Intro: Laptop Converted to 2nd Monitor
The idea is to create more screen real estate in a small package at a low price. Here in 2007, the idea of purchasing a flat screen and plunking it down on my desk as a 2nd monitor was definitely appealing, but I am still unwilling to spend that much on a display device knowing full well that a "better" unit will soon be available within my El Cheapo price range. So I embarked on this project with these things in mind:
- Low Cost (Under $50)
- Simple Interface
- Simple Construction
- Readily Available Components (i.e. no ordering, all locally available)
- Low Build Time ("weekend" or Saturday project)
- Small Footprint
- Low Weight
- Maximum Performance (given the size & complexity restrictions)
I currently run a Quadro FX3000 on my main rig, so a dual monitor setup would entail just that: a second monitor. No extra card or splitter. But then enters the world of personal politics...
See, I am a screen size junkie. Waaay back in the day, I managed to snag a matching pair of Diamond Pro 21TX's from a friend for free, and since then I have had nothing but 21" displays. (Which the womens find utterly disgusting, I might note.)
So, when I begin to look at my "cluttered" 21-inch screen and think "gee, I need more". I look at the girlfriend and smile. She, of course, says "NO!!! Your monitor takes up half the desk as it is! With two of those beasts I wouldn't have room for any of MY stuff!!!"
Keep in mind this is a custom 36x120 (that's three feet by ten feet) desk that I built from scratch with the specific intent of having more room for things like beastly monitors...
I kick it around in my head for a while, and remember that at one time or another, I had wanted to start using laptop TFT LCD's as desktop monitors. And, apparently, so have a bunch of other people. The question has always been the interface. At one time there were a few companies that sold LCD interfaces, and technically there still are.
BUT, with a purchase price between 200 and 500 dollars (see EarthLCD), it would be cheaper and easier to buy a COTS/MOTS LCD instead of an LVDS card for my main rig. What to do, What to do...
Step 1: Laptop Modification
To aid in ease of interfacing (and to be able to sneak a second computer on to my now egalitarian desk) I opted to keep the majority of the computer intact, and deal with it over a network connection.
The unit I am using is a Compaq Presario 700 Series (732US). It has a 14.1" TFT LCD screen in relatively good condition, with a good inverter and backlight. Here's a spec sheet of what it left after the system is stripped down:
Microprocessor - AMD Mobile Athlon 4 - 1.2 GHz
Memory - 256 MB 133 MHz SDRAM
Video Graphics - 4X AGP with VIA Twister K Graphics
Maximum Resolution - 1024 x 768 x 16M (24-bit)
Video Memory - 16 MB shared
Multimedia Drive - DVD/CD-RW Combo Drive
Display - 14.1 inch TFT XGA Display
Card Slots - Type I/II/III PCMCIA w/ 32-bit CardBus
Network Card - Integrated 10/100 Ethernet
A few things to notice: No hard drive listed. No floppy drive listed. No battery life listed.
The HDD, FDD, battery, speakers, keyboard, touchpad and every "non essential" has been removed. This system has effectively been turned into a "Processor-based Panel PC". My only real bitch (as you will see later) with this entire system is that the rear reflector for the backlight is integral to the screen shell, not the screen itself.
I will be skipping the disassembly phase of this project, as each laptop disassembles differently. And besides, UTFSE for your model and you should be able to find something.
I started by hardwiring the power brick into the motherboard on a 6" pigtail, as I intended to mount it inside the "case" with the screen and everything else.
Step 2: Picking Parts
What has to fit? Well, the motherboard, power brick, and screen. Also, I decided to add a USB card reader in case I wanted to swap files without the network present. I also opted to install a four port USB 2.0 hub in place of the paltry 2-ports on the motherboard.
At this point the removed laptop components are still in working order, and I have narrowed the component listing down to where I want it. I was still a little sketchy on final unit size, but I really needed some dimensions before I firmed up on those details.
It's time to break out the digital caliper and go to town.
Step 3: Dimensions
After measuring this assembly, the DVD drive and the screen dimensions, I was able to draw up the following set of DXF's (Courtesy of QCad. Thanks Knoppix!). The main image shows a colored layout of the components. The second image shows the dimensions of the mounting holes and their locations. The final picture shows the plate with holes, free of dimension lines.
Step 4: Construction
Materials, Materials, Materials. What a question. Referring back to my original goals, I needed the casing material to be cheap, light and locally available. I needed the same from the fasteners. Part of being a cheap component is the workability of the component, or simply "Do I have the tools to do this, or am I gonna have to buy the part AND the tools..."
For construction ease, I wanted everything mounted to one common backplane. I opted for a 12"x24" 22Ga. Steel sheet. For the fasteners I decided on 4-40 hardware, as the ground donuts on just about everything in this laptop has 4 Ga. holes in it (go figure) and 4-40 hardware was available locally. Let me say for the record that I really, really, really wish I could find 4-40 threaded rod, or a beefy rod with 4-40 tapped ends. Really, really wish. To get the necessary height on the LCD, I ended up threading six 4-40 jackscrews end to end, as you will see here in a minute. This is a far less than ideal situation, and I will probably have to buy some aluminum tubes to go around the screws to reinforce them at some point. For now they work, but they're not quite bulletproof enough for my tastes. (I tend to be extremely hard on things, to the point that I have been known to twist screwdriver handles off their shafts.)
