Your simplest solution(s):

1) Use only one clock.
2) Use both clocks and set the clocks to the same time.

 

Hello,

There are so called "radio controlled clocks" around:
https://www.canford.co.uk/CANFORD-RADIO-CONTROLLED-CLOCKS
https://www.ebay.com/itm/Jumbo-Larg...-Version-Large-3-27-inches-Time-/253949195711

Bertus

 

From where? I couldn't find any suitable.

They are also commonly called "atomic clocks" such as these.
I have one of each type at home and they are always within a second of each other.
(Watching one of the analog versions reset itself to the correct time is interesting to observe).
But I don't know if they work wherever you are (since you used the word analogue, I assume it's not the US).

 

Circuit (photos attached I hope)

Poorly focused pictures are never a substitute for a schematic.

For starters. We need to know what state the clocks power up in, whether they advance before time is set, how time is set, and how the displays are driven.

 

I designed a clock using a scrolling LED matrix (currently a single character). It runs from a Raspberry Pi or C.H.I.P. ARM based single board "computer". When they're booted, they check with a time server to correct the time and that time is used by the clock program.

 

How about a combined analog(ue)/digital clock, such as this.

 

OK, there is enough room in that enclosure to add a tuned amplifier to pick up the crystal oscillator frequency and drive a short coaxial cable to connect it to a simple receiver circuit in the second clock. That circuit would be a simple tuned circuit driving another IC to bring the signal amplitude up to a level that could replace the crystal in the oscillator portion of that second clock. That would assure that both were running at exactly the same frequency.
A suitable tuned amplifier circuit should be in the application notes of either Analog Devices or Linear Technology, two companies that produce suitable IC devices. The advantage of using circuits from the application notes is that they have already been optimized for those parts.

 

Thanks, Crutschow, best readymade so far but unfortunately: "Note: the LED display is design for time checking at night. The numbers will be invisible at daylight if you install the wall clock in a very bright room "
Here is, if I'm lucky, an in-focus photo of circuit board.

 

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.

That is an entirely different problem, and probably impossible with commercial products based on a microcontroller or ASIC clock chip.

Link to the clock vendor?

Why is there a USB port on the board? Is that accessible to the user?

ak

 

Hello,

It looks like there are more versions of the clock.
I see on the right upper part of the PCB places for parts.
Also there seems to be a printed antenna in that area.
The antenna could be for bluetooth or more likely wifi.
Maybe the RF is used to synchronize with a NTP server.
Now the clock has not that capability.

Bertus

 

Hello,

It looks like there are more versions of the clock.
I see on the right upper part of the PCB places for parts.
Also there seems to be a printed antenna in that area.
The antenna could be for bluetooth or more likely wifi.
Maybe the RF is used to synchronize with a NTP server.
Now the clock has not that capability.

Bertus

Indeed! Making the clocks run at the same speed is not that hard, making them adjust at the same time is a much bigger challenge. At that point I would suggest an analog clock with a very large dial, perhaps 12 to 18 inches, and a cutout for a digital display towards the center, either above or below, depending on the shape of the hands driving mechanism. But that is suddenly a much bigger project.
The simple way will be to do it all in software with a large screen monitor, which can be a cheaper low resolution kind. Then a simple clock program along with enough memory to recall a different hands position display for every minute. That avoids creating an analog hands algorithm and uses just a simple memory look up table. Possibly tedious but not hard. And setting would be only one clock to set, but two perfectly tracking displays. If you used PDFs of the hands then the program could even be done in BASIC, or possibly even in EXCEL.

 

Hi Reloadron,
From where? I couldn't find any suitable. Any information gratefully received.
Ta.

I started with a Google of "Synchronized Analog & Digital Clocks" which yielded a bunch of hits. Likely rearranging the wording would yield more results. Since I don't know your location hopefully Google can get you some local results.

The images are a little out of focus making it hard to see a crystal or what could be a crystal for the clock oscillator. Looks to have a micro-controller in there.

Ron

 

Hello,

@Reloadron , the processors seems to be an allwinner F1S100s.
https://search.yahoo.com/search?n=1...vf=all&vm=i&fl=0&fr=altavista&p="f1c100s"&vs=
The crystal on the board is 24 Mhz.

Bertus

 

Thanks, Crutschow, best readymade so far but unfortunately: "Note: the LED display is design for time checking at night. The numbers will be invisible at daylight if you install the wall clock in a very bright room "

There's an analog and digital "interface." Which one one is "LED?" From the pictures, it looks like both are LED or LCD. Is your current clock visible under conditions of the classroom and if so, which interface is it?

 

The onboard RTC is AnalogTek AT8563T which uses a standard 32768Hz xtal on pins 1 and 2.
No xtal is installed which leads one to assume that the clock signal is externally generated and applied to pin 1.