Simple Pi Rack Mk II


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by brigo » Wed Apr 24, 2013 1:58 pm
I've redesigned the Simple Pi Rack, the network switch and USB powered hub are now underneath, and the Pis are mounted on the HDMI connector:

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Front view
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It all now fits neatly on a desk beside other kit:

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Beside the laptop
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and in a shoe-box (along with PSUs and cables), for easy transporation, without any need for dismantling:

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Size UK 10, EUR 44.5
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Hope you like it!
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by dan3008 » Wed Apr 24, 2013 2:05 pm
Part of me wants to build one, and keep it in a shoebox, so that if someone broke in, they wouldnt even look at it twice, and it'd be safe lol. Nice build
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by gabriano » Sun May 05, 2013 3:09 am
Hi brigo

I'm working on a somewhat similar project.
Would you have more details on various connectors and cables you used? What hdmi connector did you use, for example?

Any info appreciated. Thx in advance
gabriano
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by brigo » Sun May 05, 2013 3:36 pm
I found the HDMI connectors more expensive to purchase in small numbers than buying really cheap
cables and reusing there's. If you cut the connectors off, and cut away all the molded plastic (mind your
fingers), you end up with something like this:

hdmi_male_plug.jpg
HDMI Male Plug
hdmi_male_plug.jpg (13.43 KiB) Viewed 23705 times


Next I had to embed these into the plyboard by chiseling out a series of mortices, filling with PVA glue, and inserting the HDMI connectors. This is the finished plyboard plate:

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Oblique elevation
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and, when viewed from the back you can see all the mess, but then no one will be looking at that:

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The back
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by brigo » Sun May 05, 2013 3:48 pm
Next, I added another plyboard plate, for holding the network switch, and connected them together with nuts and bolts, and to protect my table's worktop I capped it off with some domed bolts. The whole thing
is quite adjustable:

DSC04817.JPG
Second plate with network switch
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Next, I used longer bolts, and added in the USB powered hub on the underside of the first plate (see earlier pictures.)

I hope this helps - but, just ask if you need any more details!
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by SirLagz » Sun May 05, 2013 3:53 pm
Just out of curiosity, why the switch to the HDMI ports ?
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by brigo » Sun May 05, 2013 3:57 pm
Oh, for cables! I just went shopping on Amazon for the shortest possible. The network cables are 25 cm,
and the USB 20. Try your hardest not to get charged any postage, and if you do, make sure you don't get
charged for each one!
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by brigo » Sun May 05, 2013 4:10 pm
Why did I switched to HDMI:

    I found placing and boring the holes for the audio and video connectors too tricky
    I wanted the edge of the Pi to rest on the plyboard for support
    Using the HDMI, you get clearer access to the SD card and USB device ports i.e. no cables getting in the way
    Just cleaner and sturdier all round
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by SirLagz » Sun May 05, 2013 5:17 pm
Is the next step integrating the power supplies in and then just using one kettle power cord to power the whole thing ? :D

I'm impressed, very clean looking and portable
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by dan3008 » Sun May 05, 2013 7:58 pm
SirLagz wrote:Is the next step integrating the power supplies in and then just using one kettle power cord to power the whole thing ? :D

I'm impressed, very clean looking and portable


the whole thing is powered off one mains cable to the powered usbhub anyway, so why change it?
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by SirLagz » Mon May 06, 2013 1:03 am
dan3008 wrote:
SirLagz wrote:Is the next step integrating the power supplies in and then just using one kettle power cord to power the whole thing ? :D

I'm impressed, very clean looking and portable


the whole thing is powered off one mains cable to the powered usbhub anyway, so why change it?


I would have thought there would be 2 cables, one for the network switch and one for the hub.
But if there's only one already then rejoice !
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by dan3008 » Mon May 06, 2013 9:19 am
fair point. I'd missed that...
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by brigo » Tue May 07, 2013 9:01 pm
You made me curious, so I took one of the Pis off the rack, and used its powered USB port along
with a special little hacked together cable to power the network switch:

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All the Pi lights are on...
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...and the same for the switch
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So, only one PSU now, but perhaps we are pushing the Hub a bit!
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by SirLagz » Wed May 08, 2013 1:02 am
haha
Time to get a stronger power supply for the hub ? :lol:
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by rmwebs » Wed May 08, 2013 8:55 am
Blimey that must be a pretty beefy hub! All the powered ones I've tried have been next to useless for anything more than a hard drive and wifi dongle!

Which one are you using out of interest, and what sort of power supply?

Also, what do you plan to do with this amazing array of Pi's? :)
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by brigo » Sat May 11, 2013 9:20 am
I went shopping for a powered hub, and chose the Plugable 7 Port USB 3.0, because it has a 4A adapter, which it needs to meet the power requirements of each USB 3.0 device attached to each port. It certainly not the cheapest on the market, but I've since discovered that its manufacture by Orico, so there may be a way of getting it cheaper, but of course make sure it has a 4A adapter!

