220V AC, 48V AC, 24V DC, 5V DC - seeking advice

I’m seeking your guidance on how to best manage my need for various power sources of different types.

I’m building a circuit that will act as a « mother-clock » for a relatively old « daughter-clock » (from 1952!) that operates by receiving specific impulses. You might have seen those at train stations for example (i.e. the clocks would be relatively « dumb » and be controlled by a central high-precision system).

The clock I’m working on right now requires:

  • 230V AC - this is to switch on the internal bulbs at night (note: this is in EU, so no conversion required here, this is the main voltage)
  • 48V AC @ 50Hz - synchronous motor, needs to be constantly on (note: this is in EU, so the main frequency is already at 50Hz, no conversion required here)
  • 24V DC - used to generate impulses every minute (either 24V or -24V, in alternance)

And, on top of that, I also need to power my Arduino, which, depending on the device/input I pick could be anywhere between 3.3V and, say, 12V DC.

So, I should ignore the 230V bit I suspect as I might want to control it through other means and not mix high-voltage with the rest. Correct?

But then, I’d like to avoid if possible to have 3 different transformers to generate my 48V-AC/24V-DC/12V-DC, especially as I’d really like to have my system i) take relatively little space (and. 3 transformers all hooked into 230V won’t help) and ii) ideally, minimize the cabling going into my system (this is for aesthetic considerations given where I might put the system).

What’s your advice on this? How would you go at it?

Thanks for your lights!

I will answer a bit, as I was in high school in 1952 and the school had such a system with "daughter" clocks in each classroom. You are MISSING a very important piece. That is how to synchronize the actual clock displays. I can recall seeing all the daughter clocks resetting them selves to 12:00 and then rapidly clicking to match the master clock setting.
How will your clocks be able to do the similar synchronization?
The various AC voltages require transformers to provide that power.
I guess you have not looked very long for powering your clocks and Arduino.

I would generate the 24VDC then add a buck converter to drop it to maybe 8 volts and then power the arduino via Vin. This allows you to use the additional filtering on the Arduino. As Paul_KD7HB indicates you will also need to send a sync signal, it use to be a third wire that you would send a string of pulses and then the clock reached the hour it would not accept pulses from that line but receive them until 11:59. This allowed the clock to catch up but got interesting when it was ahead.

Hello Paul,

the clock I'm working on doesn't have such sophisticated behavior :slight_smile: It can only move forward and the sender has no way to know what the current time displayed on the clock is. As such, the role of the master clock is only to send the right minute "drum-beat". If any issue happens locally (which should never happen unless disconnected/unwired), then a local operation is required on the clock itself. Happy to provide more information if you are curious, but the clock is a Moser Baer that you would find in all Swiss railway stations, with the running second stopping at position "59" (doing the full circle in 58.5 seconds). A small article here (swap to see more pictures, the default one at the top of the article only shows simpler clocks that doesn't show the seconds). Time flies: iconic Swiss railway clock turns 75 - SWI swissinfo.ch

I've already built the electronic for a simpler but similar watch from FAVAG, which also eventually got acquired by the same company that owns both brand (Mobatime). For that first project, I didn't have to play ith that many voltage types though, hence my question on this forum :slight_smile:

The code I wrote for that first watch was simple enough, with the exception of handling DST (by "not" sending the signals for 60 minutes at the right time, and sending 60 fake signals when DST is over)


Thank you Gilshultz,

I looked into your solution. So, you would not start from a 48v AC, but solely from 24V DC and provide the 48v AC through a different system, right?

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That appears to me to be the most cost effective. You stated you need the 48V AC for the motor and it would be more reliable in my mind to leave the 24V DC on instead of cycling the power supply. Buck converters for 24VDC are inexpensive, much above 30 they get more expensive and with the 48VAC you would need to convert it down and 48V stuff is not as common as 12 and 24.

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You are welcome, that is what we're here for and it is great when somebody lets us know we did good!

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