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Ray_GTI-R
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Re: Cases - fundamental problem

Sat May 05, 2012 1:26 am

Onboard connectors will get broken easily- discuss!

Why?

This issue has bothered me from the outset. Subconciously, after I saw an early spider-cable-connection video of a RPi mounted on a wall, something about it looked - ummm ... just wrong. I've seen loads of very enticing case styles - very well done to all you 3d design geniuses.

But a fundamental issue kept bothering me subconciously. Then I got it ... this is a tiny board that weighs almost nothing with relatively BIG, HEAVY cables exiting in all directions - think 2D physical then add gravity all 'round. Add cable removal/reinsertion/effect on ALL 'board connectors etc etc. Hope you understand that this is a positive forum post for further positive discussion.

Ray

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tzj
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Re: Cases - fundamental problem

Sat May 05, 2012 2:29 am

I see where ya getting at... the cases need a way of supporting the connectors on ALL sides without preventing connections being made. like a tiny lips to support the in-out forces... yes that sounds odd but you get the idea.
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Ray_GTI-R
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Re: Cases - fundamental problem

Sat May 05, 2012 2:48 am

See http://s65.photobucket.com/alb.....eIssue.jpg ... an over-simplified 2-D vision of this problem which I humbly subit for further  discusion.

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Ray_GTI-R
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Re: Cases - fundamental problem

Sat May 05, 2012 3:01 am

tzj … maybe, but FWIW it"s a given that this is a teeny tiny board. Socket-fixing socket lips won"t solve internal on-board solder joint stress fracture due to realtively large/heavy cable / twist force vs repeated removal/reinsertion over even a very short time.

Something lateral needs to be thought up IMHO.

Solidly encased in potting compound springs to mind but seems  - erm - ugly.

Still trying to think positive.

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Jongoleur
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Re: Cases - fundamental problem

Sat May 05, 2012 5:42 am

It may look ugly and be difficult to assemble, but internal buttress moulding inside a case, supporting the back/top of connectors may be essential for high use (eg school) Raspberries.  The fragility of the micro-USB connector has been raised before, but  I'll have to wait for my Pi to arrive to get a physical feel for the problem.

Good call!

Of course, f you had a naked Pi mounted on a varnished piece of ply or whatever for display, there's nothing stopping the use of cable clips (self adhesive or nailed) to provide stress relief.
I'm just a bouncer, splatterers do it with more force.....

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tzj
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Re: Cases - fundamental problem

Sat May 05, 2012 5:46 am

the only other option I can think of is short flexable extentions, to ease the stress, of which would be encased by the case to hold them imn place.
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raspi
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Re: Cases - fundamental problem

Sat May 05, 2012 12:00 pm

tzj said:


the only other option I can think of is short flexable extentions, to ease the stress, of which would be encased by the case to hold them imn place.


I think this is probably the only way to go, but allowing for connections to be brought out to a more robust clamped area will increase the case size considerably. But there again cables sprouting from three sides means a large area is needed anyway.

I measured up various cables when I designed my case at http://raspi.co.uk/?p=87 and there seems to be quite a difference in the various connector housing sizes that people might use. I don't see an easy way to alleviate cable stress by adding tight fitting supports in the case itself.

I can see a demand for a plug-in device that bring all the connectors around to one side that is itself more robust, as you suggest.

Once kids get their hands on RasPies I can see premature failure of the connectors being a big issue.

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Mike Lake
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Re: Cases - fundamental problem

Sat May 05, 2012 3:29 pm

rapi

Excellent point about getting all the connectors onto a common panel side wall.  The same would apply to any daughter boards that one designed.

The downside is the cost, physical size and quality of the cables to do the linking.

So, maybe panel mounted sockets with pre-soldered linking cables for the commonly used ports:

USB x 2
Ethernet
Power
HDMI

would be enough.  I understand that HDMI is fussy about quality though - nasty RF problems can result from bad connections.  (I don't know what I am talking about, but that's what I have read.)

Maybe even a PCB mounted to a sidewall to use PCB sockets?

I will fire up the CAD and knock up a side wall for the PiHouse (http://www.thepishop.org/cases.htm).  Also time to dig around for some suitable panel sockets.

The real problem is that the darn plugs stick out such a long way before you could bend a cable round to fit to a side panel wall.  The size of the overall package starts to get big - which somewhat defeats the idea of having a "Pi in the pocket" or in the school bag - there are mini-ITX gadgets which would be smaller <g>

One good thing, a wireless keyboard/mouse adapter only takes up a tiny space sticking out of the USB port.  Ethernet is a lump - at least 50mm to bend the cable.  Maybe a tiny WiFi dongle would be better.

Power is a pain if trying to bring it out to a side panel.

I think it highly unlikely but does anyone know if the RPi can be powered from the 5V GPIO line?  If so, bringing out a power connector would be simple.

