LED LCD backlight replacement


[Keith]‘s cousin gave him a LCD with a noisy backlight. He decided to replace it with a series of high output LEDs. He sourced some locally in the form of cheap LED headlamps from an auto-parts store. The results look pretty good – and the write up contains this gem: “…One [LED] also exploded due to an accidental overvolt. Shot me in the Chest. Panel okay though” Nice work.

Comments

  1. Toxyn says:

    1st post ^.^

  2. beanMosheen says:

    You can file LEDs flat on the tip to fit them better. Also sounds like the author didn’t use the correct current limiting resistors. Great idea though. He could have used hot glue for the LED’s and reworked it later.

  3. Crash says:

    Nicely documented, unlike a lot we see here. Also, can you enable the password?

  4. Current Limiting resistor, I’m a mechanical engineering student therefore totally incompetent with electricity – so I didn’t put one in.

    I want to try luxeon Star super brights. I think they would do better as well.

    I thought about filing the LED’s flat, but thought it would dull the light to much, never tried it though, may look into it.

    Can you be more specific on the password issue? It’s my university server so sometimes it does crazy stuff. I’ve checked to make sure permissions for all pictures were set correctly.

    As for the Super glue, yes that was a really stupid choice… however it was what was currently on my desk at the time. The reflectors aren’t glude to the plexi-glass so i can still take off the LED assembly and replace it. I was going to use some 1/4″ aluminum plate first but didn’t want to bother with machining it.

    Keith

  5. dioxide says:

    it isn’t a great idea to wire leds in parallel. youve already lose 9 of 40, thats almost 25%. the electricity that is no longer being used by those 9 is being spread throughout the remaining 31. the more leds that die, the shorter the remaining few will last.

    (this is aside from the fact that running any diodes in parallel is bad because for whatever reason, all the current will end up using only one led, until it does, then using the next least resistive led, etc.)

  6. Darkcobra says:

    Nice project and very well documented.

    I’ve super-glued LEDs into holes drilled into a metal bracket as well. Then I found that 8 of the 24 were defective. After a moment of panic, I was able to remove them easily with a hammer and punch. The sharp impact breaks the brittle super glue.

    Also, I’ve heard (but have not tried) that roughing up the lens of the LEDs with some sandpaper does a good job of pre-diffusing the light and helps to eliminate hot-spotting.

  7. japroach says:

    hm I would like to know a few more things about this project: what is the power source for the LEDs?

    and what is the power use of the LEDs vs. the cathode?

    If I attempted this I would try to somehow integrate it into the CCFL driver supply as that would allow me to change the brightness.

    Also I would either try to match the voltage drop of the LEDs to the supply voltage, or get a proper driver for them (to ensure high efficiency). hmm but then that wouldnt work with adjustable brightness… needs some more thought.

  8. Johnny SuperStar says:

    diodes? more like Dio!

    Holy Diver! You’ve been gone to long in the midnight sea!

  9. Power Source was a lithium-ion cell pulled from cheap cell phone batteries, they are now run from a cheap selectable wall wart which gives me two brightness settings.

    I hope to do some more looking into this and try some other LED’s. Their is a blue green tint to the ones I have which I don’t like. Its not like its a really high colour temp, more like just an off white.

    I did some current readings before I attempted a rewire and these are nothing like the 1 Watt superbrights. The total current draw at 3.2V before some LED’s died was 600ma (which has all been either a result of me putting 12V over 2 in series which was more of a mistake or because when i was solderin the wire near the plastic bodies they randomly decided to stop working, i assume because i overheated them) None have died as far as I can tell since I’ve been running the monitor with the wall wart and its been runing for hours today.

    Right now at 3v its 404ma and with 4.5 its 765ma, so 3.5 watts max.

    Since this was more of a test, I’m glad people’s main thing have been my lack of caring on the electrical side rather than the project itself. I take that as a bonus.

  10. Kevin K says:

    From an electrical engineer to a mechanical engineer, Do not run that until you put that current limiting resistor in. You are killing the LEDs and will eventually cause a short on that wire (technically it is now), and just smoke up you junk.

