die@dieconsulting.com said:

How many of those are really interested in low power?

The only one I see on your list that might run off batteries is water
sprinklers.  All the rest use enough power that a GPS unit would be in the
noise.

I think the main argument for WWVB receivers vs GPS receivers would be cost.
In either case, you have to get the antenna outside the metal enclosure and
that may be the major cost.  (I suppose a sprinkler controller could be
mounted in a plastic enclosure.)

"school crossing signs" is another possibility.  In the last year or two,
I've seen several setups around here that have solar powered LEDs mounted at
street level at pedestrian crossings.  They are great at night but not so
great during the day.  (But during the day the pedestrians are easier to see.)

--
These are my opinions.  I hate spam.

On Fri, Jul 13, 2012 at 09:47:12PM -0700, Brooke Clarke wrote:

And that is important for most routine civil human use.

Nor something that could somehow be added to GPS which is

worldwide in scope without adding lots of message information and
dealing with all the crazyness of international time zones and
political jurisdictions.  WWVB serves the US (and maybe Canada)
where DST start and end is pretty much global.

Besides the costs greatly favor WWVB receivers... as the

authors of the paper point out their whole decoder would fit neatly
in a tiny corner of the silicon of a typical SOC chip these days...
and AFAIK there is no practical current way to do this with GPS.

And while it is true that good Faraday cages like metal

enclosures with tight seals kill the LF, a good sized bush might take
out GPS and won't impact LF reception, which also works pretty well
inside many buildings and in particular common wood frame houses unlike
GPS.

--
Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

On 07/14/2012 06:47 AM, Brooke Clarke wrote:

One reason GPS doesn't have it is that it is not coordinated globally.
For instance, US is not shifting DST at the same time as Europe. There
is no obvious "right" here.

Keeping track of the time-zones and their changes keeps the time-zone
folks alert and requires a constant maintenance. Keeping it in the GPS
signal would require mapping of position to time-zone area, and only
then it could be keyed down. These mappings does not stay stable, so any
downlink format would need to describe them and would take considerable
time. This is why it is best managed by the user himself.

Cheers,
Magnus

Hi

I think the answer to "how many places would it be used" is to simply count the number of things that have the wrong time on them each time the power burps. There are maybe a dozen gizmos like that in this room (yes I'm in the kitchen).

Bob

On Jul 14, 2012, at 12:41 AM, Hal Murray wrote:

I don't see why school crossing signs, water sprinklers, street or outdoor
lighting need 1 second timing. Ten minutes, or a photocell, would be more
than adequate.

Synchronized traffic lights, perhaps. But there are other cheaper, ways of
doing that like a simple radio link.

-John

===============

On Sat, Jul 14, 2012 at 06:15:14AM -0700, J. Forster wrote:

While there are many many other applications, the issue for most

of these devices is not 1 second accuracy, but automagic setting of the
time without operator intervention or manual procedure required. For
many ordinary folks the always slightly different push button gyrations
required to set the time on a device with limited buttons and display
are all too often a complete barrier to getting the time set right (this
is the VCR "blinking 12:00AM" phenomenon).  And in outside environments
clock oscillator thermal behavior will ensure something preset to the
correct will wander pretty far out quite quickly  (plus of course DST
needs to be set too).  And working with only approximate time is
another source of terrible confusion for users... if they set it to go
off at exactly 11 PM and it goes off at 11:08 PM they are likely going
to be confused and frustrated... especially if difficult or even
impossible steps are required to correct the time.

Photocells don't work for situations where the desired on or off

times are civil times (not turning on the water sprinklers until 11 PM
for example or turning off the tennis court lights at 10 PM)... at best
it takes lots of software to convert light and dark from them to
anything approximating a 10 minute accurate estimate of the time of day
and shadows and sun angles and so forth ensure that this is never going
to be particularly accurate.

I refuse to believe that a reliable mile or more range RF

link would be cheaper than a loopstick and maybe a couple of passives
tied to pins on a SOC chip...  and there are all those situations
where even a mile isn't enough or obstacles or RFI block ISM band
links.

--
Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."