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Ask Slashdot: Alternatives To "Atomic" Clocks?
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?
No wait, it's still atomic
“He’s not deformed, he’s just drunk!”
Build one out of a Pi 2 with one of those cases designed for it and a specific same-dimensions screen. Adafruit had them as a package at one point because LifeHacker had an article about using the same kit to make a portable CLI hacking thing..
Anyway. Pi 2, $70 screen, $20 case. 5v adapter. Done.
With a Raspberry Pi, a GPS dongle and a LCD or LED matrix, you could build one easily and well under 100$.
If NTP is enough, even less.
First : why do you need a wall clock to be *that* accurate?
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 don't read AC A human right
The Global Positioning System can do more than just tell you where you are. It can also tell you when you are.
If it weren't for deadlines, nothing would be late.
The cheapest clocks that use NTP over Wi-Fi cost around $400.
Seriously? I can get a Chumby for less than that. About a tenth of the price.
And it does a lot more than just tell time.
National Time & Signal has more traditional clocks though, if that is what you want. Analog and LCD, WiFi supported.
Where are you searching?
An Arduino project that's been in the back of my mind for a while. Listen to the output from an FM channel (eg National Program here in NZ). Do some cunning sampling/filtering of the sound and detect the pips on the hour -- synch your RTC to that.
"Are there any reasonably-priced wall clock alternatives, that use something other than shortwave to set the time?"
Buy an Amazon fire for under 50$ or any cheap tablet and use one of the clock apps.
WWVB Coverage Maps:
http://www.nist.gov/pml/div688/grp40/vb-coverage.cfm
But it won't work for a wall clock. Signals are weak and even with a good receiver you need a view of the sky.
I'm sure you can build yourself an NTP clock for less than $400, but personally (if I cared and I don't) I'd just buy a cheap tablet or wifi enabled digital photo frame and do some hacking.
Why you'd bother when you'll end up with something that needs mains power rather than a battery replaced say every 5 years is beyond me though.
As cheap as 50$ on ebay, some are GPS-disciplined. Small, available. About the same tech currently on the GPS satellites themselves.
I have seen quite a few very well done setups that consist of a Raspberry Pi (or a clone), and a monitor or cheap HDMI TV.
If you want an analog clock, and not just a digital display of one, then you have a harder job cut out for yourself.
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 $30 (make sure the display is fine) and stick it in screensaver mode. (You can use a bluetooth mouse to operate it.)
Oh, don't do this if you're married and the clock is for one of the "good" rooms. B-)
In the U.S. it is extremely accurate. Any analog clock with a regular synchronous motor or digital driven by line frequency will keep near perfect time if the power doesn't cut off.
“He’s not deformed, he’s just drunk!”
The iWatch's got a retina display. It's what retinas crave.
Not exactly what you want but you could make it work for under 50 bucks. Get creative.
http://www.instructables.com/id/Arduino-Internet-Time-Client/
I was just reading an article somewhere about cheap 40$ 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...
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. :)
Having setup ntp for small network (100 workstations before ntp was installed on the OS [solaris, hpux, sco, auspex, netapp]), we just set one system to sync to the outside, opening a hole in the firewall for it's MAC address. It sync-ed to a public stratum 2 server. That was enough to do the rest of the servers which all ended up on stratum 3.
A real atomic clock used to use the Ce-oscillator or some such and connected to a machine through a serial cable. That host became a stratum 1 server. I doubt the OP needs anything that accurate. I use 2 wall clocks that sync to the NIST time signal and they're good enough. If he's not in an area that offers good radio reception but has internet, he could build something from a Rasberry Pi using Linux and sync his network off that.
The wall clocks will have to be synched by hand. That's why you have servants.
:)
Just buy a cheap DVB-T dongle like the RTL2832U and use any TV Broadcast to synchronize your NTP on it. Bonus you can play with GnuRadio for the same price. https://wiki.gentoo.org/wiki/T...
Cheapo tablet with custom clock, or being pi day get a raspberry pi or arduino and roll your own. Perhaps driving Nixie tubes.
Silence is a state of mime.