  11. Jim says:

    as #5 said, when the leds burn out, it will force the current through less pathways, increasing the current through each. (this phenomena can be seen with some old-school christmas tree lights wired in parallel). A solution to the runoff caused by too much current as well as a solution to his note that current will flow unevenly is to use one current limiting resistor for each LED, with the resistor, LED segments in parallel. This solution is a bit more wiring and a tiny bit more expensive, but it is much more versatile and immune to runoff.

  12. neg says:

    where did the contest entries go? i liked those…

    –neg

  13. TJ says:

    Not to be an ass, but we already have seen this done on a Jornada.

    http://www.hackaday.com/2006/05/23/ccfl-backlight-replaced-with-white-leds/

  14. dioxide says:

    any of you know if you can use acrylic cement on leds? that would be fantastic, as that type of cement actually melts the two parts together. ive only use it with plexiglass, but if the plastic of the led is compatible, it would seem like flattening the dome and melding the led directly to the difuser would be the most efficient way of passing all the light. no idea whether it will make big hotspots though. maybe ill try it, make a small backlit wet-erase board or something.

  15. kasmoie says:

    chchceck it outt!

    http://led.linear1.org/led.wiz

  16. Fragged says:

    Nice, just when I was looking at doing something like this to an old laptop LCD…

    I wish there was more documentation, but seeing as i’ve already dissasembled the laptop without any photo’s or documenting any of it it I cant really complain :)

    One question, do I _NEED_ an inverter to replace it with LED’s, is there any way out of it?

  17. japroach says:

    Interesting.. I would actually avoid the superbrights as it would result in much less uniform lighting (assuming less were used to compensate for their higher output). They might also require heatsinking.

    Best would probably be a huge strip of surface mount LEDs, say 50 or more per side :).

    And it looks like cold cathodes are a fair bit more efficient than an LED atm.. so we wont see any decrease in power usage.

  18. NFNNLN says:

    “LG raises the bar by ditching the fluorescent backlights from most LCDs and using a matrix of light-emitting diodes. In addition to way deeper color, the LEDs give Samsung that ability to selectively darken or brighten the backlight in different parts of the screen. This yields a contrast ratio of 100,000 to 1, they say.”

    An LED matrix is the way to go!

  19. PatulaWiFi says:

    I did this to a LCD monitor back in september 06, I use 27 UltraBright LED’s on each side (54 in total) and a 5V external AC adapter directly as a power source, it works fine

    until today it still works ok, none of the LEDs burn yet :)

    Here’s my version of this hack:

    http://arribasanjuan.com/webs/patulawifi/electronica/lcdleds/index.htm

  20. john says:

    I did a backlight upgrade using 1w luxeon high brite led’s… I was able to get this screen to be 100% sunlight visable, but it had to be liquid cooled….

    check it out here:

    http://www.mp3car.com/vbulletin/showthread.php?t=43743

  21. newb says:

    umm…. im trying to do the same thing with my old lcd monitor, but mine has two sets of fluorescent tubes. It says they run on 3kV, so it there some way to integrate the LED’s into the monitor, without having to create a seperate board for the LED’s and running it with a seperate power supply

  22. Martin D says:

    Dear Friends,

    please help me with the following problem. I saw most of the sites postes here, and I don’t have experience or proper training in electronics.
    I want to replace the fluorescent tubes with leds on 19 inch monitor (AG Neovo KB-19), but I don’t know how to make it work with the tubes disconected, because the electronics of the monitor turns it off when the tubes are disconected or when it can’t light one of them, I think. Seeing all of your work, I imagine that there is a way to eliminate them…
    Are you so kind to indincate me a simple way to achieve this, on the adress mpclarice@yahoo.com.
    Thank you, Martin.

  23. Roy says:

    i just want to ask something about backlight. some camera fones has a built-in flash, and for some the flash is just a bright backlight. i own a nokia 5700 and it has one. may i know if the 5700’s camera flash replaceable, but not with another backlight but an infrared emitting diode (hsdl-4220 to be exact)? i want to take pictures in total darkness with my fone. please tell me if it’s possible and if so, how to do it and what should i need (tools, IR ed, resistors, etc). please help!

  24. Where is the article? The link is gone. If someone has it, could it be posted to the site as a PDF or something?

  25. Mac says:

    Will LED’s operate safely when connected in series?

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