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Mike Lake
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Re: Requirements specification for RPi case

Sat Mar 03, 2012 11:51 am

Shouldn't we discuss/agree the requirements for a case before starting to design it?

Where are we:

1) The current RPi design does not having fixing holes.  (Why? No space?)
2) We have some drawings but we haven't seen an "as-shipped production" board yet (every picture on the net seems slightly different.)
3) The current design has bits sticking out awkwardly - connectors are not aligned to edges, SD card sticks out.
4) I am NOT being negative, but is this the best layout within the size adopted?  Would a little more space have made things more "elegant"?
5) I am willing to bet that the current RPi board will not be the same as the education one in six months time.

All the above will influence the case design - and the life of a case design.

My take on case requirements:

1) Transparent.  Kids like to see inside things.  (So do I!)
2) Small, slim, simple, elegant, robust.  (Screws not clips to hold it together!)
3) Allow access to all ports - especially GPIO.  Making things "happen" via GPIO will be a major educational requirement.
4) Fixing points for stand-offs to allow piggy-back boards to be attached (Stacked? Daisy chained?) to the case.
5) Fixing point for optional battery pack enclosure designed to match the rest of case.  (4 x AA Alkaline/NiMH?  Li-Ion mobile phone battery?)

A bit of sexy industrial design might not go amiss here - anyone from eg technology in Cambridge interested (http://www.egtechnology.co.uk)?
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Re: Requirements specification for RPi case

Sat Mar 03, 2012 5:16 pm

Totally Agree with everything said here

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Mike Lake
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Re: Requirements specification for RPi case

Sun Mar 04, 2012 10:57 am

Does anyone have a photograph of the production board WITH the SD card in-place?

I saw one layout with the SD card holder sticking well proud of the board and marked as "temporary".  Is this the case on the first batch of boards?

It comes down to "which PCB should one be designing a case for?"

Having power alongside the SD card makes a plug-on battery pack slightly awkward.
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Re: Requirements specification for RPi case

Sun Mar 04, 2012 11:38 am

Mike Lake said:


Does anyone have a photograph of the production board WITH the SD card in-place?


No.

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Re: Requirements specification for RPi case

Wed Mar 07, 2012 11:42 am

... and light pipes to make the on-board LEDs visible on the surface of the case.

How about a sponsored competion involving school students for the best design?

How much would tempt schools to give it a go?
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Re: Requirements specification for RPi case

Wed Mar 07, 2012 1:48 pm

What about something like this?

http://img-europe.electrocompo.....097-01.jpg

Rather than a case as such, have a kind of lunch box affair that houses cables and assorted widgits as well as the actual R-Pi itself.

Could even have a moulded bit in the lid that will allow the Pi to rest / fit nicely in and still give access to plugs and what-have-you.

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Re: Requirements specification for RPi case

Wed Mar 07, 2012 4:01 pm

I would worry about that.

The RPi can handle high level stuff (wp, spreadsheets) as well as low level stuff.  If packaged well I assume it would travel with the student, just as a calculator does.  So, it would be used at home and at school.

Hence the need for "robust" in the spec.
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Re: Requirements specification for RPi case

Wed Mar 07, 2012 4:30 pm

Me and the RaspberryPi /2

this looks like a good solution

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Re: Requirements specification for RPi case

Wed Mar 07, 2012 4:48 pm

Nice ... but ... opaque, no access to GPIO, uses plastic clips to hold together.

It's good that people are having a bash - both in the real world (3D printing) and in CAD.  However, a clear and agreed spec should be a starting point.

I still reckon a prize offered to school students would generate some good ideas - and they are the main target market.

Question is, how big would the prize have to be to encourage schools to take part?
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Re: Requirements specification for RPi case

Wed Mar 07, 2012 5:06 pm

Why should it have to be a single case design? The way it's presented will have a big effect on what people see it as and what it's potential uses are.

Putting it in a fixed case like a calculator gives it a level of robustness but as a drawback does not invite people to think 'I wonder what will happen if I attach a signal generator to the clock pin and turn it up' or other such inspired crazy foolishness.

Providing the bare board in a kit box with lots of gubbins and wotsits to play with does invite that sort of thinking but at a detriment to robustness (but having said that at 15 quid for a replacement when you blow it up, it's not the end of the world)

I think there is potential for lots of exciting ways to package it. I personally don't think there should be one definitive case.

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Re: Requirements specification for RPi case

Wed Mar 07, 2012 5:48 pm

I had a production board in my hands today for a short while.

1/ The SD-card holder does NOT stick out, it sits completely under the board.

2/ The GPIO connector was in place too: male, top. I have asked and this is not guaranteed for all 10.000 but is likely to be present on the first 2000. So that might set the standard**.

3/ I could see no obvious differences with the beta boards prototype series.

