why do some regular bedside digital alarm clocks go out of sync by a minute or two over th eperiod of time?
In: Technology
Cheap crystal oscillators I bet.
The easiest way to get an oscillating frequency wave (that can be squared into pulses used as a digital circuit ‘clock’ is to use a quartz crystal. If you put a voltage across one it sends out a wave at its resonant frequency…. and its resonant frequency depends on its physical characteristics, namely its thickness.
So the cheaper a crystal, the less care in its manufacture, lower tolerances in maintaining its thickness. So maybe a crystal is supposed to drive a circuit at 60 Hz, but is crappily made so it resonates at 59.6 Hz. That would cause a drift over time since the digital clock is essentially counting these clock ticks. Maybe 60 = 1 second or whatever.
Also, the AC frequency of your electrical network provider has to be stable, if it’s 51Hz instead of 50, the base frequency used is wrong, and thus all the “analog” AC to DC conversions frequencies will be off.
It happens with my microwave here in Europe since we started “importing electricity from abroad with this issue
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