Possible grounding issue between Feather RP2040 & LEDs

Other Hardware General Electronics
1

Hello,

I have an Adafruit Feather RP2040, with an Adafruit Music Maker FeatherWing (non amplified) on top, and an Adafruit 20W amplifier controlled via I2C on the feather. I have these set up in the empty shell of a retro 80s boombox, along with:

I've hooked up the following connections:

  • on 12V power supply, hot to hot, neutral to neutral, ground to ground
  • +5V output from step down converter directly to the USB pin on the feather & to the 12V power screw block on the 20W amp
  • -5V from step down converter going to feather's GND pin & -12V screw block on 20W amp

The power supply has 3 sets of screws for the 12V bus, list of what's on each:

  1. 1 set of lights' +/-
  2. 2nd set of lights' +/-
  3. the 12V side of the stepdown converter

Finally, the data line of the lights go from Feather -> Logic level converter (from 3.3v to 5v) -> Lights. The logic level converter LV is plugged into the 3.3V bus on the Feather, with the HV plugged into the USB/5V pin on the Feather.

I am using Arduino IDE with the FastLED library to program this. I have a fairly complex program set up on the feather that plays music, and adjusts the lights as though they were Christmas lights with the occasional special effects. When I test things with the feather plugged into my laptop's USB (& 12V PS off to not fry my laptop), everything works perfectly, even powering the 12V lights (I limit it to 1 strip to not kill the feather, or my laptop USB port) with 5V. However, when I unplug USB, and plug in mains power to the power supply, the feather powers fine, and executes the program fine, but the LEDs do not light correctly--they'll flicker weirdly, and usually will be the wrong color. I've heard that a common issue is grounding when lights don't behave as expected, but I've tried the following ways to ground:

  • Connected Feather's GND to the 12V supply chassis
  • Connected Feather's GND to the GND of the mains input
  • Connected Feather's GND to -12V bus

However, the problem persists in each case. I'm kinda out of ideas as to what I'm missing. Any ideas?

2

Maybe your logic level converter doesn't get HV of 5V when the USB is not connected?
Maybe connect it directly to the 5V of the step down.

3

Posting an annotated schematic showing exactly how it is wired including power, ground, power sources and links to technical information on the hardware parts will save all of us a lot of time and get you a much better answer. Personally I do not do well with word problems or frizzies.