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Ask Slashdot: Alternatives To "Atomic" Clocks? 291

Posted by timothy from the wall-mount-a-7"-gps dept.
Tony Isaac writes: "Atomic" clocks that you can buy in stores synchronize time using the WWVB shortwave band from NIST in Boulder. The problem is, this signal is notoriously weak, making these clocks very sensitive to interference by other RF or electronic devices, or less-than-ideal reception conditions. In many locations, these clocks are never able to receive a time signal, making them no better at timekeeping than a cheap quartz clock. There are other ways to synchronize clock time: NTP over WiFi, GPS, or cellular. The cheapest clocks that use NTP over Wi-Fi cost around $400. Really? And while there are plenty of GPS-enabled smartwatches in the $100 price range, there don't seem to be any similar wall clocks. Are there any reasonably-priced wall clock alternatives, that use something other than shortwave to set the time?
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Ask Slashdot: Alternatives To "Atomic" Clocks? More

Ask Slashdot: Alternatives To "Atomic" Clocks?

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  • Sundial (Score:5, Funny)

    by fustakrakich ( 1673220 ) on Monday March 14, 2016 @06:26PM (#51696303) Journal

    No wait, it's still atomic

    • As alternatives to atomic clocks, sundials would probably be best for daylight hours. At night and for cloudy days, I would suggest a wind-powered clock, which would provide perfectly accurate results twice a day. For Germans, I suggest a coal-fired clock, which though more carbon intensive, would get you up in the morning in time to drive your Bagger 228 through still another village.

    • schmitt trigger (Score:5, Funny)

      by goombah99 ( 560566 ) on Monday March 14, 2016 @07:37PM (#51696813)

      You kids. in my day we used a schmitt trigger, a resistor, and a capacitor to keep time and we glad to have it. My grandfather used to feel his pulse and bang on a hollow log, so we had it easy. Atomic clocks. Luxury!

    • Here's one on Etsy that can use NTP, GPS for $70. there's other for $30 out there if you google.

      https://www.etsy.com/listing/2... [etsy.com]

      • My "Atomic" clocks (got 3) were a whole a $15 bux with shipping which was 5 or 6 dollars, so $30 is expensive. Just have to know where to look on the web...

  • I think the problem that you're having with finding such a device is that it's simply not necessary at this point. People use their phones and such for the time. If they're buying an alarm clock, it's generally accurate enough as is, and if they're putting a wall clock up they're doing it for the ambiance as much as having the time available.

    GPS indoors is iffy anyways.

    • Re: (Score:3)

      by hawguy ( 1600213 )

      I think the problem that you're having with finding such a device is that it's simply not necessary at this point. People use their phones and such for the time. If they're buying an alarm clock, it's generally accurate enough as is, and if they're putting a wall clock up they're doing it for the ambiance as much as having the time available.

      GPS indoors is iffy anyways.

      Perhaps for home use, but after repeated requests, my office finally put up wall clocks in all of the conference rooms and common areas. They use some central syncing mechanism, but I'm not sure if it's wifi or proprietary radio.

    • Actually, there is a better option over GPS that works better indoors but no one seems to be using. Cell phones set their time over the cellular network and can do so without GPS. I've seen cell phones sync to local time even without an active cellular plan, so there seem to be no reason that a wall clock couldn't sync over a cell network without an active plan as well.

      • The cool thing about CDMA is that it won't work without precision time standards in each of the base stations - i.e., GPS receivers with antennas fed through known lengths of feedline (or, alternatively, GPS receivers with known lengths of wire providing a 1 pulse per second reference). Net result is that CDMA can give sub-ppb time reference, and it works great indoors, too. Probably overkill for getting the kids up in the morning. :-)

      • This assumes that your cellular provider isn't too cheap to pay the licensing fee required to be allowed to include time data in the info the BTS broadcasts.

        (It's like monopoly telcos in the 1970, everything is a value-added extra).

    • Re: (Score:2, Insightful)

      by Anonymous Coward

      I think the problem that you're having with finding such a device is that it's simply not necessary at this point. People use their phones and such for the time. If they're buying an alarm clock, it's generally accurate enough as is, and if they're putting a wall clock up they're doing it for the ambiance as much as having the time available.

