Jan
23

Building a High-Def Video Wall

Categories:

by

So recently, I’ve been working on a building a large video wall out of high definition televisions. I was asked to help design and build the system to drive the displays, control them, and wire it all up. This wall was designed to be a “wow factor” item in a new engineering building at the University where I work part time as an adjunct.

So what did I have to work with?  I was given nine (plus one spare) 47″ Sharp high-definition “Information Display” TVs. Normally, If I was going to build something like this, I would have liked to pick out the displays, mounts and everything. The world isn’t a perfect place, and I was allowed to start working after the displays were picked out, and mounted on the wall. These displays have a really thin bezel and are designed to be run continuously. I did get on piece of input before everything was hung – I wanted a junction box behind each display with conduit running into the ceiling.

The Wall - TVs mounted, ready for wiring

The Sharp displays (model PN-E471R) are around $1500 each. The mounts that were used are spring-loaded and can be used to pop each display out about 6-inches to aid in wiring. The mounts were (apparently) around $1000 each. So, by the time you pay for shipping everything (also including the cost of spare display), getting the displays and mounts cost a whopping $25,000. That $25k didn’t get much in the way of “wow factor” other than “wow you can spend money”. My job is to get these displays playing nicely together, and drive them at their astounding full resolution. Nine 1080p displays at full resolution means there are a lot of pixels to push. Ideally, we could have wired behind the displays before they were mounted, but I didn’t get that option.

So, as these displays are designed to be nothing more than giant monitors, they have two inputs – VGA and HDMI. No kidding. You can buy an optional expansion card that provides a plethora of other input options, but for our purposes, HDMI will likely be the best option. I decided to use use HDMI extender wall plates that push the HDMI signal over a pair CAT6 cables. These extender plates are simple, cheap, and effective. We ordered 10 sets of the extender plates along with twenty pre-assembled 50-foot CAT6 cables – I’ve crimped my life’s share worth of cables already. Running the cable wasn’t too bad, and we had each display running individually rather quickly.

Cables for the HDMI Extenders Pulled

Testing with four ports lit

 

Pushing the Pixels

After talking with my boss (months ago) we decided that building one large computer to power the whole wall was likely going to be easier to manage than syncing nine little single-board machines (like an Asus EEE Box or a BeagleBoard). So, I threw together a list of parts to buy – a 3.0GHz+ quad-core processor (Sandy Bridge i5), 16GB of DDR3, and Three ATI/AMD video cards that could each drive 5 displays (the Radeon 6770 “Eyefinity” edition). I wanted to spread the load across three cards, just to ensure everything ran really smoothly. I Hit a snag, as the parts vendor only had two of the video cards I wanted to use. Changing vendors was going to cause paperwork problems (yay large organization inefficiency!), so I decided to suck it up and deal with using only two cards until the vendor restocked them. Each of the these video cards have five mini-displayport connectors.

Active? Passive? Fail.

So, to connect to the HDMI extenders, I ordered ten mini-displayport to HDMI dongles. After getting everything together, I learned that I might have a problem- each of the dongles needs to be “active” and actually do the conversion from native displayport to HDMI/DVI with an IC inside the adapter. Unsure whether the adapters I had were active or passive, I took one apart, during which I ended up destroying the adapter. I found a powered-IC, so I figured that meant I was dealing with active dongles. Nope. The dongles contained an active IC, but they did not do the crucial native displayport conversion inside.

Lots of mini Displayport goodness

Without active adapters, I’m limited to driving two “legacy” displays per card (DVI/HDMI). We found a native displayport monitor, and proved that with a native displayport device, I could indeed power a fifth display. I found that AMD/ATI has a list of certified “active” adapters. So I ordered 10. Those adapters are on order (somewhere in the nightmarish paperwork pipeline). So in the mean time, I fired up four of the displays.  VLC has a nifty feature called “image wall” where you can play a video on a bunch of simple extended displays- and here is what it looks like running!

Four displays running

Parts are on order – more to come.

This post has no tag

Dec
23

Animated Sign out of Christmas Lights

Categories:

by

Update: looks like this post was put up on hackaday !

