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I wanted a clock that never needed setting. Things escalated

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Re: I wanted a clock that never needed setting. Things escalated

#91

Post by seba_dos1 »

m463 wrote: post #59
Frost1x wrote: post #11

I’ve had a Phillips “atomic” alarm clock beside my bed for 23 years that just sets based on radio signal and auto restores if the power is lost, to which it has a backup 9v battery. There’s a time zone setting offset slider and a DST slider. I basically touch it twice a year, maybe another if I move time zones. I’ve only had to touch it for DST (never switched time zones). Takes me conservatively 10 seconds to find a…

I did went GPS+ntp route. I have a few raspberry pis on my lan that serve NTP time. (you need more than one) Over the years I've experimented with various flavors. Right now I have a mix: 1) a pi3 with a gps hat and a battery backup for the pi itself. It uses ntp 127.127.20.20 for gps time, and 127.127.20.28 for PPS. The SMA antenna goes to receiver at the window 2) a pi3 with USB gps on a cable going to the window 3…

> I've also kind of wondered if GPS might be able to give you a time less accurately but quicker. Sometimes I look at the NMEA GPS output, and it sometimes doesn't have a position fix, but it does give out a time + week number

No. Accurate time is one of the prerequisites for acquiring a position fix, and it's the one that's the easiest and fastest to obtain from the sky. Typically a receiver should be able to get time within seconds from cold start if there's enough sky visibility, and once it does it is as accurate as it gets regardless of position fix status (unless you care about sub-nanosecond precision, but you need to be able to somehow consume that anyway and you won't with a Pi).

That said, NMEA output will usually contain the time from the module's internal clock that gets synchronized with GPS time when available rather than GPS time directly. Some modules can be configured to report when they have synced their time though, and you could pay attention to the time jumping to infer it too.

Re: I wanted a clock that never needed setting. Things escalated

#92

Post by ButlerianJihad »

breppp wrote: post #80

I don't know how practical but I always thought of extending the Wifi protocol with a clock broadcast That way all the microwaves of the world could listen in and update their clocks accordingly

Consensus Time https://m.xkcd.com/2594/

Re: I wanted a clock that never needed setting. Things escalated

#93

Post by FearNotDaniel »

ksenzee wrote: post #33
codazoda wrote: post #22

Earlier quoted context omitted.

I was going to mention an Atomic Clock. I use one in an RV and it sets itself even outside of cell phone range. I know it uses a radio signal of some type but I have no idea how it works. It rights itself within a few minutes of time changes, battery loss, or the like.

It's fascinating reading if you're interested in finding out the details: https://en.wikipedia.org/wiki/WWV_(radio_station)

Or for Western Europe there is DCF77 https://en.wikipedia.org/wiki/DCF77

Re: I wanted a clock that never needed setting. Things escalated

#94

Post by martheen »

breppp wrote: post #80

I don't know how practical but I always thought of extending the Wifi protocol with a clock broadcast That way all the microwaves of the world could listen in and update their clocks accordingly

Nokia proposed using SIB9 5G time transmission as time syncing in clocks, the idea being that transmission is available openly even for non-subscriber. Softbank later proposed commercializing the service, which is unclear to me since surely the public transmission would be enough for casual users and anyone requiring more would already use full 5G to control the device anyway.

Re: I wanted a clock that never needed setting. Things escalated

#95

Post by rcxdude »

seba_dos1 wrote: post #91
m463 wrote: post #59

Earlier quoted context omitted.

I did went GPS+ntp route. I have a few raspberry pis on my lan that serve NTP time. (you need more than one) Over the years I've experimented with various flavors. Right now I have a mix: 1) a pi3 with a gps hat and a battery backup for the pi itself. It uses ntp 127.127.20.20 for gps time, and 127.127.20.28 for PPS. The SMA antenna goes to receiver at the window 2) a pi3 with USB gps on a cable going to the window 3…

> I've also kind of wondered if GPS might be able to give you a time less accurately but quicker. Sometimes I look at the NMEA GPS output, and it sometimes doesn't have a position fix, but it does give out a time + week number No. Accurate time is one of the prerequisites for acquiring a position fix, and it's the one that's the easiest and fastest to obtain from the sky. Typically a receiver should be able to get ti…

>Typically a receiver should be able to get time within seconds from cold start if there's enough sky visibility, and once it does it is as accurate as it gets regardless of position fix status.