**For all of you who wanted female connectors: female connectors are more expensive then males and I personally prefer ANY connector then none.
It would be great if the Foundation+RS+Farnell could agree on keeping it in the BOM, even at a slightly higher cost so nobody needs to take out a soldering iron.

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Re: Requirements specification for RPi case

Thu Mar 08, 2012 8:53 am

+1 to gert
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Re: Requirements specification for RPi case

Thu Mar 08, 2012 9:38 am

Excellent about the SD card and connectors.  Given the importance of GPIO in education it would be great if the connectors were always there.

I would have though it was essential to have access to the GPIO port while the RPi was in the case.  Not sure about access to the CSI and DSI ports when cased - what do people think?

To get economies of scale, and a low-cost case, we do need to agree a spec and get a design that meets most needs - no single design will please 100% of people, but maybe we should give priority to what is required by schools and students.

Does the Foundation intend to fund the development/manufacture of a case?

It would not make commercial sense for anyone outside to design/produce a case only to find the Foundation did its own thing.

Still no comments from teachers about the idea of a prize for a design by students/teachers/schools.
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Re: Requirements specification for RPi case

Sat Mar 10, 2012 7:57 am

I like your list, Mike, although I would prefer robust clips over screws - we want to encourage kids to open it up, and having to find a screwdriver, dropping the screw(s)/screwdriver across live pins that shouldn't be shorted, and other Murphy events all add up to a negative experience.

I am completely surprised that no one else seems to have mentioned this anywhere, but, as Eben amply demonstrated in at least one of the videos made at a trade show while he was hawking the R-Pi, when you connect all of the futkaka cables to a credit-card sized computer, and they attach to literally every edge of the board, it winds up floating in mid-air due to the torque that's always present in all those multi-conductor cables (and it never even floats parallel to the ground, it gets torqued this way, or that).  That means that mounting screw holes are absolutely required on the bottom portion of any case.

However, the connectors-around-the-edge phenomenon means that, even when screwed down, it's still going to look like some splayed-out relative of a praying mantis with cables askew in every direction.  That may be fine in electronic lab environments, where there are going to be wires going every which way but loose anyway, but, snagging one, or more, cables in a teaching environment is going to make the R-Pi look pretty boring (no power/video/USB/Ethernet/whatever = blank or unresponsive display).  So, a somewhat larger case is needed, where either the cables can be routed around the edges of the board and exit the case along one side, or the sockets on the board are extended out via short stubs to replicated connectors mounted along one side of the case, to help organize the snake pit that otherwise ensues.  Eben knocked a connection loose during one of his demos, and he had to scramble to try to troubleshoot and fix it on-the-fly while still continuing his pitch.

I'll draw up some ideas based on this, unless someone else likely beats me to the punch.  Ironically, I grew up as a paper/pencil/scale/compass/spline engineer, and eventually earned an MSCS with network-distributed 3-D graphics object modeling as my thesis.  However, I'm slow as molasses on the current crop of 3-D modeling software tools! ):
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Re: Requirements specification for RPi case

Sat Mar 10, 2012 9:56 am

Jim

Some good points.

The waving about in the air problem may be solved by the weight of the case alone or we could put a lump of lead (sorry, I forgot elf and safety – "an elegant piece of sheet steel") in the bottom.  The problem is that added weight means added shipping costs.

Putting the cables inside the case and getting them to emerge at one point would be a) ugly – all those nasty wide bends, b) big and c) not provide access to those ports where things may need to go in and out fairly regularly – like USB.  You could end up with cables inside the box brought to a common area (like the back of a PC) where everything connects.  That means added costs for internal cables and sockets

Personally I think this would kill the joy of the RPi – its smallness.  We could end up with something looking like a Mini-ITX case!  Added volume increases shipping costs.

We need small if this is going to be portable so students can take it home with them.

I also worry about the clips suggestions.  We could have a hinged box – one of those full-length plastic hinges.  This has an advantage – the whole box can be moulded in one piece keeping cost down – though it does restrict the choice of plastic you can use – some break rather than bend.  The downside is that the top would tend to flop about and get in the way.

Clips have to be opened.  This may be by inserting something and twisting (recipe for breaking), it may be by squeezing one part of the box to release the clips or it may be some sort of external clip – which spoils elegant lines and makes it feel like a lunch box.

One extra requirement – the RPi could be used as stand-alone controller on things like Robots (I have a project in mind, anyone know a good PCB designer?)  It would be nice to have some way of fitting it to a platform.  I don"t know how to do this (apart from screw holes in the bottom outside the area of the PCB) – after all, a spec does not define an implementation.

(Late thought: with good design the same holes that fix standoffs for the RPi PCB could be used for a fixing to fit the case to a platform.)

Summary so far:

Transparent/translucent – tinted.

