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Topic: Beginner question about RGB (Read 136 times) previous topic - next topic


I recently bought some RGB LED's to make a setup I've been thinking about. As I started building the circuit, I realized that the red requires 2-2.2V while the blue and green require 3-3.2V. I know how to get the 3 volts to the blue and green, but I don't know what I can do about the red. Does anyone have any ideas?


Jun 30, 2020, 08:05 pm Last Edit: Jun 30, 2020, 08:21 pm by PerryBebbington
Hello and welcome.

You don't power LEDs with voltage, you power them with current. This typically means having a voltage a bit higher than the Vf of the LED and using a resistor to limit the current. I suggest you start with 5V and about 270Ohms or thereabouts in series with each LED; that's 3 resistors, one for each LED, not 1 resistor shared across all 3.

I'm guessing you are new to electronics. There are 2 important laws basic to all electronics and understanding them makes the answer to a lot of basic questions like this easy to work out. They are Ohm's Law and Kirchhoff's circuit laws. It will be well worth your time to learn them if you are serious about electronics.

If you search this site you will find loads of topics explaining in more detail.


Yes, I am new to electronics. I was using Ohm's Law, but I was using it to calculate the number of ohms needed for the voltage, not the current. I guess that's the reason why I got such weird answers (0.0002 Ohms).

Thanks for the information!


I don't really understand what you have done. Have you understood what I have explained? I've not given you a complete answer because I want you to have the pleasure of finding the answer yourself, plus the answer is here to be found if you search.

Enjoy your new hobby.


Jun 30, 2020, 09:28 pm Last Edit: Jun 30, 2020, 09:29 pm by OsmanMansurov
Yes, I have.

I ran into a new problem. I only gave it a blue input and ground and nothing happened. Could the LED's be faulty?


Anything can be faulty. If you have been connecting power to the LEDs without a resistor they have probably been damaged. Do yo have a multimeter? Are you connecting them the right way round?

Once you start asking questions about actual circuits it helps a lot to post a schematic, hand drawn and photographed is fine. Also a clear photo of what you have and how you have connected it.
How to post an image

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