Connect with us

WS2811B addressable RGB LED to 12V RGB outputs converter

Discussion in 'LEDs and Optoelectronics' started by CXgamer, Nov 12, 2017.

Scroll to continue with content
  1. CXgamer

    CXgamer

    3
    0
    Nov 12, 2017
    Hi,

    My new workstation computer build will feature lots of fancy RGB lights, which can be programmed through my motherboard's SDK. The motherboard, however, only has two headers which can connect to said components, and I want all of my 9 RGB components to be individually controllable. So luckily, I also have a connector for addressable RGB strips. The idea is to intercept the data signal, give it 12V from the power supply and provide standardized headers which are to be used by the components.

    It's very important that I won't fry my motherboard, and I don't have a lot of experience with PCB's, which is why I've come to the experts to advise my plan. So without further ado, here's what I've come up with:

    [​IMG]
    Molex in is the connection coming from the power supply. The molex connection's 12V and 5V lines are rated at 11A, which should be plenty for 8 RGB components.
    Data in is the addressable header coming in from the motherboard, rated at 3A. I've unknowingly connecting the 5V line and the Ground to the Molex in's lines. I don't know if it's dangerous, but I need to make sure that data's voltage is within ±0.5V of the 5V line. Is this how I should do it, or is there a safer way?
    RGB outputs are the connections going to the components. My motherboard weirdly swaps red and green, so I need to bridge the red line, in order to not require a second side to my board. The motherboard's specification is 2A for these connections, but I will make sure that my components don't add up to 11A.
    Data out is the same connection as data in, to make it possible to chain these PCB's in order to add even more components.
    WS2811 is the IC which will be able to decode 8 bits per channel and output a voltage value for it.

    The WS2811's specification provides an example 12V circuit which has some additional components added to it that I don't have here:
    • A bypass capacitor at each of the VDD connections.
    • A 33Ω resistor at the data input or output for impedance, to prevent reflection and hot-swap protection.
    • A divider resistor at the OutR line. I'm assuming RGB component manufactures will have this in their own component and that I don't specifically require this one.
    I don't quite understand what these are for, do you guys think I need those?

    Useful links:
    Thank you in advance!

    Sincerely,

    CX

    EDIT: Oh and now that I come to think of it. I will be first trying this out on a prototype board. Anyone know any input signal source which I can use to test it?
     
    Last edited: Nov 12, 2017
  2. kellys_eye

    kellys_eye

    4,276
    1,146
    Jun 25, 2010
    Bypass capacitors are essential. 100nF. Can be mounted on the reverse of the board if required but should always be right adjacent to the power pin.
    33Ω recommended - limits spikes (always present in data signals) so use it.
    The divider resistor IS required - it is not part of the RGB device and has to be included on your board. Calculate the value using the data applicable to your chose RGB LED.
     
    CXgamer likes this.
  3. CXgamer

    CXgamer

    3
    0
    Nov 12, 2017
    Thank you very much for your feedback, kellys! I learned a lot from your comment. So here's the updated version which now includes all the components you described. I also discovered that the IC's are half the size of what I had originally, so the board is now also smaller.

    [​IMG]

    Some remaining questions:
    • Is it fine to connect the +5V and GND lines from data in and molex in? Is there something I need to do to safeguard my motherboard? I would be fine putting in a fuse somewhere.
    • Are my lines wide enough? The smaller ones are 0.64mm, the fat ones 1.52mm. The most one RGB output will consume is about 0.6A.
    • Is there anything making this difficult to solder?
    • Any general tips are also welcome!
    Once more, thank you guys in advance!

    EDIT: Oh yeah I noticed the size of the capacitor is 1000 times too big, no biggy.
     
    Last edited: Nov 13, 2017
  4. kellys_eye

    kellys_eye

    4,276
    1,146
    Jun 25, 2010
    5V connected to the molex is fine. Fusing is optional since most PSU's have short-circuit protection anyway (ever seen a fuse on a mobo?) Laptops, yeah..... can;t sasy I've seen one on a PC mobo though (anyone care to correct me?).

    Line (trace) width - dodgy..... you have to consider the TOTAL current in the trace, not just the individual take-off points. There are loads of online trace width calculators out there so suggest you familiarise yourself with one (like this http://www.4pcb.com/trace-width-calculator.html)

    Soldering should not be an issue if you use the correct iron/tip. Easily managed with most amateur equipment, nothing special needed.

    Got a solder mask sorted? That'll make soldering even easier - safer too.

    Don't try to milk a bull <- general tip.
     
    CXgamer likes this.
  5. CXgamer

    CXgamer

    3
    0
    Nov 12, 2017
    Thank you very much! According to the width calculator, the width would have been a major problem indeed. I updated the design to incorporate this. If I want to max out the spec, I would need a secondary ground line even, but I'm not going that far, since my components are not going to pull 11A together.

    [​IMG]

    Thanks a ton for your help. I'll give you credit when show this to people. :D
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-