TLDR; If you see ink flooding around the die when you touch a Sharpie to the face of a Neopixel, you should probably throw away the batch. Disturbing video example after the jump.
I recently found a huge lot of WS2812B Neopixels on Alibaba for $3/meter, which is about 1/2 the going rate in China and about 1/8th the price for similarly spec’ed strips on Adafruit. So I bought a lot (both meanings) of them. A NeoPixel is a NeoPixel, right? How bad could these NeoPixels be? Very bad, it turns out…
I started building panels with the new strips and the pixels were literally dying faster than I could finish the panels. Some pixels would fail with one color stuck on, but most would fail completely, which killing the whole rest of the string because of the way these pixels daisy chain. Yikes!
Is there any way to tell Neopixels are lemons before you start building stuff with them?
The Sharpie Intrusion Trick
In a high quality pixel, the clear potting should form an airtight bond with the rest of the case. This seal keeps moisture away from the sensitive parts and holds everything solidly together.
This is what happens when you touch a Sharpie to the seam of a low quality pixel…
It’s so bad it physically hurts to watch it. Don’t even give that batch of pixels to your rival hackerspace.
PIXEL HALL OF FAME AND SHAME
- Zhitao Zhang via Alibaba– EXCELLENT
I have purchased more than 100,000 of these pixels from Mr. Zhang of the past year and have yet to get a bad one. I have many that have been running continuously for months. Note that when I order from him (my strips are all custom length), I specifically ask for the “best quality” pixels, although I don’t know if that changes what I get.
- Unnamed Seller – CRAPPY!
These are the pixels form the above article and they are unusable. They have a DOA rate of about 1 per 100 and then a mortality rate of about 1 per 100 per hour. The failures seems to be due to the terrible silicon potting, so don’t necessarily judge a pixel to be crappy just because it has this layout- do the above sharpie test to check.
FAQ
Q: We want names!
A: I don’t want to name the goody factory that sold me these crappy pixels because I know people who love them. My guess is that this was a bad batch and they knew it, and that’s why they listed them so impossibly cheap. It would have been nice if they said something about it in the listing, but when you see something for 1/2 the normal price in the bazaar…
Q: Can my highschool/hasckerspace/LED club have your crappy pixels?
A: If you can convince me that your project is a good match for free but really crappy pixels, then they are yours. Projects where the pixels are destroyed in the process of being used are encouraged!