[time-nuts] Re: My AC measurement project & question

[Bob kb8tq]

Hi

On a similar note:

If the transformer works well up to 600Hz, isn’t that high enough to capture
anything that actually is grid related (as opposed to local to your home / 
neighborhood )? 

One could easily argue that the other end is the pinch point. There may well
be interesting things going on well below the main frequency. Of course you 
then get back to all those other transformers upstream of you …

Bob

> On Jan 23, 2022, at 5:55 AM, Andy Talbot <andy.g4jnt at gmail.com> wrote:
> 
> But do you want to measure anything other than mains frequency?   IF not,
> waveform distortion in immaterial.
> Or am I missing something here?
> 
> My mains monitor uses an old wall wart with 9V rectified but unregulated DC
> out - 5V regulator on the display board.  I added an extra wire to one side
> of the transformer winding which goes via a DC block capacitor and resistor
> of a few kΩ to the Schmitt timer input of the PIC microcontroller.   At
> several volts peak to peak, it's more than sufficient to take the Schmitt
> well beyond its two switching thresholds.  Clamp diodes to Vdd and GND
> within the PIC keep it to safe limits.
> 
> 
> Andy
> www.g4jnt.com
> 
> 
> 
> On Sun, 23 Jan 2022 at 10:44, Dave B via time-nuts <time-nuts at lists.febo.com>
> wrote:
> 
>> On 23/01/2022 08:30, time-nuts-request at lists.febo.com wrote:
>>> Stick with the transformer. The use of a capacitive divider is
>> predicated on the line waveform always being a sine wave. Dream on! All it
>> takes is one good spike down the line, maybe only 20-30V amplitude, and
>> your capacitive divider passes it right on to that ADC that has a much
>> lower (3.3V?) limit. Guess what goes poof?
>>> ------------------------------------------------------------------------
>> 
>> Transformers distort the waveform, unless specifically designed for that
>> need.
>> 
>> 
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