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From: D Yuniskis on 20 Jan 2010 19:54
Hi Mark,

Mark Borgerson wrote:
>> I'm now thinking about putting "consumer" flash memory
>> devices in a design in lieu of equivalent components
>> soldered onto the PCB. E.g., mount an SD socket and
>> use an SD *module* (or other media choices).
>>
>> The point is, this is done AS IF it was a permanently
>> attached device. I.e., imagine fab'ing the board,
>> slipping an SD card into the socket, and then encasing
>> the entire assembly in a sealed box (so the SD card is
>> socketed yet never removed).
>>
>> But, I'm not sure that these types of sockets are
>> really intended for this type of long term use.
>> I.e., do they *expect* frequent insertions and removals
>> to wipe the contacts clean periodically?
>
> Many cell phones use micro SD cards for music and
> picture storage. They often put the music on
> through a USB connection. The pictures are often
> taken and sent out via the phone. I've never
> removed the 2GB sd micro in my phone, but it
> still works fine after more than a year.

Yes. I think cameras are probably a more "abused"
device in this regard. E.g., I do a remove/insert
cycle each time I use one of my cameras. But, they
are SD, MS (I've since discarded the SM camera).
I think my phone has a mini SD (not micro)

> A lot of digital cameras use SD memory and have the
> capability to upload the photos via high-speed
> USB. The card may stay in the camera for many
> months at a time.

I have found it easier to remove the card.

But, even if the card sits in the camera for ages,
it *can* be removed to "freshen" the connection.
What if removing the card is complicated (e.g.,
imagine your oceanographic probe spending a few
*years* under water)

> I came to the conclusion a few years ago that SD
> and SD micro sockets were OK for data storage,
> and have incorporated them in a number of
> data loggers. Before that, I had only used
> CF cards for storage---but they had worked out OK.
>
> I'll add the disclaimer that I'm using the
> SD and SD micro cards primarily in oceanographic
> data loggers. The loggers are in sealed pressure
> cases, so dust and humidity are not an issue.

But, they aren't filled with inert gases, are they?
(i.e., there still is *some* atmosphere that they
are exposed to)

> (If anything gets wet, it's generally a catastrophic
> failure!).

A wee bit of a leak... :>
From: D Yuniskis on 20 Jan 2010 20:05
Hi Theo,

Theo Markettos wrote:
> In comp.arch.embedded news(a)rblack01.plus.com wrote:
>> Lots of embedded-PC-based systems (including ours) boot from a Compact
>> Flash card. These usually have gold-plated contacts on both sides; our
>> oldest machines have been in the field for about 5 years with no
>> problems in this area.
>
> One of the new Freescale ARM CPUs has an SD interface for flash, and enough
> logic in it to be able to boot from SD. So you can have (micro) SD as the
> only nonvolatile storage on the board.
>
> I know one consumer device (the Chumby One) that does just this. It has
> hidden microSD inside - accessible if you unscrew it from the board, but
> otherwise intended to be hidden (the idea is easier user fixing of
> problems... brick your box? Just pop the firmware card in a Linux box and
> run 'dd')

But, what if they solvent welded the case shut?

E.g., you can find wireless routers that have PCMCIA wireless
cards buried within. You *know* they aren't expecting anyone to
remove that device but just opted to take that approach for
whatever manufacturing/availability reason...
From: Joel Koltner on 20 Jan 2010 20:24
"D Yuniskis" <not.going.to.be(a)seen.com> wrote in message
news:hj88mi$vam$3(a)speranza.aioe.org...
> E.g., you can find wireless routers that have PCMCIA wireless
> cards buried within.

Mini-PCI WiFi cards seem popular in routers too -- even in brands like Netgear
where they're going after very high volume markets and you'd think it'd be
cheaper for them to just solder down the chips.