Lots of stuff that still requires time to be manually set. It's insane. I dread Daylight Savings changes and I keep a list so that I don't forget things twice.
Buy a tablet. Connect it to your home wifi. Install the clock app you want, peg the thing to the wall. Maybe even with a power cord or something.
Boom, instant, accurate wall clock.
Maybe you can build a *transmitter* for DCF77 to re-distribute accurate time indoor?
WWVB transmits on 60KHz. This is longwave not shortwave - The wavelength is 5 kilometers.
To avoid seeing this message again, always shut down your computer properly by selecting Shut Down from the Start Menu.
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. If you're truly stuck return it.
(*) 15 years ago I had 2 or 3 desktops that were always powered on, and they generated a lot of interference. Now I have one desktop that I rarely power on. The laptop, tablet, smartphone, and other devices don't make a dent in WWV reception.
Location: Michigan.
First, you did not say what accuracy you need.
Or if you have clear view of the sky for GPS.
A run of the mill gps receiver module with a good view of the sky should have a 1pps output good to 100nS.
(The 1pps signal rising edge should match the actual time within +-100ns.)
Given this, it is a question of transporting the accuraty to your aplication.
Perhaps a ras-pi gps shield and an ntp o 1588 server?
There may be some GPS based nav devices whihc ar even cheaper.
Depends on your skills and desire to figure out how to put something together.
When you are done, how will you know if it works?
>" 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 once to add another WWVB transmitter to help but it never happened. 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. It is cheap and simply technology. GPS is not generally a good option because it doesn't penetrate buildings well and they and WiFi clocks are complex and expensive.
http://www.nist.gov/pml/div688/grp40/radioclocks.cfm#what
... but I kept losing it.
GPS is a good way to get an accurate time signal. You don't need a full lock to get time, just any signal from any sat. And you're not moving. Should be easy indoors after a few minutes.
Someone probably makes and off the shelf product but I'm not finding many.
You could make one yourself. Search "arduino GPS" on ebay and you'll find units for about 10 bucks - Couple that with a 5 dollar ardunio knockoff and you've got the brains for a pretty fun project.
I'm suspecting the big hurdle here will be battery life. An ordinary wall clock can get months or years of service out of a single AA cell - You just put it up on the wall and forget about it until next year when the second hand stops moving.
While GPS chips are dirt cheap in 2016 you're still talking about quite a bit of processing power and a fair bit of engineering to get the power down low enough to make the thing last a while on conventional batteries.
If you're going to go whole hog I'd guess you'd have to come up with a scheme where the Arduino wakes up the GPS, waits for a lock, sets the time, then powers down the GPS again. You'll probably also have to add a stable oscillator or get a dedicated RTC module because I doubt the arduino would be stable enough to keep accurate time for very long. (Search 'arduino rtc' on ebay and you'll find battery backed rtc modules for about 5 bucks)
Well, and while the arduino is pretty low power, it's gonna wear down any battery after a few weeks.. But bunches of L-ion cells and charging/protection boards are pretty cheap on ebay too.
And then you've got a clock face to drive too. That's got it's own power requirements and your battery isnt going to last long if you just drive it with a stepper motor 24/7 (Probably easier to go digital with an LCD or something)
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...
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Wait! I thought he already left...
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!
Some drink at the fountain of knowledge. Others just gargle.
I don't know if it's actually accurate or not, but it sure looks accurate.
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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. It can be found on Digikey.
Many Slashdot readers already have an alternative to those atomic clocks that'd cost the essentially. Simply run an old cellphone off AC power, turn off sleep, and runs any clock or other apps that displays the time. I run a weather app that way on my ancient iPhone 3GS. I not only get the precise time, I get the temperature, weather, and a spinning globe with cloud cover.
ESP8266, epaper display or LCD, NTP sync once per hour/day over wifi. If you use the power saving modes right, this should be doable as a battery powered device.
Let me Google that for you, https://www.google.com.au/?gfe...
and set it yourself once a year, doofus.
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...
Some drink at the fountain of knowledge. Others just gargle.
