As someone new to the world of FastLED,

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As someone new to the world of FastLED, am trying to figure out how to address a subset of LED’s in a WS2812B. Here’s what I’m trying to do with the Arduino connected.

I’m trying to make a color organ that lights up different LED’s depending on the amplitude of the signal.

Lets say I have a strip that has 30 LED’s. I want to set LED 0-9 to Blue, 10-19 Red, 20 - 29 Green…based on an analog input. When the amplitude of the input changes, I want to set 0-7 Blue, 10-14 Red, and 20-26 green.

I’ve only been able to find information on changing strips or multiple strips connected to different outputs. Any suggestions of where to look for sample code? Thanks.

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The LEDs are setup in an array. Your code can modify the array however you want. In this case you would set 0-7 to Blue, 8-9 to Black, …
This can be done in a for loop with conditions.

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Thanks Dushyant, I hadn’t thought of it that way. I’ll give it a try.

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Sounds like a fun project. How many LEDs do you think you’ll use? I’m curious how you’re sampling the signal too.

If you get stuck with your code post to http://gist.github.com and share the link and we’ll try to help.

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I’m using a MSGEQ7 to sample the music and drive digital outputs on the Arduino, but the trick is to merge the outputs to 7 different strings of WS2812. I’m wanting to use 20 led’s for each of the seven channels, and map the A/D input so that the number of LED’s that are lit in each channel is porportional to the strength of the audio for that channel. If I can get that to work, would look at varying the brightness too if the processing is fast enough.