Simple, elegant, attractive, robust.

Must fit in a school bag.

Ease of internal access via screws or clips.

Access to all ports including GPIO.

Top fittings for daughter boards.

Bottom fittings for use as a stand-alone controller.

Light pipes to bring light from LCDs to surface

Provision for external battery pack.

What if someone offered £1,000 for the best student design that went into production?  Would that attract interest?

BTW: on the design front I am incredibly fast with 2D stuff on TurboCAD, I use it for lashing up ideas on everything, but I am much slower in 3D stuff with Alibre Design.  (I like Alibre – I am still using the demo version!)  I use it to prototype some 3D ideas but I leave the real stuff to professionals – they can allow for the things I forget – like, draft angles for mouldings.  Protomold has some great design guidelines on their web site:

http://www.protomold.co.uk/Des.....lines.aspx

and, on request, they will send some little models showing the right and wrong way to design stuff for quality mouldings.
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Re: Requirements specification for RPi case

Sat Mar 10, 2012 10:15 am

Mike Lake said:



What if someone offered £1,000 for the best student design that went into production?  Would that attract interest?


Personally I would raise it with the head of technology at my own school and see if he would promote it and enable the work to take place but wouldn't there need to be a general agreement from the foundation about (a) judging (b) production?

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Re: Requirements specification for RPi case

Sat Mar 10, 2012 11:04 am

Absolutely.

I would put up the money IF the Foundation went for it and IF schools would do it.
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Re: Requirements specification for RPi case

Sat Mar 10, 2012 5:23 pm

Mike Lake said:

Does the Foundation intend to fund the development/manufacture of a case?
It would not make commercial sense for anyone outside to design/produce a case only to find the Foundation did its own thing.


Just quoting Liz, from the relevant part of this post here, which was written in August of last year;

liz said:

A plastic case isn"t necessary for hobbyists, who are our target for the initial release; in fact, lots of people here have asked for a naked board so they can get busy with the soldering irons. The educational release, which is scheduled for early 2012, and which will be our standard product, will have a case for reasons of robustness (although a case-less board will always be available too if people prefer that). That case hasn"t been designed yet, but it"ll be removable with a screwdriver for any kids who fancy a bit of hardware hacking.
So I"m afraid you"ll have to buy a hub (and we"ll be selling hubs which I hope will be branded on this site if you want to support the project), but you *can* have a case if you can wait until next year.


I could have sworn there was another post somewhere, wherein it was mentioned that the official case would be transparent, but I can't seem to find it now, so take that info with a pinch of salt.

I hope this is useful in some capacity.

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Re: Requirements specification for RPi case

Sat Mar 10, 2012 5:49 pm

This is one of the problems anyone is going to have with a case - we don't actually know what the board will look like when it comes to volume/educational production.

Of course, that may mean it will have mounting holes - which would be nice.

The offer to fund a competition stands - if the Foundation wants to go that way.

Personally I don't see the point of a half-hearted temporary effort - best to get it right from the beginning.

Still worth keeping a spec up to date with ideas.
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Re: Requirements specification for RPi case

Sun Mar 11, 2012 6:54 am

No need to ship metal weights - that's the nuclear-weapon-to-swat-a-fly solution  It would be possible to identify already-available metal plates with threaded holes to which the case could be bolted (e.g., something like the VESA standard used to mount flat-screen TVs on swivel arms/frames, etc.).

Screw mounting holes should be the locking keyhole type where the screws are mounted in a panel/wall and the case is slid down over the screws to lock it in place.  I guarantee that any situation where the case is allowed to flop around at the whim of cables is going to eventually cause failure of the sockets on the board (I'm a mechanical engineer, computer scientist, and have lots of classroom/lab experience with the target educational audience )

Despite anyone's opinion outside schools, _someone_ is going to wind up administering and supporting these, and it may, or may not, be a teacher with a lot of experience with computing (many science and math teachers aren't even experts since they often are transplants from liberal arts teaching).  Having cables coming out of more than one edge _is_ going to be a problem where these are part of the infrastructure, and bringing the connections to one side of the box is going to be very much appreciated by people who wind up crawling around under desks/benches/etc., to set up and troubleshoot large numbers of these.
The design of the R-Pi board to be minimally sized means it can't have mounting holes, the connectors have to be along all of the edges, etc., and that's fine for the more rough-and-tumble, experimental situations (e.g., kids tossing it into their bags to take home), but, it doesn't mean that's the only configuration that needs to be addressed.  As we've now seen that upwards of four million unique visitors made their way to the R-Pi site and suppliers on launch day (with millions more since then) there are going to be a lot more uses for the R-Pi than originally imagined, and so, there are going to be a lot more variations in how and where they'll be used.  It would be ideal if we could come up with a design that allows for variable configuration (e.g., optionally-used expansion panels to allow for the cable stubs/connectors for the all-connections-on-one-side configuration), as then, cost could be spread over the largest number of cases manufactured in the largest lots possible.