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 have 'corrected' the thing). Then you have to go through FCC regulations because you're creating a transmitter and that will set you back a few $1000's and months of engineering time. That's your entry cost without any ongoing 'tech support' you have to have live for people that can't figure out the thing, security updates (as if) and time zone and daylight savings management/updates.
That's a LOT to get done, even if you boot for a few minutes every 24h to sync the time (and what if you don't have a WiFi signal right then and there) and your market for that tech will be relatively low; most people don't mind spending 1 minute every few months fixing their $5-25 clock, having them spend more money only to get the privilege of changing their battery just as often as they need to change the time is not worth it, the product is dead before you even have it marketed.
If you need such accurate clock, they do exist, they are expensive because the people that need them neither see the direct cost nor have the objection to pay thousands for an accurate clock. The other 'markets' are so niche they already have custom products that don't rely on buggy WiFi/TCP/OS implementations.
GPS has similar cost problems as far as the tech goes, it takes too long to lock onto the required GPS satellites especially indoors where it just becomes a very expensive broken clock.
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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.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
such as ask slashdot, ntp driven wall clocks exist.. if you'd just, i dunno, spend two minutes and look for them.
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...
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.
It is actually rather difficult to obtain accurate time. Many people do not realise that phones can be off by many seconds, yes, even when the GPS is enabled. The latency of the display of tablets is also in issue. Even the time pips on radio broadcasts in Australia, if listening on the digital system, are late by up to about 5 seconds. The 'talking clock' in Australia is now privatised and the accuracy is no longer able to be taken for granted.
My solution was to build a simple kit from:
http://qrp-labs.com/clockkit.h...
Accuracy to the millisecond level and amazingly cheap. Adapt the display to wall size and it's very much cheaper than the commercial clocks that are accurate.
Chip Scale Atomic Clock - 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.
"The agriculture ministry is not in charge of Gundam" - Japanese ministry official.
https://www.google.com/search?...
An ESP8266 module with an LCD or LED display.
You would need an ESP module like the ESP-07 or ESP-12 with multiple I/O pins or a NodeMCU board to drive the display, but you can program it to sync with a time server every day or so over your wireless network.
You can add a DS3231 precision real time clock chip (cheap breakout boards are available on eBay) for better accuracy.
http://www.buxtronix.net/2015/...
Perl Programmer for hire
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.)
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
The next logical step after atomic clocks seems to be hydrogen clocks, or "H-clocks" as they are known.
Here's a bunch of different ones you can build. If it was me I'd just get a Raspberry Pi with a screen as that would be easiest.
Raspberry Pi Based:
Pong Clock, GPIO Clock, another one, AlarmPi, some more examples
Arduino Based:
type 1 type 2
expert mode,another one, ye olde tux style
Why not a clock that has multiple redundant time sources? So it can get a time even under challenging conditions.
Of course then the problem is, which source is considered "The Standard". I mean NTP has mechanisms for resolving multiple, differing time values. However I'm not aware of a Standard Of Standards.
OK, here's my totally B.S. design for such a system. First you need a quartz clock movement. Inexpensive and accurate and it will keep decent time off-grid. Then a hierarchical system, chosen by the "gee I hope this is right" method for assumed accuracy!
1). Atomic radio signal from the NIST facility in Boulder;
2). GPS clock signal;
3). Cell system clock;
4). NTP sourced clock from the Internet, over Wi-Fi or maybe Low Power Bluetooth.
I placed NTP as #4 not for accuracy purposes but because I'm concerned about power consumption. LP Bluetooth is great but how often can you get a signal? Wi-Fi is much more ubiquitous IMO, but I'll bet it's a power hog by clock standards. However maybe a cell receiver system is too, for that matter. And how does that compare to running GPS chipset and receiver?
So much here is beyond my ken. I do like the idea of multiple independent time sources though.
What does WWVB stands for? I cannot find using my favorite search engine.
You can sync your computer or smart phone directly with NIST (aka WWV) by visiting http://www.nist.gov/pml/div688/grp40/its.cfm and selecting one of the sync options. The screen saver will work as your 'clock'.
