Results of the tests:
The noise remains even after disconnecting the connection and its cables of nextion
Noise still exists, but less loud if I remove the module SI5153 (For me the continuous program to turn blind)
We can clearly see that the crude corresponds when sending data (Pulses) from the arduino (leg no 26 or 27 corresponding to the TX) don't remeber
I tried to put the jumpers resistors on the legs 26, 27 >> No improvement, same if I add a small capacitor.
but it is not the same type of mounting that I had done on the encoder (review the diagram)
Pulses come at the amplifier input. Weak and drowned in background noise.
You can see them better if the oscillo is connected without ground!! back to the ground of electrical connexion 220V?
And as already said, if I connect electrical ground on power ground, you ear 50HTZ.
So for me, the signal must interfere with lines on the copper, or there’s a mass loop, not obvious to find.
I spent my afternoon on this, so I’ll look again later