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If your school, or kids school, or other location relies on a central master clock that is broken, you may have a use for this device. New master clocks are available of course, but school budgets are under extreme pressures, and it really is a satisfying project if you have the necessary skills.
This master clock controls the signals sent to the slave clocks, and keeps them synchronized. The firmware in the clock currently supports the National Time synchronization protocol. The master clock also controls the bells that can be set at scheduled times during the day. The firmware in the clock currently supports two bell zones (indoor and outdoor bells).
The firmware in the clock also automatically adjusts to daylight savings time (this can be turned off). This library might also be useful for other clock-projects (make sure to also get the modified DateTime library).
The clock is set up by connecting it to a computer via the Arduino USB port, and running a Java control program with a GUI interface. Once the time has been set, and a bell schedule loaded, the computer can be disconnected.
The design of the clock emphasizes simplicity, with a minimum of controls. Any complex setup is better handled by running the control program on a computer and temporarily connecting to the clock. The picture shows the front panel of the clock. The switch allows bells to be turned off completely if bells are not wanted (holidays, teacher training days etc.) The LEDs are normally all green, anything else indicates an unusual state.
This master clock controls the signals sent to the slave clocks, and keeps them synchronized. The firmware in the clock currently supports the National Time synchronization protocol. The master clock also controls the bells that can be set at scheduled times during the day. The firmware in the clock currently supports two bell zones (indoor and outdoor bells).
The firmware in the clock also automatically adjusts to daylight savings time (this can be turned off). This library might also be useful for other clock-projects (make sure to also get the modified DateTime library).
The clock is set up by connecting it to a computer via the Arduino USB port, and running a Java control program with a GUI interface. Once the time has been set, and a bell schedule loaded, the computer can be disconnected.
The design of the clock emphasizes simplicity, with a minimum of controls. Any complex setup is better handled by running the control program on a computer and temporarily connecting to the clock. The picture shows the front panel of the clock. The switch allows bells to be turned off completely if bells are not wanted (holidays, teacher training days etc.) The LEDs are normally all green, anything else indicates an unusual state.
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Signing UpStep 1Find out about the master clock you are replacing
The master clock that was replaced by this project was a "Rauland 2490 Master Clock". It had stopped working during a storm with heavy lightning. The slave clocks were moving very quickly (continuous synchronization signal), and the master clock was subsequently shut off.
Thus the clocks in the school all showed about the same time, but all wrong, and always wrong. This proves that the expression "even a broken clock is right two times a day" is false.
You will need to know:
* what protocol is used by the slave clocks (can probably guess based on the make of the clocks)
* how many zones are used for bells (indoor, outdoor, different buildings etc)
Your school (or other location) may even have documentation in the form of wiring diagrams. These can be very helpful when installing the new clock.
Thus the clocks in the school all showed about the same time, but all wrong, and always wrong. This proves that the expression "even a broken clock is right two times a day" is false.
You will need to know:
* what protocol is used by the slave clocks (can probably guess based on the make of the clocks)
* how many zones are used for bells (indoor, outdoor, different buildings etc)
Your school (or other location) may even have documentation in the form of wiring diagrams. These can be very helpful when installing the new clock.
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Just a quick note to say that this is an awesome project.
Cheers!
Zak
How do I download the schematics?
thanks.
(1) You only stop the clock 2 minutes before the hour, and then apply the correction signal on the hour. You could only stop/start once per hour though.
(2) If you used a higher frequency (120Hz) the clock would run twice as fast, maybe that could be useful?
It would be so much simpler with a digital clock!
Perhaps taking an analog clock apart could help, I don't know exactly how they work.
Also, there are other slave clock protocols. Some advance only when sent a signal by the master clock. I think these are referred to as "impulse" control. I don't think they have second hands though. Maybe driving the second and minute hands separately somehow can achieve what you need.
Sorry I don't have a clear answer. I'll think some more and try to come up with something!
I could go with option 1 then.
How does the master clock know the position of the hands on the slave clock?
Thanks for replying so quickly.
So if the slave clock is slow, it will be corrected. If it is a little fast, nothing happens (I think), if it is very fast (or ahead), it will be an hour ahead after the sync. Hence the 12 hour sync, when everything will be 6 (pm or am looks the same).
