On 6/22/2012 4:22 PM, Dave M wrote:
Adrian C wrote:
On 22/06/2012 18:10, wrote:
Why do all the atomic clocks require batteries?

Makes no sence that I woul dbuy aclock to not have to reset
the time just so I can play with the batteries instead.

Anyone know of a simple analog atomic (naval time by radio) wall
clock that uses only 120v ac and no adaptor? (Online specs?) Much
obliged.

For flexibility of placement, quartz wall clocks have run on batteries
for many years. Having a visible power cable is ugly.

Radio controlled clocks have inherited this design requirement
unfortunately.

USB Power adaptors are pretty small, some not that larger than a plug.
Have a look at iPod or mobile phone accessories. If necessary adjust
the voltage downwards with a suitable series regulator. Single
transistor, resistor, capacitor and a zener should do it.

Another quite valid reason for "atomic" clocks being run from batteries is
that the clocks query the time sources for the exact time during the night,
when signal propagation is best. If the clock loses power during the day,
it needs to reset itself when power is restored, but probably won't be able
to receive a signal strong enough to be able to make a correction of the
time until late at night. Being on battery power solves this problem by
never having a loss of power except when the batteries finally die.

Well, that is true sometimes, but I have had good results replacing
the battery in the middle of the day. The clock normally resets just
fine.

I am very seldom up in the middle of the night to replace the battery.

Bill