NeoPixels are great when they work, but I’ve managed to create many circuits that didn’t.
They failed in every imaginable way — NeoPixels that wouldn’t turn on, NeoPixels that flickered, NeoPixels stuck on a color (blue seems to be my NeoPixels’ favorite) and — the most baffling of all — NeoPixels that worked when powered from one USB port, but not when powered from a different USB port.
Despite the wide range of symptoms, almost every one of these failures had the same underlying cause: powering NeoPixels with 5V, but connecting their data line to a 3.3V microcontroller.
The root of the problem here is that — according to the NeoPixel data sheets — the NeoPixel data line voltage (in logic-high state) has to be at least 0.7× the NeoPixel power voltage.
In other words, the power voltage has to be at most 1.43× of the data line voltage. Therefore, if the data line is at 3.3V, then the highest voltage you can put on the power line and still have a reliable NeoPixels is 1.43 × 3.3V = 4.71V.
As a result, if your NeoPixel power is close to 4.7V, the NeoPixels will be unreliable in interpreting its data line, resulting in flicker and random color changes.
Similarly, if your NeoPixel power is substantially higher than 4.7V, then the NeoPixels will not see any data on the data line, which will lead to it being stuck on black (for most NeoPixels) or blue (for some older NeoPixels).
Most notably, powering from USB (which provides 5V) does not work if your microcontroller logic is at 3.3V.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, or even use Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for MakeCode, CircuitPython, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Python for Microcontrollers — Python snakes its way on the SparkFun SAMD21 Mini, Hackaday.io, 10k thanks, and Tim’s magazine #Python #Adafruit #CircuitPython @circuitpython @micropython @ThePSF @Adafruit
Get the only spam-free daily newsletter about wearables, running a "maker business", electronic tips and more! Subscribe at AdafruitDaily.com !