Heathkit clock available
On Thu, Aug 11, 2016 at 4:03 AM, Chris Albertson albertson.chris@gmail.com
wrote:
Digital clocks are just not the amazing technical wonders they once
were.
No, but it's interesting that they've considered the interface rather than
using the common one supported by generic clock chips. Phone interfaces are
rarely good for use in a semi-conscious state, and are inclined to run out
of battery charge.
“Far out in the uncharted backwaters of the unfashionable end of the
western spiral arm of the Galaxy lies a small unregarded yellow sun.
Orbiting this at a distance of roughly ninety-two million miles is an
utterly insignificant little blue green planet whose ape-descended life
forms are so amazingly primitive that they still think digital watches are
a pretty neat idea.”
― Douglas Adams http://www.goodreads.com/author/show/4.Douglas_Adams, The
Hitchhiker's Guide to the Galaxy
http://www.goodreads.com/work/quotes/3078186
On 8/10/16 8:03 PM, Chris Albertson wrote:
But for sure a GPS module, a handful of buttons, 7 7-seg LEDs (I’d display a 10 Hz digit), a little phototransistor dimming circuit and an ATMega… $99 retail? Certainly doable.
Almost everyone one Earth already owns a GPS sync'd alarm clock. My
iPhone does all I need, pretty decent sync to UTC, big numbers I can
read without glasses and it makes noise when I need to get up. The
iPhone sells for way over $100. But any cheap $99 android tablet can
function as a digital clock. All You need is a stand. These phones
has pretty much obsoleted alarm clocks, cameras, Dedicated GPS
receivers for car navigation, and 100 other things
Except where you're in an environment that cannot tolerate devices with
radios or portable data storage; both of which a mobile phone provides.
That's where a conventional clock (alarm or otherwise) or timekeeper is
needed.
One can argue, of course, that one does not need "time-nuts" level alarm
clock accuracy in such an environment, and if you did:
a) you would go through the hoops to bring a GPS receiver and associated
computing devices/electronics in
b) you'd probably just buy an off the shelf box - you'd have the budget
AND the hoops would be easier to jump than with something homegrown.
before you buy AC line disciplined clock read that
Alex,
That old article from 2011 is misleading. It correctly describes what was being /proposed/, but it turns out NERC chose not to implement what the article (fears) talks about. There are lots of time-nuts postings about this in the 2011 archives if you want to read more. Or google for TEC (time error correction).
So your 60 Hz timekeeping is probably fine and still loosely locked to UTC. Several of us time nuts continuously monitor mains frequency & phase for fun. It's an interesting and low-cost entry into the world of time & frequency measurement, long-term data logging, data analysis, Allan deviation, etc.
Here's a quick plot showing the last 2 months (US western grid). Someone else (Hal?) can double check it.
http://leapsecond.com/pages/mains/mains-june-july-2016.gif
/tvb
Alex (et al),
There is also the FNET project here: http://fnetpublic.utk.edu/
They have monitoring boxes that various people set up to monitor line frequency, disciplined to GPS, and upload to their servers. I have one of these boxes in my office (Unit #1033 here: http://fnetpublic.utk.edu/tabledisplay.html).
All and all, the US power grid is pretty close to 60Hz. =) It is fun to watch how each of the interconnects here in the US lead/lag 60Hz depending on the time of day, and the load on the system (at least, I assume that’s the cause).
Thanks!
-Ryan Stasel
On Aug 12, 2016, at 11:03 , Tom Van Baak tvb@LeapSecond.com wrote:
before you buy AC line disciplined clock read that
Alex,
That old article from 2011 is misleading. It correctly describes what was being /proposed/, but it turns out NERC chose not to implement what the article (fears) talks about. There are lots of time-nuts postings about this in the 2011 archives if you want to read more. Or google for TEC (time error correction).
So your 60 Hz timekeeping is probably fine and still loosely locked to UTC. Several of us time nuts continuously monitor mains frequency & phase for fun. It's an interesting and low-cost entry into the world of time & frequency measurement, long-term data logging, data analysis, Allan deviation, etc.
