i want to do something similar but based on the ESP-8266 (as my PI is not located near the energy meter.)
but as i also have a very old meter (1970) i only have the turning disk.
now i bought a CNY70 which in theory does the same as your idea.
it has a IR led and IR photo-transistor in 1.
I also came across your post @ tweakers forum (Dutch) http://gathering.tweakers.net/forum/list_message/43482152#43482152
and i saw that the schema was a bit different, first ofcourse a different model of the 555 but that doesn’t change much.
But i was wondering, what are the capacitors for?
And for the CNY70 can i use the same resistors?
and 1 final question: with what (if possible) can i tweak the sensitivity of the 555 and with which one the sensitivity of the photo-transistor?
As the sensitivity is a lot more crucial when reading a turning disk instead of “catching the blink of a LED”
ps. if i’m not mistaking, the new scheme (github) will make the output high when it senses something, and the one from the forum will make it low correct?
Hope you will answer my questions!