(Pssst, there is an update at the end of this page!)

(Pssst 2, I got pisnes running from kodi on OSMC. Theck it out here!)

The idea

Since two years I have Raspberry Pi running as a media-server, small web server and NAS. It was a hobby project of mine during my Christmas vacation that time. For this I could finally make use of a tree stump I had picked up some years before that. I hollowed it out and placed a Raspberry Pi and a hard drive in it (and an USB hub and an extension socket and lots of cables). I installed Raspbmc on it and all was fine. But after some time I got bored with it and some web applications ran rather slow and the raspberry pi 2 was released (… and while writing this the raspberry 3 🙂 ) . It was time for an update. At first I was thinking of making something out of wood again, as it is a rather easy material to craft and I don’t have any other experience. My search for inspiration for something new and different out of wood was however fruitless. Then one evening I stumbled over an article about a beautiful concrete lamp. I instantly liked the design and I quickly realized this might be what I was looking for for a new media centre. Googleing for more examples strengthened this idea. And so the idea was born to make a media centre out of concrete.

Brainstorming and Google

OK, so then I had some vague idea about what it should look like and what it should do, but then what? First I started of with some sketches and jotted down the functions it should have. I used some lessons learned from my previous system for this. for example, I had learned that I did not need multiple USB sockets for peripherals. One was more than enough, removing the need for an USB hub. Also, the previous system was mainly built from stuff I had lying around like a big 3.5″ hard disk that needs external power and therefore an additional socket. This time I was going to spend a little more money for a better end result.

I listed the functions it should do, based on my wishes and what I had learned by experience was possible:

Media center, for watching movies, series, photos and Youtube/Vimeo and “Uitzending gemist” (Dutch service for watching public television) on my television (Kodi)

Shoutcast streams, mainly for listening to Studio Brussel and my music collection without having to turn on the TV (MPD)

Network file storage, for sharing files and photos with my wife (Samba)

Backup of our laptops, Ubuntu on mine, Windows on my wife’s (Unison for Ubuntu and Samba+Synctoy for Windows)

Play SNES games, as I never got to do this as a child (Pisnes)

XMPP Server for chatting without using an external provider (Prosody?)

Webserver for playing around, mainly with Hubzilla and some simple pages. (Nginx).

And for the hardware:

Concrete (look)

Raspberry Pi 2

2.5″ Bus powered hard disk 1+ TB (so I don’t need additional power sockets. A smaller hard disk and no sockets reduces overall size) 1*

(so I don’t need additional power sockets. A smaller hard disk and no sockets reduces overall size) 1* A power button. On my previous system a reset required me to open the case and remove the power plug. Not handy…

One external USB socket, for USB stick or game-pad

1*) Well. Nice try, but it did not work. See below…

Carpentry

Now, with these requirements listed, it was time to get to work. I was going to need two boxes: One inner box to hold all the components and one outer box to use as mould for the concrete. I made both these with materials I had laying around. The inner box from MDF as it is a rather soft material which would make it easy for me to screw stuff into. The outer box/mould I made from an leftover IKEA kitchen cupboard door as this is a very smooth material and the concrete would not stick. With no previous experience, this seemed a good idea, so I just got started. I had a friend of mine saw the pieces of both boxes using a sawing table. When at home I assemble the pieces and did some additional sanding to make the pieces line up perfectly.

The inner box I just glued together. In the bottom of the box (the top when completed and turned over) I drilled four holes, not completely through. In this I put dowels in them with a small hole trilled in the top as a support for the pi. Also I drilled four holes in the top half so I could put small stick through it to support the hard disk. Finally I drilled some larger holes in the side where I can put some PVC tubes in to hold the switch (right on photo) and the USB connector (top) and to put the cables (left) through (power, network, HDMI, audio). The tube for the switch I cut in two so I could glue the screwing ring for it halfway. Once the tube would be fixed in the concrete I can simply screw the switch in the case…

The mould I screwed together instead of glueing because I would have to pull it apart once the concrete had set. I luted the corners both to create nice, round angles and to keep the cement in the mould.

