If you look at a data sheet for WS2812B RGB LEDs (commonly known as NeoPixels), you’ll see that they need an input voltage of between 3.5 V and 5.3 V, and a signal voltage of at least 0.7*input voltage. The vast majority of microcontrollers now on the market operate at 3.3V, with additional voltage outputs of 5 V and 3.3 V. This causes a problem because it means that there’s no way to connect NeoPixels directly to the microcontroller without going
out of these ranges. If you connect the NeoPixels to the 5 V power, then they need at least 3.5 V to operate, which is more than the microcontroller’s data pins output.
Of course, just because a data sheet says that they need at least 0.7*input voltage, it doesn’t mean that they do. Many people connect NeoPixels up directly to 3.3 V microcontrollers without problems. Here at HackSpace magazine, we’ve been wondering what we should advise people to do – follow the data sheet even though that leads to more complexity, or ignore the data sheet and cross our fingers as many people do. We decided to run some tests to see what the actual real-world limits are.
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