A heads up: This is actually something I build almost a year ago (February 2011).  I only have pictures of some of the parts, as I didn’t photograph each step alongthe way.

One of my friends that I have known for a very long time, was helping out with a stage production. I was hanging out helping him with some computer stuff and some of the other people there were talking about building a large sign out of christmas lights. I like making things, and christmas lights are, well, electrical, so I inquired further.  I’ll help build stuff..I could even help make the sign animated. And so it was a project!

Step one was to figure out how to control the strands of lights electronically. I had several different microcontroller platforms laying around, but I grabbed an Arduino for the sheer simplicity. An Arduino is complete overkill for simple bit manipulation I ended up doing. A $2 ATtiny or Freecsale microcontroller would have done fine, but I had an Arduino within arms reach when I was playing with the lights. I figured I would use some relays to toggle the lights. The relays I borrowed (and returned) were from a home-made model train setup and triggered at 12v (made by Omron). So, that meant I couldn’t just use the IO pins on my 5v Arduino to flip them on and off. I could have bought 5v relays, but then I would have two problems – I would have paid for relays and likely still wouldn’t have been able to drive them directly – the Arduino’s IOs can’t supply enough current to latch the relays. So, transistors to the rescue!

I had some large power FETs (IRL2203N -PDF warning) lying around… which were complete overkill, but cost me nothing to use since I already had them. I could trigger them with the Arduino, and use the FET to trigger the relays to control the christmas lights. I likely could have used the venerable 2N7000 FET instead, but so far I had managed to find everything I needed in my lab. With that awesome luck, I threw together this simple proof of concept:

So, they wanted to make letters for this sign out of plywood, about 18 inches tall each, to spell out the theme for the show – “burlesque”.  They had planned on outlining them in sharpie on the plywood and cutting them out by hand. That sounded very labor intensive and imprecise. Technology to the rescue! I offered to cut them out using a CNC machine to which I had access, which made them look much, much cleaner.  Laying out large letters in CAD took all of 10 seconds each. Cutting out all of the letters on a CNC mill took under two hours. Not too bad for how well they looked. Next, after painting the letters silver, they wanted to drill holes to mount christmas lights along the edges. I didn’t know what kind of spacing they wanted and such, so I didn’t use the CNC machine to make the holes. A small army of volunteers made drilling the holes easy. The next part was to mount strands of christmas lights in the holes drilled along the perimeter of each letter. Hot gluing the individual lights seemed easy, and since we had a bunch of people, and a bunch of hot glue guns, it went quickly.

While the army of volunteers (6 people?) were drilling and hot gluing, my techie friend and I started wiring the backing to which the letters would mount. We used 18 gauge stranded wire to connect to each of the relays, which were positioned behind each letter. To connect the chains of lights on the letters to the relays, I simply cut one side of the power connection and added the appropriate connector to plug into the relay. We used a bus bar and terminal block from home depot to help distribute the 12v power and ground to each relay. 12v power was supplied from an old ATX power supply that I recused from a dead computer. Here’s a photo of some of the wiring:

The Arduino code for running the sign (which I cannot find…) was simple – flipping an IO on/off turned a letter on/off, so an appropriate set of digitalWrite() commands gave me an animation. I was certainly going for functional with minimal effort over elegance with the code – worked out fine.  So after all the wiring, gluing, and mounting, the sign looked really nice. I really enjoyed the project. The sign was dismantled a few weeks after it was used in the show so that I could return the pricey relays to their home. I plan on building a similar sign in the next few months for a different purpose, and I’ll photograph it as I’m building all the pieces.

This post has no tag

Dec
23

Mohbius: an engineer’s blog

Categories:

by

My name is Andrew, and through this blog I will share some of my adventures and experiences in being an engineer and building things. I might posts projects from work, projects I do at home for my own amusement, or things friends have asked me to help them build.

But who am I? I’ve been posted on slashdot and hack-a-day (my photo tour of Advanced Circuits on Base2), presented at DEFCON 18 (Training the Next Generation of Hardware Hackers), and worked on a large number of projects related to computer security, embedded electronics, and all kinds of things in between. I work at in an electrical engineering department at a decent-sized university doing this, that, and the other.

So, look forward to some interesting posts every now and then!

This post has no tag