Bob Yes indeed click, click, click. Ed agree with your coment that a 30 or greater year old led may be dimming. I expect better from HP. Not really. With respect to the clock it did run off the 24 volt battery and the display shut down on power failure. There is a button on the front labeled standard read that you can press to see the time while on battery. Thank you for the comment.
On Fri, Jan 4, 2019 at 4:38 PM Bob Bownes <[email protected]> wrote: > 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 <[email protected]> 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 -- [email protected] > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
