[time-nuts] Mains Frequency

[Tim Shoppa]

The classic 70's LED clock used a 60Hz mains transformer and yes it was
easy enough to for the solid state electronics count pulses derived from
the low voltage secondary winding of the mains transformer. If your
appliances are from the 70's or 80's yes it is very likely the LED clock is
counting AC line frequency.

A vanishing small amount of consumer electronics in the past 10+ years uses
a mains transformer.. They will all be switching power supplies. This is
not just for cost savings, but to meet energy efficiency standards.

It is possible to get line frequency output from a switching power supply.
>From 1970-1990's it was fairly common for minicomputer switching supplies
to have a line clock output but I haven't seen this as part of the power
supply in industrial equipment for decades, and never in consumer equipment
switching supplies.

Tim N3QE

On Fri, Feb 12, 2021 at 11:29 AM Thomas D. Erb <tde at electrictime.com> 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.
>
> Thomas D. Erb
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