      GPS indoors is iffy anyways.

      I think it's sort of a step backwards when a meeting is nearing the end, someone asks what time it is, and we all have to dig something out of our pockets.
      We could all leave them on the table, but they're often a distraction. It's hard to check the time without obviously checking the time, or worse your email.

      We went from pocket watches, to wrist watches, back to pocket watches and lost wall clocks somewhere in there.

      It's a minor convenience, but so were wrist watches in the first place.

    • This kind of thinking has killed the entire electronics industry, and is stifling innovation generally.

      Why can't I buy an HD Radio/alarm clock for my bedside table? ("Nobody wants one, they use their 'smart' 'phones'," I'm told. So do you get up, open your eyes, so you can see the silly touch-screen to run things -- instead of having red LEDs (don't kill your night vision), a normal button for SNOOZE and a volume knob?) Why can't I replace my 10-year old DVR with another one that works with antenna broadca

  • GPS clocks? (Score:3)

    by ClickOnThis ( 137803 ) on Monday March 14, 2016 @06:30PM (#51696331) Journal

    The Global Positioning System can do more than just tell you where you are. It can also tell you when you are. [wikipedia.org]

    • Sorry, your query was about wall clocks. Contrary to what you said in the summary, there appear to many GPS wall-clocks available. Google is your friend.

      • Yes, I searched Google for GPS wall clocks. There are lots of results, but when you read the fine print, you find out they are just plain-old quartz movements. The sellers of these clocks just tag extra search keywords in hopes of finding customers.

        There are a few kits available (not cheap), and one on Alibaba (but you have to buy 2,000), and a couple of others with prices in the hundreds.

        Since you so easily found all these GPS clocks, perhaps you could share a link or two, preferably under $100!

    • GPS itself is time based. Each of the 24 satellites sends a ~1575mhz signal containing information including the atomic time. Simplified, the GPS receiver determines the distance to the satellite (since it has the timestamp in the signal), then intersects each satellites "distance spheres" to find the receivers 3d coordinates.

      So there are 24 GPS satellites (and more GLONASS, etc) transmitting the atomic time at 1575mhz

      • Slightly more complexified, it actually determines the difference in time between the signals, which places you on parabolas or something, not spheres. It doesn't know the absolute distance, since it doesn't contain its own atomic clock.

    • I'm right now. No, now. Not then, it's now now. Ok, wait... I'm... NOW. Damn, it seems like I'm always then.

  • Cheap? (Score:4, Insightful)

    by nospam007 ( 722110 ) * on Monday March 14, 2016 @06:31PM (#51696339)

    "Are there any reasonably-priced wall clock alternatives, that use something other than shortwave to set the time?"

    Buy an Amazon fire for under 50$ or any cheap tablet and use one of the clock apps.

    • A great idea actually. I like it. Lots of old phones in my desk and cheap tablets online.

      BUT, horrible battery life necessitating constant plug in. In fairness, battery life is likely the reason nothing other than the shortwave signal is viable at the moment except maybe some Bluetooth LE and a BT transmitter in in the house :(

      • BUT, horrible battery life necessitating constant plug in.

        Sure, but is that a problem for a stationary clock? I use my old SEMC Xperia Play as a clock in the living room because I bought the dock for it, so it makes a decent one. What's cool besides being able to use it as an XBMC remote is that it updated itself for DST...

      • Re: (Score:2)

        by adolf ( 21054 )

        I have a completely-restored* Motorola OG Droid sitting in its (expensive!) factory desktop dock, running Dock Clock from the Play store and whatever the latest ancient version of Cyanogenmod was that works properly-ish on it.

        It sits on my entertainment center where it is easy to plug in. It varies brightness automatically based on ambient conditions, so it's never a distraction during movie time in the dark, and it's always bright enough during the day.

        *Yep, restored. Parts for the OG Droid were always c

    • Re: (Score:2, Flamebait)

      by mcelrath ( 8027 )

      As a long time reader, I'm pretty severely disappointed by the responses to this post. No discussion of NTP, or GSM time distribution, or CDMA time distribution, or shortwave radio, or ANYFUCKINGTHING relevant to the poster's question.

