Hi all,
Can anyone point me in the right direction why I cant get my WS2812 to work with a Teensy or RasPi? I’ve got a 5V/10A power supply that I checked and it delivers 5.5V at the strip. Weird things is that I can see some random LEDs flashing the moment I connect it to GND, but they stay black after that no matter what I feed them through software.
Any help is appreciated. Thanks
Please read this first:
Most importantly this:
Are the grounds of your power supply and Teensy connected?
Check if there is data output using a regular LED
Yeah tried to connect both GNDs, no difference I’m afraid
You may have a strip that’s picky about the signal voltage. 2812 require 5v signal, teensy is 3.3v signal. Usually you can get away with 3.3v signal but from what I’ve read there are sometimes where it won’t.
If you’ve followed all the adafruit advice to, next thing I’d do is cut the strip and test with another pixel. Try adding a 1uf (size isnt to critical) across the power rail also
@Harald_Krefting What code are you trying to use? This is a possible source of error as well.
I’ve got a bunch of strips here and they are all the same, so I don’t think it’s an issue with the strips itself.
Tried the simple FastLED samples and the Octo2812 library. I used to run these strips sucessfully with the Octo library before, but with an older Teensy3.0 and different power supplies. Will continue tomorrow by trying another power supply if I can find one. Thanks for all your suggestions so far
So far you have done/lacking a few of these items:
Try to use a signal converter from 3.3V to 5V,as described in the OctoWS2811 library page. You can also try to connect 100 to 220 ohm resistor between data signal and level converter, to cut off dirty spikes from the signal.
The 74HCT245 is the level shifter most people use for that.
I’ll also add that these strips want UP TO 5.0 volts. They can tolerate 5.1v, but 5.5v is way too high, and will almost certainly be contributing to the communication / stability problems.
WS2811/WS2812 Neopixels are extremely picky, and the hardest of the LEDs to work with. APA102 “DotStar” LEDs, on the other hand, are extremely tolerant and easy to work with. I’m migrating everything that I can toward APA102 for future projects. Now all I need are strings of “pixel nodes” with APA102…
Well I’m using an LED power supply that’s labeled 5V, so it might just be my cheap multimeter being inaccurate. I’m going to add a 74HCT245 when it arrives, even though I used to run these without the shifter before. Might have been a coincidence.
@Mark_Kriegsman APA102 pixel nodes would be awesome! I’m also waiting for these things 
Btw: where did you buy the APA102 strips? I only find good prices on RayWu (aliexpress)… looking forward for better shops
If I had to bet, I’d bet that the power supply is in fact above five volts, and that the multimeter isn’t off by very much.
Often LED power supplies are designed to run large strings of (less-picky) LEDs, and the tune it to be over 5.0v so that even with the voltage drop that comes with long strings, the end voltage is ‘high enough’. (e.g., see the first paragraph of discussion here https://learn.adafruit.com/adafruit-powerboost/overview )
And in genera that’s a fine approach for them to take. However, WS2811/WS2812 Neopixels are just so darn picky that this makes them not work well, or at all. Dan and I have seen this many times now; 5.0v is fine, 5.1v is probably fine, 5.2v is probably not reliable, 5.3v is not reliable, and anything higher is no good.
What would be the suggested way to deal with this since the voltage would drop over the length of the strips? Feed in the power from the opposite end or at multiple points along the length?
I have used copper tape successfully for a power bus:
https://plus.google.com/105445034001275025240/posts/JRzVHMHaX3x
I use to feed in power every 100 leds. Depending on your strip lenght and the content you run on it feeding power from both ends might be enough but then you better stay away from animations that use a lot of white.