Hi Tom, How about using Binary for the last couple of digits? 4 LEDs for a digit in BCD. Saves on pins and wiring.
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.
