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Continuous sweep quartz movements


John Haine
 

A bit off topic, but please could anyone link me to a decent explanation of how these quartz clock movements with continuous sweep seconds work? I assume that they have some sort of stepper motor with more steps per rev than the standard ones but I haven’t been able to find any information via Google that isn’t trivial.


Simon Taylor
 

The one I had in the late nineties had a gear wheel with loads of angled projections on and this was driven by a tiny tuning fork attached to a coil. From memory the fork vibrated and these vibrations knocked on the gear wheel one 'angled slot' at a time, so fast that smooth rotation was obtained. They were hungry though as I never saw one with anything smaller than a C or D battery.
--
Simon GPO Clocks

http://www.lightstraw.uk/gpo/clocksystems/index.html


Bepi
 

Wouldn't microstepping be enough?

On Dec 20, 2020, at 11:02, John Haine <john.haine@...> wrote:

A bit off topic, but please could anyone link me to a decent explanation of how these quartz clock movements with continuous sweep seconds work? I assume that they have some sort of stepper motor with more steps per rev than the standard ones but I haven’t been able to find any information via Google that isn’t trivial.


--
Bepi


Philip Gladstone
 

I have one of those movements and it is actually a stepper just like the ordinary quartz movement but it has 8 times as many steps. You can drive it in the same way as you drive the regular quartz movements....


On Sun, Dec 20, 2020 at 6:53 AM Bepi <pepicima@...> wrote:
Wouldn't microstepping be enough?

On Dec 20, 2020, at 11:02, John Haine <john.haine@...> wrote:

A bit off topic, but please could anyone link me to a decent explanation of how these quartz clock movements with continuous sweep seconds work? I assume that they have some sort of stepper motor with more steps per rev than the standard ones but I haven’t been able to find any information via Google that isn’t trivial.


--
Bepi


John Haine
 

Aha!  Thanks for that, I thought it would have to be a stepper o0f some sort, obviously a more advanced version of the Lavet style motor.

Bepi, sorry my question wasn't clear, I meant the type of steppers used in quartz clocks, which are very simple and have only 2 steps per rev.  They have only one winding which has to be impulsed in opposite directions for each step.  But of course you need a 120:1 reduction to the seconds hand.


Tom Van Baak
 

John,

I was curious about that too so I bought a Seiko sweep second hand wall clock. I much prefer it to the traditional once-a-second ticking style. It's also very quiet so it's a delight to both the ears and the eyes.

From the rear it looks like a typical Lavet movement but one or two of the gears move much faster, acting more like a motor than a stepper. There is also no mechanical chatter in the second hand. I suspect the inertia of the hands or the shape of the magnetic impulse or some time constant are all carefully matched to prevent the backlash seen in wall clocks with 1 Hz ticking hands.

I made some non-destructive, non-contact magnetic sensor measurements. It's not quite as simple as you might suspect. A vintage stepper looks like this:

http://leapsecond.com/pages/32kHz/

But this continuous sweep stepper appears to have 40 pulses per second, in a pattern of 5 per 1/8th second. I put some plots for you here:

http://leapsecond.com/pages/sweep/

High-speed picPET timing data from the magnetic sensor confirms 40 distinct pulses per second with various quantized pulse widths and pulse periods, as clearly seen in the 'scope traces.

There are several ways you could drive one of these movements from a Synchronome.

/tvb

On 12/20/2020 2:02 AM, John Haine wrote:
A bit off topic, but please could anyone link me to a decent explanation of how these quartz clock movements with continuous sweep seconds work? I assume that they have some sort of stepper motor with more steps per rev than the standard ones but I haven’t been able to find any information via Google that isn’t trivial.


Chris
 

Every time I hear about quartz clocks I think of the pair of 60mm, cube-format, "Rhythm" alarm clocks we bought probably in the early 1970s.
They have run without a moment's hesitation, except for rare AA battery changes, ever since. They have "dead beat" seconds hands.
I never thought to check their accuracy but they certainly don't drift enough to notice. So much for the "humble" quartz movement.
Just imagine how many mechanical alarm clocks have become "landfill" in the last 50 years. The "Rhythm" name lives on.

