Power and heat re: Heathkit WWV clock / where are the good oscillators?
Hi all – I've been reading up on the Heathkit GC-1000 Most Accurate Clock
from the 1980s, which syncs with WWV. I've seen numerous reports of the
flawed power supply and regulator, and the intense heat it generates in the
chassis, and I'm stumped. Why does it need so much power that it's getting
hot? There's hardly any computation involved in syncing with WWV, decoding
its BCD bitstream, etc. Can I expect similar issues if I build my own clock
instead of restoring a GC-1000?
Quartz watches can sync with WWVB and run for a couple of years on, what,
≈200 mAh coin cells? I'm amazed that some are able do GPS, which is far
more computationally taxing, but I think most of those are solar with a few
months of battery backup. I don't understand why a WWV clock isn't sipping
milliamps in cool silence like a watch. Is it something to do with the WWV
medium band frequencies (5-15 MHz) compared to WWVB's long wave (60 KHz)?
(Why did Heathkit sync to WWV and not WWVB? I thought the latter has less
propagation delay.)
The oscillator runs faster than a standard 2^15 Hz movement, but so do lots
of high accuracy quartz watches. I've looked for an Omega quartz ship's
chronometer from the early 80s, but they're too rare apparently. It has a
2^22 Hz oscillator and runs for a couple of years on two AA batteries.
(Scroll down to the ship's version:
https://en.wikipedia.org/wiki/Omega_Marine_Chronometer) And the new Citizen
Caliber 0100 movement runs at 2^23 Hz, in a watch... (
https://www.hodinkee.com/articles/citizen-eco-drive-caliber-0100-review)
By the way, why am I not finding any RTCs better than 20 or 15 seconds per
month accuracy? I've looked on Mouser and Digikey. It's like there's been
no progress since the 80s. That Omega was good for maybe 0.4 sec/month
drift, worst case, and the new Citizen is unbelievable at under 0.1
sec/month. What performance can we expect in a disciplined oscillator like
the GC-1000's? I haven't found any specs on its endogenous accuracy after
some break-in period with enough disciplining. I'd like to have less than
0.1 sec/day between syncs – syncing isn't possible at all hours, and GPS
won't work for my application. So a 3 sec/month clock on its own. The world
is full of quartz watch movements more accurate than that, without needing
ovens, many dating to the 1970s, so I'm confused by why movements that sit
on a desk and never move are so subpar compared to watch movements. Has
anyone leveraged a watch movement in a desktop chassis? I wonder about the
interfaces, since they're all used in analog watches and I don't know if
they express/output time in a way that can be used by a controller.
Thanks,
Joe
Hi
Backing up a bit …..
A month might be 30 days, that’s about 2.5 million ( 2,592,000) seconds.
A second a month is about 0.4 ppm ( 0.3858).
There are a lot of oscillators out there that will hold much better than a
tenth of a ppm over a month. That’s for all effects and not going with the
somewhat odd “chronometer” rating approach.
If you want to spend some money you can find devices that get into a tenth
of a PPB ( so 1,000 X better) and still not be over $100 on eBay. No, they
won’t run on a AA cell for a couple years.
For a bit more money, various outfits will sell you TCXO’s that are in the
PPB per month sort of range. They will run on low-ish power. Finding them
on eBay? not so much. Getting them to sell you less than a couple hundred?
also not so much. Still, if you have an OEM sort of “need” the parts are
available.
RTC modules are targeted at very low power. They sell into a market that
has a “good enough” approach to time, but values low power a lot. If you
want something more accurate, there are parts out there to build up what
you want. This DIY approach is pretty much guaranteed to use a bit of
power. That seems to work for the OEM’s who need it …..
Bob
On Aug 6, 2022, at 12:34 PM, Joe Duarte via time-nuts time-nuts@lists.febo.com wrote:
Hi all – I've been reading up on the Heathkit GC-1000 Most Accurate Clock
from the 1980s, which syncs with WWV. I've seen numerous reports of the
flawed power supply and regulator, and the intense heat it generates in the
chassis, and I'm stumped. Why does it need so much power that it's getting
hot? There's hardly any computation involved in syncing with WWV, decoding
its BCD bitstream, etc. Can I expect similar issues if I build my own clock
instead of restoring a GC-1000?
Quartz watches can sync with WWVB and run for a couple of years on, what,
≈200 mAh coin cells? I'm amazed that some are able do GPS, which is far
more computationally taxing, but I think most of those are solar with a few
months of battery backup. I don't understand why a WWV clock isn't sipping
milliamps in cool silence like a watch. Is it something to do with the WWV
medium band frequencies (5-15 MHz) compared to WWVB's long wave (60 KHz)?
(Why did Heathkit sync to WWV and not WWVB? I thought the latter has less
propagation delay.)
The oscillator runs faster than a standard 2^15 Hz movement, but so do lots
of high accuracy quartz watches. I've looked for an Omega quartz ship's
chronometer from the early 80s, but they're too rare apparently. It has a
2^22 Hz oscillator and runs for a couple of years on two AA batteries.