      Where did the knowledgeable people go? Because I really don't need some douchenozzle to tell me that the Amazon fire has a clock app, and see that that post has been rated +4?!?!?! WTF?!??!?!

      Give mod points motherfuckers and I will clean up this mess.

      • "As a long time reader, I'm pretty severely disappointed by the responses to this post. No discussion of NTP, or GSM time distribution, or CDMA time distribution, or shortwave radio, or ANYFUCKINGTHING relevant to the poster's question. "

        Read again, he's too cheap for one of those.

    • This is a good idea. However, there are a couple of drawbacks:
      1. Android tablets like to go to sleep when they aren't being used. The longest wake time is 30 minutes, there is no "never" setting.
      2. Because the display is backlit, it would have to be plugged in constantly. Not a deal-breaker, but the battery would tend to wear out relatively quickly. And since you typically can't replace the battery, you have to replace the whole device.

      Still, I like it!

  • Rubidium 10 Mhz clocks (Score:5, Insightful)

    by cachimaster ( 127194 ) on Monday March 14, 2016 @06:33PM (#51696365)

    As cheap as 50$ on ebay, some are GPS-disciplined. Small, available. About the same tech currently on the GPS satellites themselves.

    • Re: (Score:2)

      by msauve ( 701917 )
      Good luck with battery power. I assume, since he's asking about wireless protocols, he wants a battery powered wall clock. If it could be wired, there would be no need for wireless, he could just get a PoE clock.

    • Good idea, but these seem to lack an actual display. That's kind of important for a wall clock!

      Also, I'm not so interested in extreme accuracy, I'm really just interested in not having to set it ever!

  • Broken tablet (Score:4, Insightful)

    by dfsmith ( 960400 ) on Monday March 14, 2016 @06:36PM (#51696391) Homepage Journal

    If you don't need real hands, you can buy inexpensive Android tablets for $25. Or buy a $300 tablet with a cracked digitizer for $30 (make sure the display is fine) and stick it in screensaver mode. (You can use a bluetooth mouse to operate it.)

    Oh, don't do this if you're married and the clock is for one of the "good" rooms. B-)

    • LOL

      This is a good idea, except that Android displays go to sleep after, at most, 30 minutes.

      Also, because of the backlight, it has to be plugged in constantly, wearing out the battery, which often can't be replaced.

  • Power line frequency (Score:4, Informative)

    by fustakrakich ( 1673220 ) on Monday March 14, 2016 @06:38PM (#51696417) Journal

    In the U.S. it is extremely accurate. Any analog clock with a regular synchronous motor or digital driven by line frequency will keep near perfect time if the power doesn't cut off.

    • Re: (Score:2)

      by cruff ( 171569 )

      In the U.S. it is extremely accurate.

      Except you should be aware of the plans to relax the tolerance of the mains frequency to better deal with variations in load.

      • Not for a very long time - as in decades.

      • Re: (Score:2)

        by msauve ( 701917 )
        AFAIK, that's not to change the long term frequency, but to allow more phase noise. If you can provide an authoritative reference which says otherwise, please do.

        • Re: (Score:2)

          by cruff ( 171569 )

          AFAIK, that's not to change the long term frequency, but to allow more phase noise.

          You are right, I thought, however I had read something about the variations could run for extended lengths of time and that corrections might be applied to bring the total cycle count to the correct value only on a daily basis.

    • Power line frequency is what old alarm clocks used before quartz. It's also what old A/C electric clocks used, because the motor's speed was regulated by the power frequency.

      It's not as accurate as quartz, because while power line frequency has to be synchronized between generating plants, there is no particular reason to require precisely 60 Hz exactly. 59 Hz or 61 Hz work equally well for power cycles, but not so well for timekeeping. Those old clocks frequently gained or lost several minutes per day.

    • oooh I 'm glad someone else here said that.

      Now we're into serious nerd territory.

      This seems to be about the UK, not the US, but I expect the US tech and systems are awfully similar:

      http://wwwhome.cs.utwente.nl/~... [utwente.nl]

      TL;DR your mains clock might be up to about 20 seconds out. More than that and the grid company will schedule in corrections.

