer 1


Sounds like it -might- be working the way you need it to. What you're missing is a diffuser/combiner for the light coming from the LED. When you look directly at an RGB source that's not diffused you'll see the individual colors. As for dark grey vs white, that's a matter of relative intensity (assuming everything's balanced).

I've used ping-pong balls for diffusion- I'm sure there are better solutions but that's what I had at the time. You could also try sanding the LED lens so it acts as a diffuser.

If you let us know what you're trying to accomplish we might be able to come up with a more 'targeted' solution/suggestion for you.

  • What I am trying to accomplish... I was not thinking about some special objective, but I had just expected the various colours that I see on a monitor. So, you could say that what I was trying to achieve was "the colours we see on a typical PC monitor". I will try the ping pong ball method. I do not have a ball, but I have a thin plastic cap from a mineral water bottle somewhere. Jul 17, 2020 at 20:43
  • 1
    just shine the light on the back of a sheet of paper
    – jsotola
    Jul 18, 2020 at 20:32

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