Chris.B

On 20/12/2020 19:11, Tom Van Baak wrote:
John,

I was curious about that too so I bought a Seiko sweep second hand wall clock. I much prefer it to the traditional once-a-second ticking style. It's also very quiet so it's a delight to both the ears and the eyes.

From the rear it looks like a typical Lavet movement but one or two of the gears move much faster, acting more like a motor than a stepper. There is also no mechanical chatter in the second hand. I suspect the inertia of the hands or the shape of the magnetic impulse or some time constant are all carefully matched to prevent the backlash seen in wall clocks with 1 Hz ticking hands.

I made some non-destructive, non-contact magnetic sensor measurements. It's not quite as simple as you might suspect. A vintage stepper looks like this:

http://leapsecond.com/pages/32kHz/

But this continuous sweep stepper appears to have 40 pulses per second, in a pattern of 5 per 1/8th second. I put some plots for you here:

http://leapsecond.com/pages/sweep/

High-speed picPET timing data from the magnetic sensor confirms 40 distinct pulses per second with various quantized pulse widths and pulse periods, as clearly seen in the 'scope traces.

There are several ways you could drive one of these movements from a Synchronome.

/tvb


On 12/20/2020 2:02 AM, John Haine wrote:
A bit off topic, but please could anyone link me to a decent explanation of how these quartz clock movements with continuous sweep seconds work? I assume that they have some sort of stepper motor with more steps per rev than the standard ones but I haven’t been able to find any information via Google that isn’t trivial.




Brooke Clarke
 

Hi Don:

This might help:
https://prc68.com/I/QuartzClk.shtml
includes links to a number of patents.

--
Have Fun,

Brooke Clarke
https://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.


John Haine
 

Thanks for this information Brook.  At least one of those patents, '279a, seems to describe something like this though whether it is the original patent or an improvement I haven't worked out yet.  Interestingly, it looks like the motor configuration is the standard "Lavet style" as used in normal quartz clocks and the subtlety is in the way the drive pulses are generated and applied.  So it may be possible to drive an ordinary movement to produce continuous sweep.  Tom, can you see the motor stator assembly, does it look conventional?  I guess it might have a conventional stator but a rotor with more poles.


Bryan Mumford
 

My sweep quartz clock seems to have a different frequency. I measured the current pulse through a shunt resistor in the power line. There is jitter in the period.

- Bryan




On Dec 20, 2020, at 10:11 AM, Tom Van Baak <tvb@...> wrote:

John,

I was curious about that too so I bought a Seiko sweep second hand wall clock. I much prefer it to the traditional once-a-second ticking style. It's also very quiet so it's a delight to both the ears and the eyes.

From the rear it looks like a typical Lavet movement but one or two of the gears move much faster, acting more like a motor than a stepper. There is also no mechanical chatter in the second hand. I suspect the inertia of the hands or the shape of the magnetic impulse or some time constant are all carefully matched to prevent the backlash seen in wall clocks with 1 Hz ticking hands.

I made some non-destructive, non-contact magnetic sensor measurements. It's not quite as simple as you might suspect. A vintage stepper looks like this:

http://leapsecond.com/pages/32kHz/

But this continuous sweep stepper appears to have 40 pulses per second, in a pattern of 5 per 1/8th second. I put some plots for you here:

http://leapsecond.com/pages/sweep/

High-speed picPET timing data from the magnetic sensor confirms 40 distinct pulses per second with various quantized pulse widths and pulse periods, as clearly seen in the 'scope traces.

There are several ways you could drive one of these movements from a Synchronome.

/tvb


On 12/20/2020 2:02 AM, John Haine wrote:
A bit off topic, but please could anyone link me to a decent explanation of how these quartz clock movements with continuous sweep seconds work? I assume that they have some sort of stepper motor with more steps per rev than the standard ones but I haven’t been able to find any information via Google that isn’t trivial.