lucstechblog: Flexible led filament a first look

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In a previous story I showed how to work with led filament. These are rigid tubes that contain leds in one color and can be used for lots of projects. You can read that story here: https://lucstechblog.blogspot.com/2025/11/led-filament-first-look.html

There is however also a flexible version available. These usually consist of micro LED diodes mounted on a flexible metal base, coated with silicone for protection. They are constructed in a way that it looks as if the light of the leds shine 360 degrees. The back side of the strip though looks less bright as the front.

The led filament is indeed flexible. Bending the strip to sharp will break it. So no 90 degree corners, just a smooth bend.

These flexible leds are available in several colors: warm white, pink, green, blue and red.
and they can be bought in several lengths. I have seen lengths up to 450mm (45 cm).

Please note each of these led filaments have 1 color. They are not like ledstrips or neopixels. They have a fixed color. So make sure you order the ones you need.

Beware of the contacts.

There are versions available where both VCC and GND contacts are at one end of the ledstrip. And there are versions that have contacts at both ends, just like the rigid versions. So check which version you need before placing an order. Just be careful when experimenting as the contacts are fragile.

They are available from our usual Chinese friends. Adafruit sells them also (although a lot more expensive) and calls then nOOds (from noodles)

Power requirements.

There is surprisingly few documentation available.

There are two versions available. The first works at 12V and the second at 3V. For our microcontroller projects I advise to use the 3V version.

Adafruit suggest you can supply up to 100mA. Chinese suppliers advise a maximum of 50mA.
Better safe as sorry so I suggest stay below the 50mA.

Breadboard setup

I used the same breadboard setup as in the story about the rigid led filament.

Like in the previous story the led filament is powered by a 5V USB power supply. The Raspberry Pi Pico can not supply enough current from it's IO pins so a 2N2222 transistor is used.

The 2N2222 can supply a maximum of 800ma but that is in optimal circumstances with proper cooling. Stay on the safe side and attach up to 4 led filaments to one transistor so the maximum current the transistor needs to supply will be around 200ma.

You can exchange the Pico by an ESP8266 or ESP32 but then you will need to alter the programs to use the right GPIO.

In this setup I used a resistor of 100 Ohm. The USB wall connector supplies 5V. So the resistor reduces the current to 20Ma
If you are using a different power supply or want more (or less) current please revert to the previous story for an explanation of the calculations. You can find it here : https://lucstechblog.blogspot.com/2025/11/led-filament-first-look.html

If you want the leds to be brighter use a resistor of 47 Ohm. That will give around 40mA although I must say I did not notice any difference with my eyes. So I advise to stick at 100 Ohm.

The programs are also the same:

# -------------------------------------------
# simple test for setting filament on and off
# -------------------------------------------

from machine import Pin
import time

filament = Pin(16, Pin.OUT)

while True:
    filament.value(1)
    time.sleep(1)
    filament.value(0)
    time.sleep(1)

This sets the led filament on and off.

# -------------------------------------
# test program for dimming led filament
# with PWM
# -------------------------------------

import machine
import time

filament = machine.PWM(machine.Pin(16))
filament.freq(1000)

while True:
    min = 0
    max = 65536
    for i in range(min,max):
        filament.duty_u16(i)
        time.sleep(.0001)
    #time.sleep(.5)
    for i in range(max,min,-1):
        filament.duty_u16(i)
        time.sleep(.0001)
    #time.sleep(.2)

This program brings the led slowly to full brightness and then slowly dims it and keeps repeating this sequence.

The led filament consists of leds so if your program does not work try changing the VCC and GND contacts at the filament.

My tests.

I bought a 30 cm long pink strip which had both contacts at 1 side.

First I made a circle around a round object.

And here I draped the led filament around a wooden stick with a diameter of about an inch (2.5 cm).

The led filament is fun to play with. The filament is bright and invites to be used in several creative projects.

Till next time
have fun

Luc Volders

Friday, November 21, 2025

Flexible led filament a first look