Add a tiny speaker so you can simulate the loud 'tick' of the analog clock. ;)
On Fri, Jan 4, 2019 at 4:29 PM ed breya <e...@telight.com> wrote: > Paul, what do you mean by the display "looking pretty ratty?" As I > recall, the original buck regulator had regulated output voltage around > 5V for the LEDs. and the PMOS clock IC needed something around 12V. > Whatever the LEDs run from, it should be regulated and well filtered. If > the LEDs are dim, it could be the old displays themselves are > deteriorated, or the regulation isn't right, or maybe a bad output > filter cap on the buck converter. If the brightness is OK, but digit or > segment intensities fluctuate with count, then it's probably a > regulation issue. > > I used the shunt regulator to isolate the rest of the system from the > large variation (about 3:1) in total LED current with readout values, > and it was possible because I had made lower supplies anyway, via DC-DC > converters. You wouldn't want to linear-regulate all the way down from > the main supply around 24V, to a few V for the LEDs. As I recall, the > peak load is in the 200-300 mA range at good brightness. The efficiency > of the buck converter makes it practical to run this from the normal > supply or battery voltage. I think the original deal was that on power > failure it switched to battery mode, the buck converter was shut off to > shed the LED load, and the clock IC stayed powered up to keep the right > time. The button below the display could force it to show when needed. > Mine will work the same way, when/if I ever finish all the details, but > will have adjustable brightness, and maybe the option of still > indicating time in backup mode, with very dim LED setting. > > Ed > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.