 The BSTman cometh
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Conundrum
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Wed Mar 07 2018, 06:36AM
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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
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Hi, I've been racking my brain(s) to figure out how to sync normal clocks and watches to a local atomic standard.
Its not actually that hard to only run it for an hour (or less) a day, using micro to detect atomic lock stability then start transmitting a local time signal on a license free band once locked, comparing with GPSDO.
The plan here is to use Wifi chip antennas as they are very cheap indeed, simple micro such as Cortex M0 and some basic logic to check time elapsed against reference and determine mathematically the offset needed for the clock or watch to then be correct by increasing or decreasing clock speed for n minutes.
Most commercial clocks use a simple switch to detect minute hand has passed 12, but there are better ways such as a reed switch or even better an inductive sensor based on anti-pilfer detection strips and a free-running oscillator of my own design.
Also handy when you need to deal with daylight saving time where running the oscillator at 18% higher frequency for 8 hours will adjust it by exactly 1 hour forwards, likewise 18% lower will reverse the process.
As the signal would only ever be on late at night there should be less of an interference problem, suggest around 8pm would be a good time to transmit as it would be an intermittent signal once a minute consisting of a time/date sequence.
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