[time-nuts] Mains Frequency

[Jeremy Nichols]

The joke in USA at that time was that the power companies adjusted their
frequency by calling the local telephone company (which was ATT/Bell
Telephone almost everywhere). In that era, you could call a local number
and get the time. The power companies used that time number, it was joked,
to adjust their frequency. The telephone companies, of course, just had an
electric clock that ran on the power line.

Jeremy



On Fri, Feb 12, 2021 at 1:38 PM Alex Pummer <alex at pcscons.com> wrote:

> at the time I grew up in Eastern Europe -- "communist time" -- they kept
> he clocks using the line frequency as reference -- by counting the
> periods during the day and week and for longer time for equal time
> interval the "provided" equal number of line frequency periods, as
> longer the time interval was as more precise was the time.  That way the
> clocks were relative accurate. They could do it since everything was
> "central governed".
>
> On 2/12/2021 9:24 AM, Lux, Jim wrote:
> > On 2/12/21 8:23 AM, Thomas D. Erb wrote:
> >> "I would think they try to hold it over 1 day, so that mains driven
> >>
> >> clocks don't run slow or fast.? That being said, I wonder how many
> >>
> >> clocks are still being built using a synchronous motor drive? Given that
> >>
> >> all the clocks on appliances in my kitchen have drifted apart, I'll bet
> >>
> >> they use their internal microcontroller crystal as a reference."
> >>
> >> Actually I think all of my kitchen appliances use line frequency for
> >> time reference - it's so easy to count.
> >
> >
> > Maybe.. you've got to condition the AC from the secondary side of the
> > transformer and use a pin to bring it in on, which requires at least 2
> > or 3 passive components, and you already have a crystal for the
> > microcontroller (thinking here of oven timers and the like, which have
> > a numeric display).  These applications are super price sensitive, and
> > those 2 or 3 components cost money, in components, in board space, and
> > in assembly costs. Pennies to be sure, but...
> >
> > And the fact that my appliances drift on the order of a minute in a
> > month, differently. So maybe some count cycles and some have a rock.
> >
> >
> >
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-- 
Jeremy Nichols
Sent from my iPad 6.