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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