There are some very short cables that might do the job: http://tinyurl.com/d48k49c
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abstract
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Re: Cases - fundamental problem

Sat May 05, 2012 3:59 pm

In response to:

"There are some very short cables that might do the job:http://tinyurl.com/d48k49c"

That cable ends in a MINI USB,   The Power connector on a Raspberry Pi is MICRO USB. One smaller.....

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Jim Manley
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Re: Cases - fundamental problem

Sat May 05, 2012 5:06 pm

I identified this problem several months ago and once I have a board to work out the specific dimensions via actual board, connector, and cable hardware, I'm going to develop a modular case that brings all of the connections to one side with much more robust connectors (e.g., replacing the micro-USB connector with a real power connector).  It will be made up of six interlocking pieces (one for each side) that will require no fasteners (maybe slide-to-lock, press-to-lock, pop-together hinges, etc.).  They will be able to be built up modularly for multi-board configurations to support both cluster-processing Brambles and school situations where a single AC-to-DC power supply for multiple Pi boards will be more efficient, cheaper, and simpler (e.g., fewer cables and wall warts).

Foofy artistic 3-D renderings of pretty boxes with connectors sticking out every side are nice, but, they're just dressing up problems and not resolving them.  Sometimes, you just need to do some good old-fashioned real-world, on-the-lab-bench engineering to get the connections where they belong, and ensure the needed structural integrity is there, particularly for school environments.  I sure hope that whatever the Foundation chooses for a case for the educational version of the Pi takes these issues into account, or there are going to be some very frustrated in-the-classroom educators (as opposed to out-of-the-classroom former-educators-turned-administrators who tend to make budget and acquisition decisions).
The best things in life aren't things ... but, a Pi comes pretty darned close! :D
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Re: Cases - fundamental problem

Sun May 06, 2012 8:31 am

An easy-to-use docking station for the RasPi is going to be really hard to devise.

Kids bring in their own RasPies, want to plug them in, show off what they have been doing at home.

But actually all they need is their SD cards, don't they? Assuming they don't need to be tricked up with hardware Gert boards or Lady Ada plates, in which case all bets are off.

So if RasPies are considered to be cheap enough for both kid and classroom ownership, all the classroom needs is a rack of bolted-in RasPi boards into which a kid slots his or her memory card. Access to the SD card slot is necessary for this model to work, so the card slot has to be the front face.

The USB power is on this front face too. I think some kind of power on-off/reset will be necessary if we don't allow direct access to the USB power input, so if there is such a thing as a surface mount male micro USB connector this could go one side of a small pcb with a switch on the other, the switch or reset button protruding through the kid-proof (as if) case front. Leads trailing to the back meet up with a common power bus or individual power connector and are hardwired in.

If every class starts with kids plugging and unplugging RasPies they will not last more than a few weeks.

Pinoun
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Re: Cases - fundamental problem

Sun May 06, 2012 12:08 pm

Perhaps the solution is simpler than it first appears.

At any one time either HDMI or RCA/Audio will be used,

Power could be provided thro powered USB hub,(Discussed extensively elsewhere) which could be mounted next to USB connectors.(perhaps other on-board USB could house WiFi)

RJ45 plug with socket (socket could be mounted next to USB hub)

As access to SD card may be infrequent (depending on application)  perhaps it would be possible to open the case to change card.

Overall you would now have access from one side to all current connectors for a particular application... -and the strain would be only on the HDMI/RCA lead..

Hopefully getting a Pi shortly so i will try building something & see if theory & practice agree..

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rurwin
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Re: Cases - fundamental problem

Sun May 06, 2012 1:23 pm

Perhaps someone could spell this out in more detail, because I think I must be missing something. The back of my PC has loads of cables coming off the motherboard. All of those sockets are PCB mounted, and none of them are mounted more securely than the RaspPi connectors. (The little tin face-plate is very un-structural and apart from tightly screwed serial and video connectors is not involved at all.) All of them drape downwards, at right-angles to the socket, up to a couple of feet. I have never known a PC to fail through breaking a socket off the motherboard. My television has a HDMI socket on the side, and my PS/3 has not failed to show a picture yet.

All of the sockets on the RaspPi with the exception of the SD card are through-hole fitting. Most of them have large structural tags in addition. The size and weight of the board are irrelevant, it is the strength of the fibre-glass and the size of the tracks that is important. While I can see that having two cables pulling in different directions would increase strain, there is a limit to the strain that can be placed, and I cannot see it being more than the weight of a couple of feet of VGA, USB or Ethernet cable. The RaspPi will usually be on a desk with the cables horizontal.

It seems to me that if this is a problem, then the solution is to make a base-board with strain relief, maybe cable clamps, so that the cables come into the RaspPi from the right directions with minimal forces.

rmm200
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Re: Cases - fundamental problem

Sun May 06, 2012 3:27 pm

raspi said:

If every class starts with kids plugging and unplugging RasPies they will not last more than a few weeks.