There are some different protocols. "My" clocks use the National, or Standard Time protocol. There are some other similar, but slightly different ones.
For you, it would be a simple matter to cut the power for two minutes, and the clock hands would not move (not the second hand either). Turn on the power and it moves normally, except that it is 2 minutes behind. Apply the sync signal (for 25 seconds in my case) and the clock hands move fast to the next hour.
I hope this helps
On a radio controlled clock mechanism, when the battery is inserted, the clock turns to 12. It then stops and waits for the correct signal. If the signal is recieved, the clock turns to the correct time. If the signal is not recieved, the clock starts operating as a quarts mechanism from 12.
Do you know is there any way we could make the clock work as a quarts movement without waiting for the signal?
Thanks Niamh
Maybe if you take one apart it would be clearer.
Regular quartz clocks can be manipulated. They have a simple
motor that takes (~1.5V) pulses of alternating polarity, one short
pulse per second. If you generate these pulses (say with an Arduino)
they can be slower or faster in any way you wish. If you stop the pulses,
the clock will stop. If you send 10 pulses every second, the clock will
move 10x as fast, the second hand moving around the dial in 6 seconds!
It is tricky and unreliable to make it go backwards, as the direction is
designed into the metal parts of the motor (people make clocks that go backwards by flipping this piece of metal).
Anyway, If you use this idea, the clock (especially the second hand)
will move quickly as you "catch up" to real time. Using electronics
to generate the pulses allows for a lot of flexibility.
Let me know if I need to explain more.
Good luck!
Cool project ,are you like a Principal or teacher?
And yes, you can use the code for an alarm clock or any kind of timer.
The shift from daylight savings and back again has worked beautifully.
Just change the name of the file you download to what it is supposed
to be, and it should work. Let me know if there is a problem. It should
definitely work on Mac OS X (it may not find the right port on Windows).
I'll see if I can get you the source code somehow, that would probably
be more useful for you.
The easiest communication is just by using the serial console in the
Arduino IDE. That's a good place to start.
Here is my situation. My church has a manual electric buzzer system (push one of the 3 buttons in the church and the buzzers go off, it only buzzes for as long as you hold the button) for signaling Sunday School, Church and Wednesday night programs.
What I thought would be nice is to have an arduino controlled clock to automatically sound the buzzers at the proper time intervals, and for the proper length of time, like a short or a long buzz to signal a 5 minute warning.
Obviously this doesn't need slave clocks, it just needs to operate a relay switch to take over for the manual buzzer buttons.
Right now the bells only go off Monday-Friday, and the duration is always the same (but adjustable). Right now there are two bell "zones", but it shouldn't be very hard to add one more (need to change the Java controller software a little though).
Let me know if you need more help.
Great Instructable.
Thanks!
Maybe it could have 4 large 7-segment diplays made by using 1 led each and diffusing plastic. I have the LEDs on hand.
If the classroom has the wires already, then you could attempt to build a slave-clock. Beware that the wires could be 120V AC. The slave-clocks in the school where I installed this master-clock run on 24V AC. There are three wires for the clock, hot, neutral, and synchronization. There are a couple of other wires for the PA system housed in the same cabinet (also used for the bell signals).
The protocol for "my" slave clocks is that the sync wire goes hot on the hour for 25 seconds, except at 6 am and pm, where the signal lasts 25 minutes. To build a slave-clock, you just need a "regular" arduino clock, with some sort of connection from the sync wire to an arduino input. A diode and then two resistors (say 10K and 1K) with a capacitor (say 10 microF) in parallel. The Arduino ground goes to the neutral wire, and the Arduino input senses the voltage over the 1K resistor (this is assuming 24V AC on the sync). The Arduino input can only handle up to 5V (DC of course).
You add some code to a basic clock that senses when the sync signal goes on, and when it goes off the clock should display either X:00:25 or 06:25:00 depending on the length of the sync signal and the time (X) when the sync signal started. Thus if your clock is a little slow or a little fast, it can adjust on every sync.
Good luck! And if you are building a slave-clock, feel free to ask more questions.
* How do you interface the master clock to the other (slave) clocks? What kind of signal do they expect? Are they wired or wireless?
* Is the clock protocol openly available? (The manufacturer you mentioned doesn't appear to disclose anything)
Even though the manufacturers themselves do not disclose the protocols, they can be found on the internet.