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SOLVED A couple of n00b questions, LEDs, resistors and caps.. oh my!

Discussion in 'LED Devices Support' started by bob21, 11 May 2020.

  1. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    Hello all. I hope you are all well considering the current climate.

    To start, I want to say thanks to everyone involved with Hyperion! This is an absolutely amazing project, and I am really looking forward to making mine. I'm in the process of ordering components for a build now, and I am unclear on a few things.

    1. I thought initially that I would be able to run a W2813 strip from a Pi, but have come to conclusion that I cannot (or not easily/reliably) and would need an Arduino, so I have an Uno on order. What I am unclear on is where to connect the BI line? Is it just connected to the same GPIO pin as DI?

    2. I initially came across the Hyperion Project by this instructable: https://www.instructables.com/id/Ambilight-System-for-Every-Input-Connected-to-Your/ he mentions using a 10uf cap on the arduino between ground and reset to stop the arduino rebooting when connected to the Pi but I do not see any mention of this in any other guide (not the same as the 1000uf cap on the LED voltage). Has anyone come across a case where they needed to do this?

    3. Just looking around on a few guides on the net, some of them have different cap and resistor values for the LED wires. What should I choose for the W2813s, still R470 and 10uf same as the W2812Bs?

    Thanks! :)
     
  2. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    No one? :)
     
  3. TPmodding

    TPmodding Administrator Staff Member Administrator

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    hi

    1. di = bi, so yes you right, but you can also google the data sheet
    2. never heard it this way, think it is a nice to have but not a must have
    3. did you googled the data sheet? should be writen there whats recommended
     
  4. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    Hi! Thanks for replying.

    The datasheet doesn't seem to mention connecting BIN and DIN together: https://www.elecrow.com/download/WS2813_LED_Datasheet.pdf

    The datasheet (and also this: https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf) also doesn't mention anything of forward voltage (from what I can see) or if resistors are placed before each LED... so it's impossible to calculate the required resistance if the needed information isn't present. Adafruit's recommendation of 100R-500R seems a bit too much like wild guessing to me.
     
    Last edited: 15 May 2020
  5. TPmodding

    TPmodding Administrator Staff Member Administrator

    Messages:
    1,702
    Hardware:
    RPi1/Zero, RPi2, RPi3, +Arduino, +nodeMCU/ESP8266
  6. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    I am not sure if those are the same as I have. They work out at about 72W per 5M strip. Mine are marked as 90W per 5M and seem to fit versions C and D from the datasheet I posted. In any case, here's a look at what I will be doing:


    [​IMG]



    Hopefully this is helpful to someone else. I take no credit for this, I threw this [very bad] diagram up after I got some advice from Ian.M on the EEVblog forums.

    Edit: fixed image
     
  7. TPmodding

    TPmodding Administrator Staff Member Administrator

    Messages:
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    why you use a 2m cable from or to arduino?
     
  8. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    Because the Arduino is in an enclosure with many other components. I am prepared that it may be problematic and I will either need to:

    1. Shorten the wire - due to distance between TV on wall and box, this may not be possible by more than ~30cm
    2. Move the Arduino to it's own enclosure behind the TV, but this would require adding another board in the main enclosure because I planned to integrate a screen etc

    So my plan is to try these things in this order:

    1. Try as is
    2. Add level shifter
    3. Shorten cable as much as possible
    4. Relocate Arduino

    Note: it seems BI should not be tied to DI. It is, for each subsequent LED, but for the start of the strip connecting BI to DI will cause a mismatch.
     
    Last edited: 15 May 2020
  9. TPmodding

    TPmodding Administrator Staff Member Administrator

    Messages:
    1,702
    Hardware:
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    why you dont use a wemos d1 mini with wled?
     
  10. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    That's a good idea, I have one spare. But, I have a problem. Does the Arduino and D1 connect to the Pi with USB? The wire going from main enclosure to strip is 4 core. If I move the LED controller to the TV end, I have 2 spare wires. Is it possible to communicate from Pi > Di / Arduino with just those 2 wires?

    Like this:


    [​IMG]


    If it is, I think the D1 at the TV end is a logical choice. If it's not, I would have to run a separate long USB cable along side it, which I would rather avoid.

    I suppose, I could Frankenstein a USB cable... looks like USB data is only 2 wires....

    [​IMG]

    Or can the headers of the Pi and D1 be used?
     
    Last edited: 15 May 2020
  11. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    Like this:


    [​IMG]
     
  12. TPmodding

    TPmodding Administrator Staff Member Administrator

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    More like this
     

    Attached Files:

  13. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    Interesting, I had not considered wifi for the connection. Do you mean direct connection or via an access point (router)?
     
  14. TPmodding

    TPmodding Administrator Staff Member Administrator

    Messages:
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    Hardware:
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  15. bob21

    bob21 Member

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    36
    Hardware:
    RPi3
    That would certainly make things simpler. What about lag due to wifi? I guess more stable than 2M DIN cable....
     
  16. TPmodding

    TPmodding Administrator Staff Member Administrator

    Messages:
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    just give it a try...less cables, more fun...
     
  17. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    More fun yes, if I can manage to do it right and it works reliably. ;) I am still waiting for some components. I will post back as soon as I have tried. Thanks for the pointers :)
     
  18. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    So while I wait for a couple of the final components, something did arrive today and that is the vid cap. I think I may have fallen at one of the first hurdles though.. it identifies as:

    Code:
    18ec:5555 Arkmicro Technologies Inc.
    Which is not what I ordered.

    Looking at other threads like this: https://hyperion-project.org/threads/arkmicro-easycap-support.578/

    It looks like this is an unsupported chipset. The console shows:

    Code:
    VIDIOC_S_INPUT ERROR 25, Inappropriate ioctl for device
    My install is Raspbian Buster and Hyperion installed using the .jar. Am I doing something obviously wrong or is this chipset just outright not supported?
     
  19. bob21

    bob21 Member

    Messages:
    36
    Hardware:
    RPi3
    Marking as solved as have moved to NG and am up and running with LED strip. Ended up using BAT43s as the 54s were very small :)