[time-nuts] Precisione GPS based led clock

Flemming Larsen oz6oi at yahoo.dk
Mon Nov 7 06:48:05 UTC 2011


A straightforward solution would be to use a string of divide-by-ten and divide-by-six BCD counters (HC390).
First divide the 10 MHz output from a GPS receiver down to 100 Hz and feed that to  the input of a
divide-by-100 counter for the 1/100 seconds display, then to a divide-by-60 for the seconds and so on.
The BCD counters would feed a series of eight CD4511 or equivalent decoders as previously suggested.
The 1 PPS output from the GPS, properly stretched, could be used to reset the 1/100 s counters and to
clock the seconds counter. Pretty straightforward and no display multiplexing, but a lot of wiring.
Getting the time from the GPS to the clock circuit would be a little more complicated, and would almost
certainly require some kind of microprocessor or PIC. One solution is to synchronize the clock to the GPS
once a day at local midnight using the reset inputs to the counters. This would be relatively simple to do with
a PIC, I would think, and would still leave the clock section alone, without the need for complicated wiring
or deciphering of the display.
I designed a similar clock, although without the 1/100 s digits display and using an OCXO rather than a GPS
receiver. In the end I used an MK50250N clock chip I purchased on eBay, same chip I used back in 1974
to build a small alarm clock. This clock chip uses a multiplexed display, which might not work with a video
recorder or camera.

-- Flemming Larsen



________________________________
Fra: "paolo.martini at alice.it" <paolo.martini at alice.it>

yes, I am working with for a timestamp on a FireWire Camera (MARLIN CAMERA)
Unfortunately no  free software can timestamp frame withouth data loss.
My camera is unable to carry out  an atuomatic timestamp (it is and old version).
Thank you for info
Paolo Martini 


More information about the Time-nuts_lists.febo.com mailing list