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Blog > Building a Status Screen, part 1: Hardware

>> Building a Status Screen, part 1: Hardware

Fri, Mar 26th 12:25am 2010: IVT

A couple of weekends ago I mounted some LCD screens on the wall at Internet Vision Technologies and set them up to display a dashboard of assorted data from within the company. I wrote a blog post about it that received a lot of attention so if you want to know the "why" behind the project it would be a good idea to read that first:

Fun with LCDs

To refresh your memory this is what we're going to end up with:

What I'm going to do now is show you some of the details of how I did it so you can have a go at building something similar yourself. This will be a series of three posts covering the hardware, setting up data sources, and creating the interface.

So, on to the hardware!

Location
The first thing to consider is where to put it. Keep in mind that a company status screen isn't an advertising board for visitors, it's an internal tool that you want your staff to be able to see throughout the day and that will probably display confidential information. The IVT office is an awkward shape and it took a bit of pondering to work out the best place, but in the end I mounted the screens on a reasonably central wall where they can be seen by most staff while sitting at their desks.

Try to find a location that's fairly high. The screens at IVT are mounted so that the bottom of the screen area is at about head height, with the tops nearly 2.5m above the floor. That was partly because they needed to be mounted above desks, but it gives the additional benefit that they're easy to see over partitions and people walking around.

Other considerations are glare from the Sun or other light sources, availability of power nearby, and a location fairly close to the screens where you can place a computer to run them. The computer will also need network access but that could be either wired Ethernet or WiFi, so in most offices that shouldn't be a problem.

Screen Selection
In my case I bought a set of three identical screens second-hand from a friend so I didn't get to select what model they were, but it worked out fairly well in the end. They're 22" LCDs with a native resolution of 1680x1050, they're fairly thin as LCDs go so they sit back close to the wall, and as a bonus they remember the last power state so if their power is turned off at the wall and then turned back on again they come back in an "on" state. That's fairly unusual for LCDs: most models need the power button pressed to turn them back on again after power has been removed.

Restoring state after power-off isn't really critical but it does make things easier if you want to turn the screen off outside business hours and have it come back on again automatically. A simple appliance timer can be used to turn the screens off at the end of the day and back on again first thing in the morning, and if the screen is smart enough to turn on when power is restored it saves you having to hit the power button every morning.

If money was no object and I could simply go out and buy the most impressive screen possible I'd probably pick the one used for the Panic Software status board: a Samsung 460UXN-2. They're huge, have high resolution, and the plastic bezel around the screen is very thin.

Physical Positioning
If you have a single huge screen your job is simple: measure it, check that it fits the space you have in mind, and you're set. In my case I wanted to mount three screens side by side so things were just a little more tricky.

Obviously vertical space wasn't a problem but I didn't have much leeway horizontally. I measured the width of a screen, multiplied by 3, and discovered that it came to just less than the space available on that section of wall. Perfect.

Then I took the width of a screen, added 10mm to allow for a slight gap between the screens and give me some wiggle-room, and used that as the center-to-center spacing of the screens. That distance is shown as the "spacing" measurement in the diagram below. I then took half that value, added about 20mm to put a slight border to the edge of the wall, and measured in that distance from the edge of the wall as shown by the "offset" measurement below. That gave me the center position of the first screen, so I used a pencil to draw a small vertical line on the wall at that point.

Then I took the screen-width-plus-10mm value that I calculated earlier, measured across to the right, and drew another vertical line for the center of the second screen. Repeat the process again and I had the center of the third screen.

I then drew a short horizontal line through one of the center marks to show vertically where I wanted the center of the screens to be, and used a builders spirit level to draw horizontal lines through the center of the other two screens at the exact same height.

Stepping back and looking at the wall you'll now have three crosses: one for the center position of each screen. Make sure the spacing makes sense, maybe by getting a friend to help you hold up a couple of the screens in the correct positions so you can see if they fit as you expected.

Mounting Brackets
Almost all LCD computer monitors and TVs are designed to use a standard mounting system generally referred to as a "VESA mount." VESA mounts use four screws arranged in a square to attach a bracket to the back of the screen, and they come in different sizes. There are two size factors you need to get right.

The first is the carrying capacity. The 22" LCDs I used are fairly light but if you've ever tried to move a big LCD TV you'll know they can be amazingly heavy. VESA mounting brackets are rated by weight, so make sure you get one that is strong enough to hold your display.

The second is the screw spacing. VESA mounts use four screws in a square and the most common configuration is for them to be 100mm apart. Some small monitors have them on 75mm spacing, and with TVs getting ever bigger there are now also VESA mounts with 200mm, 400mm, and even bigger spacing.

Most mounting brackets have holes for multiple spacings but it's worth checking to be sure. Measure the spacing on the holes in the back of your monitor, then when you're buying a bracket you can check that it supports that same spacing. You'll often see packaging marked as "VESA-100", or "VESA-75", as a shorthand way to indicate the spacings they support.

