[time-nuts] Re: Crazy Clock

[Neil Baylis]

Some time ago I bought a NOS slave clock on eBay for about $25. It runs on
110V 60 Hz. It has a solenoid to reset time to 12:00 and all the clocks in
a building lijj my e a school would get the reset pulse at the time.

Well being ham fisted, I broke or burned out the reset solenoid, so no way
to set the time any more.

But I love this clock! So, I built an inverter and used a microcontroller
to generate a precise 60 Hz sine wave. I’m running it at 90 VAC and it’s
dead quiet. The second hand has continues movement. I wrote the code to
allow running the clock at different frequencies to simply setting the
time. E.g., running it at 59 Hz makes it lose 1 second per minute.

I get the frequency from a GPSDO. Once I set the time, it never drifts.

I spent a bunch of time fretting about power loss, and how to automatically
adjust the time afterwards, but realized I actually didn’t care because the
process of setting the time by running the clock at the wrong speed was
kinda fun.

I can’t begin to tell you how much time I’ve spent staring at this thing
while listening to WWV on the phone, and tuning it so the new minute begins
when the second hand is in the center of the black dot at the 12 position
on the dial.

I do have lights that blink if it loses power, or loses the 10 MHz
reference so I know I need to set it.

I was careful to make a very clean inverter as I didn’t want any harmonics
causing vibration in the synchronous motor.

I can post pics, but it’s just an institutional wall clock like you used to
see in schools or railway stations.

Neil


On Wed, Dec 14, 2022 at 9:11 PM Bob Camp via time-nuts <
time-nuts at lists.febo.com> wrote:

> Hi
>
> I realize that this is a bit of an odd project, but this is Time Nuts …..
>
> I want a analog wall clock that reads out GPS time. As far as I can tell,
> nobody
> is crazy enough to make one and sell it in the open market. If indeed
> there is
> one out there, that would be great. This does not have to be a project.
>
> If it is a project, I’m lazy, I don’t want to set the thing and then count
> on it never
> missing a beat. I want a movement that has some form of feedback. The
> WWVB clocks have a movement like this. I could tear one apart and try to
> reverse engineer the guts. That sounds like. a project inside a project.
>
> Does anybody sell feedback movements like this in the hobby market? If so
> has
> anybody used one and can vouch for it working for more than a few months?
>
> Indeed, doing it with a display of some sort would be easier in some
> respects.
> For now at least, I’m looking for a mechanical gizmo with hands that move.
> If it reads out 12 hour time that’s ok. 24 hour time would be super cool,
> but
> it’s not vital.
>
> Anybody know of a source?
>
> Thanks!
>
> Bob
>
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