I have a control system made with an arduino nano and a LoRa Ra-01 to turn a three phase bore-hole pump on and off but the system seems to stall at random when either the contactor for the pump goes on or off. I've tested the system with random 220V items and I don't get the same problem as when I've hooked it up for it's intended use. My reasoning is that there is some kind of EMF spike from the contactor that turns the pump on and off.
The arduino remote board uses a 5V relay to bring in one of the coil wires going to the pumps 3 phase contactor so I would have imagined that it wouldn't actually have to deal with any real inductor load itself on the arduinos PCB.

I know it's stalled because the board is supposed to be sending a status message every 5 seconds to the other end and that stops at random whenever the pump either goes on or off. Also it doesn't seem to matter if I turn the pump on via the arduino board or the manual button at the pump.

Suggestions?

 

Is this controller circuit inside some sort of shielded enclosure? Can you show a picture of it with detail around K2 and the connector to the contactor and wiring.

 

Is this controller circuit inside some sort of shielded enclosure? Can you show a picture of it with detail around K2 and the connector to the contactor and wiring.

Not for a few days I can't but no, there is no enclosure. Everything on that schematic is on a 150mm x 100mm PBC with K2 way the hell away from the low voltage components in one corner. The pump contactor is in a concrete box on a DIN rail with all it's isolators and circuit breakers and such and I mounted the pcb in a corner as far from all of it as possible. When that didn't work I just used some wires and tried it about 2m away from the whole enclosure with the same results.
Googling some more The only real thing I can think of is using a high voltage snubber cap across the contactors terminals.
Edit: I also realised since the contactor uses two lives for the coil its effectively a 380V coiled contactor. Not sure if that datum helps at all.

 

Not for a few days I can't but no, there is no enclosure. Everything on that schematic is on a 150mm x 100mm PBC with K2 way the hell away from the low voltage components in one corner. The pump contactor is in a concrete box on a DIN rail with all it's isolators and circuit breakers and such and I mounted the pcb in a corner as far from all of it as possible. When that didn't work I just used some wires and tried it about 2m away from the whole enclosure with the same results.
Googling some more The only real thing I can think of is using a high voltage snubber cap across the contactors terminals.
Edit: I also realised since the contactor uses two lives for the coil its effectively a 380V coiled contactor. Not sure if that datum helps at all.

Yes, a snubber for the contacts and the coil might help. Once that random lockup is under control you might want to look at fail-safe solutions for the controller like a watchdog timer that will reboot the arduino nano. It's not the cure for a hardware generated lockup, it's a countermeasure that can keep things running until the issue is properly fixed.
https://www.instructables.com/The-Arduino-Hang-Guardian-Arduino-Watchdog-Timer-T/

 

Do you have a star ground system for the pump, contactor and control system, to prevent 'ground-bounce' from causing problems?

 

Yes, a snubber for the contacts and the coil might help. Once that random lockup is under control you might want to look at fail-safe solutions for the controller like a watchdog timer that will reboot the arduino nano. It's not the cure for a hardware generated lockup, it's a countermeasure that can keep things running until the issue is properly fixed.
https://www.instructables.com/The-Arduino-Hang-Guardian-Arduino-Watchdog-Timer-T/

Oh there's no need to keep it running at the moment. Right now it's just an issue of "The tanks are empty, damn now I have to walk my lazy butt to the other side of the farm to start it again" kind of thing so I'd rather get it running properly without issues.
As a side I have this.
It's by no means the finished idea but I need a working prototype before I design the casing and the rest of the functions.
Future versions have current/voltage monitors for safety as I've had a number of pumps burn out due to old wires that even the phase protection unit didn't catch (faults in the wires AFTER the contactor aren't in it's job description.) and pulling 65m of piping and pump out of the ground isn't fun.
Thanks for the help.