  • I was just reading an article somewhere about cheap 40$ chinese tablets... not much use as tablets... but for something like this... you'd probably be able to set it up 'just so'.

    a clock app, with wifi sync is trivial. a few settings to keep the screen on, and you'll leave it plugged in 24x7...

  • There is a battery movement that auto sets DST (Score:5, Informative)

    by Chronos56 ( 652646 ) on Monday March 14, 2016 @06:42PM (#51696449)

    Clockmaker here, fix things like this for a living.

    There is a simple analog battery movement with a secondary clock inside that resets the clock for DST and back again. They work well, are reasonably accurate and inexpensive. Pretty much a "replace single AA battery one a year and ignore it" movement. I have replaced several of the old "Atomic" movements with these.

    If you want digital, we call them cell phones these days. :)

    • Recently I went on the hunt for a new alarm clock when my iPhone had a bug that prevented the alarm from working. Why can't I find an atomic clock with a persistent memory to store alarm settings? If the power goes out and back on, then it resets itself without losing the alarm. There has to be a better way than battery backup with a 9v battery since computers kept time even when unplugged with a watch battery on the motherboard. It can't be so hard to reinvent the alarm clock.

      • Re: (Score:2)

        by adolf ( 21054 )

        Race to the bottom? That socket for a CR2035 coin cell doesn't happen for free, you know!

        Besides, why do you need a backup battery, when The time is set Automatically, Sir? [/sarcasm]

        OTOH, Aldi (US, some states only) has Medion tablets right now for $59 with a 7" IPS touch screen, an Intel Atom CPU, 1GB of RAM. Such a thing is not only a battery-backed alarm clock, but also a potentially awesome late-night Netflix/Youtube snoozumentary device.

        Add a Bluetooth speaker with its own battery ($10-$400), and n

    • Re: (Score:2)

      by xorbe ( 249648 )

      We tried hanging a cell phone on the wall, but it just wasn't the same.

  • Easy (Score:2)

    by wbr1 ( 2538558 )
    Cheapo tablet with custom clock, or being pi day get a raspberry pi or arduino and roll your own. Perhaps driving Nixie tubes.

  • Maybe you can build a *transmitter* for DCF77 to re-distribute accurate time indoor?

  • ""Atomic" clocks that you can buy in stores synchronize time using the WWVB shortwave band from NIST in Boulder"

    WWVB transmits on 60KHz. This is longwave not shortwave - The wavelength is 5 kilometers.

    • I'm also not sure it's in Boulder. I live right by NIST and was always under the impression that they transmitted somewhere out east to avoid the rocky outcroppings behind their facility. I think it's transmitted from tinmuth near fort collins.

    • Re: (Score:2)

      by TheBrez ( 1748 )
      Unless they're referring to WWV rather than WWVB. Which broadcasts on 2.5/5/10/15/20/25 MHz.

      • Re: (Score:2)

        by msauve ( 701917 )
        If you can point to one of the common "atomic" wall clocks which uses WWV, please do.

  • And let it sync to an internet time server.

  • I've never had a problem with interference (*) that repositioning my atomic clock did not fix. Good models have a signal strength meter. Another thing to note is that you don't even need constant WWV reception. Good clocks will sync up when WWV can be detected. For well over a decade, my clock has never off by even one minute. It does not display seconds. Its battery consumption is also ridiculously low: 2 AAA cells last 2 years. So don't give up easily. Find a clock online for $50-100 and see how it goes.

  • >" In many locations, these clocks are never able to receive a time signal, making them no better at timekeeping than a cheap quartz clock"

    Yep. In the Mid-Atlantic (east coast) the signal is very weak and easily overpowered by just about anything. I have 7 atomic clocks in my house. Only 4 reliably get a signal and the other 3 have to be moved to different rooms to sync, which is very annoying. And the power/reliability changes pretty greatly throughout the year with the seasons.

    There was a proposal

    • Re: (Score:2)

      by CoderJoe ( 97563 ) *

      I don't know why there isn't a standard based on FM radio- since just about all the FM stations now broadcast digital information, including the time.

