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Powerand control for small neopixel projects
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Powerand control for small neopixel projects

by Rcayot on Fri Sep 11, 2020 4:50 am

I guess my question is whether a level shifter is required for an Adafruit microcontroller running at 3.3v for say an 8 neopixel strip/board? How about 16 neopixels? ( two 8 neopixel strip boards).

I have a larger project, and it appears I will need a level shifter for that, but I want to start learning to program neopixels and dotstars first usung my Metro M4 express.

I guess I can always just try it, but feel more comfortable with a bit of guidance.

Thanks in advance!
Roger

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Re: Powerand control for small neopixel projects

by adafruit_support_mike on Fri Sep 11, 2020 5:09 am

You probably won't need one.

The NeoPixels we carry use the 5V-CMOS signal protocol, which defines HIGH as anything more than 70% of the supply voltage and LOW as anything less than 30% of the supply voltage. On a 5V supply, those come out as 3.5V and 1.5V.

The thresholds are minimum requirements though, so all real devices accept values a bit below 3.5V as HIGH and a bit above 1.5V as valid HIGH and LOW inputs to guarantee they'll do what they're supposed to at 3.5V and 1.5V.

Our NeoPixels usually accept 3.3V as HIGH, even when running from a 5V supply.

The number of pixels in the strip doesn't matter, because each pixel acts as a signal buffer to the rest of the strip beyond it. After being told to accept new color values, a pixel will consume the first 24 bits it sees on its DIN pin, then copy any other bits on DIN directly to its DOUT pin. So once you get past the first pixel, all the data to the rest of the strip obeys the 5V-CMOS protocol.

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Please be positive and constructive with your questions and comments.