12V LED + NodeMCUv3 Working; 5V LEDs not working

Hi,

I have one NodeMCUv3 Lolin flashed with WLED connected to a 12V WS2811 Led Strip using a 12V to 5V Buck converter working superb.

Now I was trying another one but this time with a 5V WS2811 Bulb Strip (Like Christmas Lights). If I connect all of it through an External Power Supply, the NodeMCU doesn’t boot and the lights do not light up. BUT If I press the Reset Button on the NodeMCU board the LEDs all light up ok but the NodeMCU board isn’t still accessible via WLED Wifi. Connection as per below:

If I power the NodeMCU through Laptop USB it boots and the lights also but since they don’t have the same GND the lights flicker which is normal.

I have tried 3 Power supplies, 2 or 3 NodeMCUs so the issue isn’t with those components I guess.

Thanks in advance for the help.

Doing some more tests. If I connect the LEDs and the NodeMCU but without the D4 pin connected the NodeMCU works. And I connect after it boots the D4 Data Pin and everything seems to work apart from a flicker on the LEDs from time to time.

Well it was solved by connecting the 5V output from the PS to the 3.3V PIN on the nodemcu instead of the 5V.

Hi, most likely the LEDs are pulling the D4 pin low which prevents it from booting (no wifi + no lights). Usually placing a 3.3kOhm resistor between 3.3v and D4 resolves this issue.

Connecting the 5v to the 3.3v pin of the NodeMCU is not a good idea at all! I’m surprised it didn’t get fried by that, but it could at any point since the maximum operating voltage is 3.5 volts!

If you want to get rid of the occasional flickering as well, I’d recommend getting a 3.3v -> 5v levelshifter like the SN74HCT125N :slight_smile:

Yep you are right. I thought it could withstand the 5V even on the 3.3 rail. I tried your solution with the 3.3K resistance and it worked. Thanks