Actions
Forum Thread Details
  • State Verified Answer
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 179 subscribers
  • Views 1045 views
  • Users 0 members are here
Related

Adafruit NeoPixel Eagle vs Datasheet

gonsays@gmail.com

/Hey guys,

 

I've a issue regarding the NeoPixel LEDs from Adafruit (WS2812B LEDs).

 

In the datasheet of this LED model (https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf ) it says that we should add a 0.1uF capacitor for each LED.

 

If you check the .sch and .brd for the NeoPixel Ring 24x LEDs (https://www.adafruit.com/product/1586 ) - WS2812B -  we have 24 LEDs and only 15 capacitors (https://github.com/adafruit/Adafruit-NeoPixel-Ring).

 

I'm doing my own board with WS2812B LEDs. Should I use 1 capacitor/LED -or- should I do as Adafruit and use 15 capacitors for 24 LEDs?

 

Thank you very much in advance!

  • 0

    If your own project is a simple personal one and you've got the space, put a 100nF with each LED and include a placement for some bulk decoupling [a tant or an aluminium electrolytic] where the power comes on to the board. That way you cover all the bases.

  • 0

    On 30.08.2016 19:40, gon says wrote:

    /Hey guys,

     

    I've a issue regarding the NeoPixel LEDs from Adafruit (WS2812B LEDs).

     

    In the datasheet of this LED model (https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf ) it says that we should add a 0.1uF capacitor for each LED.

     

    If you check the .sch and .brd for the NeoPixel Ring 24x LEDs (https://www.adafruit.com/product/1586 ) - WS2812B -  we have 24 LEDs and only 15 capacitors (https://github.com/adafruit/Adafruit-NeoPixel-Ring).

     

    I'm doing my own board with WS2812B LEDs. Should I use 1 capacitor/LED -or- should I do as Adafruit and use 15 capacitors for 24 LEDs?

     

    Thank you very much in advance!

     

    This is really not an Eagle question, but general electonics development

    question.

     

    First, the WS2812B is a WorldSemi product. http://www.world-semi.com/

    Their webpage may be a bit unstable since its hosted in Asia.

     

    The datasheet RECOMMENDS one decoupling 100nF cap pr led, but this

    doesnt necessarily mean its needed for it to function. The one cap pr

    digital device is a good rule of thumb that you should follow unless

    there is a very good reason not to. Adafruit's ring seems to have space

    issues. Also they seem to keep the leds very close, so maybe they

    decided it was ok to merge a couple. Maybe they have larger caps too, so

    they can partly take the bulk function as well.

     

    If you have long wires between the powersupply and the device, you'd

    probably want a larger bulk cap close to where the power input is. These

    LED's can draw significant power (~50mA pr LED), and you dont need many

    to make the wire resistance cause significant voltage losses. When they

    are all flashed at the same time at full white brightness, you have the

    worst condition. You may want to test that.

     

    If you don't know the expression decoupling and bulk and don't care,

    just make sure you have wide power tracks throughout the path and add a

    few caps here and there. Most likely you will have no problems unless

    you have a mad number of led's.

     

     

     

  • 0

    Thank you very much for your answers! Now I understand why it is done the way it is image