Display mounting brackets add a little bit of space between the monitor and the wall, particularly brackets that provide pan and tilt adjustment. In my case I wanted the monitors to sit as flat against the wall as possible and didn't care about pan/tilt, so my choice of bracket was based on getting something as thin and simple as possible.

In the end I grabbed three brackets like these from Bunnings for about $20 each:

It's really just two pieces of folded metal, but they work very well and add minimal space behind the screen. The bottom piece in that picture attaches to the wall (more about that in a moment) while the top piece screws onto the back of your monitor. Because the sides are not quite parallel you can then slide the monitor down onto the bracket on the wall and it'll sit firmly in place.

If you're working with a big screen you'll probably need something a bit stronger, and it's likely you'll end up with a bracket that looks more like this:

Fitting the Bracket
Carefully place the screen face-down on a flat surface, preferably with something soft like a towel or blanket underneath so the screen surface won't be scratched. Remove the desk mounting stand since it'll just get in the way. That can be harder than it sounds, with the mounting stand often fitted using screws that are concealed behind plastic covers. In my case I had to pop a plastic moulding off the back of the monitor before I could even see the screws.

Next, attach the appropriate section of the mounting bracket to the back of the screen using the screws that should have come with the bracket. Some monitors have unfortunate plastic mouldings that protrude behind the back face of the case and in that case you may have to use spacers (typically supplied with the bracket) between the bracket and the back of the monitor. Avoid using the spacers if possible though because they make the gap to the wall bigger and increase the torsional force applied to the wall mount.

Mounting the bracket to the wall is the bit that you absolutely must get right. If you get it wrong your monitor may well end up on the floor in broken pieces, and we don't want that!

Most interior walls are faced with plasterboard (called "drywall" in the US) which gives a nice surface but has little structural strength. If you have a heavy monitor you'll need to locate the framework within the wall and make sure that at least some of the screws you use penetrate through to the timber or metal "studs" (verticals) or "noggins" (horizontals) inside the wall. Most mounting brackets come with a large number of holes in them so that you can place the bracket in your desired position and then put screws through whichever holes correspond to the location of the frame inside the wall.

Whatever you do, don't just put regular metal screws straight into bare plasterboard and expect them to hold strongly!

If you're using light monitors like mine you can get by with regular metal screws combined with "plaster screws". A plaster screw is a special screw with a very large thread so it can bite strongly into plaster and spread the load across a large area. They have a small hole through the center so you start by driving the plaster screw into the plasterboard using a screwdriver (they're self-tapping, so there's no need for a pilot hole although it can help sometimes) all the way in until they're flush with the face of the wall. You can then screw a regular metal screw into the center of it with the result that it'll bite firmly into the plaster screw and you'll have a fairly strong mount.

If the monitor is mounted fairly close to the wall with a thin bracket the majority of the force exerted will be vertical. There will also be a small horizontal force applied to the screws at the top of the bracket because the monitor will try to tilt forward and down, resulting in torsion (twisting) applied to the bracket.

Whew, just about there! With the brackets in place it's time to lift your monitor(s) onto the wall, step back, and admire your work. Hopefully you won't watch in horror as they crash to the floor.

Concealed Cabling
If you want your status screens to look really slick it's important to conceal the cabling as much as possible. You can cut a hole through the wall directly behind the screen and feed the cable through it, but in my case I was lucky enough to have a pole next to the screen so I just ran the cabling behind and then used velcro cable ties to attach it to the pole. It's not as neat as having the cable run through the wall but it's good enough for this situation, and it looks acceptably neat.

One thing to keep in mind is the length of cable you'll require. Whatever length you estimate it probably won't be enough: you need to allow extra for the end of the cable to loop around a bit behind the monitor, to follow curves, and to reach to the location of the computer that will drive the whole contraption. Do some measuring, figure out how long you need, and add another metre or two for safety. I used 5m DVI and VGA cables for the video, and fitted IEC extension cables (like the ones that are sometimes used to connect a monitor to a computer power outlet) to the power cables so the bulky plugs wouldn't be visible.

Because I used three monitors I ran the power cables for all the monitors to the same location and plugged them into a power strip. That makes it easy to use a single appliance timer to control the power strip and turn on all the monitors at 8am and turn them all off again at 6pm automatically.

Computer(s)
The computer used to drive the screens doesn't need to be anything special, but one important consideration is that it should be quiet and preferably not a power-guzzler. It'll be running 24x7 so try to pick something low-power. At IVT we often upgrade machines and there's always a slush-pile of about the last 4 or 6 most recently replaced machines sitting around as spares and for use in testing, so we just grabbed two of those. At the moment we have one computer with a dual-head video card driving two of the screens, and the other computer driving the remaining screen. The plan is to condense it all into just one computer running all three screens but we had problems with video card compatibility and haven't got that far yet.

At this point you should have your screen(s) mounted on the wall, cabling in place, and a computer connected to drive them.

Stay tuned for the next installment, which will cover setting up the data sources to grab the information you want to display on the screens.



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