Here's a quick plot showing the last 2 months (US western grid). Someone else (Hal?) can double check it.
http://leapsecond.com/pages/mains/mains-june-july-2016.gif
/tvb
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Thank you Tom, I have a very primitive frequency comparator built some
thirty years ego, which compares the line frequency to WWVb 60kHz, since
the new format for WWVb was introduced it does not work so great any
more, but it is still good enough to see if the line frequency is to
fare off. Basically it is just counting the periods of the line
frequency and the counter's gate time could be set for hour/day/
week/month and the reset time is derived from the WWVb datum. I have
seen also some daily deviations of the 60Hz similar what your picture
shows, but interestingly the long time average -- one whole year -- up
to now is correct
73
KJ6UHN
Alex
On 8/12/2016 11:03 AM, Tom Van Baak wrote:
before you buy AC line disciplined clock read that
Alex,
That old article from 2011 is misleading. It correctly describes what was being /proposed/, but it turns out NERC chose not to implement what the article (fears) talks about. There are lots of time-nuts postings about this in the 2011 archives if you want to read more. Or google for TEC (time error correction).
So your 60 Hz timekeeping is probably fine and still loosely locked to UTC. Several of us time nuts continuously monitor mains frequency & phase for fun. It's an interesting and low-cost entry into the world of time & frequency measurement, long-term data logging, data analysis, Allan deviation, etc.
Here's a quick plot showing the last 2 months (US western grid). Someone else (Hal?) can double check it.
http://leapsecond.com/pages/mains/mains-june-july-2016.gif
/tvb
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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There are two systems that affect line frequency anywhere in the world.
One is the use of multiple power producers generating steam for turbines
that turn huge generators. The generators are synchronized by the
distribution networks that connect them. A generator rotates at the
frequency determined by all of the other generators, If its turbine is
receiving less energy than is required to keep up, the generator will
take the balance of power from the network. If the turbine produces more
energy than is required, it will cause the line frequency to increase a
very little bit. Change 'steam' to 'water' for hydro-electric plants.
A networked connection of generators and loads requires a perfect
balance of power produced with power consumed to maintain constant
frequency. This can only be done for very small networks. You cannot put
a PID controller on each turbine and set it for a GPS derived frequency.
The control actions would fight each other and destabilize the network.
In the early days, each power station had a clock driven by the
generators and a reference clock. An operator would increase steam to
the turbines a bit if the station clock fell behind the reference clock,
or decrease steam slightly if it was gaining time. There was (is) no way
to predict the behavior of the loads, except from general experience of
the effects of weather and holidays.
Today's networks are much too large for control by station clocks. A
large region has a central power dispatching station. A dispatcher
tracks the difference between network time and GPS time. If the network
is losing time, the dispatcher calls the necessary number of generating
plants and asks them to increase power. It is common to lose time as the
loads of the manufacturing day increase and to make it up after 4 AM or
so. (During the 50s, the Air Force determined that 4:30 AM was the time
of minimum human activity, and so a probable time for an enemy to strike
with missiles.) I visited the Pennsylvania, New Jersey, and Delaware
(PennJerDel) region's dispatch center in the seventies. Very impressive
wall maps of major generation stations and load centers with their data.
It is expensive for a plant to change power, and so they hatched the
plan to stop trying to hold the time difference to zero over a day.
There was sufficient outcry to abandon the plan.
The other system comes from the use of high voltage DC tie lines to
exchange power between networks isolated by geography, such as the West
Coast and Texas. The DC lines use high voltage, high power solid state
inverters to convert DC to AC or reverse the direction when power could
flow the other way. The inverter frequency can be precisely controlled,
but it is controlled to balance the power flow, not hold the line
frequency. A network pays for the tie line power it produces or
consumes.
Different regions can have different phase behavior. I have only seen
West Coast plots on this list. When I did some work with this in
Minnesota in the eighties, the phase variation was only about 6 seconds
during a day and zero from day to day.
This is my understanding of the system. People with more knowledge,
please correct my misconceptions.
Bill Hawkins