Here's the Amazon link:

http://www.amazon.co.uk/Plugable-Power-Adapter-Mains-Chipset/dp/B009EX24T4/ref=sr_1_6?ie=UTF8&qid=1368261401&sr=8-6&keywords=plugable+usb

Power is definitely a problem though, and I want to add some local disk storage - that's my next challenge!

As for the Pis - I work for large organisations doing Configuration Management and Monitoring mainly, and its nice to free yourself from that a bit, and go and explore all the different toolsets, especially FOSS, without having to get permission or find budget for it. A while back I wanted to put together a number of inexpensive servers for the purpose, and around about that time the Raspberry Pi came along, and filled that position exactly. These were some of my criteria:

  • its inexpensive (I have a very limited budget)
  • doesn't use much power - they need to be able to run continuously, and have a small carbon footprint
  • doesn't need much space (I have one Ikea Billy bookcase to house such things)
  • runs Linux (and its FOSS toolset)
  • in terms of computing power its powerful enough for my requirements

I'd be interested to know what other uses such a rack of Pis could be put to?
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by Gary Littlemore » Sat May 11, 2013 8:14 pm
This might be a dumb-ass question, but what do you do with that many Pi's altogether? :oops:
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by brigo » Sun May 12, 2013 7:02 pm
I intend to do lots of continuous monitoring, in particular early detection of aberrant behaviour, see:

http://static.usenix.org/publications/library/proceedings/lisa2000/full_papers/brutlag/brutlag_html/index.html

Also, I can see lots of reasons for having a number of Pis in the Server forum, but I'd be really interest in knowing what others might use such a rack of Pis for?
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by chriswilliams » Mon May 20, 2013 12:43 pm
Very nice!
Looking at using a Pi Rack to emulate and test Puppet deployments (why not) instead of paying AWS actual real money.

Would you be able to supply the measurements for the HDMI spacings? Lazy I know...
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by brigo » Tue May 21, 2013 7:26 pm
Sounds like another very good use!

Distance between centres of the HDMI connectors is 25mm. This is what I used for the original Simple Pi Rack, when I was mounting on the audio and video jacks:

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=40&t=34987

back then I used the HDMI connector for pulling the Pi out of the jacks. What I didn't think about, when turning the Pi round, was that the audio and video jacks are so much thicker and that sticking with 25mm would mean so much less room to get your fingers in to pull them out. Adding an extra 5mm should help, but them the whole assembly might not fit in the shoe box.

Speaking of which, I've been experimenting with stripping the outer coating and unused twisted pairs from the very short Cat5 cables. Reasons for this are that they are very inflexible, and take up more room than they should, and that the protective coating is unrequired in my environment. And, I reckon the original standards were designed for much longer cables, and will have practically no bearing on Fast Ethernet over a distance of 20cm. Also doing the same for the USB power cables, for much the same reasons (though did leave the unused data lines in, otherwise they were too flimbsy.) Compare the difference:

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With and without
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The assembly is much narrower now, though the nakedness of the cables takes a little getting use to:

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Freedom
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And, of course, it all fits in the shoe-box much neater:

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Room to spare
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I'll update if any problems result!
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by chriswilliams » Tue May 21, 2013 7:53 pm
You know. there are a couple of options for the networking, you can get ribbon cat5 but I couldn't find any short stuff. You could also use those micro WiFi connectors and some kind of AP as long as you get the drivers sorted.

Let us know about the effects on de-shielded cat5
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by psergiu » Wed May 22, 2013 9:26 am
Get a RJ45 crimping tool, some unshielded CAT5 "patch" cable (thin and flexible) and RJ45 connectors and make your own cables as short as you want. Its easy and in the medium-long run cheaper than buying ready-made ethernet cables.
There's no need for shielding on 100Mbps Ethernet and even Gigabit works perfectly on home made unshielded cables. For short (under 1m) runs you don't even need twisted wires on 100Mbps - you can use a flat ribbon cable (from old IDE/floppy cable).
It's not that hard to chimp an ethernet connector - just remember the color code mantra: "white-orange, orange, white-green, blue, white-blue, green, white-brown, brown".
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by brigo » Thu May 23, 2013 9:46 am
Thanks for the info and suggestions. Particularly liked the ribbon cable idea, so tried it out:

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Just perfect!
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A bit of a myopic experience making it though!

When I have then all done (and after a visit to the opticians) I'll send a picture of the completed rack.
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by brigo » Fri Jun 14, 2013 9:38 am
Added another layer to the Pi Rack, to keep the powered hub and the network switch separate, finished the network ribbon cables (no problems so far), and finished it off a bit more:

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Alfa Romeo power cables
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The lights are on...
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I think that's about it for the Simple Pi Rack Mk II. Working on the Mk III, which will have a radically altered power supply to support local USB disk space, and an individual power switch for each Pi.
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by dan3008 » Fri Jun 14, 2013 9:57 am
I'm mega impressed with these :D

you should sell them :D
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