Not sure if this is the best place to ask for help, but I’m going insane and not sure where to find the answer. I’m running WLED on a NodeMCU using the latest update. 100 LED’s that are 12v ws2811. I have sacrificed a led to send the signal over a data cable about 2m. The last section is flickering a random colour. I have tried adding power both ends but this makes no difference. I’ve also noticed that sometimes the sacrificed led will flicker. Checked all connections and still unable to figure out issue. Any help will be great. Thank you.
Are you skipping the first LED? How thick is the power wire to the end and how far is it?
Hi. Yeah first led skipped. The cable is max 2m the cable is standard 12v speaker cable 24 strand.
You need logic level shifter. https://github.com/Aircoookie/WLED/wiki
https://github.com/Aircoookie/WLED/wiki/Compatible-hardware
The 2811 chips have a VDD of around 5V (even if the LED’s are driven at 12V, see the example voltage divider circuit in the datasheet: https://cdn-shop.adafruit.com/datasheets/WS2811.pdf ).
The data signal should be close to VDD, if you’re driving it straight from an ESP8266 that’s 3.3V which sometimes works (on 2812s driven with a 5V supply I’ve never had a problem even though its a little out of spec), but its likely VDD is driven a little higher in your 12V 2811 pixels and 3.3V is just a little too far off.
As srg74 says you should level shift the data signal. Its kind of pain there are 3 voltages in a 12V string. I put an off the shelf buck regulator in my board to get 5V from 12V, that drives the D1 (or nodemcu) which has a 3.3V regulator on the module and the 5V drives the level convertor. I’ve attached a concrete level shifter example using another cheap chip (a CMOS level shifter) not mentioned on the wiki – this is nice because you can tune VEXT if needed for long lead ins (don’t put 12V on VEXT, that will blow up a 2811). I remember having a hard time finding concrete 12V pixel based examples when I did this last year.
4 Likes
Thank you. There’s a lot of information that will take me some time to get my head around.
Flickering at the end is not
The lack of a logic shifter it is lack of power. Many factors go in to injecting power. Step one is measure the voltage at the end of the string. If it is below 10.5 you definitely need power. I would say 11.2 personally to be safe, but there is some margin of error. Needless to say flickering at the end is power.
As far as adding power back in you need to make sure your supply can handle the total amount of current that your lights will draw. Also, if the lights themselves are using 22awg wire vs 18 you may need to inject in the middle of the string. Using a meter is your friend the data will steer you were you need to be.
On the flickering sacrificial pixel. If you have this but only sometimes I would review your connections. It could also be related to the lack of power in the whole system or a bad ground. Out of all the variations that I run until this year, been doing this for a few. I have not ever used a level shifter. Level shifters are also not required if you put a pixel next to the nodemcu.
Last common mistake I have seen is not having proper grounding when powering the nodemcu. If you are using a nodemcu the vin pin will handle 7-14 volts using 12v on the node mcu helps reduce the risk of improper grounding through the dc-dc converter to get 5v. I had this happen to me one 12 to 5 converter worked the other causes flickering on pixel 1.
Forgot one more thing. To troubleshoot if problem is data vs power. This has worked for me. Set strings to one color full brightness then disconnect the data wire from the controller. Solid colors don’t require data to constantly be sent. The string should stay solid that color of it flickers you have a power problem. Next do the same thing for white. White draws more power and will shake out any bugs at a lower power.
The other thing I have done is light up just the flickering section of strip. If it functions when doing so then Your have power issue. I use xlights or fpp to do this. Wled would need segments setup.
1 Like
You can always try this mod from my other post. Works for me and easy to construct if your not that technically minded. See the pic in post 8.
Thank you for all the information. The power coming out of the end of the string is 11.7v I will tonight check all the other ideas you have suggested. Thank you
I would definitely use a logic level shift with the output gpio for a stable 5v .
Also be certain to always run Data and Gnd from the controller (NodeMCU)
to your pixels . The Gnd is referenced from the controller by the Data .