On Aug 19, 9:11 pm, Lewin A.R.W. Edwards <la...@larwe.com> wrote:
> rickman wrote:
> >> You're kidding, right? No two of those are the same, and the shelf
> >> life of any given model is about twenty minutes. You need a pretty big
> >> physical envelope, and some innovative anti-vibration strapdown
> >> system, to be able to accept any arbitrary USB disk.
>
> > I would think that *you* were kidding.  The ones I have seen are
> > pretty much the same.  They are all about the size of a stick of gum.
>
> Have you ever actually looked at them? Looking in the "spare USB stick" drawer
> right in front of me I see devices ranging from 0.75" long to 3" long, 0.25"
> to 0.75" wide and 0.25" to 0.5" thick. Some of them are asymmetrical. The ones
> that are asymmetrical have no standardization as to whether the thick side is
> "up" or "down" relative to the USB conncetor. This is precisely what is meant
> by "no mechanical standard".

I don't get what you are freaking out about.  Yes, they come in
different sizes, but you can buy what you want and what will work.
You don't have to buy a 3" long device and you don't have to buy a
0.75" long device.  Most of them run around 2". You can just leave
space for a 3" one if you want.  Or it would be a very easy job to go
to the store and buy one that matches the tick marks on your ruler.
That is my point.


> > As to the strapdown, a strap would be perfect.  Just a piece of rubber
> > band or o-ring stretched across the body between two hooks.  Very
>
> Unless the body of the drive is properly supported at the bottom, you're
> applying bending stress in the worst possible way - levering the connector
> leads off the PCB using the mechanical solder-mounting points at the front as
> a fulcrum.

I have no idea what you are picturing.  I am seeing a device on a
piece of metal with a strap across it holding it flat.  I guess you
are picturing a typical PC with the USB device sticking out like a
diving board.  Again, if you want to imagine something that won't
work, then it won't work.  The original point was that the makers of
this small PC could have built in a space (much smaller than a CF
card) that would accept a USB stick or an SD card and hold it
securely.  It is getting pretty silly to say this can't work.


> > leave the mating connector floating as a cable end so that you don't
> > have to worry about stressing the connector.  I expect that could
>
> That is probably the best solution, I agree.
>
> However, CF is in many applications a superior solution. Nobody (TTBOMK) makes
> industrial-rated USB sticks; industrial-rated CF cards (temp range and
> availability of spare sectors) are fairly easy to come by. The reliability of
> USB media isn't even characterized since they are all strip-mined out of the
> anonymous electronics rockface in China.

Yes, most of them are "strip mined".  However, I did a quick search
and found several "industrial" temp USB memory sticks.  Here's one...

http://www.altec-cs.com/h_en/prod/aktu/usb_sticks/fm_stick/index.htm

I also found that the PCs we are talking about putting them in are
*far* from even commercial temp much less industrial.

Fit PC: Operating temperature: 0-45C

The eeBox didn't even spec temp, but I am sure it is about the same.

So what is all the noise about?  With SD or USB you can do a lot in a
smaller package and you can either go the super inexpensive route with
retail units or you can go with rugged, industrial temp units.  I
guess there are some USB memory that is raised up the old fashioned
way...

Rick

"rickman" <g...@gmail.com> wrote in message
news:e...@d77g2000hsb.googlegroups.com...
> I don't get what you are freaking out about.  Yes, they come in
> different sizes, but you can buy what you want and what will work.

And now try to envision that you are running a company and your customers
orders 250 of your system that takes a USB stick.
What do you prefer to do? Get out of your office, spending two days visiting
about every retailer in your area trying to get 250 sticks that fit into
your appliance or spend 10 minutes preparing a PO and simply fax it to your
trusted supplier to order 250 CF cards that fit?

That is what professionals are freaking about.....

> I have no idea what you are picturing.  I am seeing a device on a
> piece of metal with a strap across it holding it flat.  I guess you
> are picturing a typical PC with the USB device sticking out like a
> diving board.  Again, if you want to imagine something that won't
> work, then it won't work.  The original point was that the makers of
> this small PC could have built in a space (much smaller than a CF
> card) that would accept a USB stick or an SD card and hold it
> securely.  It is getting pretty silly to say this can't work.

If you design for production, you appreciate what standardisation does for
you. And USB sticks don't fit that world...
CF OTOH (and SD) do.

Meindert

rickman wrote:
> Sorry, I meant a "pack" of gum...

Ah, I should have figured that out.