Forget the wall clock and get a nice bracelet watch. More stylish than a smart watch (who needs a smart watch when we're all carrying our phones around?) I'm in Florida and I never have an issue with "weak signal" from Boulder. Picks up the atomic radio signal from four different locations on the planet depending on where you're at. Nearly waterproof. Solar powered (no more batteries!) My Skyhawk version displays three time zones simultaneously: UTC, analog of my choice, digital of my choice.
You can add GPS synchronisation to any old analog clock - see http://www.siliconchip.com.au/Issue/2009/March/A+GPS-Synchronised+Clock for details (Silicon Chip magazine also has a bog-standard GPS-synchronised clock project at http://www.siliconchip.com.au/Issue/2015/December/High+Visibility+6-Digit+LED+GPS+Clock).
https://buy.garmin.com/en-US/US/oem/sensors-and-boards/gps-18x-oem/prod27594.html
$30 Raspberry Pi running ntpd connected to a $70 monitor mounted on your wall.
The OP might not have all his RF knowledge in order, but about one thing he is right: the radio frequency spectrum is being more and more polluted. Modes like AM/SSB are almost impossible to use nowadays and frequencies from longwave to even VHF suffer from all kinds of interference (from power lines (bad maintenance) to cheap Chinese electronics). And with many houses build of re-enforced concrete (Faraday Cage) receiving anything indoors is also getting next to impossible. I am sorry to see this happen. There is a world out there on the radio, but one you can hardly hear any more.
So, your complete time solution includes a webcam in the antipodes, aimed at a second sundial.
I'm using a 5 year old 10 inch tablet that is so slow its not good for anything now. Except for a digital clock app that updates the time with NTP and the tablet has wifi to maintain connectivity. That is my bedroom clock. The screen in landscape mode provides large readable characters even for my eyes. So there's your cheap accurate clock.
Ordinary quartz wall clock can be modified to sync with GPS signal. See http://geoffg.net/GPS_Synchronised_Clock.html.
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 wrist. And with its large, white dial it just looks good.
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GPS signal is very hard to receive indoors. Smart phones these days can kind of do it, but GPS is still a very weak signal when you have a roof over your head. Wifi is going to be orders of magnitude stronger signal and easier to implement. Someone needs to throw a $3 ESP8266 into a device and start a kickstarter. If there is demand, people will come for it.
Sounds like an interesting Raspi or Embedded project. A mechanical NTP synced clock. I think I am going to try this.
The dangers of excessive individualism are nothing compared to the oppressiveness of excessive collectivism
For home use, who cares? Within +/- 5 minutes is more than good enough for everyday life.
For business use, the cost of a master/slave clock arrangement is peanuts if it actually matters (e.g. stock markets etc.).
For everything in between solutions will be expensive or homebrew.
There's a company in France and the UK: Bodet. They make their own GPS/radio controlled master clocks that can then send a signal over a licenced frequency across huge sites (30 acres+) to their client clocks.
They also have PoE based clocks and even speaker systems timed to the same signal. I promise you, they are not cheap.
Short of using a GPS module's output tied to some device displaying the time, that you make yourself, you're going to be hard-pushed to find a cheap system.
I speak as someone who runs two NTP pool servers, has all my gadgets at home and in work synchronised to GPS or NTP, and even has MSF-controlled clocks, watches and bedside alarm clocks (Daylight saving? Don't have to do a thing).
If you're out of the time signal range in your region, you're looking at GPS or NTP, and both require basically a computer somewhere (RPi or GPS modules on an Arduino, for example) doing the work, and a display of some kind (driving a traditional mechanical clock, or an LCD).
The replacement is mobile phones. I still have a radio controlled clock and rarely have issues with it. For a 3€ device it has survived a long time, and being Frabkfurt and CET based it has even handled changes to daylight savings time without any updates. That is pretty impressive, but if it died, my mobile phone would replace its function.
Hang a Kindle Fire with a clock dial app always on, up on your wall
Rome taught me patience and assiduous application to detail. Virtues which temper the boldness of great, general views.
