/diy/ - Do It Yourself

>>1277258
>The frequency from the wall socket isn't going to as precise as the internal oscillator
Internal oscillators are generally only accurate to 1% or so, without regard to temperature, unless recalibrated by the user. 500ppm crystals are accurate to 0.05%. Over the long term, mains frequency is regulated to precisely the nominal frequency over periods of several days, with deviation determined and corrections applied daily. Pic related illustrates measurements vs. standards derived from atomic clocks, conducted in the Netherlands. Corrections are clearly visible on days 17-19 and 41-43.
Granted, it still drifts from ideal over periods of minutes from time to time, and I agree that synchronizing to the actual phenomenon of immeidate interest via a zero-crossing detector is the way to go.