Hi Folks,
I recently bought a few of these:
Can’t really argue with the price, but FYI, they will power up full brightness white!
This can cause a hiccup in boot if intending to use software power control and battery power source. I’m pretty sure none of my other WS2812s have done this…is this a new chip variant in the field? They react perfectly to WS2812 fastLED driver and otherwise seem a good matrix.
Has anyone else come across this behavior?
I’ve had a couple of strips that would always power up with the blue LED on only but would act normal once I sent them data.
I seem to have exactly the same cjmcu matrix, but not that behaviour.
Interesting… I just did a few quick experiments, if I just power up the matrix with no connection to the data in they all go white and the whole thing pulls 1.5A according to my bench PSU.
If I add an MCU which is set to initialise all to full white with brightness at 255 the matrix pulls 2.95A … so it’s not powering on full white but more like 50%.
Also these things get very hot when left full white for a few minutes!
Another interesting thing: On the matrix I’m using for this test one LED does not power up white, but will go white when instructed.
I think I’m looking at an LED batch problem maybe? I have ten of these, all bought at once and they all power up bright.
Make sure you have a 1000uf capacitor between the Gnd and 5V and make sure your GND is connected to the Micro and power-supply. Seen this before.
I’ll try the cap, but they’ll all light up with nothing at all connected to the data line, unlike my other WS2812 strips, and 0v (at both ends of the matrix) is definitely connected,along with MCU 0v when testing with MCU.
I’ve got the same matrices, four pieces to form a 16x16 matrix. They power up white and bright, which brings my cheap 2 amp power socket supply down to its knees up to the point where the Nano can’t boot up anymore. Using a 10 amp supply fixes this, but I’d still prefer a dark startup.
I always have an 1000 uF capacitor at the start of the strip (or matrix), unfortunately this doesn’t fix the bright startup.
I’d really appreciate any hints how to fix this problem. 
I tried contacting the seller with a clear description “no connection to data in, but when I apply power they go white” but got a stock “please send a video of the problem” reply which I haven’t had time to (pointlessly) do yet. I think we’re looking at a bad batch of WS2812B where the power on reset doesn’t clear the MSB of each of the colour registers as none of my other WS2812B arrays (circular and strips) do this.
Maybe that explains the price. 
Sorry, have to dig out this thread again… I now have the problem, that at some point (position and time) the data stops flowing. See picture. I replaced the faulty panel and immediatly got the same problem on another panel.
All after a few minutes running. Maybe a temperature problem? When I switch it off and back on after a few minutes, it works for a few minutes.
I can’t believe, that all these panels suck. Is it coincidence that after replacing one panel I’ve got the same problem on another one?
sigh seems, I have to dump all my eight panels. They are just unreliable.
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hey guys i just bought the same item from aliexpress and i can only seem to make the first led work properly using the tutorial from fastled website.
did you guys use some other codes or configurations? a sample code would be appreciated.
im not sure if the problem is with my code or some power/current issues. im using an LM2596 buck converter to step down a 15V battery supply composed of 1850 batteries.