Soldering

One of the wishes I had was an power/reset button to both start the box and to reset the machine in the rare case the machine would hang. In my previous installation I had to put the case open and remove and re-attach the power. Which I found really not handy. This too was new territory for me. After googling around I found a rather nice looking button, with an illuminated ring. Just what I was looking for. I decided to gamble that the required 12V would be no problem for the Pi, which can provide a maximum of 5V. Creating this button would require me to do some soldering though: You have to add pins to the P6/reset header to the pi2 so it can be reset/turned on. Also, the wires had to be soldered to the button itself. Thankfully I have a colleague who was willing to do this for me. Another problem solved. After getting the Pi and the switch back and attaching it it worked like a charm. I did however have to attach the led to a GPIO pin instead of an generic 5V pin as this one would always feed the led with power as long as the Pi had power. It would then be illuminated, even when the machine was off. The GPIO can be controlled (with software, will add later). The 3.3V the GPIO supplies proved no problem for the illuminated ring.

Pouring

Then it is time to put things together. I have these two boxes and have to make the inner box “float” in the mould. And have some tubes sticking out for the switch, the USB connector and the cables. I used some clamps to keep the inner box in place during the pouring, after first aligning the inner box and the mould. For this I added some temporary sticks over the inner box so that I could “hang” it in the mould (not shown on photo). This worked very well. Particularly the clamps helped pushing the tubes against the mould so no concrete could get into or “over” the tube endings. I also filled the tube-ending with pieces of pieces of foam to prevent this.

For the pouring itself I had some help. Doing this alone would have made it more complex as i needed additional hands sometimes. I had done some experiments with several mixtures of concrete. All where available at my local hardware store. I decided in the end to use regular cement, and use a fine sand to make concrete. I had made some samples with it, and they came out very nice. I mixed one part cement with two parts sand (as instructed) and added water as I saw fit to get enough fluidness so the concrete would also flow underneath the inner box. Once I mixed enough concrete, it was time to do the actual pouring.

For this I made a funnel out of plasticized paper. While my “assistant” aimed it in the right direction, I would use a plastic cup to fill the funnel with fresh concrete. I made sure we used a levelled surface, so when the concrete would dry out it would be exactly level too. At first we had the whole construction sloped with a piece of wood under one side so that pouring concrete in the higher side of the mould would let it flow beneath the inner box. After the bottom was completely filled we removed the piece of wood so the construction was level again. we used a small stick to stir the concrete so air holes would be removed. Also I used an electric sanding machine and held it against the mould to vibrate the cement.

I think all-in-all it was a pretty flawless operation. After drying I noticed the concrete had compacted so it was lowered for about one to two millimetres (on a to total hight of about 10 centimetres).

Waiting…

I then waited for about a whole week. In hindsight it might have been better to remove the casing earlier. I experience quite some discolouration with I suspect is because of water trapped inside the mould. Had I removed the mould earlier the water might have had a chance to evaporate? Or perhaps use less water or a quick drying cement?

Result

And then the unboxing! I was somewhat nervous. Would the mould let go? Are the tubes al right? What would it look like? Well, the mould would let go perfectly. No problem at all. Also the tubes were kept free of concrete so no problem there. I was a little disappointed with the corners. Despite the lute they weren’t quite as smooth as I had hoped. I think next time I’ll use some rounded insets for a smoother edge. There was quite some discolouration when I removed the casing. But this had also been the case with the samples I had created which in the end turned out fine. Now, a few weeks later the discolouration unfortunately has stayed, unlike the sample. The sides have evened out, but the top has these very dark stains. I don’t think the will disappear, so I’ll just appreciate the artistic quality of them 🙂

Finishing the box

At first I had it dry somewhat longer. I hoped the discolouration would disappear, and held into account I might have to sand the concrete to make it more even. In the end I decided not to do this. Since it has a somewhat stained appearance which takes most of the attention there is no use in making the corners smoother. It now has more rough appearance, and the uneven corners fit this. Also there have appeared some very small cracks in the concrete. Hardly noticeable, but I will not be taking any chances by exposing the concrete to additional forces.

For the casing itself I had to sand the inner box to make it stand level. Apparently this was not so. Since the concrete had compacted, leaving the inner box stand out, this was not a problem. I added some adhesive rubber feet in the corners so the concrete wouldn’t scratch the surface of what it would be standing on.

