Connect and synchonise two digital clocks

Thread Starter

PhysicsChris

Joined Dec 6, 2019
8
Good evening all, I have bought two digital dayclocks, which have the facility to have the time displayed either digitally or analoguely (yes, I know...). I would like to connect them so they are synchronised, with one showing the digital time the other showing the analogue time. What is the easiest way to do this ? Can I just remove the 24.000 crystal oscillator from one circuit board and wire in the output from the other, ie run both circuits in parallel off one crystal? (a) will it work? (b) will it keep the clocks in sync? Or is there another (easier?) way?
Many thanks, in semi-ignorance, Chris
PS ("semi", as in about 98%)
 

dl324

Joined Mar 30, 2015
9,332
Welcome to AAC!

Without having schematic, it's impossible to determine whether what you want is possible. It's most likely that you won't be able to synchronize them.

How far away are the clocks? What is your preferred synchronization method?
 

AlbertHall

Joined Jun 4, 2014
8,818
I think you would need to remove both crystals and use one of them in a separate oscillator and feed the output of that to both clocks.
Probably...

[EDIT] What IC does the clock use?
 

Thread Starter

PhysicsChris

Joined Dec 6, 2019
8
The two clocks will be wall-mounted, right next to each other, probably both fixed to a single piece of wood. Am currently studying circuit board with magnifying glass trying to read faint chip numbers...
Sorry, I don't understand your question about synchronisation method (my fault, not yours) . The clocks are required for an examination room; I just want them to show the same time. (Some students complain they cannot read the time from an analogue clock...). And when I reset the time on one clock ( I assume it will slowly drift from the real time) I want the other to reset to the same time. Chip numbers to follow later. Thanks for your interest and help.
 

MisterBill2

Joined Jan 23, 2018
4,564
Why do you need to synchronize an analog dial with a digital display that precisely? And how can you read an analog display that precisely? If either clock drifts from actual time then it is scrap, and should be replaced.
 

Thread Starter

PhysicsChris

Joined Dec 6, 2019
8
The analogue display shows a sweep second hand. Both clocks need to show the exactly the same time so that the students don't complain that they were stopped 12 seconds early etc etc
 

jpanhalt

Joined Jan 18, 2008
8,344
The two clocks will be wall-mounted, right next to each other, probably both fixed to a single piece of wood. Am currently studying circuit board with magnifying glass trying to read faint chip numbers...
Sorry, I don't understand your question about synchronisation method (my fault, not yours) . The clocks are required for an examination room; I just want them to show the same time. (Some students complain they cannot read the time from an analogue clock...). And when I reset the time on one clock ( I assume it will slowly drift from the real time) I want the other to reset to the same time. Chip numbers to follow later. Thanks for your interest and help.
Oh come on. If your students can't read an analog clock, you need new students. Synchronized school analog clocks date way back to before 1948 for sure.
 

Thread Starter

PhysicsChris

Joined Dec 6, 2019
8
Students live by their mobile phones; many don't possess a watch. Maybe it is a special needs student who requested the digital clock. I don't judge, just try to help.
Last month, a head teachers’ union has said that schools are removing analogue clocks from examination halls because teenagers are unable to tell the time.
Teachers are now installing digital devices after pupils sitting their GCSE and A-level exams complained that they were struggling to read the correct time on an analogue clock. Malcolm Trobe, deputy general secretary at the Association of School and College Leaders (ASCL), said youngsters have become accustomed to using digital devices.
“The current generation aren’t as good at reading the traditional clock face as older generations,” he said. “They are used to seeing a digital representation of time on their phone, on their computer. Nearly everything they’ve got is digital so youngsters are just exposed to time being given digitally everywhere.”
 

jpanhalt

Joined Jan 18, 2008
8,344
So, if the students can't read an analog clock, will they be prepared to drive a car with an analog speedometer?

Just install a digital clock and define "zero time" as when the clock is started and end time whatever you say. No need to synchronize. If you really think about it, no two clocks can ever be perfectly synchronized. Tell the students that the "official time" is the time shown on your clock and nothing else.
 

Thread Starter

PhysicsChris

Joined Dec 6, 2019
8
But some students want an analogue clock: we need both on display. Some students will grow up and buy a car with an analogue speedo, some will buy a car with a digital speedo...
 

dl324

Joined Mar 30, 2015
9,332
But some students want an analogue clock: we need both on display. Some students will grow up and buy a car with an analogue speedo, some will buy a car with a digital speedo...
We still have no idea what we have to work with.

When the clocks are first powered, do they come up at the same time? Do the clocks advance before the correct time is set?

My inclination would be to use the time setting mechanism from one to set the time for both.

Why can't you simply use a digital clock? People who can read an analog clock should be able to read a digital clock.

I can't believe intelligent people can't or won't learn to read an analog clock. It's just not that difficult. Stubborn??
 

