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Author Topic: synchronised LED clocks,  how difficult ?  (Read 821 times)
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Cape Town South Africa
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Hi Guys,
I dont want spoonfeeding , but an aquaintance has a factory with several entrances, each with a wall clock, and of course they are all slightly different times, leading to the staff all coming in at the door with the latest clock, and leaving at the earliest one :-)
I know he could buy a commercial system, but I was raving about the Arduino the other night, and he asked me if I could make him some synchronised clocks. ( one master, others slaves, I was thinking with a simple 433Mhz Radiometrix or similar simplex link, to lock them every minute -  if it missed a transmission it would pick it up another time ? )

I am still a newbie, but I have made a few projects to update my old CMOS controlled designs.
Before I open my big mouth and tell him I can do it, does it sound a fairly simple project for a newbie?  I have been looking at Arduino Time library and there are sketches to set the clock from a serial input.......

I tried a search but couldn't find a previous project ( though searching for synchronous clocks brings up loads of results for the software type clocks as opposed to wall clocks ) :-/
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Manchester (England England)
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Einstein proved that synchronising clocks is a logically impossible task. However depending on where you are you might like to look into clocks that are locked to broadcast time standards. These are usually on long wave and have a wide coverage world wide.
http://www.dxinfocentre.com/time.htm

http://www.npl.co.uk/science-technology/time-frequency/time/products-and-services/msf-radio-time-signal
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Central Europe
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In Europe, get a bunch of DCF77 clocks. That's easier and cheaper than anything else.

Korman
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Cape Town South Africa
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Thanks Guys,
I am afraid we are in darkest Africa here ( actually summer is upon us with wall to wall blue skies but no time standard signals that I know of in Cape Town )

Yes wasn't it Einstein who showed that two clocks will show the same time only if one is stopped, and thats only twice a day..

I think the existing mishmash of clocks are fed from different mains wiring circuits, or I could have had a simple pulse and phantom supply ring.

The budget is not much, so GPS is out of the question.
The guy knows I make LED displays, and I think he is looking for something cheap.
The range is max 30m, but I havnt seen the layout, perhaps I should go for a mesh type wireless setup.

I have just worked out a simple way of doing it with CMOS chips, 6 in each master and slave units ( excluding the LED drive chips which I would need for the Arduino anyway )  which would update the time every minute, and have a xtal clock.

But I really enjoy using the Arduino !!!
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At that distance look into communicating through the mains.
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Cape Town South Africa
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Mains could be an option, I will have to go and look at the set up there.

If its an old factory it could have single sockets on 3 different phases, but it might be the easiest.

Incidentally I made VCR remote control extenders some years back that communicated through the mains at 38 Khz ( as received from the remote ).
I had some noise hassles, and monitored the 38KHz noise on the mains during the day, when all the factories are running, and it was much less than at night.

I didn't really look into it, but presumed that the lower impedance with all the machines and offices on in the day, dragged down the higher frequency noise.
At night perhaps with little load on the transmission lines and poorly matched to the supply, the noise increased....
I switched to a different method of sending the pulses.

Of course nowadays since the X10 etc they have newer technology that I will look at.

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nr Bundaberg, Australia
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Quote
The range is max 30m
30 metres! Can't someone just yell out "KNOCK OFF TIME"  smiley

______
Rob

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Rob Gray aka the GRAYnomad www.robgray.com

Cape Town South Africa
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LOL Rob,  but which clock does he look at before he yells :-)

and thanks for the suggestions Richard, I have quickly checked their website and there is some interesting stuff there.
I see they sell the Meanwell excellent power supplies that I use a lot of, perhaps my local supplier can get the other stuff too, I like the RF link in particular.
« Last Edit: October 19, 2010, 12:06:01 am by John_Smith » Logged

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You could put a simple setup at the remote locations, just receiving time from a main location at whatever rate you wanted to send it (once a second for example). With a Pro-Mini, maxim display driver chip like a MAX6953, four seven segment displays, and the spark-fun Tx/RF modules, wouldn't be hard at all. I am working on a fencing scoring machine right now, it does basically that - receives the time remaining and displays it. That's all you need, right? Was very easy to do after I understood the arduino some. Have the transmitter sent out a burst of 6 bytes with HH:MM:SS. Receivers catch it, can simply write each byte  to 6 registers each connected to a 7447 segment display driver and 7 segment display and then not even deal with the maxim chip.
How you get the time into the main transmitter is an exercise left to the reader, as my textbooks used to say...
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Cape Town South Africa
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I can do it without the micro or the max chip, but still have all the clocks running independently as xtal controlled clocks, but syncd to the master one every minute, with just 5 cheap chips and a remote encoder/decoder chip. ( as I use in the countdown clocks in scoreboards that I make )
I would still need the 7441s to drive the LEDs, but the system would be failsafe if the master packed up or the transmission link was compromised....
but I still fancy the Arduino way.....
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Offtopic: I hope the employees are not reading this thread, they might come up with a way of sending in their own time values :-)
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Cape Town South Africa
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When I go to check out the factory I will look at the staff and see if they look like Arduino freaks   -  I have seen all the avatars on this forum and know more or less what to look for !
« Last Edit: October 19, 2010, 02:02:00 pm by John_Smith » Logged

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Remove all clocks apart from one. Fit it with a bell.  smiley-wink

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Cape Town South Africa
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LOL,   I am sure there is a sketch for a bell in the forum somewhere .......
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