Putting it all together

Then, finally I could assemble the whole system. The Raspberry was easily fitted on the dowels (which of course I had tried before). The power button was easily screwed into the cases as it was meant and the connectors, well, connected.

On the sticks the hard-disk would be lying on I added some adhesive insulation rubber to absorb the vibrations of the hard-disk. I put the disk on it and secured it with a tie-rib. I got a bit nervous when I had to pull the cables through the hole in the back, especially the HDMI cable. It seemed the hole was somewhat small. I had taken into consideration that I had to cut of some corners from the insulation but when I had reached the metal housing of the plug it still would barely go through the hole. But in the end I managed. The rest of the cables (power, network and audio) were no problem.

Uh oh…

Then the great moment of turning it on. I had already inserted a micro SD card with OSMC on it so it would boot right away. It became however immediately apparent that there was a lack of power going to the Pi. In the upper right corner there appeared a rainbow coloured square indicating this. The system seemed to boot however, and apart from the rainbow all seemed well. I could see that the hard-disk was spinning. However, as soon as I wanted to access it, the system would “hang”. After considering several option I thought the best way to deal with this was by adding an additional powered hub between the Pi and the hard-disk. I had one stuffed in my previous project. I ripped it out of there and, with some pushing an wiggling, it is now snug in my new system.

This indeed seems to prevent the rainbow and thus the lack of power. I still get to see the rainbow every now and then so I am considering another power adapter to the hub. It is now being fed by a 1000mA adapter so I can upgrade it to 2000mA. We’ll see if this is necessary. For now it is running at least. Finally…

Lessons learned

So, this was a first time for me. I learned a lot of things and had a great time creating something with my hands. Being a first time, there are quite some things I would do different the next time:

The tube holding the ring for screwing the switch-button into had leaked some liquid concrete. Fortunately I was able to scrape it away and still screw the switch into the tube. Next time I will put some tape on the outside of ring in the tube to prevent this. The led in the button is nice, but makes things more complex and require power. Also, during the day it isn’t visible and during the night it is quite bright. Although I like it I don’t think I will use a illuminated button next time. During the pouring I made sure the surface was level so once the concrete had dried out, when tipping it over, the underside was even. I did notice that where the tubes were going through the casing, the concrete had set slightly less. It’s hardly noticeable, but it gives a subtle rounding to the underside. Perhaps next pour I might push a little concrete away from these places, to even it out. The waiting took long. Maybe to long. This might be one of the causes for the discolouration, together with using to much water. Next time I will use less water (and as a result make the concrete less fluid) and remove the mould after a few days so that maybe excess water may evaporate. I must add though that now, after about a month the stains are getting less. Also I might use quick drying concrete for preventing the stains. Another pouring thing: The corners came not all out very well. Next time I will give additional attention to those corners by pushing the concrete a little harder there. Might work. The tube for putting the cables through was barely large enough to put a HDMI cable through it, even with all insulation removed. This made me sweat :-). I have put the Raspberry Pi in the top of the box. If I ever need to reach it, for example for replacing the Micro-SD card, I will need to pull all other things out first. Not handy… And finally: I assumed all 2,5″ hard-drives were created equally, but it seems some are more equal and are a bit more greedy when it comes to power (Amps that is). Considering sources it could have worked, but it didn’t. Next time I will pay more attention to the required power for a disk when I want to have it powered by the Raspberry Pi

Update

Today I had a problem with the Pi not starting. Giving al lot of gibberish on the screen with hinting to some problem with the internal hard disk. I had to pull it out of the cupboard where it normally stands. A nice moment to take a photo of the case now. As you can see the discolouration has drastically decreased. Nice! And it smells nice too, as you can see 😉

Anyhow, the problem might have been caused by (still) a power problem. The previously described power solution didn’t give a satisfactory result. In the end, and this seems to work fine, I now have the 2.5″ HD powered by a USB hub with a 2A power adapter. The Pi itself receives a 1A current from a USB power adapter I received with an old phone. This works fine. No more rainbows. Also not after overclocking the setting ” Turbo”. Also not when running more CPU intense applications as the Youtube or Vimeo add-ons.