Do you like DYI? Take a look here. http://www.instructables.com/i... It's for DCF77 (Germany Station) but surely it can be fitted for NIST.
San Jose Navigation's FV-M8 GPS module is available everywhere (including from Amazon) for less than $30. It has an NMEA output and a 1 PPS output for time synchronization. I haven't measured the time accuracy of this module, but the module it replaces had a measured time accuracy of better than 100 microseconds, the limit of the equipment I had to measure with.
You have to build it, but it's not difficult: https://sites.google.com/site/wifianalogclock/
Almost thought this was another stupid mdsolar anti-nuclear clickbait story there....
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 broadcast? Same answer. Why do people use things like Instagram that don't even let you upload a picture from a normal PC? Same answer.
Lazy thinking like this is moving everything into the walled gardens of the megacompanies with oversight of the three-letter agencies, and sucking what little life remains in the do-it-yourself makerspace.
How has nobody suggested he spend $1,500 on an actual chip-scale Rubidium atomic clock module?!
Patch the 100MHz output to the Pi's system clock and you're laughing.
GPS clocks have lots of vulnerabilities and can be attacked easily. If you are in a stock exchange you to run rife is you spoofed a GPS signal. They also have limitations as to where they can be placed. The antenna length has limited reach and can't be too long either.
I have an idea for a PTP clock that I think would cost less than US$100 to make and would be unbeatable in terms of accuracy and security. The device would be placed on a PCIe board for ease of integration.
How's this from my home PFSense firewall? Seems my $60 MSI motherboard is pretty good at keeping time. -0.023ms offset after 512 seconds.
remote refid st t when poll reach delay offset jitter
==removed junk chars==
-ra.steadfastdns 216.86.146.46 2 u 388 512 377 14.234 -0.706 0.632
+rb.steadfastdns 216.86.146.46 2 u 144 512 377 14.356 -0.533 0.546
*dns1.steadfast. 216.86.146.46 2 u 400 512 377 14.826 -0.023 0.183
+time1.google.co 133.45.56.223 2 u 386 512 377 24.719 0.007 0.181
-time2.google.co 222.174.180.252 2 u 362 512 377 34.593 -3.214 0.550
-time3.google.co 63.32.115.164 2 u 354 512 377 38.754 -0.978 0.568
-time4.google.co 226.42.99.180 2 u 318 512 377 23.877 -0.292 0.398
I would love to have an analog looking watch, that is, one with a nice face like a Casio or Citizen. I would like it not to be atomic but rather set by local cell tower signals. They are always accurate to within a few seconds of atomic time, from what I can see. Plus when I land in another time zone (or drive to another one), it would change the damn time automatically. Daylight savings? No problem. Not observing daylight savings in Hawaii? Also no problem. In Brazil? No problem.
Wouldn't that be nice? Of course, my phone already does this and gives me a very nice and accurate time, but I love having the wristwatch to glance at the current time and date, but I strongly prefer a clear and legible analog instrumentation for the display.
My father worked in the new (and fancy) Lifeboat College in Poole, UK. Plagued by many design flaws (including direct line-of-sight from a corridor into a ladies cubicle via "architectural" windows), the steel beams that make up the structure partially blocks the timekeeping signal to the large deployment of time-syncing clocks. This makes for an amusing sight around noon, where all the clocks in the building would try to sync with the weak signal, and do many rotations round the clock face when the signal dropped out.
If you gave me a choice between a printer and a giraffe with explosive diarrhoea, i'll get my ladder and my raincoat
If you're in a facility that doesn't allow phones inside for security reasons, that wall clock, or wristwatch, is a handy thing.
Use a rooted Android tablet. You can disable the 30-minute sleep mode and install an NTP client to update the time on a schedule over wifi.
If you use the app "Screen ON by Chethan Dandgey" you don't have to root to disable the 30-minute sleep timer.
If you want an ntp client you control you'd need a rooted device. If you are good with the tablets built-in time client you can skip root altogether.
