Schematic is
I use EmonLib library like in article:
On DSO I see on R1 resistor
and at A2 input of Arduino board (on R4 resistor):
I use an LED display with 8 digit 7-segment drived by MAX7219 (I present on article namend Modul de afisare cu 8 cifre LED din 7 segmente fiecare controlate de MAX7219
I use some configuration for LedControl library (dosc at The Arduino LedControl library):
Test schematic is
I write main_voltage_emonlib_1.ino sketch and upload in Arduino board:
I made main supply voltage measured with Arduino (2) movie: