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Thread: Changing cold cathode backlighting to LEDs (+auto brightness control)

  1. #21
    What can I say? I like serial. Curiosity's Avatar
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    I got the cold white and it was fine. I may have bumped up red just a little but it looks fine to me.

    For PBCs, Sniiki could post the gerber files on BatchPCB and make them public. Then all you would have to do is buy them. Just an option. It would take about 1 month and I'm not sure the fab guys (gold phoenix) will V-score something that thin. Cost would be at least $20.

    Right angle is probably a bad idea.

  2. #22
    Maximum Bitrate bes51659's Avatar
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    OK, not right angle then.
    I do not mind makeing the board, making gerber public, and assemble for those who want it. Only hatch is that I will make it to fit my 6.5' panel:-) But I want to be sure I get a good diod first. I found a few alternatives. Trubble is how to test them. And how many mcd is required really? (total)

    EL67-21UWC SMD (states full color LCD backlight)
    19-213/W1D 0603
    12-215/W1D-AN (right angle)
    12-215/W1D-P2
    EL17-21/W1D 0805

  3. #23
    What can I say? I like serial. Curiosity's Avatar
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    Considering the strip I used was 30 LEDs, 1200mcd and look about the size of that EL67-21, and it's double the brightness, I think you could get away with anything even half that, warm/cold/natural. Even mine needs to be dimmed at night. I prefer map lights to light the interior.

    I think the important thing is to measure the space first. My CCF was a 0.100" U-shaped tube and I did like thanh150 and put them around the outside. The tube could probably fit back in, but that's because the flexible curcuit board stuff is so thin but too wide that it had to go on the outside. It also allowed some space between the LEDs and the diffuser to allow the light to spread.

  4. #24
    Maximum Bitrate bes51659's Avatar
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    So a total of 36000mcd is more than enough?
    Yes, I need to take my LCD apart and find the mechanical limitations. For now I have just dissassembled a broken LCD with LED backlight at work. With right angle LED's on flexi board.




  5. #25
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    bes,
    About the LEDs, yeah these are very bright even at half of the nominal current and dimming absolutely mandatory when driving at night. Software dimming won't do as the screen will glow quite bright even when whole screen is full of black.

    Can't say much about how many mcds are needed as don't really know how much these are producing @ 12,5 mA. With nominal current it would be ~150000mcd in total.

    Color tone is a bit greenish on my panel as these leds produce very little of red. I can fix this partly with software color tuning.

    About the PCB: Sorry, but I don't have any layout file of the PCB cause the electroforge guy actually designed it for me while we were discussing and planning the whole thing. And as the electroforge guy told you, this specific board wouldn't fit to your panel anyways so it wouldn't be any good for you.

  6. #26
    What can I say? I like serial. Curiosity's Avatar
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    It's interesting to see a factory LED backlight. Notice how far apart they are, and are diffused fine, plus they had a reason for doing that. The case left a lot more space for lighting though. The CCF ones have pretty tight space unfortunately so it's a challenge to retrofit.

    Here's another idea. These are the same as the strip LEDs they sell. All hand soldered, and even on the edge which might be an idea but I wouldn't try it. Personally, I'd at least half the LEDs so you have space for traces and a resistor in between every 3rd, plus order a thin PCB if possible.

    sniiki, just adjust the RGB gain on the monitor. It works better than offsetting the video output.

  7. #27
    Variable Bitrate
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    What about this stock here? 12V wired, all ready to go, just not sure of the distance between the LED's.

    http://www.besthongkong.com/index.php?cPath=21_76

    Available in white and warm white too, and the price is cheap, 11 bucks for a 50cm strip.

  8. #28
    FLAC
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    in my research, there is no led strip even near this density. Brightness is difficult to get it too.

  9. #29
    What can I say? I like serial. Curiosity's Avatar
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    Wow, would like to see 150 Cd. At some point well below that, black is going to be pretty bright even under normal ambient light. The thin LCD panel can only block so much light. That's why sunlight readable is a better (and more expensive) option. Dimming isn't as much a necessity. I'd like to see both in one though someday. LOL

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