By Clay Dillow Posted 07.27.2012 at 10:02 am 11 Comments

Givers of Illumination, Keepers of Immaculate Time shainelee via Flickr

Your smartphone is probably losing track of time. Most electronics with internal clocks keep them regulated via vibrating crystals (much like a quartz clock) that keep their timekeeping precise. But while far better timekeepers than mechanical clocks, even these crystals can be thrown off their regular frequencies by external factors like humidity or temperature. Which is why scientists at Hong Kong University of Science and Technology think you’re better off syncing your clock to your overhead lights.

Smartphone clocks can drift by up to 10 seconds a day, and if you’re one of the many people who rarely syncs up your handheld with your computer or otherwise docks with some mothership computer online, that means you could pretty quickly start drifting by whole minutes.

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Science, Clay Dillow, clocks, electricity, energy, physics, smartphones, timekeeping
But artificial lighting is all around us, and it to is a fantastic keeper or time. Alternating current provided by power mains runs at a frequency of 50 or 60 cycles per second, with the power delivered dropping to zero twice per cycle. The fluorescent lights in your home or office are actually flickering at very regular intervals, though its too rapid a flicker for your eyes to notice it. The Hong Kong UST team has demonstrated that any device with a camera or light sensor--so pretty much any smartphone currently marketed--can tap this flicker to keep accurate time, just like the oscillations of its internal crystals.

They think their scheme is accurate to less than a thousandth of a second per day, and since it needs no network connection it can save on the device’s battery life. That’s probably not a huge deal for most people, but for those living or working in remote places away from network coverage or an internet connection--especially places with extreme weather (and it seems like remote places with no Internet tend to be the same places that have extreme weather--like the deep Amazon or a South Pole research station)--this could have real applications.

[New Scientist]

11 Comments

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Robot
07/27/12 at 10:26 am

I have a simple\dumb\basic phone and within its settings I have it sync its time with the cell phone company. But if a person has a smart phone with GPS capability, the manufacture of the smartphone could allow tap into the time pulse from the GPS data to sync the phone.

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Charybdis
07/27/12 at 10:30 am

I wonder how many bars you canget deep in the Amazon or South Pole.
Why not just sync directly with the electrical frequency when they plug in to charge. I would however be a bit suspect of how "clean" the electricity would be off the beaten path, whether syncing with the flourescent lights, or directly with the electricity. I would think the frequency would be all over the place and less reliable than the crystals in the phone.
Just bring a decent watch and pad of paper.

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Robot
07/27/12 at 10:42 am

en.wikipedia.org/wiki/Radio_clock

Radio clock

A radio clock or radio-controlled clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock. Such a clock may be synchronized to the time sent by a single transmitter, such as many national or regional time transmitters, or may use multiple transmitters, like the Global Positioning System. Such systems may be used to set computer clocks or clocks meant for human readability, or for any purpose where accurate time is needed.

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TheArtist
07/27/12 at 12:23 pm

Apple's phones and computers all link to an Apple clock server, they all show the same time.

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jefro
07/27/12 at 5:03 pm

Pretty sure every cell tower sends out the correct time. Why do we need lights to fix it? If you are in some extreme place then the satellite sends time info. I doubt the south pole generators would be a good choice to sync to.

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tcolguin
07/27/12 at 7:24 pm

Let me get this straight, take a super accurate syncing to a cell tower/computer network and instead try to observe a flickering light, which may or may not be there from one second to the next, which is cycled by a system that is varied from time to time as power requirements change?
Yes that is right the 60/50 cycles per second is not precise.
If it was the old clocks that were running off of it would have been more precise then the clocks that replaced them (as in the ones with crystals).

In fact the clocks in computers have always had lousy methods for keeping time, cheap circuits. A $5 watch has better crystal/time keeping, but once they got synced to the atomic clocks who cares any more? (That is where the cell towers get their time by the way), not to mention that the GPS won't work without atomic level accuracy.

And even if I suppose that the lights are some kind of super accurate tick/tock. You are just getting "beat" not the time of day. So do this, start off by looking at a clock that has the exact right time. Now go outside and look at no clock, and just forget about time. Now get out a stop watch and let it count off 60 seconds, and tell me what time is it exactly?

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Paul_Wolfe
07/27/12 at 8:36 pm

I would have thought PopSci would have done more research. Old-style magnetic ballasts (for T12 lamps) have detectable flicker, due to the 60hz cycle time. Modern electronic ballasts for T8 & T5 range from 20khz to 60khz. Line frequency has no effect (other than to be converted inside the ballast) and does not contribute to any flicker in the lights.

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Patrikd
07/27/12 at 10:11 pm

What an asinine idea - in most cases, the clock in your cell phone (or the cell tower, or the GPS satellite, or any other clock source your *phone* has access to) will be much better than the line frequency.

Have a look at these results, for example:
http://hackaday.com/2012/07/24/hows-the-60hz-coming-from-your-wall/

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riff_raff
07/27/12 at 11:48 pm

The frequency of power grids in large urban areas is probably only consistent to +/-.25 percent. And in remote areas of the world it is probably far less consistent. The grid power frequency can vary based on supply/demand and on the various mix of power sources supplying it.

I'll stick with my $20 waterproof Casio watch if I need accurate time.

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berk99
08/09/12 at 8:36 pm

Aww all the best reasons why this is a dumb idea have been said. even my Casio watch observation.

Is this what passes for cutting edge research at Hong Kong University of Science and Technology?

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packstrap
08/24/12 at 3:19 am

There are many apps out there for iPhone and android that can sync their time nicely. How about checking this video out: a clash of the titans 3: http://www.youtube.com/watch?v=-7uL-DON5FU



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