Posted on December 29, 2015
Portable LCD Monitor
Ever upgraded your laptop, and wished that you could use the screen on the old laptop for something useful? I feel like I’ve seen a lot of posts on the internet, and myself have looked into reusing the bits and pieces from old machines so as not to throw them away with still working parts inside!
I recently nabbed a severely water-damaged macbook pro 17″ (mid-2009) from the e-waste pile at work. Someone had already taken the hard drive and memory from the machine, but there was still a perfectly functional screen in there, so I took it home. These displays have a 1920×1200 panel inside. Mine in particular happens to be a Samsung LTN170CT10-105, which has an LED backlight and a nice matte finish. It’s still a TN panel (not a nice IPS like my x220 has), but it still looks pretty good.
The big difference with laptop displays vs. your average desktop computer monitor is that they don’t have a standardized connector. Most of them these days are LVDS, but LVDS doesn’t describe the LCD timings, just the method of signaling to the display. There are also a number of different varieties of tiny delicate connectors to plug into the display. For laptop manufacturers this isn’t a problem since you aren’t going to be swapping LCDs all the time, you just need to drive the one display with one set of timings, and doing it this way eliminates chips to convert to a standard like DVI and back again, lowering your BOM and thus your price point. This is why it’s complicated to rip a laptop LCD off the laptop and just use it like a monitor – it doesn’t have that ability! You need to add some intelligence in between since the laptop’s video card is specifically designed or programmed to send out the correct signals for the LCD of that device. I think this is beginning to change now that some newer displays, notably the Retina iPad display, come with embedded DisplayPort on board which makes interfacing to them much less of a pain. The ever-awesome Adafruit sells them as the Qualia 9.7, if you’re interested!
I did a bit of research, and I found out that someone seems to have decided the market niche for reusing laptop displays is worth pursuing. There are loads of auctions on ebay for different variants of the M.NT68676.2A boards, which are capable of being loaded with different timings for nearly any LCD using an LVDS connection with up to 2048×1152 resolution. I found an auction for the M.NT68676.2A board, plus a backlight driver board, the correct LVDS cable, and a control button board for about $50CAD, which already had the timings for my Samsung display programmed into it. Plug and play:
Once the board arrived, I (very excitedly!) plugged it into the monitor, and it worked right away. Perhaps it was lucky, but it was super easy to get working. The driver chip supports RGB adjustment, so I may even throw a white frame up and see if I can get it close to accurate with the spectrophotometer at work.
The bulk of the work of this project has been in attaching the driver boards and constructing a stand for it. The eventual goal is to have the stand work somewhat like an ipad smart cover, but made out of fabric-wrapped acrylic. The first step was to mount the new electronics to the monitor, which required some new holes in the nice shiny machined aluminum – the slots are for the LVDS data cable and the backlight power cable:
And then with the boards attached:
After that, I decided I was going to need some protectors for my spanky new electronics, which I quickly whipped up in inkscape and cut on the hacklab laser cutter. I also cut two pieces of acrylic for the front, one which attaches to the screen’s original hinges (to allow it to fold up), and one which will fold under the first piece to act as a stand. Here’s what that looks like:
The final step is to wrap everything in fabric to hold it together. The fabric will attach with high-strength spray adhesive, and also acts as a ‘hinge’ to allow the cover to flip down and under to support the whole thing. Here’s what it looks like, with bonus cute cloud fabric:
I’m super pleased with how this project turned out! It’s great when doing things that require a little more space than the 1366×768 resolution of my thinkpad, like pcb layout (which I am soon to be doing a lot of) or writing code where I need to have an API reference available – or as a Raspberry PI monitor for the initial stages of configuration.
I’ve posted the inkscape files I used to my github – they are pretty specific to this particular project, but if anyone’s doing a similar thing perhaps they’ll be helpful!