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Light intensity drop over time / temperature?

hongsheng zhang
Prodigy 65 points


I have EVM DLP3000, since beginning of this week, it begins to show some pinkish background color, i.e.: when I set the pattern to internal pattern, and I choose chessboard or solid white, the device generate correct pattern, but the white is not real white, it has some pinkish color in the white. I use this device for 3D scan, this begins to affect my  scan quality. Whenever this happens, I have to shut down the DLP (unplug both power and USB) and let it cool down, Sometimes even unplug doesn't work, now I get correct black/white level on random base, have to try to turn if off/on several time for it to project correct white color level. Does anybody encounter similar issue? Any input is highly appreciated. (I will try to capture some images when it happens next time).

Thanks,

Hongsheng

  • 0
    TI__Intellectual 1565 points

    Hello Hongsheng,

    It looks like the LED currents are probably set to certain value that is causing one of the LEDs to burn out. If the LEDs are heating up, then its going to lower the light output. On the LightCrafter EVM, there is one heat sink for both Green and Blue, so if the blue and the green LEDs are heating up or burning out then, its gonna lower their Light output and the supposed to white output might start looking pinkish. 

    What are your LED current settings? Also refer to section 2.4 in the LightCrafter Users guide which talks about "Setting up the LED Current" and the maximum allowed LED current without any extra heat sinks.

    Adjusting the LED current will also be a good way to fix the white point.

    Hope this helps.

    Regards

    Manasi

  • 0 in reply to Manasi Navare
    Prodigy 65 points

    Manasi,

    Thanks for your reply. I thought I has something to do with LED currents too, all currents are default to 274, I did not change it since day one. I don't have any external heat sink for the EVM. The device is sitting on a aluminum bar, hope the bar will transfer some heat away. Here is a screen shot of the current setting:

    This morning, the pinkish happened again, and this is the first time I turned it one since last Friday, the EVM should be cool down, here is the screen shot of the pinkish chess board, pay attention to corners.

    When I turn it on second time, it showed some greenish chessboard, here is a screen shot:

    After several tries, it finally went back to normal, this is what it supposed to be:

    Any idea? Does the EVM do some kind of white balance when it is boot up? Does the screen color matter when the EVM boot up? Do I need to contact technical support for this issue? Any input is highly appreciated, please help.

    Hongsheng

     

         

  • 0 in reply to hongsheng zhang
    Intellectual 750 points

    Hi Hongsheng,

    We've seen this phenomena sometimes in our lab. Either the Blue LED connection on the flex-circuit has become bad, or their is a component in the Blue LED driver section that has a cold solder joint on the DMD Driver board. You can also try to reseat the LED flex-circuit going into the DMD driver board to see if that is not making a good connection.

    Regards,

    Adam Kunzman

    Keynote Photonics

  • 0 in reply to Adam Kunzman
    Prodigy 65 points

    Adam,

    Thanks for the response. Is it possible for me to reseat the LED flex circuit? Is there any help section on manual or forum on how to reseat it? I just don't want to damage it, I don't have much luck with electronic components. :)....

    Hongsheng 

  • 0 in reply to hongsheng zhang
    Intellectual 750 points

    Hongsheng,

     

    You will need to remove the top board (System Board) first. There are four screws than you must remove on the corner of the PWB. 

     

    Next, gently pull the PWB away. It is plugged in along the left side of the board if you are looking at the Lightcrafter from the top, projecting away from you.

    You should see a brown flat cable that plugs into a connector towards the middle of the bottom board (the DMD Driver Board). There is a small latch that you must pull up gently. This allows the flex cable to be removed. You can unlatch, then try to shift the cable to ensure it is fully pushed in to the socket, then push the latch back down. 

    Replace the System Board and the screws. Hopefully this solves your problem. If not, there are other more serious issues. Depending on where you purchased your Lightcrafter from, you may be able to get a replacement unit. I'm not sure if TI can assist.

    If you are not comfortable with this kind of work, please contact your sales company and directly negotiate a replacement. 

    Good luck.

    - Adam