Brightness/Color problem with 6803 based LED matrix

Discussion in 'The Projects Forum' started by clantogw, Jul 13, 2013.

  1. clantogw

    Thread Starter New Member

    Jul 13, 2013
    4
    0
    I have a unique problem. I hope this is the correct place to post this. If its not, I hope someone can point me to a more appropriate forum.

    I have a LED curtain I purchased from China about a year ago. It has 462 LEDs in a matrix. Here is the exact model I have: http://www.youtube.com/watch?v=Yl2p9yBmWmg

    My problem is that every other two strips have a problem with their color or brightness. When I had it new the color and brightness was uniform over all LEDs, but overtime this has diminished. Here are two examples of what I'm talking about:
    [​IMG]

    [​IMG]


    From inspecting it I have discovered that the columns that have perfect brightness and color are directly connected to the power supply box that tells the curtain what to do, shown here:

    [​IMG]

    [​IMG]

    If you cant tell from those pictures, every other two columns are connected with wires at the bottom directly, and the other two columns are not. This continues throughout the length of the curtain.

    My LEDs are interesting, I can not find any similar ones online.
    (shown here)

    [​IMG]

    [​IMG]


    The chip on the back of the LED says "LPD6803S 1049"

    More details:
    The Red, Green, and Blue colors are more or less uniform, but the brightness of the two bad columns is noticeably lower than the good columns. In the other colors (purple, teal, yellow, white) the two columns show other colors, still at a lower brightness. For example, when it is supposed to be Yellow, the other two columns show Red.
    Also, when I put it in solid color mode and lower the brightness overall, the colors gradually get more uniform, becoming solid at the lowest brightness.

    My question is, is this a problem with the power supply, bad wiring, or some type of poor connection between the LEDs??
    Has anyone had a similar problem to this, or know whats going on?
     
  2. absf

    Senior Member

    Dec 29, 2010
    1,492
    371
    Wow, That's a lot of PCB and RGB LED. Since it is a modular design, I think it would not be to difficult to troubleshoot the problem.

    Let's take one string first----

    Code ( (Unknown Language)):
    1.  
    2. controller - good - good - good - good - good - good - bad - bad - bad - bad - bad
    3.                                                                                                  ^          ^
    4.                                                                                                2nd      1st
    5.                                                                                        suspect    suspect
    6.  
    change the 1st suspected with a good PCB and check the connecting 4 wires for connectivity etc. Should be simple.

    Case 2 ----

    Code ( (Unknown Language)):
    1.  
    2. controller - bad - bad - bad - bad -  bad - bad - bad - bad - bad - bad - bad - bad - bad  
    3.             ^          ^
    4.          2nd      1st
    5.    suspect    suspect
    6.  
    In this case it could be the first PCB is giving problem or the controller's output is faulty. The controller output fault could be a bad driver chip or a bad transistor, depending on the design.

    I attached the datasheet so others may use it for further suggestions.

    Good luck and I like the display presentations.;)

    Allen
     
  3. clantogw

    Thread Starter New Member

    Jul 13, 2013
    4
    0
    thank you for the reply!
    i am embarrassed to say i dont fully understand it though.
    [​IMG]

    this is what i see ^^

    I think I know what youre trying to tell me though. I have replaced the first two LEDs in the line to see if that would fix anything, and i changed the ones around where it starts to change color. It did not change anything.

    I would like to add that the color change is gradual in the columns, like for example in a "good" column you can see the color beginning to change at the top of it, then getting worse in the next column. Until it gets to a point where the cables from the source reconnect, then its good again. Thats what leads me to think its the power supply or something else to do with the box.

    I just opened it up and it seems to be a 5v 10a supply
    [​IMG]
    [​IMG]
    [​IMG]
     
  4. absf

    Senior Member

    Dec 29, 2010
    1,492
    371
    I see that there's only one power supply of 5V 10A, right?

    If so, the problem cannot be due to power supply. Otherwise all the strips would also be dim. The reason you ssw led lights travelling from bottom to top is because the data is travelling from bottom up clocked by the clock line in sequence. It sounds like the clocks for every 2 alternate strips have slowed down. By right the clock should be faster so the hunan eye can retain the image like watching a movie

    Without a schematic of the controller or proper test gears like ascilloscope. It would be tough for us to troubleshoot remotely. And I see that one of the chips has the ic number scratched so I guess you're not going to get much information of the controller unless you buy another new one. Dont know what other members would say...:rolleyes:

    Allen
     
  5. clantogw

    Thread Starter New Member

    Jul 13, 2013
    4
    0
    Youre right of course. I got another power supply in the mail today, same problem.

    here are some pictures of the main board if that helps at all....[​IMG]
    [​IMG]

    It would be amazing if i could get my hands on another one of these. Do things like that exist or are they specialized?

    my curtain is not a perfect grid. the columns alternate between 17 and 16 LEDs each. I dont know very much about this technology obviously... but would any other SD controller work as long as i put my SD card in it? My guess is not...

    So its nothing to do with the wiring or the LED modules themselves... is there anything I can do from here to trouble shoot it?
     
  6. clantogw

    Thread Starter New Member

    Jul 13, 2013
    4
    0
    Reading this a second time, it sounds like you think the problem i am having is that the bad streams look like they are moving up from the bottom. I should say that this is not the case, they do not appear to be flickering to my eye, the patters are normal, but on these 'bad' columns, the colors are different than they should be and the brightness is not at 100%
     
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