[time-nuts] Atomic Clocks: It is important that they keep good time, Part 1

[paul swed]

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 <bownes at gmail.com> 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 <eb at 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
> >
> >
> >
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