The problem i'm facing is, i've got my arduino connected to a SHT31 sensor, an OLED display and a 2 channel relay with an opto-coupler.
So i've got all my programming done, everything runs fine on "synthetic" testing, but my issue comes up when i put a load on the relays.
So i have a 0.75kw pump and a 0.95kw air con that switches on and off to regulate a climate in a small greenhouse, keeping inrush currents in mind i've not connected the motors directly to the relay, rather i've wired the coils of 2 contactors to be switched, this seemed like it should work but when the contactors pull in the OLED goes berserk, even turning power off to them doesn't rectify the issue until i reset the arduino.
I have a separate power supply for the relays and the arduino only supplies the signal circuit so i can't understand why it's doing this, could the in rush current of the contactors really be so high?
They're fairly small a "Lovato BF9" and some other weird brand, same amperage, both 220VAC coils.
even energizing one at a time makes no difference.
The relay and arduino run off separate power supplies, 5v for the relays and a 9v for the arduino.
I've reading from someone with a similar issue (except his arduino hangs when the coil turns off), someone suggested an RC snubber, "The snubber is just a resistor and capacitor in series across the relay contacts", but would this work in my case since the problem starts from the initial coil pulling in?
I don't think its noise interference, it seems like its a voltage or current back feed as the coil energizes, as if it messes with the clock for that split second and kills the OLED, the general operation of the board still functions fine ei. the sensor still switches the relays on and off, i just dont get any working display until i reset.
Though i thought the whole idea of having an octocoupler was to negate such events?
What is the device on the far left? A power supply?
Is the I2C wiring those blue and green wires that are sitting right on top of mains wires?
It appears that you have mains interspersed with low voltage. With bundles of wires run in parallel with one another, it’s induced currents from the inrush currents of contractor coils which are pure inductive loads and yes, it’s interference.
Snubbers or mov’s across the contactor coils will help but proper segregation of your wiring may be required to eliminate the issues which may get even worse when you power the a/c and pump.
Hi,
I suggest you get a bigger box and spread your project out so that you can keep the low voltage controller devices away from the 240Vac wiring and relays.
I wrote a whole thing in the quick reply bar, posted and it took me to the start new topic page....
Long story short, clock wire from screen came loose, desynced screen with contactor inrush current, moved arduino to its own isolated box, everything works fine.
Thank you all for your suggestions, will still look in to protecting board from inductive spikes.