From: D Yuniskis on 20 Jan 2010 20:44
Hi Joel,

Joel Koltner wrote:
> "D Yuniskis" <not.going.to.be(a)seen.com> wrote in message
> news:hj88mi$vam$3(a)speranza.aioe.org...
>> E.g., you can find wireless routers that have PCMCIA wireless
>> cards buried within.
>
> Mini-PCI WiFi cards seem popular in routers too -- even in brands like
> Netgear where they're going after very high volume markets and you'd
> think it'd be cheaper for them to just solder down the chips.

Yes. This sort of thing is counterintuitive to me.
Which makes me second guess my initial assumptions.

Of course, with wireless stuff, they may simply be
"buying the certification". Especially on the short
term.

<shrug> Dunno. The economics and the practical
aspects are often out of sync...
From: Mark Borgerson on 21 Jan 2010 02:21
In article <hj8826$uo8$1(a)speranza.aioe.org>, not.going.to.be(a)seen.com
says...
> Hi Mark,
>
> Mark Borgerson wrote:
> >> I'm now thinking about putting "consumer" flash memory
> >> devices in a design in lieu of equivalent components
> >> soldered onto the PCB. E.g., mount an SD socket and
> >> use an SD *module* (or other media choices).
> >>
> >> The point is, this is done AS IF it was a permanently
> >> attached device. I.e., imagine fab'ing the board,
> >> slipping an SD card into the socket, and then encasing
> >> the entire assembly in a sealed box (so the SD card is
> >> socketed yet never removed).
> >>
> >> But, I'm not sure that these types of sockets are
> >> really intended for this type of long term use.
> >> I.e., do they *expect* frequent insertions and removals
> >> to wipe the contacts clean periodically?
> >
> > Many cell phones use micro SD cards for music and
> > picture storage. They often put the music on
> > through a USB connection. The pictures are often
> > taken and sent out via the phone. I've never
> > removed the 2GB sd micro in my phone, but it
> > still works fine after more than a year.
>
> Yes. I think cameras are probably a more "abused"
> device in this regard. E.g., I do a remove/insert
> cycle each time I use one of my cameras. But, they
> are SD, MS (I've since discarded the SM camera).
> I think my phone has a mini SD (not micro)
>
> > A lot of digital cameras use SD memory and have the
> > capability to upload the photos via high-speed
> > USB. The card may stay in the camera for many
> > months at a time.
>
> I have found it easier to remove the card.
>
> But, even if the card sits in the camera for ages,
> it *can* be removed to "freshen" the connection.
> What if removing the card is complicated (e.g.,
> imagine your oceanographic probe spending a few
> *years* under water)

The CF versions have spent up to 9 months underwater--but only
collected data for about 6 months because of battery
life.

The SD card versions are heading for moorings on the
equator this summer. I'm hoping that gold-on-gold
contacts, and a dry temperature-stable environment will
prove reliable.
>
> > I came to the conclusion a few years ago that SD
> > and SD micro sockets were OK for data storage,
> > and have incorporated them in a number of
> > data loggers. Before that, I had only used
> > CF cards for storage---but they had worked out OK.
> >
> > I'll add the disclaimer that I'm using the
> > SD and SD micro cards primarily in oceanographic
> > data loggers. The loggers are in sealed pressure
> > cases, so dust and humidity are not an issue.
>
> But, they aren't filled with inert gases, are they?
> (i.e., there still is *some* atmosphere that they
> are exposed to)
>

Many instruments and loggers are flushed with dry
nitrogen or argon before they are sealed to avoid
condensation. They generally get assembled at about
20C, but spend most of their logging time at 5 to 10C.
> > (If anything gets wet, it's generally a catastrophic
> > failure!).
>
> A wee bit of a leak... :>
>
It doesn't take much salt water when there are a few
volts across the pins.

The worst situation is when there is enough water in the
case with the batteries to generate some gases.

Back in the 70's a leaky case generated enough
hydrogen that a friend was injured when opening
the pressure case. I once opened an instrument
that had been on a mooring for several months and
it started hissing as I loosened the screws. I
set it down and left the room for 24 hours. After
that we added some pressure relief capability
to the design.

Two pounds of lithium batteries and 3 ounces of
salt water is a scary combination!

Mark Borgerson


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