General > General Technical Chat
Clock circuit design idea
David Hess:
--- Quote from: SiliconWizard on July 26, 2020, 07:02:51 pm ---That's because most cheap clocks use crappy oscillators. You wouldn't need anything really fancy. I gave some figures - you can expect a few seconds drift a year with a decent TCXO, but many cheap clocks have more like 100 ppm oscillators, and it can get worse than this in cars due to large temperature variations. And why is it so? Cost mainly. Even though a TCXO is not expensive these days, it'd still add a few bucks in the BOM, in a world where we shave off every cent. Secondly, because manufacturers likely don't even care - probably because in turn customers have been used to get crap clocks in common devices including cars, so they are not expecting any better.
A related thought regarding the market - what manufacturers sell, what consumers expect and buy: the clock ("watch") industry has followed this trend for a long time. Very accurate clocks with low drift have been considered luxury items for a long time, and often come at a premium. So in a car for instance, you're more likely to find an accurate clock in a luxury car.
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Power limited clocks like wristwatches are more limited in their selection of clock source because they are restricted to 32kHz sources which are not ideal for temperature compensation.
--- Quote from: duckduck on July 30, 2020, 06:10:02 am ---Amazon will sell me an "Atomic wall clock" delivered to my front door for US$20. When the shortwave time-keeping stations are shut down, your idea may find a place in non-internet-connected locations if dedicated GPS-set clocks are still fairly expensive, as they are now.
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I think it more likely that better TCXOs will be used in applications where power is not a limiting factor.
--- Quote ---There's at least one utility that does time trimming via software for the built-in clocks in personal computers. The software doesn't actually modify the hardware, but uses software to modify the time based off of comparisons with NTP. I remember using this around the year 2005 or so. Nowadays I can't be bothered and everything is internet-connected anyways, right?
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Would that be Tardis? I still run it on my systems.
https://www.mingham-smith.com/tardis.htm
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