In the U.S. the power grid is very accurate over long periods of
time. But what are the odds of running six months without a single
power interruption?

Christopher Tidy wrote:
Hi all,

I'm thinking of building an electronic clock control circuit which uses
the 50 Hz mains frequency for time keeping. The reason for this is that
the clock dial is rather large, so probably wouldn't run for long on
battery power, and I don't fancy spending £40 buying a programmable
quartz oscillator chip.
....

From my point of view I'd regard an acceptable error as 5 minutes every
6 months. Does anyone know the typical time error seen on the UK grid,
or where I might find this information? Any suggestions would be much
appreciated.

It really depends where you are - if you are in a rural area with above
ground lines and lots of ice storms, hurricanes, etc. then not too good. In
an urban area with buried lines, power may go uninterrupted for years at a
time.

If it's critical that the clock not stop you can put it on a UPS battery
backup.



"Mike Berger" wrote in message
...
In the U.S. the power grid is very accurate over long periods of
time. But what are the odds of running six months without a single
power interruption?

Christopher Tidy wrote:
Hi all,

I'm thinking of building an electronic clock control circuit which uses
the 50 Hz mains frequency for time keeping. The reason for this is that
the clock dial is rather large, so probably wouldn't run for long on
battery power, and I don't fancy spending £40 buying a programmable
quartz oscillator chip.
...

From my point of view I'd regard an acceptable error as 5 minutes every
6 months. Does anyone know the typical time error seen on the UK grid, or
where I might find this information? Any suggestions would be much
appreciated.

Jack Denver wrote:
It really depends where you are - if you are in a rural area with above
ground lines and lots of ice storms, hurricanes, etc. then not too good. In
an urban area with buried lines, power may go uninterrupted for years at a
time.

If it's critical that the clock not stop you can put it on a UPS battery
backup.

Interesting thought. Would the clock then be driven by the
line frequency or the oscillator frequency of the UPS?

Mark

The latter during power cuts, the former the rest of the time, the way most
UPS's are designed.


"Mark and Gloria Hagwood" wrote in message
news:fLT%f.41355$bm6.26995@fed1read04...

Interesting thought. Would the clock then be driven by the line frequency
or the oscillator frequency of the UPS?

Mark

Jack Denver schrieb:

If it's critical that the clock not stop you can put it on a UPS battery
backup.

Great idea! In order to save the odd $40 for a quartz oscillator (read
the OP!), you spend at least $100 on a UPS device. :-)

SCNR and best regards,
OP

Mike Berger wrote:
In the U.S. the power grid is very accurate over long periods of
time. But what are the odds of running six months without a single
power interruption?



Depends where you are, I used to have outages a couple times a year, now
the house I'm in I've had exactly one outage in almost 2 years and it
was a pretty good storm that went through.

Aside from that though in both the US and UK the mains frequency has
excellent long term stability. It may gain or lose a few seconds over
the course of the day but it will be dead on over weeks/months.