One more idea: Buy one of those "Atomic Clocks" that run off WWVB. Then use time code to modulate a very low power 60KHz radio transmitter. The clocks will pick up your signal and sync to it. The clocks run on battery power and you don't need wires.
But then I did notice you can buy exactly what you asked for $99. /DS%5FTimeDisplays.pdf<http://www.symmetricom.com/media/files/downloads/product-datasheets/DS%5FTimeDisplays.pdf> On Mon, May 27, 2013 at 9:40 AM, Bob Camp <[email protected]> wrote: > Hi > > If you are doing this from scratch today, would you go IRIG or would you > go RS-485 for a wall clock? Both will drive more cable than you are likely > to have in a house. Both are reasonably noise immune. With RS-485 there's > less to do. It's a serial stream like any other bunch of "stuff" into a > UART. > > Some math: > > YYMMDDHHMMSSCR = 13 ASCII characters. With one check byte it would be 14. > A baud rate of 115.4K isn't stretching things on RS-485 or on most UART's > these days. > Sent it at 7N1 you have 9 bits per character, 126 bits in the message. > Message takes a bit over 1 ms. > > Time it to anywhere in the string and the clock should be within <+/- 2 > ms. That's better than I can see on a clock. Better yet, time it to the > first (or last) character in the string. More or less a 10X improvement. > You could also drop the year / month / day if the clock isn't going to use > them. > > Take any of the Arduino (or what ever) LED display boards and drive them > with something cheap. I doubt the "clock" end plus the drivers would be > over $30. I suspect IRIG would cost a bit more once you got it all worked > out. > > Bob > > On May 27, 2013, at 11:03 AM, Chris Albertson <[email protected]> > wrote: > > > I've seen LLCD computer monitors used as clocks. Seems this would be > > the perfect use for a Rasbury Pi. and a cheap monitor. $100 or maybe a > > low-end Android tablet. > > > > The way it is more commonly done is you have you computer that is > > using NTP produce an IRIG time code. Then there are any number of > > commercial clocks and large digital LED displays that will use IRIG. > > IRIG displays are not cheap but they sure are easy to find. > > > > On Mon, May 27, 2013 at 6:29 AM, Miguel Barbosa Gonçalves <[email protected]> > wrote: > >> Hi! > >> > >> I was wondering if anyone knows about a not so expensive wall digital > clock > >> that gets its time from an NTP server... > >> > >> TIA, > >> Miguel > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] > >> To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > > > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
