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Topic: synchronised LED clocks,  how difficult ? (Read 978 times) previous topic - next topic


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.

With my mobile phone I can call people and talk to them -  how smart can you get ?


The range is max 30m

30 metres! Can't someone just yell out "KNOCK OFF TIME"  :)


Rob Gray aka the GRAYnomad www.robgray.com


Oct 19, 2010, 07:05 am Last Edit: Oct 19, 2010, 07:06 am by John_Smith Reason: 1
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.
With my mobile phone I can call people and talk to them -  how smart can you get ?


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...
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.


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.....
With my mobile phone I can call people and talk to them -  how smart can you get ?

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