[Tfug] Opine: Bricks, warts or...?

[Bexley Hall]

--- On Tue, 8/5/08, Brian Murphy <murphy+tfug at email.arizona.edu> wrote:

> I'm going to hate myself for extending another
> ill-defined no answer good enough Bexley thread but...

Sorry, but that's the nature of Engineering -- every solution
has trade-offs.  If you can't identify the shortcomings of a
solution, you can't evaluate the trade-offs associated with it!

Feel free to "define" the thread better, if you like...
 
> Quoting Bexley Hall <bexley401 at yahoo.com>:
> > The problem with USB is you can't *rely* on having
> that
> > available.  I.e., you, as the designer of a product
> that
> > will plug into a USB hub, take a risk when you assume
> the
> > user will have a hub that can "spare" that
> much current for you.
> Snip...
> > Also, both of these (USB & PoE) assume you are
> talking about
> > "computer related devices".  Do I have to
> buy a special
> > cradle to charge my cell phone from my ethernet jack?
> 
> No you don't have to buy a special cradle to charge
> your cell phone from USB.  That is, I don't.
> My Motorola phone charger has a small wall wart
> on one side and a USB mini plug on the other.

Yes, but your manufacturer took this into consideration
(i.e. trade-offs) and opted to put the extra cost into
the product based on *their* assumption that the feature
would be worthwhile to their targeted consumer.  I have a
"universal power adapter" that is similar -- a flip-out
AC power plug, 12VDC ("lighter") plug and a USB port
that *just* supplies power (of course, since there are no
brains in the adapter).  And, another little "kit" that's
a retractable USB cord with an assortment of telephone
and "2 pin" power connectors (like you find on a wall wart).
But, it will only supply ~2W at up to 12V.

> If I'm at home or traveling, I have the AC charger.  If I'm
> at the office or a friend's house and need a boost, I just
> hook up via USB for a charge.  It's the best of both worlds...
> people not around computers can use the supplied
> AC adapter and people who spend a lot of time around
> computers can mooch from the USB port if they prefer.

But it only handles that *one* appliance.

No, I'm not picking nits.  The trend is for more and more
low voltage, portable devices.  Since our power system is
*not* low voltage, that means lots of requirements for
chargers, adapters, etc.  Each one wastes space, resources
(to fabricate it) and power (e.g., even a very efficient
computer power supply throws away 20-30W just to operate).
And, they are *inconvenient* (an extra item to deal with,
another competitor for "outlet space", etc.).

> Here are adapter pics:
> http://www.cellphoneaccents.com/manufacturer-motorola-phone-accessory-rizr-z3-chargers.html
> 
> As far as your other comment about needing a cord to power
> up, don't be dense.  Of course you'll need a cord of some sort.

Since you didn't cite the original passage, I'll assume it was:

[PoE]
>> But then you are telling the user he has to have a WIRED
>> network in his home (?) *and* put the power supply for
>> PoE *somewhere*.  Note that people use wireless NICs simply
>> to get away from having to run wires...

In which case, you missed the point.  People dont want to have to
run CAT5 through their house to "have a network".  That's why
wireless NIC's find such widespread acceptance (as does HomeNet,
PLC modems/phones, etc.).

So, for these folks, PoE doesn't buy them anything -- their
house isn't wired!

Or, are you suggesting they buy a PoE *switch* and *don't* bother
running the CAT5 throughout their house (so they have power taps at
each network outlet) and, instead, just use the switch as a giant
wall wart (with a short CAT5 cable -- "a cord of some sort" -- to
connect it to their "device")?

:-/