(Scroll down to the ship's version:
https://en.wikipedia.org/wiki/Omega_Marine_Chronometer) And the new Citizen
Caliber 0100 movement runs at 2^23 Hz, in a watch... (
https://www.hodinkee.com/articles/citizen-eco-drive-caliber-0100-review)
By the way, why am I not finding any RTCs better than 20 or 15 seconds per
month accuracy? I've looked on Mouser and Digikey. It's like there's been
no progress since the 80s. That Omega was good for maybe 0.4 sec/month
drift, worst case, and the new Citizen is unbelievable at under 0.1
sec/month. What performance can we expect in a disciplined oscillator like
the GC-1000's? I haven't found any specs on its endogenous accuracy after
some break-in period with enough disciplining. I'd like to have less than
0.1 sec/day between syncs – syncing isn't possible at all hours, and GPS
won't work for my application. So a 3 sec/month clock on its own. The world
is full of quartz watch movements more accurate than that, without needing
ovens, many dating to the 1970s, so I'm confused by why movements that sit
on a desk and never move are so subpar compared to watch movements. Has
anyone leveraged a watch movement in a desktop chassis? I wonder about the
interfaces, since they're all used in analog watches and I don't know if
they express/output time in a way that can be used by a controller.
Thanks,
Joe
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The Swiss MicroCrystal claims +/- 1ppm accuracy and +/- 0.09 seconds
per day for their RTC modules.
https://www.microcrystal.com/en/products/real-time-clock-rtc-modules/
On Sun, Aug 7, 2022 at 5:53 AM Bob kb8tq via time-nuts
time-nuts@lists.febo.com wrote:
Hi
Backing up a bit …..
A month might be 30 days, that’s about 2.5 million ( 2,592,000) seconds.
A second a month is about 0.4 ppm ( 0.3858).
There are a lot of oscillators out there that will hold much better than a
tenth of a ppm over a month. That’s for all effects and not going with the
somewhat odd “chronometer” rating approach.
If you want to spend some money you can find devices that get into a tenth
of a PPB ( so 1,000 X better) and still not be over $100 on eBay. No, they
won’t run on a AA cell for a couple years.
For a bit more money, various outfits will sell you TCXO’s that are in the
PPB per month sort of range. They will run on low-ish power. Finding them
on eBay? not so much. Getting them to sell you less than a couple hundred?
also not so much. Still, if you have an OEM sort of “need” the parts are
available.
RTC modules are targeted at very low power. They sell into a market that
has a “good enough” approach to time, but values low power a lot. If you
want something more accurate, there are parts out there to build up what
you want. This DIY approach is pretty much guaranteed to use a bit of
power. That seems to work for the OEM’s who need it …..
Bob
On Aug 6, 2022, at 12:34 PM, Joe Duarte via time-nuts time-nuts@lists.febo.com wrote:
Hi all – I've been reading up on the Heathkit GC-1000 Most Accurate Clock
from the 1980s, which syncs with WWV. I've seen numerous reports of the
flawed power supply and regulator, and the intense heat it generates in the
chassis, and I'm stumped. Why does it need so much power that it's getting
hot? There's hardly any computation involved in syncing with WWV, decoding
its BCD bitstream, etc. Can I expect similar issues if I build my own clock
instead of restoring a GC-1000?Quartz watches can sync with WWVB and run for a couple of years on, what,
≈200 mAh coin cells? I'm amazed that some are able do GPS, which is far
more computationally taxing, but I think most of those are solar with a few
months of battery backup. I don't understand why a WWV clock isn't sipping
milliamps in cool silence like a watch. Is it something to do with the WWV
medium band frequencies (5-15 MHz) compared to WWVB's long wave (60 KHz)?
(Why did Heathkit sync to WWV and not WWVB? I thought the latter has less
propagation delay.)The oscillator runs faster than a standard 2^15 Hz movement, but so do lots
of high accuracy quartz watches. I've looked for an Omega quartz ship's
chronometer from the early 80s, but they're too rare apparently. It has a
2^22 Hz oscillator and runs for a couple of years on two AA batteries.
(Scroll down to the ship's version:
https://en.wikipedia.org/wiki/Omega_Marine_Chronometer) And the new Citizen
Caliber 0100 movement runs at 2^23 Hz, in a watch... (
https://www.hodinkee.com/articles/citizen-eco-drive-caliber-0100-review)By the way, why am I not finding any RTCs better than 20 or 15 seconds per
month accuracy? I've looked on Mouser and Digikey. It's like there's been
no progress since the 80s. That Omega was good for maybe 0.4 sec/month
drift, worst case, and the new Citizen is unbelievable at under 0.1
sec/month. What performance can we expect in a disciplined oscillator like
the GC-1000's? I haven't found any specs on its endogenous accuracy after
some break-in period with enough disciplining. I'd like to have less than
0.1 sec/day between syncs – syncing isn't possible at all hours, and GPS
won't work for my application. So a 3 sec/month clock on its own. The world
is full of quartz watch movements more accurate than that, without needing
ovens, many dating to the 1970s, so I'm confused by why movements that sit
on a desk and never move are so subpar compared to watch movements. Has
anyone leveraged a watch movement in a desktop chassis? I wonder about the
interfaces, since they're all used in analog watches and I don't know if
they express/output time in a way that can be used by a controller.Thanks,
Joe
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To unsubscribe send an email to time-nuts-leave@lists.febo.com
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Hi Joe:
The DS3231 is specified at 2ppm/year out of the box. But it can be tweaked to much better performance.
