[time-nuts] Building a mains frequency monitor

[Nick Sayer]

> On Apr 9, 2016, at 10:20 PM, Bill Hawkins <bill.iaxs at pobox.com> wrote:
> 
> The schematic is too simple. There is noise on the power line from
> switching things on and off, leakage from dimmers and switching power
> supplies, and the occasional animal that gets across the HV distribution
> line, not to mention lightning, induced or direct.
> 
> A simple capacitor will reduce high frequency stuff. The purist will
> invest in an L and C that resonates at 60 Hz. Alternatively, use a
> synchronous motor driving a load with sufficient inertia in combination
> with a slotted disk and photo pickup. Perhaps an old record turntable
> will do - but not one with a regulated DC motor.

I invite you to perform the same experiment with and without the extra filtering and report exactly how much benefit the extra filtering conveys. Otherwise, it’s just Monday morning quarterbacking.

> 
> The science fair folks got enough interesting data without all that, but
> the precision is not known.

So, the “science fair folks” is me. It wasn’t a real science fair entry, per se. I titled it that way because it seemed to me to be a great idea for someone to use in a science fair if they wanted.

In any event, unless you’re suggesting that the data is wrong, then I would assert that the precision was sufficient. Perfect is the enemy of good.

> 
> The link didn’t have any reference to code at all.

Really? Did you miss the 3rd and 4th pages? The ones with the Arduino sketch and the Linux monitor program? In C? That code?

> 
> This is a way of looking at frequency variations with natural causes
> that does not require expensive equipment, if done right.
> 
> Bill Hawkins