LED Flickering

Issues
1

I’m trying to set up some LEDs outside. Have a ESP NodeMCU 8266 powering 600 LEDs (2 strips of 300) with a 15amp power supply. I split the power/data wires close to the NodeMCU after running through a sacrificial LED because the two strips are independent and my data wires are about 20 feet long. Using 18 gauge wire for the runs.

I power everything up and it mostly works but I get some flickering (https://streamable.com/0tbavn). Mostly it’s on one strand but the other does it occasionally as well. Solid colors are better but still some flickers. Lowering the brightness helps a lot too but still see some flicker. Any effects are the worst (though rapidly changing ones are the worst).

I’ve read a bunch of the GitHub issues and see a few potential solutions and hoping to see if I’m missing anything obvious:

  1. Bad sacrificial LED? I can try a different one and/or get a level shifter if that’s “better” but not sure this is the problem.
  2. Insufficient power supply? I’d followed Dr. ZZZ’s “zimple” rule of ~50 LEDs per amp so 15 felt like enough but maybe I need more like 20-30? Given that lowering the brightness seems to help the most this is the way I’m leaning.
  3. Should I set the LED count to 600 even though it’s only 300 on a single data wire?
  4. Bad data wire?

Any help would be appreciated!

Edit: Bit more further testing after reading https://github.com/Aircoookie/WLED/issues/230. I turned the LEDs on and then set them to a color and disconnected the data wire from the NodeMCU. No more flickering. Connect it and it flickers. So I think I can rule out the power supply (#2) but still has me wondering what to do with the data wire.

2

Hi!
Thank you for the detailed report! I am quite sure that the signal the sacrificial LED is receiving is not high enought to reliably detect it. Everything else about your setup sounds good. Yep, 300 LEDs is the correct setting for 2 strips with 300 LEDs each.
There are two options, either you get a levelshifter or a board like the QuinLED Dig Uno equipped with one, or you could use the diode trick to lower the voltage of the sacrificial LED :slight_smile:

3

Thanks for confirming, I tried a different sacrificial LED without luck so went ahead and ordered the level shifter. That seems like it’s pretty much guaranteed to work.

4

I had some flickering once also apparently one string of leds was more sensitive than the rest. Adding a sacrificial led of the type I knew worked solved the problem.

Think you are on the correct path. Hoping the level shifter works.

5

Got the logic level shifter and still had flickering. Disconnected one strand and it worked fine. Tested the other strand and it also worked. Tried together, nope. Tried splitting the signal BEFORE the logic level shifter and presto magic. Huzah!

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6

Which level shifter did you use? I have multiple setups where I run several strips in parallel from the same level-shifted output pin and haven’t seen any issues myself.

7
8

Interesting. I thought I saw someone say that the I2C-type is too slow.

9

Working fine for me, but I’m not running effects super often.

10

Yes, it’s certainly not the ideal level shifter, some say it works, others say it doesn’t, scope on it doesn’t look too great. It’s also bi-directional which might have caused an issue while connecting multiple strips to a single pin, feedback might become an issue at that point, not sure.

Still good info! In the future we should have multi-channel boards which will solve these issues altogether. :slight_smile:

1 Like