Anyway, i thought of making the wall clock modules get the time from an ntp server, but then again i realized this is of much of a work, since to have to deal with a connection from digital world to an analog mechanism. I quickly gave up on this idea since i couldn't find any ready made mechanisms on that.And also using ethernet or any other cables on those will require too much work on walls, since these clocks are hang in the middle of the wall. I completely needed a wireless solution. Then i found out ready made DCF77 wall clock modules on AliExpress, which are about 15 USD each. That's my kinda modules, i love cheap electronics...
DCF77 is an atomic clock transmit tower which is based in Germany; It send clock signals to all over Europe with a roughly 2000km coverage area. Once the DCF77 modules get the signal, they automatically sets themselves to the correct time. OK my home is a little bit of about ~2000km away, i was wondering if i really get the signal. Especially during night time, the signals get a little stronger just because of some wavelength atmospheric something something..
OK the module look like this:
The width is the same with any standard quartz wall clock module, the height is just a little bit higher about 5 mm.
I simply take away the parts of the clocks, take the quartz modules out and put the DCF77 ones in. Perfect fit for all 3 of them. The clock hands are not easy to fit, some of them wide, some of them narrow, what a crazy thing, the module sizes are standard but not the clock hands hole diameters! Luckily, the company sent me some ugly looking clock hands for a perfect fit on these modules:
Then i screwed back the last bits, throw away the extra thingies (Event for a simple wall clock, i had too many extra thingies which i don't remember where i took it out from, anyway it looks like they're gonna work without these pieces). Hanged the clocks back to the walls, and wait for the signal.
After 2 nights which i do not get any signal, i started to look for a solution. Since the clocks are showing now some unrelated time (wife started complaining, time to take some urgent action...), i decided to make my own DCF77 transmitter. The amplitude of the sigals are very important, since if you make a powerful transmitter, which is forbidden for almost all governments, you could meet your friendly neighbourhood policemen.
As an urgent solution, i realized an application on IOS, called Clock Wave, which supposedly sets the time on DCF77 clocks with the sound it produces. You have to volume up your iphone to 100% and put it very close to the DCF77 module.
I tried it, and by the second try voila! The wife complaining situation is handled with success.
Now for the second part, i have to make a transmitter which transmits the signal 7/24, since the module updates its value from the signals every hour. And the power should be greater than a few centimeters, but small enough to stay in my house premises.
For that i'm going to try to implement the transmitter server on a raspberry, it could be the very same rpi that domoticz is installed. There's a transmitter project for rpi on https://github.com/F5OEO/rpitx which uses a wire on GPIO18 as an antenna. There's already a python script SetTime.py for that purpose. I'll let you know about the result.