[RndTbl] transistor wall-clock

[Hartmut W Sager]

> When the A/C grid is heavily loaded the generators slow below 60Hz.
The[y] make up for it in later by generating higher than 60Hz. That's why
the old A/C clocks with synchronous motors never need correction over long
periods of time.

Yes, Daryl beat me to the answer.  This was true back in the 1960's and
into the 1970's, when Manitoba and Winnipeg Hydro went to these lengths to
keep people's synchronous motor clocks running extremely accurately for a
long time (sometimes well over a year with barely a one second deviation),
and usually a power outage would be the limiting factor.  However, I've
noticed in the last 1-2 decades that this no longer seems to be the case,
probably for lack of need.  AC synchronous digital clocks I've observed
(like on kitchen stoves) don't do that "catch-up/catch-down" any more.

> Most cheap digital clocks haven't had the oscillator regulated so their
time creeps off.

Yes, that is (or at least was) one of the benefits of a multi-$100 watch.
A $300 Seiko watch I bought around 1981-1982 was guaranteed to deviate no
more than 3 seconds per month, and my actual sample was within 2 seconds
per month!
​ ​
Hartmut W Sager - Tel +1-204-339-8331, +1-204-515-1701, +1-204-515-1700,
+1-810-471-4600, +1-909-361-6005


On 17 October 2015 at 23:02, Daryl F <wyatt at prairieturtle.ca> wrote:

> On October 17, 2015 6:09:21 PM CDT, Tim Lavoie <tim at fractaldragon.net>
> wrote:
>>
>> The AC frequency as a clock source will also be a problem of the utility happens to mess with that timing. Forget why the do, but it happens.
>>
>>  On Oct 17, 2015, at 14:36, Trevor Cordes <trevor at tecnopolis.ca> wrote:
>>>
>>>  Off-topic, but cool:
>>>
>>>  http://www.transistorclock.com/?imm_mid=0da80b&cmp=em-prog-na-na-newsltr_20151017
>>>
>>>  A guy selling kits to make a all-parts-exposed digital wall clock that
>>>  uses *no ICs* and *no crystals*.  You build it yourself, 1250 parts to
>>>  solder onto a custom board.  Too pricey for me, otherwise I'd love to put
>>>  one together.
>>>
>>>  ICYW, I dug around the FAQ and he is cheating a bit: he's using the 60Hz
>>>  of the AC as a timer source.
>>>
>>>  Hmm, since it plus into AC, does that mean touching some parts of the
>>>  exposed circuits might give you a nice zap?
>>> ------------------------------
>>>
>>>  Roundtable mailing list
>>>  Roundtable at muug.mb.ca
>>>  http://www.muug.mb.ca/mailman/listinfo/roundtable
>>>
>>>
>> ------------------------------
>>
>> Roundtable mailing list
>> Roundtable at muug.mb.ca
>> http://www.muug.mb.ca/mailman/listinfo/roundtable
>>
>>
> When the A/C grid is heavily loaded the generators slow below 60Hz.
>
> The make up for it in later by generating higher than 60Hz. That's why the
> old A/C clocks with synchronous motors never need correction over long
> periods of time.
>
> Most cheap digital clocks haven't had the oscillator regulated so their
> time creeps off.
>
> NTP fan, Daryl
> --
> Daryl F
>
> _______________________________________________
> Roundtable mailing list
> Roundtable at muug.mb.ca
> http://www.muug.mb.ca/mailman/listinfo/roundtable
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.muug.mb.ca/pipermail/roundtable/attachments/20151018/b30aee4f/attachment-0001.html>