UPDATE: Thanks to Parallax I now have replaced the wobbly stack of screws with a single 4-40 standoff.
Anyway, enough about parts, and on with construction.
First and foremost, I had to get that 12x24 sheet cut down to two 12x10's, and in that there was a choice to be made on how to cut it. Do I use snips? A nibbler? A mechanical shear? Snips bend the metal as they cut, so they're out, and a shear would have taken an extra three days to cut it at the university (weekend project after all...) so I used a manual nibbler. Yes, I know. Stupid.
All in all, I nibbled over five linear feet in two days on this project, BY HAND and I have the bruises to prove it. For the love of <expletive deleted> find someone with a shear (or at least a pneumatic nibbler)!!!
After cutting (argh...) the plates, I measured the bottom one, drilled it and mounted the hardware.
(You'll notice the four large holes at the top for the power unit are missing, and there is a standoff on the right side that was not on the original layout. The new standoff is for a mobo mounting hole that I originally missed, and I did not drill the four holes for the power unit since I found a new way to permanently attach it to the plate without drilling holes. (Kneadatite epoxy putty. Buy some. You'll need it. It's like JB Weld that really does what the label claims it does))
Step 5: Mounting
So far, everything fits. I didn't get a picture of it, but the strain relief on the USB plug connected to the side of the card reader had to be shaved down, as it was in the way of about 1mm of motherboard.
It is also a good thing to take such careful measurements, since laptops tend to have tight tolerances anyway. In the second pic you can see the almost non-existent clearance of the sound I/O board to the DVD and motherboard.
The colored twisted pair wiring has been soldered in place of the original power button, power LED, and card reader activity LED. Again, UTFSE for SMT soldering techniques.
Step 6: Screen Mounting
Hey, it fits! And it's surprisingly square...(Wonder how that happened???)
So far all the pieces fit as planned, so I began to work on the faceplate that would go over the LCD. Nothing too fancy, but I did want it cut as a solid piece. So I HAND NIBBLED (Let me once again state how painful this is and that you should NOT do this unless you really, really, really hate yourself...) the faceplate out so it would fit the LCD, and have a nice surround to mount LED's and such on.
Step 7: Power Button
Still rough, but almost done. The power buttons still need to be mounted. As noted earlier, they have already been wired on to twisted pairs.
You can see my original mount for the power button on the lower right of the screen frame. Yeah, it didn't really fit there. LCD in the way and all. Whoops. Also need room for a 2nd button.
So I decided to rivet a small metal plate into the top to hold the Power and Fan Power buttons. I know no one else will agree with me on this, but frankly, I don't see the point of doing a homebrew electronic project unless it's got a ZARKING GIGANTIC RED BUTTON on it.
That, and this fine lil, delicate LCD computer all fast and pretty in its shiny steel plating, zooming along with an atrocious, junk bin "Panic Button" on top like a satellite antenna just makes me smile. Every time I feel that switch and its positive engagement when I turn the fans on, it reminds me of my corporate surplus 286 with a big red toggle on the side, 2400 baud and Jolt Cola. Ah, youth...
So far so good, everything is in place, let's see if it still works...
The Fan Power button controls an independent +12v linear supply driven off a 7812 with a TIP2955 "laddered" in. Once again, UTFSE...
Step 8: Smoke Test
I have a friend who claims computers run on smoke, because "Once you let the smoke out, they don't work anymore." Well, I sure wasn't going to let the smoke out of this one...
What, me worry? It's fine!
Step 9: Completion
Well, it works. I'm actually surprised. I fully expected to fry something along the way. The final footprint ended up at 12x10x2 and it weighs in at 4.5 pounds. Not bad for a $40 investment.
So, how did this "re-cased" laptop become a second monitor for my main system? Easy! I cheated!
Once the monitor has booted Knoppix off of its CD, A program called MaxiVistaViewer (running under wine) takes over. The main system picks up the Viewer off the network, and with MaxiVIsta Server, creates the equivalent of a super fast RDP. The main system then stretches its screen onto the 2nd monitor. The second monitor runs well enough over the network that I can watch DVD's on it. Also, with MaxiVIsta I can "chain" up to 4 monitors together into one display, or even utilize it as a "Soft-KVR" using one keyboard and mouse to control all four systems.
Disappointed? Yeah, I was too when I discovered the limitations of laptop screens for desktop use. This just seemed the cheapest and easiest option available to me.
On another note, the screen made its first real appearance as a component of my 3D design final, once it had its "appropriate patina" (i.e. rust) and had been attached to its oh-so-crufty copper pipe mounting system!