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piglet
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Mechanical clock hands, position set by pi or controller?

Mon Sep 09, 2019 2:09 pm

I'm sure such a thing exists, but I've not been able to find clock hands that can be positioned by pi or microcontroller.

I've seen plenty of analogue "radio controlled" clocks that set the clock hands based on time from the MSF signal...but have no idea how to find a set of clock hands I can control like that in something I can build myself.

Maybe I'm searching for the wrong thing.

Has anyone any idea how to find such a thing to buy as a module/component?

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Burngate
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Location: Berkshire UK Tralfamadore
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Re: Mechanical clock hands, position set by pi or controller?

Mon Sep 09, 2019 5:56 pm

I've got several of those MSF clocks around the house, and discovered they all have their own fixed error. The cause is my cack-handed positioning of the hands relative to the motor unit and the clock face. And, of course, the low level of the Anthorn signal this far from the civilized reaches of Cumbria.
But I think it would be possible to tear down the motor unit so there's only the bare motor, and drive that from the Pi.

They seem to have two motors, one driving the seconds hand and the other driving the minutes and hour hands, each providing a top-dead-centre signal. It can't be beyond the wit of man to drive each motor until TDC is found, then provide appropriate pulses to keep them syncronised with the Pi's time.

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rpdom
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Location: Chelmsford, Essex, UK

Re: Mechanical clock hands, position set by pi or controller?

Mon Sep 09, 2019 8:36 pm

I have a few different clocks like that.

I agree they seem to have two motors, one for the Seconds and one for the other two hands.

They seem to work differently for the calibration though. One of my clocks seems to be able to detect when the hour hand hits 12, 4 and 8, while the others only seem to detect 12. All seem to only detect the minute hand hitting 0.

One of my clocks got dropped and broke part of the plastic surround. I might think about taking that one apart to see how it works.

PhatFil
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Location: Oxford UK

Re: Mechanical clock hands, position set by pi or controller?

Mon Sep 09, 2019 9:28 pm

piglet wrote:
Mon Sep 09, 2019 2:09 pm
I'm sure such a thing exists, but I've not been able to find clock hands that can be positioned by pi or microcontroller.

I've seen plenty of analogue "radio controlled" clocks that set the clock hands based on time from the MSF signal...but have no idea how to find a set of clock hands I can control like that in something I can build myself.

Maybe I'm searching for the wrong thing.

Has anyone any idea how to find such a thing to buy as a module/component?
grab a cheap quartz clock movement and salvage its concentric drive shaft?

otherwise

eBay item number:202650393346
and
eBay item number:392334030486 1 x 2mm and 1 x 3mm

the 3mm tube will rotate freely within 2 x bearings and a lubed 2mm tube should rotate within 3mm tube, and a <1mm od pin should provide a base pivot point for the inner tube

drive both with elastic band drive belts perhaps?

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Imperf3kt
Posts: 2774
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Location: Australia

Re: Mechanical clock hands, position set by pi or controller?

Tue Sep 10, 2019 12:10 am

You could make it mechanical.
Drive the second hand with a motor at 1RPM and use some concentric gears to turn each other 6° (minute hand) and 30° (hour hand) after one full rotation.
55:55:44:44:4C
52:4C:52:42:41

hippy
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Location: UK

Re: Mechanical clock hands, position set by pi or controller?

Tue Sep 10, 2019 9:56 am

Some of those MSF / DCF controlled clocks have a separate radio decoder and clock handler. For those one can cut the connection and feed in an MSF / DCF compatible signal which will cause the clock to automatically match whatever time that signal indicates.

For those with an integrated radio decoder and clock one can fake a local MSF / DCF radio signal.

It will likely be necessary to remove the clock's receiving aerial and feed that radio signal in via appropriate coax attenuated to the low signal levels the receiver is expecting to avoid actually transmitting MSF / DCF which is likely illegal or against some regulation or other.

An actual transmitter with aerial does work so that may be appropriate if you can contain that in Faraday cage to comply with legislations and regulations.

The downside is that not all clocks track the transmitted timecode continuously, and it may be as little as once a day to conserve battery power. Those synchronise then run on local time.

Otherwise, strip the existing electronics out and just drive the existing hand motor(s) as suggested.

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