Long run of WS2811 leds losing color

After seeing how smart you guys were when it came to helping me through my last issue, I figured this was the best place to ask about another.

So I have 200 leds (4 strands of WS2811's) all connected together. The problem is that while they should all be blinking one color (yellow), they start to turn red as they reach the middle, then super red by the time it gets to the end. I did a bit of research and learned that this is was probably because of something called voltage drop. The problem is that my head is swimming from all the ideas about fixing it. I've read about hooking up a power supply to both ends. Using a single supply with the positive at one end of the LED and the negative at the other. I've read about a power supply with more amps. I've also read about connecting the power directly at different points of the strip (though I'm not quite sure how that would work).

So basically I think I know what the issue is, but have no idea what the best idea would be for actually solving it. But I know guys always have great ideas.

Here's a little diagram of things right now. It's just the 200 leds connecting to the arduino which is being powered by a 5volt psu.

Thanks in advance!

Here's a little diagram of things right now. I

where?

This is a common problem, it comes from the voltage dropping as it goes through that much small foil track .
Just take some thicker wire and wire the ground at the start of the strip to the ground at the end. Do this for the +5V line as well.

If you have four strips then do the same for each strip if just doing it for the whole strip does not work.

Grumpy_Mike:
where?

This is a common problem, it comes from the voltage dropping as it goes through that much small foil track .
Just take some thicker wire and wire the ground at the start of the strip to the ground at the end. Do this for the +5V line as well.

If you have four strips then do the same for each strip if just doing it for the whole strip does not work.

Sorry, for some reason the image wasn't showing. Here is the link: Imgur: The magic of the Internet

So I had heard of doing the power at one end and the ground at another, but you're saying connect both ends? So I assume I'd then have to do a three way splice with another power supply? Or am I misunderstanding you? Here's a quick sketchup of what I think you're saying: Imgur: The magic of the Internet

Let me know if I'm a clown!

but you're saying connect both ends?

Yes.

So I had heard of doing the power at one end and the ground at another

That is simply stupid, it has no advantage at all. Must have been suggested by someone who knows little about how electricity works.

So I assume I'd then have to do a three way splice with another power supply? Or am I misunderstanding you?

Yes I think you are.

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OK, an obvious problem here is that you are suggesting that you are wiring the 5 V through the Arduino which is not realistic. The power supply goes to the LED strip and the Arduino.


Starting to get the idea regarding the LED strip, but if the power supply is adequately regulated, you only need one and the ground at least must be connected to the Arduino. Run the power to the Arduino back from the connection with the first strip so that it is paired (that is, all three wires together) with the data wire - in green on your diagram.

Now, you said you had four strips wired in series. So what you need is a power cable - at least 1 mm2 - running alongside the strips and connecting at every junction between the strips, five points in total. Always have the power wires - as with the data wires - running as a pair; a single two wire cable wherever they go.

Grumpy_Mike:
Yes.
That is simply stupid, it has no advantage at all. Must have been suggested by someone who knows little about how electricity works.
Yes I think you are.

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Thanks for the guide. Hopefully now you can see what I'm up to.

Pic of what I have:

Pic of what I thought you meant:

Pic of what I think you mean now:

Pic of the leds on their own power unit so they don't get fed from the thin arduino wires:

Any of these close to right?

The last one but use only one power supply, the lower one and connect it to the Arduino’s power and ground as well as the LED strip.

Grumpy_Mike:
That is simply stupid, it has no advantage at all. Must have been suggested by someone who knows little about how electricity works.

No advantage at all? I don't think so. When you connect power and GND at the same end of the strip the resistance of the wires will cause the LEDs further from the PSU to "see" less voltage. It is exactly what causes the problem described in OP. But when you connect power to one end and GND to the other all LEDs get (roughly) the same voltage. Also the voltage drop is only half of voltage drop at the furthest LEDs in the original scenario! Surely it is not as good as connecting both ends, or even connecting at multiple points but I think it is definitely better than connecting to only one end. Why do you think it is stupid?

Smajdalf:
No advantage at all? I don't think so. When you connect power and GND at the same end of the strip the resistance of the wires will cause the LEDs further from the PSU to "see" less voltage. It is exactly what causes the problem described in OP. But when you connect power to one end and GND to the other all LEDs get (roughly) the same voltage. Also the voltage drop is only half of voltage drop at the furthest LEDs in the original scenario! Surely it is not as good as connecting both ends, or even connecting at multiple points but I think it is definitely better than connecting to only one end. Why do you think it is stupid?

No, that trick only works for a constant load, where the voltage drop is constant:

Assume a voltage drop of 2V. Provide 7V to Vcc at one end and 0V to ground at the other, and the
2V of drop will be spread out and mean the voltages at one end are 7V and 2V, at the other 5V and 0V,
and each piece of the distributed load sees a 5V difference.

However if the load can vary, this means you zap all your WS2811's with 7V and they all fry, since at
start up there is little load and no voltage drop, so everything sees 7V difference and burns.

Connect thick wires to every strip, and if needed to both ends of every strip. Keep wire runs as short as
possible, and you can calculate the worst case voltage drop using online tables or simple physics to see
what wire thicknesses are necessary.

MarkT:
No, that trick only works for a constant load, where the voltage drop is constant:

Of course the trick woks for ANY load if you know what you are doing.
The LEDs are able to tolerate some voltage drop without change of color. If the voltage drops further it suffers from the "red shift". Let say the color does not change for 4-5V (they are constant current drivers) and starts to shift to red when supply is less than 4V.
Define Scenario A as both Power and GND connected to one side of the strip wile Scenario B is when Power is connected to one end while GND to the other.
Imagine that the strip is too long to be powered as in Scenario A: when the LEDs should be at full power they need too much power - the LEDs at the beginning get 5V but those at the other end "see" only 3V due to voltage drop over long wires - they suffer from significant "red shift". When we connect the same LED strip to the same PSU but as in Scenario B there will be voltage drop to 4V over the whole strip - the colors are still as intended. In short in Scenario B the strip may be twice as long as the strip in Scenario A - for free!
Scenario B has another advantage over Scenario A. When the power supply is too weak the LEDs at the far end of the strip have largest voltage drop while the LEDs at the beginning still get full voltage - they are different color despite they should be the same color. OTOH in Scenario B all LEDs "see" the same voltage - they still suffer from the "red shift" but all the same - much harder to notice for the user IMHO.