BobaMosfet

Joined Jul 1, 2009
892
Students live by their mobile phones; many don't possess a watch. Maybe it is a special needs student who requested the digital clock. I don't judge, just try to help.
Last month, a head teachers’ union has said that schools are removing analogue clocks from examination halls because teenagers are unable to tell the time.
Teachers are now installing digital devices after pupils sitting their GCSE and A-level exams complained that they were struggling to read the correct time on an analogue clock. Malcolm Trobe, deputy general secretary at the Association of School and College Leaders (ASCL), said youngsters have become accustomed to using digital devices.
“The current generation aren’t as good at reading the traditional clock face as older generations,” he said. “They are used to seeing a digital representation of time on their phone, on their computer. Nearly everything they’ve got is digital so youngsters are just exposed to time being given digitally everywhere.”
Stop pandering to children. You provide a clock, they need simply as a matter of being able to function, to learn to read it, just as their parents did, and their grand parents, and everyone before them. It is *NOT* difficult to read analog .v. digital. If you are forced to use one, use digital and tell the analog folks to figure it out. If they can't, drop them from the class.

Pandering to such nonsense only encourages it.

Now, having said that, if you insist on pursuing this madness, you gotta give us some information about each of your clocks- brand, model, make, so we can look at them....
 

Reloadron

Joined Jan 15, 2015
4,725
The problem here is you already have the clocks. Synchronized Analog & Digital Clocks can be purchased including clocks which periodically synchronize to NIST time signals removing any argument as to what time it is. I have two grandchildren age 16 and both can read an analog or digital clock just fine and shame on their parents if they lacked that ability. The large manufacturing facility I retired from had synchronized clocks which displayed NIST time in digital format and that time was the rime our bargaining unit employees were expected to go by.

andering to such nonsense only encourages it.
That is my thinking. You are the authority and you define what time it is.

Anyway, short of actually seeing schematics of what you have there is no simple answer to your question.

Ron
 

MisterBill2

Joined Jan 23, 2018
4,564
Students live by their mobile phones; many don't possess a watch. Maybe it is a special needs student who requested the digital clock. I don't judge, just try to help.
Last month, a head teachers’ union has said that schools are removing analogue clocks from examination halls because teenagers are unable to tell the time.
Teachers are now installing digital devices after pupils sitting their GCSE and A-level exams complained that they were struggling to read the correct time on an analogue clock. Malcolm Trobe, deputy general secretary at the Association of School and College Leaders (ASCL), said youngsters have become accustomed to using digital devices.
“The current generation aren’t as good at reading the traditional clock face as older generations,” he said. “They are used to seeing a digital representation of time on their phone, on their computer. Nearly everything they’ve got is digital so youngsters are just exposed to time being given digitally everywhere.”
No student should be looking at a phone during an exam because that is an easy way to be cheating. No room for arguments there. All phones should be switched off and put in their backpacks or briefcases.

As for large digital clocks losing or gaining time, it is possible to adjust most of them, but worst case you would need to adjust a minute or so each day, if you had a really poor quality clock. An average digital clock should be correct within a minute per month. How big are the displays on the clocks that you have? Digit height, and dial diameter?

The real solution is to provide a count-down clock that shows the testing time remaining, since those being tested do not need any other time information until they have completed the test. That could solve the problem completely.
But if both clocks use the same 24 Mhz crystal, then it should be possible to pick up the signal from one clock and amplify it enough to drive the crystal oscillator of the other clock to synchronize them.

And as a personal prejudice, I would not hire any individual who was not smart enough to figure out how to read an analog clock.
 

Dodgydave

Joined Jun 22, 2012
8,592
Good evening all, I have bought two digital dayclocks, which have the facility to have the time displayed either digitally or analoguely (yes, I know...). I would like to connect them so they are synchronised, with one showing the digital time the other showing the analogue time. What is the easiest way to do this ? Can I just remove the 24.000 crystal oscillator from one circuit board and wire in the output from the other, ie run both circuits in parallel off one crystal? (a) will it work? (b) will it keep the clocks in sync? Or is there another (easier?) way?
Many thanks, in semi-ignorance, Chris
PS ("semi", as in about 98%)
You should be able to disconnect one of the oscillators and buffer the output to feed the other clock for timing, most clock xtal oscillators have two pins and use two capacitors to gnd,.

Ideally see if you can get the number of the chip and look for the datasheet of it..
 

MisterBill2

Joined Jan 23, 2018
4,564
My cheap electronic clocks all seem to be within a few seconds of WWV and each other for weeks after setting them. So now I suggest first checking them against each other before starting any modifications. You may not have any need to change anything.
 

Thread Starter

PhysicsChris

Joined Dec 6, 2019
8
Circuit (photos attached I hope) contains: AT8563T (real time clock?), 24.000 (crystal oscillator?), F1C100S (audio/video playback chip?), W25Q32JVSIQ (serial flash memory?), AMS1117 (voltage regulator?), LTK8002D (audio amp?), SS14 Schottky rectifier?), G1908 190926 (no idea), 1AM transistor, 4XTK (no idea), KDCAM (no idea), KFCAM (no idea).
From Amazon reviews, some tend to drift quite a bit from correct time, so the chances of my two clocks staying in sync is small.
If people could stop commenting about students and offer some electronics advice, that would be appreciated.
IMG_20191207_150519.jpg
IMG_20191207_150532.jpg


Moderators note : removed double images
 

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