A polyethylene case with a bendable hinge is an interesting possibility, although the hinge has to be designed to be robust, as I've personally had many of them crack and split due to chintzing on the amount of material causing too small a radius in the bend.  Polyethylene is somewhat flexible and can be translucent, but, not transparent, so, blinking LEDs can be seen in aggregate (but, light pipes can bring them out to individually-labeled spots on the exterior).  However, in order to look at the board directly, the case will need to be opened (which the hinged, latched/clipped cover will make simple ).

Polystyrene plastic (e.g., airplane/ship models) is cheapest and can be transparent, but, cracks and breaks very easily, while polycarbonate (e.g., Lexan) is transparent, nearly indestructible, but, the most expensive, and polyethylene is in-between in both strength and cost (closer in cost to polystyrene).  Then, there are synthetic rubber, silicone, and other materials, but, they can't be transparent and tend to cost somewhat more than polystyrene and polyethylene.  Again, actual individual utilization situations will dictate what should be used, and since the R-Pi looks like it's going to be a mega-hit, a variety of materials seems supportable.  Injection molds may need to be different due to the flow properties of the various materials, such as melting point, viscosity, etc., if injection molding is used.

3-D printing is fine for prototypes and refining designs, but, in the long run, they're just not competitive with molded products in terms of cost, volume, strength (for cheaper materials), surface quality, etc.

Analysis, as they say, continues ...
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Re: Requirements specification for RPi case

Sun Mar 11, 2012 7:48 am

All the connectors on one side would also have the benefit that a dock could be designed to make connection at school much more easy and less likely to connector failure do too the board being jockey around by the cables as the dock could be fastened to the surface and it take all the stress.

Just a suggestion.
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Re: Requirements specification for RPi case

Wed Mar 14, 2012 11:25 pm

Hi- New to this but as a jewellery designer and creative type forever doing things on the cheap I'd like to hazard saying that keeping it simple is absolutely key.

So what we've got is:


fun tiny computer for kids without case on purpose for educational scope
case if added ought to really be see-through and added by user
case ought to be cheap and available
not sure what precise size case should be and where to put holes
case ought to involve kids in making/modding it and perhaps be customisable
case should be portable and help make the cute computer easy to take home
case should encourage and stand up to repeated opening and shutting

If its education and kid and hobbyist-centric then perhaps some thickish transparent plastic pre-existing shape which can be cut with scissors would be a good idea?

How about popping it into an A5 transparent plastic wallet or file? This would give enough space around it to effect a sort of control on the cables, too perhaps? It would protect it a bit whilst in a school bag and enable very easy opening, shutting, personalising etc. The kids can cut holes in them, decorate them, etc.

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Re: Requirements specification for RPi case

Wed Mar 14, 2012 11:33 pm

Mike Lake said:


Absolutely.

I would put up the money IF the Foundation went for it and IF schools would do it.


£500-£2000 is a reasonable number for a national competition winner (or a class set of RPis etc),  but its more about how the competition is marketed.

Basically teachers want something fun and interesting to do with the kids for a lesson or a series of lessons. Give them something that'll engage the kids and they'll do it prize money or not.

Oh and make submissions easy or they probably wont get round to it!

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Re: Requirements specification for RPi case

Wed Mar 14, 2012 11:49 pm

I think a competition is a great idea.

I loved the Model B when I was a kid.

can't wait to get my RasPi and get cracking! I have SO many old monitors and cables keboards etc lying about.....!

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Re: Requirements specification for RPi case

Thu Mar 15, 2012 5:25 pm

fionafiona said:


How about popping it into an A5 transparent plastic wallet or file? This would give enough space around it to effect a sort of control on the cables, too perhaps? It would protect it a bit whilst in a school bag and enable very easy opening, shutting, personalising etc. The kids can cut holes in them, decorate them, etc.


Not sure if this is what you"re thinking of, but, forum member tzj has created a PDF that can be printed on Mylar overhead projector sheets that are then cut out with scissors and folded up into cases:

http://pdfcast.org/pdf/raspber.....revision-1

It may need to be updated once the production R-Pi boards have been received to verify the exact locations of the USB, Ethernet, composite video, audio, power, and HDMI connectors, and SD card slot.

The transparent nature allows the board to remain visible while protecting it from short circuits and mechanical shock, and if any text is printed, if it"s set up backwards on the PDF, when printed, the graphics and text can be on the inside of the case, protecting them from being scratched off.  At pennies per sheet, this has to be the absolutely cheapest possible case for the R-Pi, yet, it will meet virtually all of the requirements cited for a case, and is completely customizable by modifying the text and graphics on the PDF and using scissors.
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