https://www.maximintegrated.com/en/products/analog/real-time-clocks/DS3231.html
For example if a clock with a much better stability used the DS3231 as a backup, then it could be tweaked while the main
clock was running.
https://prc68.com/I/PRC68COM.shtml#07092006
--
Have Fun,
Brooke Clarke
https://www.PRC68.com
axioms:
- The extent to which you can fix or improve something will be limited by how well you understand how it works.
- Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
Hi all – I've been reading up on the Heathkit GC-1000 Most Accurate Clock
from the 1980s, which syncs with WWV. I've seen numerous reports of the
flawed power supply and regulator, and the intense heat it generates in the
chassis, and I'm stumped. Why does it need so much power that it's getting
hot? There's hardly any computation involved in syncing with WWV, decoding
its BCD bitstream, etc. Can I expect similar issues if I build my own clock
instead of restoring a GC-1000?
Quartz watches can sync with WWVB and run for a couple of years on, what,
≈200 mAh coin cells? I'm amazed that some are able do GPS, which is far
more computationally taxing, but I think most of those are solar with a few
months of battery backup. I don't understand why a WWV clock isn't sipping
milliamps in cool silence like a watch. Is it something to do with the WWV
medium band frequencies (5-15 MHz) compared to WWVB's long wave (60 KHz)?
(Why did Heathkit sync to WWV and not WWVB? I thought the latter has less
propagation delay.)
The oscillator runs faster than a standard 2^15 Hz movement, but so do lots
of high accuracy quartz watches. I've looked for an Omega quartz ship's
chronometer from the early 80s, but they're too rare apparently. It has a
2^22 Hz oscillator and runs for a couple of years on two AA batteries.
(Scroll down to the ship's version:
https://en.wikipedia.org/wiki/Omega_Marine_Chronometer) And the new Citizen
Caliber 0100 movement runs at 2^23 Hz, in a watch... (
https://www.hodinkee.com/articles/citizen-eco-drive-caliber-0100-review)
By the way, why am I not finding any RTCs better than 20 or 15 seconds per
month accuracy? I've looked on Mouser and Digikey. It's like there's been
no progress since the 80s. That Omega was good for maybe 0.4 sec/month
drift, worst case, and the new Citizen is unbelievable at under 0.1
sec/month. What performance can we expect in a disciplined oscillator like
the GC-1000's? I haven't found any specs on its endogenous accuracy after
some break-in period with enough disciplining. I'd like to have less than
0.1 sec/day between syncs – syncing isn't possible at all hours, and GPS
won't work for my application. So a 3 sec/month clock on its own. The world
is full of quartz watch movements more accurate than that, without needing
ovens, many dating to the 1970s, so I'm confused by why movements that sit
on a desk and never move are so subpar compared to watch movements. Has
anyone leveraged a watch movement in a desktop chassis? I wonder about the
interfaces, since they're all used in analog watches and I don't know if
they express/output time in a way that can be used by a controller.
Thanks,
Joe
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
On Sonntag, 7. August 2022 23:21:46 CEST Brooke Clarke wrote:
The DS3231 is specified at 2ppm/year out of the box. But it can be tweaked
to much better performance.
That's roughly a minute per year off or about 1 second per week (both rounded
down). I have one DS3231M (the one with an actual quartz) that I tuned up and
then unplugged about a year ago (or maybe a bit longer already), I should
probably have a look how far it went off. Anyway the new (pretty much the
only ones available right now) DS3231SN come with a MEMS oscillator instead
and are very different beasts as they need much more aggressive intervention
to compensate the larger temperature dependency. I implemented a software PLL
that keeps it within ~50µs of system time (set from GPS / PPS) while connected
to the computer and it takes about ±6 LSB of the aging register to keep it
there since the PLL also fights against the temperature compensation algo on
the chip that obviously runs on different time scales (note: the DS3231M looks
at the aging register once every 64 seconds, the DS3231SN every second). The
upshot is that while the RTC easily meets spec, it can run past the ±2ppm
boundary in the short term when presented with large and fast temperature
changes and only produces nominal performance if nearly correctly compensated
for the mean temperature over the longer time span. I would think that this
is not easy to ascertain for many applications, so beware.
Regards,
Achim.
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
Factory and User Sound Singles for Waldorf rackAttack:
http://Synth.Stromeko.net/Downloads.html#WaldorfSounds