Why do some WS2813 LED strips shift/randomize colors?

Question

The Problem

I have a project using multiple WS2813 LED strips, one variant which uses a white PCB and one that uses a black PCB. When setting the colors of these LED strips multiple times, I noticed that the black PCB strips frequently show an incorrect result. Most of the times it shifts the colors by a few LEDs but it will also change the colors or shift the LEDs by 10+.

The PCB

The strips are both WS2813 (at least they were advertised as such). I've attached an image of both the strips below.

Video Example

The following gifs demonstrate the problem I'm having. Both strip types got the command to set leds 25 to 50 to Red.

Gif of Black PCB shifting

Gif of White PCB not shifting

Gif of white & black PCB on the same data pin. Data is coming from the right, so the shift is always later on the strip.

Connections

The strips are connected as follows:

Strip	Teensy 4.0
+5V	External 5V
D0	Teensy Output pin (i.e. 19)
B0	External GND
GND	External GND

The Teensy is also powered by the external power supply.

The LED strips are connected in parallel, with every strip on one of the following pins: 19, 18, 14, 15, 17 and 16.

The strips are only connected at the front, not the back.

Edit: Connecting the back to the power supply does not seem to have any effect on the shifting.

The external power supply is an RSP-200-5 (5V, 40A).

Voltage measures with only 5 LEDs active

• LED #0: 4.99V
• LED #60: 4.97V / 4.98V
• LED #110: 4.95V (Sometimes drops to 4.84V on the white PCB)

Datasheets

White PCB LED Datasheet

Diagram

Answer 1

The Teensy revisions 3+ use 3.3V internally. The pinouts will provide no more than this voltage. The LED, on the other hand, requires 0.7 x 5V = 3.5V as high input.

You need a voltage translator or buffer chip. Any 74ACT or 74HCT logic chip will do. It also helps to connect a 100 Ohm resistor between buffer output and LED data input. See https://www.pjrc.com/store/octo28_adaptor.html for related information.

Answer 2

Typical issue of voltage drop or lack of capacitance.

The led strip does not have a small decoupling capacitor per led or even per few LEDs. You also didnt add a large capacitor to the front.

I see you did connect power to both ends of the led strip. But what is the measured voltage in the middle where the strip is bugging out? For most led strips its recommended to have voltage injected every 2.5 meters.

It could also be a faulty strip. The connections could be bad so the LEDs there are resetting. This could be bad from the factory or someone flexed the strip to an extreme degree and the solder broke.

Answer 3

I can see in your pictures that the two strips are not using identical parts. Note the location of the IC inside the LED package. The strip that is not working as you expect may not actually be what you think you bought. There is also the possibility of counterfeit. I suspect if you tried your setup with another strip of the white variety your issue would be resolved.