12V supply for Wemos D1 mini & 2812 LEDs



  • Hi,
    I'm having trouble getting an external supply to work.

    I have a D1 mini and WS2812 LEDs that work just fine when connected to a USB supply, including a 1000uF cap across the GND/5V to smooth out any bumps as per https://learn.adafruit.com/adafruit-neopixel-uberguide/power.

    Now I want to run everything off 12V, so I bought a 3A 12V-5V stepdown converter https://www.aliexpress.com/item/Standard-Power-Supply-Module-Adjustable-Step-down-3A-DC-DC-Converter-1pc-New-SG053-SZ/32429458452.html. However, the rig doesn't work. :( I've checked the voltages.... there's 12V going into the converter, and 5V coming out, and 5V across the 5V and GND pins on the D1 mini and across the LED supply, and the polarity is correct. I've only checked with a multimeter, but there doesn't seem to be any fluctuation in the 5V level. There does seem to be a momentary flash of the LEDs when the power is connected/disconnected.

    Can someone help me please with this? It seems to me that it should just work.


  • Mod

    @frankv could you describe whay you mean with "rig doesn't work"? Doesn't the D1 start? Do the lights not light up?



  • @mfalkvidd Nothing seems to happen when connected to the 12v supply. If I disconnect that and plug into a usb supply, the 2812 LEDs light up and flash as per my program.


  • Mod

    @frankv how do you connect the output from the power supply to the D1? Through the USB port or on some pin?
    How do you connect the power to the LEDs?



  • Hi all,

    Thanks for the replies. Turns out my D1 was faulty, or becoming faulty. When I double-checked on the USB supply, it didn't work there either. Are they particularly static-sensitive?

    The output of the converter goes to the 5V & GND pins on the D1, and also to the 5V and GND connectors on the LEDs. I use pin D2 of the Wemos to send data to the LEDs, via a 470 ohm resistor.

    I specifically wanted to add the 12V to 5V converter because I plan to run these lights at the end of long wires (Xmas decorations), and was worried about voltage drop across the wires. Maybe it's a bit of overkill... when I checked, the lights work OK on 3.6V

    Cheers, Frank


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