On Sat, 19 May 2012 21:39:04 +0000 (UTC), "Geoffrey S. Mendelson"
wrote:
Jeff Liebermann wrote:
The 1pps output can be used to run a digital clock, but I would hate
to see the final cost.
We are talking about a clock here, something most people are to seeing
display hours and minutes. Few of them have seconds. None have 10ths,
hundreds, etc.....
1pps is one pulse every seconds. A second hand is quite common and
useful.
While an NTP interface with wifi would do for probably 90% of the world,
the few people that don't have any internet access, would need a GPS unit.
I've watched several "wired home" type projects flounder and
eventually fail. I'm still somewhat optimistic, but not much. One of
my friends bought a refrigerator that's connected to the internet via
wi-fi.
http://en.wikipedia.org/wiki/Internet_refrigerator
He thinks it's cool. His wife hates it and hangs a towel over the
display. I saw much the same reaction as I watched the fully
automatic microwave oven fail miserably. It's going to be a while
before we have a wired (or wireless) home.
If you can get one in a cheap cell phone these days, how much would it cost
to put in a clock? I understand that it won't give you milisecond accuracy,
but a window view that can "see" 3 or 4 satellites (or an outside antenna
would do.
Not too expensive using a SONET GPS chip, which has a convenient 1pps
output:
http://www.analog.com/
pr/AD9548
http://www.analog.com/en/press-release/6_11_09_Clock_IC_First_to_Harness_GPS/press.html
For a commodity alarm clock, the chip does not need to be powered
continuously. Wake it up a few times per hour, grab the time, update
the alarm clock, and go back to sleep. A WWVB 60KHz clock is cheaper,
but a GPS clock is "cool".
Note that you do NOT need to see 3 or 4 birds. You need that if you
want a lat-long-altitude position fix, but only one bird is needed for
the time, which is sent by all the birds as part of the almanac.
http://en.wikipedia.org/wiki/GPS_signals#Almanac
However, I'd happily buy 5 or 6 of them with wifi.
There are several SBC (single board computah) that will run Linux.
Adding an cheezy dot matrix LCD display and running NTP is fairly
simple.
I'm tired of battery
run analog or even line operated digital clocks ones that are off several
minutes a week.
Well, we could make a wind-up digital clock, but I don't think it will
sell. I gave up wearing a watch long ago and use the clock in my cell
phone or smartphone. Verizon (CDMA) keeps very accurate time.
Yes, they have a design flaw, but I can't return them after they start
showing the time gain or loss, it takes too long to show up.
It might have something to do with the internal construction. I'm
running into the same mid-life mortality issues with cheap weather
stations. The problem is that the old designs used discrete parts,
SMT parts, and packaged devices. These days, the junk from China uses
COB (Chip On Board) construction. The main chip is buried under a
blob of epoxy or other goo. The epoxy has a different coefficient of
thermal expansion as the PCB. It's not much, but over a fair number
of thermal cycles, it will eventually rip the underlying chip apart.
http://www.empf.org/empfasis/dec04/improve1204.htm
Geoff.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558