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Question: Do LCD controllers intimidate me?
Yes. - 0 (0%)
Yes, a lot. - 2 (100%)
Total Voters: 2

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Author Topic: LCD controllers=Confusion  (Read 5945 times)
WDITrent
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« on: June 30, 2011, 01:01:53 AM »

I can only post a poll, I guess, so there's the poll. Smiley

Hello everyone! I'm new here, obviously, and I've been researching how to take my Intuos 4 Large and cintiq-ify it. So I've danced around the idea of the Samsung LTN154MT07, which is the panel Apple uses in the new Macbook Pros. I'm drawn to the LED backlight and resolution.

Allright. LCD controllers are about the most intimidating thing in the world. After some research, I know I need to find just the right controller for just the right LCD and just the right operating system. I'm running Mac OSX 10.6. I don't really know where to begin. Any advice is appreciated. Thanks!
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bernard
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« Reply #1 on: June 30, 2011, 02:32:26 AM »

Welcome WDITrent.

LED-based panels (and newer panels in general) tend to be harder to "drive" from "after-market" or "real cheap" boards. Not all LCD work the same (and the LED portion especially). Most LVDS controllers are built to work with an "inverter" that drives the CCFL lamps.

I was not able to find the datasheet for the Samsung LTN154MT07.  But I think I saw "TN" panel, matte, "2 channels LVDS" and 6-bit colors (which is quite standard for TN panels).  I was looking for the datasheet to understand the LED driving requirements.

Typically, you have to email the LVDS vendor your panel model brand and number -- read our wiki page about this: http://wiki.bongofish.co.uk/doku.php?id=bongofish:lvdsvendors 

"just for the right OS" is not a concern.  Once it works, it works for all PC/Mac.  This is not a "video card" we are talking about, but is more like a "monitor". (i.e. all monitors work with all machines nowadays).

Make sure the screen image matches the size (physically) of the intuos active area. The screen can be smaller, but I do not recommend a bigger screen.  Some folks have built DIY cintiqs without opening the intuos case. Like tabletmod.com

(for spam-limiting reasons, you need to post at least once before you can create threads)
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WDITrent
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« Reply #2 on: June 30, 2011, 05:32:48 AM »

Than you very much for the helpful advice, bernard. My Intuos working area is the same size as a standard 15" 16x9 display. I plan on doing this addition a la TabletMod, placing the display in an enclosure.

EDIT:
I've done tons of searching and no one is selling LCD controllers for the displays I like. Is there anything else I can do?
« Last Edit: June 30, 2011, 06:13:04 AM by WDITrent » Logged
bernard
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« Reply #3 on: June 30, 2011, 07:06:17 AM »

Here's how I would do this personally if I really wanted that particular display:

*If* you can find the datasheet (pdf) for your LCD, then there might be enough data in there to interface it. (Note: I searched, but could not find it).   If you cannot find the datasheet, then you are shooting in the dark, BUT looking at other, similar datasheets AND inspect your LCD (once in your hands) might just do the trick and you might get lucky.

Here's another LED-based Samsung one: http://www.displayalliance.com/storage/LTN141AT12.pdf for reference. Also, Chocochan was looking at the 9.7" iPad screen which uses LEDs -- (AFAIK, this has not been going very far yet) but here's (one version of) that iPad screen datasheet: http://www.displayalliance.com/storage/1-spec-sheets/LP097X02-SLAA.pdf    This LG screen has the LED signals on the same connector as the LVDS.  The Samsung one uses a separate 12 pin connector (see page 19) and its LVDS connector is a standard 30 pin connector.

In other words, if your LCD resemble that other Samsung one, then a "normal" LVDS driver would work for the LVDS part.  For the backlight portion, then we would need to do more searching for a solution. But driving leds can be a little tricky, it is nonetheless quite standard stuff and probably not-that-complex. (unlike LVDS!).

*If* the LED connection is bundled within the LVDS connector (like the iPad screen), then: You would take a "normal" LVDS driver with its bundled cable. You then try to find that specific macbook's internal replacement LCD cable (or any LCD cable that you know was meant to work with this LCD Panel). You would modify the cables and "merge" the LVDS driver cable with the other one to make a custom cable. (LVDS signals will be compatible, I am sure).  You would not connect the LED signal to that board but re-route them to another board that would be used to drive the backlight LEDs.

The iPad contains "6 LED Strings" and we have the pinout on the connector (but not much electronic info on the LED String itself in the ipad datasheet). I have found a MAXIM chip that is called a "6 Strings LED driver" but this is not a board, it is a standalone "chip" and the package is not the easiest to solder for DIY work.  

For the samsung one the 12 pin connector has "up to 8 channels" of LED (which I bet corresponds to the LED Strings).  That datasheet had the LED electrical characteristics :


* samsung_led_spec.jpg (74.52 KB. 665x250 - viewed 401 times.)


* samsung_led_spec2.jpg (97.59 KB. 644x727 - viewed 409 times.)


So there might be hope, I never really looked at this aspect very carefully yet, but more and more people are asking and have the same problem. I would like to find a cheap solution for this. Some board that would work off 12v and would be able to drive a number of "led strings" sounds like a common thing we need.

People like NJYtouch or luly *might* help (that's far from being proven). You might even go as far as sending them your LCD Panel for them to try to drive it. (not sure how much would that cost though).

EDIT: I found another samsung one, but the connector appears to be the same as the iPad. http://www.displayalliance.com/storage/1-spec-sheets/LTN154BT03-001.pdf (6 LED Strings). Here's a portion of the datasheet:


* samsung_led_spec3.jpg (97.71 KB. 668x399 - viewed 414 times.)


* samsung_led_spec4.jpg (43.14 KB. 679x224 - viewed 367 times.)


* samsung_led_spec5.jpg (83.63 KB. 653x336 - viewed 603 times.)

« Last Edit: June 30, 2011, 07:41:37 AM by bernard » Logged
WDITrent
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« Reply #4 on: June 30, 2011, 05:45:51 PM »

Thank you once again. This should be helpful. I've actually been looking around some more and wondering if people are really selling these LCDs with the controller attached. Does that happen often? Otherwise I may take a controller from a broken Dell Inspiron that I already have and find a display to match that.
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bernard
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« Reply #5 on: July 01, 2011, 04:57:59 AM »

Controllers cannot be "taken" from a laptop. The LCD Panel is about the only part that one would rip out of a laptop. The controller is within the laptop motherboard and cannot be re-used to make a "monitor" (a device that you connect with a VGA or DVI plug).  You need a monitor kit (a.k.a. LVDS controller board).

The only piece of functionality you can get out of a laptop is the inverter (when the laptop is CCFL). And even then, there are issues to use interface it with a another controller board.

Even if you had found a way to take a controller out of a laptop, you will probably face the issue that the screen specifications won't match your LCD Panel and it would be unusable. These are not plug & play devices(!!).

Selling controller along with LCDs?  Actually, it is the reverse: controller vendors sometimes sell LCD Panels as well. Reason: A *whole lot* of people are selling LCD Panels.  Not much people are selling LVDS controller boards (a.k.a. Monitor kits).
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