The 50/60Hz powerline frequency is notoriously strong and ubiquitous, touch one end of an amp cable or an oscilloscope probe or an AM radio, forget a pull-up/pull-down resistors and resistor capacitors on an Arduino, you have your 50 or 60 (depending on your locale) Hz reference. Now in order to compensate for load differences, steam/hydraulic pressure at the turbines... that frequency is allowed to go up and down a bit... but over the course of a day, it must be very stable.In the US, for example the standard (once) required that the 60Hz power line averages out to exactly 5,184,000 cycles in any day, But if you live in the US, YMMV as this guarantee seems to be no longer written in stone
d. Digital clocks in plugged-in devices such as microwave ovens use this. Swiss Grid has a very good explanation and time deviation on their website. So synchronous clocks and clock radios of the 1960s and 70s might have held their time better than your untethered Seiko or Rollex ever did. Which makes me wonder why they didn't rely on this instead of the built-in crystal that might have been off by a second or more per month depending on temperature, humidity and how many times I tried to tweak that little variable capacitor with a jeweler's screwdriver.
“Far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy lies a small unregarded yellow sun. Orbiting this at a distance of roughly ninety-two million miles is an utterly insignificant little blue green planet whose ape-descended life forms are so amazingly primitive that they still think digital watches are a pretty neat idea.” Douglas Adams, The Hitchhiker's Guide to the Galaxy
This amateur has done what you're looking for: http://leapsecond.com/
From what I read from the OP, he wants a wall clock that keeps in sync. The first thing that comes to mind would be the Android tablets as posted above, as they can be synced via the cell network or NTP.
This might just be a niche market. Take an Arduino with Wi-Fi capability, add an inexpensive LCD touchscreen, add some code to handle timezones, manual time setting, and so on, and call it done. Toss in a FONA cellular antenna/modem whose sole purpose in life is to get the time from the cell network for accuracy, and that is another avenue of getting things working if Wi-Fi connections are not doable.
If you need accurate time, would a wall display clock really be the thing you are going for? I have an alarm clock and the sole reason I bought one was because I keep forgetting to change the summer/winter time and either come in too early or too late.
As nice as it is, I only look at the minutes and any other clock would be acutrate enough. moreover, since a few years I hardly use it as I have a phone with me that keeps the time. I also spend most of my time looking at a screen that has a time.
So as nice as it would be to have a cheap one that would be able to do what is requested, it is at most a nice-to-have not a must-have and if OP really thinks it is a must have, start selling one.
In all other cases: A standard clock wall is accurate enough. If precise time is needed, a clock wall will not be a good solution. Those who need a solution will already have one.
Don't fight for your country, if your country does not fight for you.
Can you get in trouble for having an atomic clock in a public place. After all it is atomic and sounds scary so you must be a terrorist if you have one.
WWVB operates on a frequency of 60 kHz in the longwave band. Its primary purpose is to provide a digital radio signal for clock synchronization. Its sister stations WWV (in Colorado) and WWVH (in Hawaii) operate on 5, 10, 15 and 20 MHz in the shortwave band, and serve primarily as frequency standards, and to provide time and other information in audio format.
I am not a number - I am a free man!
<!DOCTYPE HTML>
// <!-- ;
// -->
<html>
<!--
Free "atomic" clock
Author: Matthew Mellon <Slashdot user 51228>
Copyright: This code is released to the public domain
Usage: Open this in a Web Browser. It will display a pretty darn close approximation to actual local time (adjusted for the difference in your CPU clock from reality). You could use this to turn an old phone into an "atomic clock" (emphasis on the quotes). The offset is re-checked hourly.
Notes: You might want to make this pretty using one of those new-fangled Cascading Style Sheets, or maybe you could display an SVG image of an analog clock and use a bit of scripting to update it. This step is left as an exercise to the reader.