      Two possible reasons:
      1) the receiver would still be more complex
      2) lack of a single, standard frequency to set the receiver for.

  • I had a subatomic clock (Score:5, Funny)

    by island_earth ( 468577 ) on Monday March 14, 2016 @07:05PM (#51696597)

    ... but I kept losing it.

  • Just get a quartz clock and calibrate it.

    People working on trains and airplanes etc. have to (or at least had to) get their watches calibrated. I remember calibrating my Seiko quartz watches myself back then (1970) to +/- 1 second a month. I could probably have done better.

    http://tf.nist.gov/general/pdf... [nist.gov]

  • I don't know if it's actually accurate or not, but it sure looks [schoolhouseelectric.com] accurate.

  • Easy (Score:2)

    by Yunzil ( 181064 )

    Are there any reasonably-priced wall clock alternatives, that use something other than shortwave to set the time?

    Thousands of them, and they're very cheap! They use your hand to set the time by either pushing some buttons or turning a dial.

    Glad I could help.

  • If you plan on building it yourself, there are plenty of accurate oscillators out there at ~100ppb. After a year, at worst you would be off by a few seconds. You would want to make use of a GPS PPS signal to perform the initial calibration but from then on it could run completely isolated from wireless and powerline references signals.

    Here is an example oscillator rated for 50ppb http://www.conwin.com/datasheets/tx/tx395.pdf [conwin.com]. It can be found on Digikey.

  • The reason these things are expensive is because it's neither cheap nor easy to "just" implement something with WiFi-to-NTP. You need some sort of an interface to enter WiFi settings, you almost need an entire OS with a DHCP daemon, TCP stack, NTP daemon, you need the WiFi chip and be able to power it (you would hope) using a battery for ~1y. Then you also need a way to fix your clock either using a stepper motor or some sort of time stretching mechanism (where you ignore or add a number of ticks until you

  • That's how the banking system does it. The chips are cheap. If your house clock has to have better accuracy than 1 billionth of a second, then you need to re-prioritize. Heck, if your house clock is quartz based and you can't afford to lose a second per month on what you're looking at to cook and watch your favorite tee vee program and get to work on time, it's still bad.

  • The modern clock chips (eg the Maxim DS3231) are incredibly accurate, eg around a minute per year without user calibration.
    http://theradioboard.com/rb/vi... [theradioboard.com]

    Alternatively there are many projects using a cheap GPS module to provide a time and date readout.http://geoffg.net/GPS_Synchronised_Clock.html

    I'm not sure about commercial products though, sorry.

  • Chip Scale Atomic Clock [popsci.com] - OK, at $1500 it's not super-cheap, but it's your own, it will work whether there is Internet or not. Heck, it will work whether there's civilization or not! Imagine having accurate time during the zombie apocalypse.

  • Get the cheapest Android tablet. Root it. Connect to local WiFi. Install ClockSync, some nice-looking clock and a blanking disabler. Hang on the wall.

    There. NTP-synchronized wall clock.

    (root is needed so that ClockSync could sync time without user interaction.)

  • The next logical step after atomic clocks seems to be hydrogen clocks, or "H-clocks" as they are known.
  • What does WWVB stands for? I cannot find using my favorite search engine.

    • In March 1960, the call sign WWVB was obtained by NBS for the 60 kHz station. The “B” in the call sign probably stands for Boulder, the site of the original transmitter. However, one interesting theory is that the “B” could stand for Brown. W. W. Brown, one of the designers of the Fort Collins station, was employed as a contractor by NBS when the call sign application was submitted. Perhaps not coincidentally, his initials were W. W. B.

      Source: http://www.nist.gov/pml/div688... [nist.gov]

  • I have been wearing a Seiko wristwatch for years now. It has a solar cell for a dial, and one day in bright daylight is more than enough for it to run all year (together it gets with the exposure from being worn daily). Right now, it still runs on the charge it got from me being in the Sonora desert, last summer. It is very accurate, with a deviation in the order of magnitude of a few seconds per year. When all those dumbos whipping out their cell phones when they want to know the time, I just flick my wris

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