FEATURE
Testing NeoPixel Voltages
f 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.
The setup was a fairly simple solution. We used a 5 V
microcontroller (the Arduino LilyPad Plus USB was the first 5 V
controller we came across rummaging through the HackSpaceI
By Ben EverardFind out what these LEDs can handle
Testing
NeoPixel
Voltages
Testing
NeoPixel
Voltages
Figure 1
A strip of WS2812Bs,
running with their
signal line shifted
to under 3 V, running
an animation
without problems