Yo,
I got a lot of WS2811 LED strips that I set up in my room and most of them work perfectly. I tested the 2 strips that I ran around the ceiling with jumper cables and loose wiring and they worked fine. Then, I soldered them to the wires I put up to link them to my Arduino and power supply (the wire's like 10ft, don't know if length matters), but after I do this, only the first 3 LEDs will light on both strips. I de-soldered, & resoldered the whole thing, and the problem still exists. I checked over literally the whole thing and I can't find anything wrong with my connections.
I am almost positive it's not the wires that I'm connecting the led's, I can clearly see their path from the Arduino, all the way to the LED Strip, and is there is nothing wrong. I also tested the resistance between each of the pins, and none of them have a connection, so there is obviously no shorts...
I am really confused and am starting to lose my mind, I have no clue why this is happening... :o
If anyone has any troubleshooting advice, that would be awesome! 
Jumper cables?
You aren't clear if you are using the exact same wires as when you tested the strips. The distance is important because it affects the quality of the PWM signal. Here's a quick test- move the Arduino to the first strip and wire it directly, eliminating the ten ft wire.
Do you have power to each end of the strips?
I know that your setup is simple, but a schematic would help. Hand drawn is fine, Fritzing is not.
Also, do the LEDs that light work as expected? Color, effects, etc?
I'm not home rn, but here's a schematic/diagram I just drew... I bet it's the length of the wire screwing up the pwm.
Thanks for the schematic, often I have to beg and plead for that. Are you sure they are 12V strips? Also 5V to Vin on the UNO is incorrect. That will force the 5V through a linear regulator that is designed for higher input voltages.
Adafruit recommends a capacitor across the power and a resistor in series with the data line, and they have a couple of other recommendations. (They say to use a 6.3V capacitor but of course if you're using 12V strips you'll need one rated for more than 12V.)
Can your power supply provide the required current? (I believe the 12V strips are wired in groups of 3 LEDs in series so I'd estimate 20mA per LED "worst case" with all white and full-brightness.)
aarg:
Thanks for the schematic, often I have to beg and plead for that. Are you sure they are 12V strips? Also 5V to Vin on the UNO is incorrect. That will force the 5V through a linear regulator that is designed for higher input voltages.
Yes, they are definitely 12V strips, It says 12V on the PCB, and they have worked before when I used 12V.
As for powering the Arduino, should I connect the 5V supply directly to the 5V of the Arduino (I can't use 12V, The standby of the PSU is only 5V)?
DVDdoug:
Adafruit recommends a capacitor across the power and a resistor in series with the data line, and they have a couple of other recommendations. (They say to use a 6.3V capacitor but of course if you're using 12V strips you'll need one rated for more than 12V.)Can your power supply provide the required current? (I believe the 12V strips are wired in groups of 3 LEDs in series so I'd estimate 20mA per LED "worst case" with all white and full-brightness.)
I added the capacitor and the resistor, no change, I'm still trying the other things on the website...
Yeah, the PSU is rated for over 15A, and my power wires to the led strip are 16 AWG.
I'm starting to think that it's the long data wires... I think I'm going to try using a CAT 5 cable, maybe there will be less interference...
should I connect the 5V supply directly to the 5V of the Arduino
Yes.
tommyokie:
I'm starting to think that it's the long data wires... I think I'm going to try using a CAT 5 cable, maybe there will be less interference...
No, that would be worse. Cable capacitance is what kills the quality of PWM signals, and CAT5 cable is pretty high in capacitance. I use 18/3 LED wire and the longest runs I have made to the first LED is about 3 meters.
Please answer my questions above.
SteveMann:
Jumper cables?You aren't clear if you are using the exact same wires as when you tested the strips. The distance is important because it affects the quality of the PWM signal. Here's a quick test- move the Arduino to the first strip and wire it directly, eliminating the ten ft wire.
Do you have power to each end of the strips?
I know that your setup is simple, but a schematic would help. Hand drawn is fine, Fritzing is not.
Also, do the LEDs that light work as expected? Color, effects, etc?
I tryed it wired directly to the arduino, and nothing at all happended, yes, power at each end, the led strips (when they actually worked) were giving off all the right colors.
I need to take a break, everything I have tried didn't work, my led strips must just be cursed.
tommyokie:
I tryed it wired directly to the arduino, and nothing at all happended, yes, power at each end, the led strips (when they actually worked) were giving off all the right colors.
I need to take a break, everything I have tried didn't work, my led strips must just be cursed.
Let me be more specific.
When only the first three LEDs light, do they light as expected or are they just some random color.
They seem to be a random color
They filcker a little too
tommyokie:
They seem to be a random color
They filcker a little too
OK, that tells me that the first LED is not getting good data.
Did you only buy enough LED strips for your project? An easy fix is to use a sacrificial WS LED at the processor to condition the data signal. This fixed the problem every time I had the same issue.
The power supply and the Arduino must be adjacent. The data wire must always travel along with the ground wire to the strips (and of course, the power wire must also travel along with the ground wire to the strips). No open loops in the wiring.