LCD content gets corrupted on start/stop 3-phase motors

Hi,

I’ve this setup:

Arduino controls 3-phase contactors, through optoisolated relays array (powered separately).
Arduino is not on the same box as contactors (1 meter away).

When it starts/stops few of them (or I start/stop some of them manually) characters on LCD get corrupted.
This happens randomly.

As far as I can sense it is some kind of interference, but I did not manage to find anything on forums.

As far as I can sense it is some kind of interference, but I did not manage to find anything on forums.

Try using the term LCD motor in the search box at the upper right. You might find something in the 26 pages that result.

Don

Thanks.

Behold! - Here begins all the "fun" of applied electronics...

You may want to: set the cursor position clear that line set the cursor position print that line

I've implemented scheduled loop to reprint all the stuff on screen every hour, but this thing may uproot the problem. Interference may interrupt other parts of this system.

After reading so many posts about motors and electronics my head started aching. There are so many techniques of grounding, decoupling, enclosure shielding, twisted pair cabling, noise filtering... It seems that the half of electronics engineering is about protecting the stuff from environment.

I "believe" that first I should test system with AM radio, and somehow filter the arduino power supply, since it is connected to 1st phase cable. Ferrite rings?

The problem lied in cheap AC>USB adapter.
When few ventilators are being stopped at once voltage instantly fluctuates from 210 up to 270.
Regarding that I added delay between stops into my code.
Yet it still did not solve the problem, because other non related hardware is being controlled from that same control room.

So the cheapo adapter could not cope with these voltage fluctuations and arduino did not like that for sure.