The SD card connector is too inexpensive for daily use. Best classroom model I have thought of is use the SD card for booting, then have each student with his rootfs on a USB stick. Then he only needs access to a USB port, which are pretty durable. Of course he would have his own Pi at home also.

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Re: Cases - fundamental problem

Wed May 09, 2012 7:59 pm

raspi said:


If every class starts with kids plugging and unplugging RasPies they will not last more than a few weeks.


rurwin said:


I have never known a PC to fail through breaking a socket off the motherboard. My television has a HDMI socket on the side, and my PS/3 has not failed to show a picture yet.


I am the guy with a soldering iron and people know it. Word gets around fast. I personally have had several camera charging stations fail through repeated strain on the connectors. After the first repair fails they are usually only fit for the bin.

I get a steady stream of people dumping their devices on me for a fix of some kind and I have seen more than a few failures because of cable strain.

Mind you my neighbour's kid dropped his games machine in the toilet and I couldn't get that working - he'd switched it on, silly boy.

My wife put my iPod nano through the washing machine. I put it in a bag of rice, with the bag top open, next to the heating and hot water cylinder. The damp hot air is evaporated and absorbed into the rice. A week later I charged it up and it worked fine. My wife repeated this experiment on another occasion with a USB memory stick, which also works fine after many repeated uses.

Mechanical breaks on small tracks with surface mount components are harder to keep fixed. Unless you epoxy resin it all down after the mend it usually fails a second time for the same reason it did the first.

I think the difference here is that with Rurwin's devices he is not plugging and unplugging a portable device on a regular basis, such as might be expected with a RasPi.

secretreeve
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Re: Cases - fundamental problem

Wed May 09, 2012 8:50 pm

how many people throw away thier laptops/notebooks/netbooks or have to get them repaired because the power jacks have broken off the boards?

ALOT!

too many, would it kill these manufacturers to add a peice of plastic on the top or bottom plastic to press on the power jack so it didnt move as much?

anyways, PI cases all have the same issue, i been thinking this since the first case popped up. just didnt wanna burst anyones bubble

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Re: Cases - fundamental problem

Wed May 09, 2012 8:54 pm

Yup my wife's HP G60 suffered this (caused by hamfisted previous teenage owner)
Steve N – binatone mk4->intellivision->zx81->spectrum->cbm64->cpc6128->520stfm->pc->raspi ?

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Re: Cases - fundamental problem

Wed May 09, 2012 9:29 pm

secretreeve said:


anyways, PI cases all have the same issue, i been thinking this since the first case popped up. just didnt wanna burst anyones bubble


So far I know there is not a official case brought out yet...

The only cases I see now are just from people who are very enthusiastic...

I will probably never connect a keyboard or screen to it, only the power and maybe a network cable (or perhaps instead a wifi adapter), so those cases are sufficient for me.

But I agree that all those connectors around the pcb makes it hard to design something which resolves all that... It is also a question of how large such a case would be, how practical it would be and how much it will cost...

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Re: Cases - fundamental problem

Thu May 10, 2012 9:20 am

And I thought I was the only one who was concerned about this problem...

I'm looking at a few possible cases for my Pi (which I think is due to arrive today ), and the two current front-runners are the ModMyPi enclosure and the Yoctopuce transparent "sandwich" (with the latter just edging ahead, as it's transparent and carries the RPi logo!).

However, I'm a bit nervous about the possible lack of reinforcement given by the cases (especially by the Yoctopuce) to the RPi's connectors. I don't know how often I'll be plugging and unplugging things - hopefully, not often, once I get the machine "settled in" - but I suspect I'll take as much care as I can to be gentle...

Perhaps I should hang on a while longer, and see how (if?) the "official" RasPi cases tackle this issue?
---
Raspberry Pi Model 3B+ (2019) ("ayeka") - CentOS
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Jim Manley
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Re: Cases - fundamental problem

Thu May 10, 2012 2:51 pm

It's not the "case" (pun fully intended) of just plugging everything in once and never touching it again that's of concern, it's the cyclic stress of repeated insertions/extractions, especially in a classroom environment where lots of SD cards and cables may be swapped in and out.  A typical PC's motherboard connectors are generally never touched again once it's set up, and most connectors have integral stress relief tabs that mechanically secure the connector to the board.  I have had laptops where the power connectors failed because they were only secured by the solder joints on the power terminals.  If a Pi is going to be connected once and then never touched again, then there won't be a problem, but, the use-cases being touted where it's tossed in a backpack and taken to and from school, or shared by many students, are going to be problematic.  Once there are so many of them that they're ubiquitous, this may not be such a big deal, but, we're a very long time from that point.
The best things in life aren't things ... but, a Pi comes pretty darned close! :D
"Education is not the filling of a pail, but the lighting of a fire." -- W.B. Yeats
In theory, theory & practice are the same - in practice, they aren't!!!

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