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Controlling DLP4500 LEDs with an external driver

Johann Hynek
Prodigy 50 points
Other Parts Discussed in Thread: DLPC350

I couldn't find an answer to this question, although it seems trivial. 

I want the DLP LightCrafter 4500 projecting binary images at 1440Hz, by transferring the bitplanes into time (60 * 24). Therefore I want the LEDs to be on constantly. As far as I can see from the user guide I have to set the jumper J28 and J30 to disable the internal LED driver and set the external control voltage range (0-3.3V or 0-1.8V). The connector 15 (labeled J29 on the device) which is referred to as "External LED Driver connector" in the user's guide, is the place to feed in my external voltage to drive the LEDs, right? 

Now my question:

Which of the 14 pins on this External LED drive connector is/are for the ground, which for the blue, red and green LEDs? 

Thank you very much!

Johann

  • 0
    Prodigy 50 points

    Ok I actually found a technical drawing of J29. Page 26 of this document: http://www.ti.com/lit/df/tidr157/tidr157.pdf

    But some questions remain. Where is pin 1 on the J29? 

    And could you please tell me what these abbreviations mean:

    P12V_LD

    BLU_LED_PWM_CON

    BLU_LED_EN_CON

    Thank you! 

  • 0 in reply to Johann Hynek
    TI__Expert 4720 points

    Hello Johann,

    Please reference the connector datasheet for the J29 pin-out: http://www.jst-mfg.com/product/pdf/eng/ePHD.pdf

    The abbreviations you listed are the following:

    • P12V_LD
      • This is the 12V supply used through out the board which applies some filtering to the barrel connector voltage.
    • BLU_LED_PWM_CON
      • This supplies a pulse width modulated signal for external LED drivers to specify the current settings from the controller.
      • For example, 0% PWM would signify the lowest current setting while 100% PWM would be the maximum.
    • BLU_LED_EN_CON
      • This the LED enable signal. If this signal is active the external LED should be powered.

    Hope this helps!

    Best regards,

    Blair

  • 0 in reply to Blair Conner
    Prodigy 50 points

    Thanks a lot Blair! This answers my initial question, but I think I misunderstood the purpose of this connector - I though it let's me externally control the intensity of the LEDs inside the LightCrafter. 

    Is there any way to keep the LEDs on full light intensity constantly, while controlling the actual DMD chip by sending a stream of images? This would result in a stream of binary images, but at a higher frequency than the 60Hz which can be achieved with 8bit color images. 

    Thank you!

  • 0 in reply to Johann Hynek
    TI__Mastermind 30875 points

    Hello Johann,

    Is there any way to keep the LEDs on full light intensity constantly, while controlling the actual DMD chip by sending a stream of images?

    [Sanjeev]

    You don't need to touch the hardware, there is software way of forcing the signal to HIGH always. Please see below details.

    There is an option in GUI to force LEDs to be running ON always, the problem is that keeping LED at full intensity causes overdrive and thermal issues in the system. 

    The option available in the GUI via LED Selection -> Manual, select the LEDs check box.

    This is also documented in DLPC350 Programmer's guide http://www.ti.com/lit/ug/dlpu010d/dlpu010d.pdf Section 2.3.7.1 LED Enable Outputs.

    Forcing 'manual' is essentially forces the LED_EN signals always ON so will the LEDs be physically on.

    NOTE: At full intensity (maximum currents) be cautious about LED overdrive and thermal issues may sometime cause LED and/or LED driver damage.

    Regards,

    Sanjeev

     

  • 0 in reply to Sanjeev
    Prodigy 50 points

    Dear Sanjeev,

    Thank you very much for your answer. I was wondering if I could bother you with another question. I need to drive the mirror array with a higher frame rate through the HDMI input. Basically, as I use only blue light, and I do not need the 8bit depth, 1bit on/off will be enough for me. For that I am assuming that I need to have constant time bins for every bit I send. In addition, I somehow need to remove the shuffling of the temporal presentation of the colors. Is there a simple way to do that.

    Thanks a lot,

    Johann

  • 0 in reply to Johann Hynek
    TI__Mastermind 30875 points

    Hello Johann,

     For that I am assuming that I need to have constant time bins for every bit I send.

    [Sanjeev] yes you are correct.

    In addition, I somehow need to remove the shuffling of the temporal presentation of the colors. Is there a simple way to do that.

    [Sanjeev] Can you please clarify what do you mean by temporal presentation of colors? you can select whichever color you are interested in this case blue, so it will apply same constant time bins + blue color.

    Regards,

    Sanjeev