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Original question:

DLPDLCR4710EVM-G2: How I can change led current below 1423 ma!

DLPDLCR4710EVM-G2: How to change duty cycle of red,green,blue led?

jack man
Intellectual 360 points
Part Number: DLPDLCR4710EVM-G2
Other Parts Discussed in Thread: DLPC3439, DLPA3005, DLPDLCR3010EVM-G2, DLPDLCR230NPEVM

Hi,

In default duty cycle of green about 47% blue about19% and red about 34%.

How to change duty cycle of red,green,blue led?

What is the look and sequence? I saw in the dlpc3439 programmer's guide file that the duty cycle for LEDs is a look or sequence subset, but I did not understand what these are and whether the duty cycle can be changed or not.

  • 0
    TI__Genius 9971 points

    Hello Jack,

    Welcome to TI E2E forums and thanks for showing interest in the DLP technology. 

    In a particular firmware of DLPC3439, it is not possible to change the duty cycle settings as they have been set to achieve a display of a specific color temperature. 

    May I know the reason for your request, why do you want to modify the duty cycle settings?

    Regards,

    Mayank

  • 0 in reply to Mayank Khandelwal
    Intellectual 360 points

    Hi,

    According to my previouse post about decrease current of led below 1400 mA I want to decrease duty cycle of led to decrease mean current of it.

  • 0 in reply to jack man
    TI__Genius 12575 points

    Hello Jack,

    The following description is taken from the Help (?) icon on the DLP LightCrafter Display GUI's Video and Color page:

    The EVM supports three different color temperatures:

    • Cool (9200° K)
    • Medium (6400° K)
    • Warm (5500° K)
    • User Defined

    Each color temperature setting is referred to as a 'look', which comprises several settings such as the duty cycles of the RGB LEDs, as well as the LED current values used for a full-on white image.

    Potentially, each EVM could have unique settings, due to the mix of LEDs used by the optical engine. Arriving at the settings requires some amount of calibration, which is usually done by the optical engine manufacturer.

    Please note: When changing looks, the EVM LED currents might change in order to meet the specified white point. The means the LED currents could potentially be lower, which in turn means the projected lumens would be lower.

    A CIE Chromaticity chart shows the relative temperatures of the three looks in comparison to each other. Note that the color temperatures are measured when displaying a full-on white image. The color temperatures should all fall on the white line that runs across the center of the diagram. Temperatures further to the left are more blue, or "cool", and temperatures further to the right are more red, or "warm".

    The User Defined look can be customized by changing the RGB duty cycles of the look. To change those values, update the flash image file (*.img) using the Firmware page and follow the instructions provided in the Update Flash Image wizard. Finer white point adjustments can be made by changing the LED currents in the IntelliBrightTm page.

    For an explanation of sequences, please read sections 2.3 and 3.1 on the Augmented Reality Application Report.

    Regards,

    Austin

  • 0 in reply to Austin Snyder
    Intellectual 360 points

    Hi,

    Thanks austin

    But it means I can not change the duty cycleBut it means I can not change cycle in the moment I do?

    How many user definedHow many definition of the user can be defined?  

  • 0 in reply to jack man
    Intellectual 360 points

    Hi,

    Today, I created a flash file by lightcraft software and for example reduced he green duty cycle to a minimum of 14 (red 31 and blue 55)(14+31+55=100), and after update firmware of the board, the amount of green light decreased, but the image became noisy and its quality is not comparable to the other 3 looks at all.

    Why?

  • 0 in reply to jack man
    TI__Expert 3360 points

    Hi Jack,

    Something to note with RGB duty cycles is that the white point will change with different RGB duty cycles, assuming that LED current remains the same between the different looks with their own RGB duty cycles. This can affect image quality.

    There are a lot of other variables as well when evaluating image quality and achieving the best image quality. We need your help in determining what you are trying to achieve with this new RGB duty cycle:

    1. Are you looking to reduce brightness but maintain image quality ?
    2. Are you looking to improve contrast ?
    3. Are you looking to achieve a new color temperature or maintain white balance ?

    Can you upload three images to help us troubleshoot:

    1. Reference image
    2. Ref image displayed using look#0 (cool)
    3. Ref image displayed using look#4 (user-defined)
    4. Ref image with what you expect it to look like displayed (using Photoshop, for example)

    Please help us understand what is your end goal with this effort so we can provide the best support in helping you get there.

    Thank you,

    Chris

  • 0 in reply to Cody Smith
    Intellectual 360 points

    Hi,

    I changed the firmware of the board and now I can not send photos

    The image quality was bad, meaning that there were a lot of pixels with incorrect colors in the whole image, but I checked with 55 green, 15 blue and 31 red. This was not a problem.

