Hi all,
This is an interesting thread. I have built many clocks using the mains as a
reference and have settled on a "belt and braces" approach that works well
and does not seem to pass noise or transients. I begin with low voltage AC
from the mains transformer and use it to feed the input diodes in a dual
optocoupler back to back through a single pole LPF made up of the
appropriate current limiting resistor and as big a cap as I can get away
with. On the output side the phototransistors are paralleled and thus
produce pulses at double the mains frequency. These are used to injection
lock a free running oscillator made from one stage of a 1489 quad line
receiver followed by another stage in cascade. The end result in a nice
train of clean square waves. It's cheap and easy and doesn't take up too
much PCB real estate.
Morris
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