-->
<head>
<title>Time</title>
<script>
var difference = 0;
var syncTimer
var updateTimer = setInterval(updateTime,13);
var req = new XMLHttpRequest();
function setTimers()
{
syncTimer = setInterval(sync,1000*60*60);
updateTimer = setInterval(updateTime,13);
}
function sync()
{
req.open("GET", "http://www.timeapi.org/utc/now", true);
req.onreadystatechange = function()
{
if (req.readyState == 4 && req.status == 200)
{
lastFetchedTime = Date.parse(req.responseText);
lastSystemTime = Date.now();
difference = lastFetchedTime - lastSystemTime;
echo(lastFetchedTime);
}
}
}
function updateTime()
{
ts = new Date();
ts.setMilliseconds(ts.getMilliseconds() + difference);
document.body.innerHTML = ts;
}
</script>
</head>
<body onload="setTimers(); sync(); updateTime();">
</body>
</html>
What I think some people don't know is that while the 60KHz WWVB signal penetrates most buildings very well, the antenna inside these clocks is a loopstick type, and is very directional; you have to know how it's oriented in the clock in question, and you need to know which direction Fort Collins is, so you can place the clock correctly. The Sangean atomic clock-radio I have in my bedroom even has the WWVB antenna in a separate housing on a cable, so you can orient it however you need to in order to get the signal. As stated above I have 4 of these type of clock (likely a 5th soon enough) from three different manufacturers, and all of them get synched at least 90% of the time. The worst that will happen is your clock will be off by a second or two until it's next scheduled sync, and if you can't tolerate that then I'd have to say you're expecting way too much of it.
Are YOU using the TOOL, or is the TOOL using YOU? Think about it!
- and then i and leave it there overnight so it can 'reset' itself. We have three, i just do that the night before than gather them up and re-hang them on the wall. Not that this is any faster than manually changing the time on a normal clock, but, well, that is what i do.
Watches and wall clocks made in Switzerland need no synchronization, they are accurate ab ovo and will last your grandkid.
Most people (like 99.9999% literally) simply do not need atomic clock accuracy!!! That accuracy is in nanoseconds (atomic clocks actually have pretty horrible phase noise but that's "a feature" of Heisenberg uncertainty). Crystal timing has far lower phase noise than atomic clocks and thus far better short-term accuracy after being set!! Millisecond accuracy that is regularly adjusted is still overkill for the average user but it's easily available. For a visual clock, that is producing human consumed real-time, you are wasting your time seeking more than 100 milliseconds accuracy. If you aren't going to continually update timing, this is easily available from ANY quartz referenced timing system.
BTW accuracy is NOT repeatability or forward precision of timing! That's entirely different; it's important to understand the difference between accuracy, precision and repeatability otherwise it's a useless conversation in toto.
If you need better accuracy than that, then NTP connected to your instruments that require it but trivial and cheap (less than $400 though the instruments likely cost more). This includes computers seeking to synchronize timing for LAN or Radio communications. This is not a human consume usage however.
When I see questions like this I know several things:
-- the person asking doesn't know shit about clocks or timing
-- the person probably doesn't understand accuracy, precession and repeatability (or things like phase noise which are critical with atomic clocks)
-- the person is mathematically illiterate because they incorrectly believe that "more digits is better"; that is trivially wrong!
-- the person is likely a tech wannabe - which is fine when you are young but it's Epic Fail if you are older than ~25 yo
-- the person is projecting an ego (short penis?) problem and is trying (too hard) to project an image of being a tech alpha male
Check out this dude's page: http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html
I built a similar setup using a ublox max7q module. Very reliable. Been in service for over a year w/o any issue and very consistent drift.
sudo rdate -s time-b.nist.gov
Casteism
You can buy "radio controlled" clocks across the EU which rely on LF transmitters in Germany/UK/others.
These start at about $10 - https://en.wikipedia.org/wiki/...
WWVB operates a transmitter at 60kHz which is receivable across the lower 48 states. https://en.wikipedia.org/wiki/... and there are supposedly a large number of radio-controlled clocks available in the USA which utilise the signal.
There are known to be reception problems in the east coast of the USA (covered on the Wikipedia page) and NIST have attempted to (but been blocked from) setup an east coast transmitter. The NIST page advice should be noted. Modern houses with foil-lined insulation are effectively faraday cages at low frequencies and positioning of the clocks for best reception is important.
If you wish to improve the situation, mudge your congresscritter about it.