[time-nuts] Low cost synchronization, kitchen appliances

[Magnus Danielson]

From: "Tom Van Baak" <tvb at leapsecond.com>
Subject: Re: [time-nuts] Low cost synchronization, kitchen appliances
Date: Sun, 21 Aug 2005 07:03:56 -0700
Message-ID: <000401c5a659$2caf18e0$7a18f204 at computer>

> > > For some countries will 60 Hz or 50 Hz no longer be maintained on 24 h
> basis, so it may be
> > > a bad idea to depend on it.
> >
> > I keep hearing, on this group, that the powerline is no longer sync'd to
> utc, and evidence for
> > that fact being a lack of motorized wall clocks.  Well, clocks that sync
> to the powerline are in
> > universal abundance in the US.   Virtually every clock on kitchen
> appliances is sync'd this way.
> > The clocks on VCR's may be reset from time to time by a tv station, but
> the timing signal is
> > still the powerline.  Basically, any appliance, or device that plugs into
> the powerline is likely to
> > use the powerline for its timing function.
> >
> > -chuck
> 
> Correct, my measurements clearly show that
> mains power is steered to UTC. See:
> http://www.leapsecond.com/pages/mains/

I think you are makeing the wrong conclusion, just because some powergrids is
steered to match UTC does not mean that all powergrids is steered to match UTC.
Similar is the discussion relating to cellular phones, just because some have
it others may not have it.

> If there's anyone from the power industry on the
> list I'd be interested to hear first-person technical
> details of how phase is synchronized, both short-
> and long-term.

I know who to talk to, at least for a deep understanding of the US power-grid.
I had him explain how the power-grid shutdown in east US could possibly occur,
very enlightening I might add. Frequency correction methods where explained in
the theory part of the explanation. The short story is that frequency
regulation is performed by balacing energy production and energy consumption in
the powergrid as a total. Overproduction results in higher frequency, under-
production results in lower frequency. Over and under production is produced
and shared among the producers in order to maintain overall frequency.
This comes at a price (coordination) and the larger powergrid the less eager
to coordinate one might be. I'll see if I can't dig up his post. However, that
would only give some theory and some detail relating to the US situation, but
people live elsewhere and situation is thus different (besides different
frequency and voltage).

> But I'm not sure I agree with your claim about
> kitchen appliances. It seems to me almost every
> kitchen, electronic, wall-clock, and entertainment
> appliance being sold these days uses quartz-based
> clocks, regardless if they are mains, wall-wart, or
> battery powered. I'm not sure how to confirm the
> accuracy of this hunch, though.

Simple. Use a frequency synthesizer, poweramp and a variable transformer in
backwards and then adjust frequency and see if the the clock speed changes
accordingly. I think for most things, a 32 kHz oscillator is being used, since
it can be used for simple processors too.

> I suspect there are several factors in the trend
> away from mains-clocks to quartz-clocks:
> 
> 1) Digital or analog quartz movements are dirt
> cheap (so it's a cost saving measure).
> 
> 2) If the product is intended for sale in Japan
> (where both 50 Hz and 60 Hz mains co-exist).
> 
> 3) If the product is intended for sale world-wide
> (there is a healthy mix of 50 vs. 60 Hz and 120
> vs. 240 V across the planet).

Markets are global now. Also, there is some odd frequency (such as 24 Hz) grids
still in operation in the US if I recall things correctly.

> 4) The explosion in the use of switching power
> supplies in home electronics (which are immune
> to local voltage / frequency conventions).
> 
> 5) The explosion in the use of microprocessor
> based control of appliances (where the CPU(s)
> are driven by an n MHz XO and date/time/display
> functions are managed in firmware).

I agree with all these points. There are really few things that effectively
depends on it, so these days control of the frequency is not as important as
it used to be back in the old days when the industries punch-out and wall
clocks all had their frequency from the mains.

With that background, releasing the "tight" control becomes less of a problem
than it used to be, for good and bad.

I think I recall Poul-Henning mentioned that Nord Pool removed their frequency
control some time back. Maybe I should measure the frequency locally. I can
make some investigation of the local situation.

Cheers,
Magnus