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The Problem

I have a project using multiple WS2813 ledstrips, one variant which uses a white PCB and one that uses a black PCB. When setting the colors of these ledstrips 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.

Image of Black PCB

Image of White PCB

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 Black PCB shifting

Gif of White PCB not 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.

Gif of White & Black PCB on the same data pin

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 ledstrips 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 4.84 on the White PCB)

Datasheets

White PCB Led Datasheet

Diagram

Electrical Diagram

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  • \$\begingroup\$ What to check for when buying an electronic component or module. Please provide data sheet links. \$\endgroup\$ – Andy aka Jun 15 at 10:29
  • \$\begingroup\$ How are the LED strips connected? Are they connected one after another as a single long chain, or both directly to Teensy as two parallel chains? How are they powered with 5V, from only from one point, or are both strips powered from both ends? \$\endgroup\$ – Justme Jun 15 at 10:41
  • \$\begingroup\$ @Justme, I've updated my post with the information. \$\endgroup\$ – Veleon Jun 15 at 10:47
  • \$\begingroup\$ @Andyaka, I've added one datasheet. For the other one I'm still waiting to hear from the retailer. \$\endgroup\$ – Veleon Jun 15 at 10:48
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    \$\begingroup\$ Have you got a large electrolytic cap anywhere? Typically, these strips require 10-100uF across the supply at the start of the strip. Without it, you can get unpredictable results \$\endgroup\$ – SiHa Jun 15 at 13:12
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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.

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  • \$\begingroup\$ The voltage in the middle is the same as measured with only 1 end connected to the power supply. Currently I think that it's an issue with the timing, as all 200+ meters of black pcb ledstrip have the same problem. \$\endgroup\$ – Veleon Jun 15 at 13:43
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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.

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