Guru
Joined: 02/02/2017
Location: AustraliaPosts: 1470
| Posted: 04:29am 25 Feb 2026 |
I've been playing with various means to remove noise from this thing.
now it is a lot better.
I filter the 20V AC using a Sallen-Key low pass filter with a -3db frequency of 50 Hz
Also I run the 3.3V, GND and opto-coupler output wires 2x through a couple of ferrite
rings before they get to the Arduino Due microcontroller board.
This helps with the noise from various things in my office.
before filter:
after filter:
so the 3rd and 4th harmonics of 50Hz are low less. I wanted the 100Hz harmonic to be
reduced too but it seems not much was done to it.
the resulting frequency graph is a lot cleaner though.
