OT Clock synchronization

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You're just buying the wrong stuff. I have clocks that are set by the atomic clock via satellite [though because of where we live the clocks have to sit in a west facing window to be set]-- my DVR sets itself through the cable- I suspect that's where my VCR figured out what time it was- my InfoGlobe sets itself through the telephone lines.

My $20 clock radio [one of the 'would-set-itself-if-I-left-it-in-the-window-at-the--end-of-the-house-clocks] has a battery so I only need to set it once every few years. I hope I didn't pay much for the unhandy feature of being able to set itself.

Jim

Its a pretty common feature in devices anymore. Even my 5 year old low end weather station has a receiver that listens to WWVB and gets very accurate time and additional stuff like automatic DST changes since they set a flag when we transition to DST.

Same here. I have one of the Crosse Technologies wireless outdoor/ indoor temp displays and it sets the clock via WWVB. Works great. I agree they should put this in more appliances or at least a battery so that it will keep time for a few hours if the power goes out. Around here, the power loss isn't frequent and when it does, 90% of the time it's for less than a minute. I suspect the reason they don't put the radio link in appliances is that unlike the wireless thermostat, a lot of time you don't have much control over where to put it. And it might not get pickup, then people would be complaining.

As for why not transmit it over the powerline, I think it comes down to who would pay for it? You can't just have one transmitter at the power plant. There would have to be eqpt installed closer to the distribution endpoints and there is no incentive for the power company to shell out the $$$.

Actually it's set by direct transmission from a ground station. Same idea though. These clocks are often, amusingly, labeled "atomic clock". Just a minor elision there ...

It's already so cheap to pick up this signal that investing in another one would be mostly redundant -- not always but usually.

GPS receivers get the time from the GPS birds, and that's an extremely precise time. But a GPS receiver chip, even a very low end one, would be considerably more expensive and would usually fail indoors.

Edward

"Metspitzer" wrote

See, you know the answer. The old motor driven analog clocks were very accurate with the 60 cycle electricity. Digital are timed differently and drift. They use a crystal oscillator that is not a perfect cycle of 60. I'm sure someone can explain it better.

My tall case grandfather clock always keeps the time during a power outage. The pendulum just keeps on a-swinging. :-)

This technology has been on the gonna happen shelf for a long time. It may be getting a lot closer. Power companies are begining to charge by "net metering" Cost per KWH will depend on the time of day you use it. Your power meter will be in relatively constant communication with the PoCo so the data will be on the the powerlines. When this happens added circuitry in a device to set clocks should only cost a few cents. The chip in your clock that does the main work probably isnt a dedicated clock chip. More than likely it is in fact a microprocessor so most of the hardware to do this job is already there.

Jimmie

Plug-in digital clocks use the powerline frequency, just like analog clocks do. For battery backup, they can use cheap RC oscillators (no crystal).

The plug-in clocks with battery backup I've used are usually fast during a power outage. If the outage is longer than 5 minutes, you may need to reset those clocks.

This is true for the "Intellitime" clock that PRETENDS to set itself.