    Why total time light Green and Red and Blue should 100 and why each between 14% 55% are? Where is the dark time period? (According to page 7 of "Application Report Optimizing DLP® PicoTm power consumption for Augmented Reality (AR) and power-sensitive applications"

  • 0 in reply to jack man
    TI__Expert 5290 points

    Hi Jack,

    Each LED has their duty cycle % that must add up to 100% for the sequencing to work properly. These values are kept between 14-55% for the same reason too. Any deviation to a certain extent will cause issues for the sequencing and result in display errors.

    Thank you,

    John

  • 0 in reply to John McKnight
    Intellectual 360 points

    Hi,

    15+15+70=100 but I can not do this because max dc of each led is 55!

    Where is the dark time period?

    According to page 7 of "Application Report Optimizing DLP® Pico power consumption for Augmented Reality (AR) and power-sensitive applications" file, dlp can work with lower power consumption by adding dark time to r+g+b time period!

  • 0 in reply to jack man
    TI__Expert 3425 points

    Hi Jack

    As you rightly pointed out if there are dark times included in the sequence the sum of all the LED duty cycles need not be 100.

    Could you please state what is the end objective you are trying to achieve as requested by Chris,.

    We need your help in determining what you are trying to achieve with this new RGB duty cycle:

    1. Are you looking to reduce brightness but maintain image quality ?
    2. Are you looking to improve contrast ?
    3. Are you looking to achieve a new color temperature or maintain white balance ?

    Regards,

    Akhil

  • 0 in reply to Akhil Guntumadugu
    Intellectual 360 points

    Hi,

    I am looking to reduce brightness but maintain image quality

    Minimum current of each led by dlpa3005 with dlpc3439 is 1400mA so I want reduce duty cycle to reduce brightness.

    Dlpc3439 can handle dark time period?

  • 0 in reply to jack man
    TI__Expert 3360 points

    Hi Jack,

    The best way to reduce brightness while maintaining image quality is to lower the LED currents or change the display size of your projector. Changing the duty cycles will also affect image quality. Especially by lowering the green color channel duty cycle, image quality will not be maintained.

    Dark time can be implemented in the projector, but this will greatly reduce image quality as well. If you want to have dark time, we can provide special firmware that will have pre-determined dark time up to the limitations of our system. Please note that adding dark time can reduce image quality. 

    Please share what is your intended application for this effort (ex: end equipment example). We have other EVMs that may be better suited for your application.

    Thank you,

    Chris

  • 0 in reply to Cody Smith
    Intellectual 360 points

    Hi,

    I want to make a portable projector that work with battery with minimum brightnes ( I want to control it from 0 mA) and work with external power supply with maximum brightness ( to 16A )

    In total from 0 to 16A.

    If you can send for me a firmware generator to make red and green and blue and dark time period with 0 to 100% for each one and only total=100% is constraint

    Because when I deactivate a led, why should it be wasted time? this time can be used for more light in other situations

  • 0 in reply to jack man
    TI__Expert 3360 points

    Hi Jack man,

    Unfortunately we cannot support your request for dark time period of range 0 to 100 %. We can provide firmware with one or two preset % of dark time. If you are interested in our lower brightness solutions, we have the DLPDLCR230NPEVM (1080p, 100 lm) and DLPDLCR3010EVM-G2 (720p, 220 lm). These are both viable EVMs to evaluate if DLP technology can meet your system requirements.

    Thank you,

    Chris

  • 0 in reply to Cody Smith
    Intellectual 360 points

    Hi,

    In the release note of dlcp3439 firmware v7.7, I see that was generated with dlp composer v13 . Where I can download this software? Can I make a firmware with dark period with that software?

    Can you send for me a firmware with this looks:

    1-red30 green55 blue15 dark0

    2-red15 green28 blue7 dark50

    3-red7 green14 blue4 dark75

    4-red6 green8 blue1 dark85

  • 0 in reply to jack man
    TI__Expert 3360 points

    Hi Jack,

    Firmware with dark time is custom generated internally, so you would not be able to make such firmware with DLP Composer. 

    Unfortunately we cannot support this request for such high dark time. I will look into the limits for the R,G,B,dark % ranges and get back to you by middle of next week.

    Thank you,

    Chris

  • 0 in reply to jack man
    TI__Expert 3360 points

    Hi Jack,

    We will provide the following looks in our firmware to you:

    1. R30G55B15   0%DT
    2. R30G50B20 25%DT
    3. R33G34B34 50%DT

    This is in line with the limitations of the system. Please accept my friend request so we can start the process for sharing this firmware with you.

    Thanks

    Chris