[time-nuts] Clocking a PIC16F628A from a Rubidium Standard

Chuck Harris cfharris at erols.com
Mon Nov 28 11:00:17 EST 2011

David VanHorn wrote:
>> Come on, folks. never hook anything directly to the power line. The
>> source is just too stiff. Use an opto. I used fiber optic isolation with
>> my big DC power supply.
>> Don
> I used to agree, until actually tried it myself. Now this is how
> I do my picPET 60 Hz data logging:
> Dangerous.. A single component failure puts you hot to the line, without current limiting.

If that bothers you, don't use unfused 1M resistors, use a fuse and pairs of
500K resistors in series.  That way it takes a double component failure...
And if that still bothers you, use triple 330K...  Or add a pair of safety
rated series capacitors.

Even a common lamp cord is only a single "component" failure away from
being hazardous.

Somewhere or another there should be a compromise that makes you happy...
you will, however, never achieve true safety as long as you are alive.

-Chuck Harris

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