Hi, > Hi Tom, > How about using Binary for the last couple of digits? 4 LEDs for a digit > in BCD. Saves on pins and wiring.
I had the same idea, although my idea was to just make it completely binary and use OCR on the photograph to find the time. Maybe adding 2 surrounding always-on other colored LEDs to frame the sequence would be nice? Greetings, Pieter. > > Robert G8RPI. > > > > > ________________________________ > From: Tom Van Baak <[email protected]> > To: Discussion of precise time and frequency measurement > <[email protected]> > Sent: Thursday, 3 November 2011, 16:29 > Subject: Re: [time-nuts] Precisione GPS based led clock > > I also have had need of a high resolution display clock for > photographic time stamping. > > For those of you working on this make sure not to use a > LCD or VFD display. The response time is too slow. Also > you can rule out any sort of TV display. > > If using LED make sure not to multiplex the digits. This is > a common trick, especially when using microprocessors, > and works well for human eyes, but fails completely with > high resolution photos. > > So having ruled out everything but direct drive LED the > only other concern is to make sure the decade counters > which drive the display are synchronous or at least that > all the digits are latched at the same time. Otherwise you > get false readouts due to ripple carry or sequential scan. > > Be careful using a microprocessor for this. For millisecond > displays you need a total of 21 pins; for microseconds you > need 42 pins. An external serial-parallel (e.g., shift register > with latch) chip might be safer since neither a PIC nor an > Arduino can update that many pins in one instruction. > > /tvb > > > _______________________________________________ > 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. > _______________________________________________ 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.
