Andy,
Perhaps one of the little openlog units from sparkfun, or one of the
clones would work for logging?
https://www.sparkfun.com/products/13712
Honestly, I have two and a pair of 32Gb Cards, but have not tried them
yet. Seems like a good solution for a project like this. I don't know
how they buffer writes to the microSD, or what the write life on an
SDcard would be like.
Dan
On 2/24/2021 7:35 AM, [email protected] wrote:
My monitor uses a 16F628A PIC device clocked from a 10MHz TCXO. 50Hz
mains is fed to the capture/compare module which is set to measure the
number of periods of the prescaled clock in every fourth cycle of the
mains. A simple integer division and the answer is the mains frequency in
milliHz units.. I only measure to about 0.002Hz resolution as the
variation is so wide (~~ 0.2Hz RMS) this is quite enough .
Completely separately, a four bit counter is incremented by this divided
mains signal every 80ms, and also decremented every 80ms by the divided
down clock. Software is written so that increment and decrement cannot
clash.
The result is a 32 bit twos-complement count, to 80ms resolution, of mains
timing difference from that of the TCXO. A bit of arithmetic and the
answer can be shows as a timing discrepancy in seconds on the display.
It would be a matter of just a few minutes of extra code writing to add a
serial output to transfer data to a logger . Which I may yet do, but that
would require getting an old laptop out of storage and leaving it on 24/7
to do the logging - don't keep my main PCs on continuously.
Not sure this list passes-through attachments; if not the oicture is here
http://www.g4jnt.com/DropF/img2783.JPG
Andy
www.g4jnt.com
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