It'll be good to far better than seconds when it first gets a signal and will get more accurate (microseconds to nanoseconds) once it has a position fix because it can then compensate for the delays in the signal propagation (you can think of a gps fix as a 4d fix because it also needs to solve for time). You will probably need to use the PPS output to resolve this, though.

Re: I wanted a clock that never needed setting. Things escalated

#96

Post by seba_dos1 »

rcxdude wrote: post #95
seba_dos1 wrote: post #91

Earlier quoted context omitted.

> I've also kind of wondered if GPS might be able to give you a time less accurately but quicker. Sometimes I look at the NMEA GPS output, and it sometimes doesn't have a position fix, but it does give out a time + week number No. Accurate time is one of the prerequisites for acquiring a position fix, and it's the one that's the easiest and fastest to obtain from the sky. Typically a receiver should be able to get ti…

>Typically a receiver should be able to get time within seconds from cold start if there's enough sky visibility, and once it does it is as accurate as it gets regardless of position fix status. It'll be good to far better than seconds when it first gets a signal and will get more accurate (microseconds to nanoseconds) once it has a position fix because it can then compensate for the delays in the signal propagation…

What I meant was that it will take seconds to get an accurate time from the sky (as accurate as it gets without specialistic techniques or equipment to consume it, and better than NTP already).

Re: I wanted a clock that never needed setting. Things escalated

#97

Post by nkvoll »

bombcar wrote: post #63
rekabis wrote: post #48

I think a single clock-output-only microcontroller would be nifty. Something where you can save settings, such as NTP servers and an all time change dates, but that’s it. Pair it with PoE Ethernet and you wouldn’t even need a power supply, only an Ethernet jack in the wall. With the right display you could make it super thin.

POE clocks are SURPRISINGLY expensive. https://www.american-time.com/shop/?fwp_product_brand=power-... Someday, my precious, someday. (My dream clocks would have a smooth-sweeping second hand, no ticking (silent) and be PoE and NTP.)

I have these, which has the feature-combination you asked for: https://www.bodet-time.com/products/clocks/metal-analogue-cl...

My main gripe with them is that they reset at midnight (plus every now and then), and take 5 minutes to adjust themselves.

Unfortunately I’ve caught them a few times just showing a seemingly arbitrary time as well. This has always corrected itself after a few hours, but still..

It’s very nice looking clocks, but the reliability is just too low for my liking, as I don’t feel confident enough just looking at them that they currently show the exact actual time.

Re: I wanted a clock that never needed setting. Things escalated

#98

Post by bux93 »

>damned if I could find one with a red seven-segment display that I liked (maybe someone else’s search kung-fu is better than mine?).

The secret to finding an inexpensive radio-controlled clock/alarm/watch of your liking it to be German. They LOVE their Funk-Uhren! Sadly they typically only support Germany's DCF77 signal. You can also trivially find DCF77 receivers as components to use in a project.

Re: I wanted a clock that never needed setting. Things escalated

#99

Post by haritha-j »

its a lovely ritual for me, setting the clocks twice a year. Makes you appreciate the passage of time (arguably a key feature of a clock), plus I enjoy the slight confusion in the morning, my phone says one thing, my bedside clock another, did I wake up an hour late or hour early? who knows.

Re: I wanted a clock that never needed setting. Things escalated

#100

Post by bux93 »

breppp wrote: post #80

I don't know how practical but I always thought of extending the Wifi protocol with a clock broadcast That way all the microwaves of the world could listen in and update their clocks accordingly

Apparently at least Bluetooth has something called Current Time Service (CTS) (BLE GATT service 0x1805). If you pair a cheap "smartband" to a phone, it'll set itself, even without using any apps. Neat! I guess it uses CTS?
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