Hello,
I have an Arduino mini for the garden control.
It would control 2 valves and just as feedback, I would like to get info about pump activation and thermal protection. It meas that the pump is handled outside my control, we wait a pressure switch: when the pressure is lower than 1bar than the contactor closes and it start working.
Well.. the contactor has very high level of disturbance, many spikes visible everywhere.. but specially on the Arduino it's a problem, it stuck and should be restarted (not always but happens).
Searching on the web and in this forum, I found many suggestions but all in the direction of suppressing the disturbance that could enter by the solenoid of contactor in case I'm driving it.. in my case I have to stabilize the power or avoid disturbance on the main power of Arduino.
The connections between Arduino and pump contactor is 2 auxiliaries contacts (one on contactor itself to know when it's active and a second one on therma protection).
I tried to isolate these wires removing them completely but I can see again disturbances at open/close of contactor most probably because some other cables pass "close" to contactor lines, I can't avoid this..
So.. do you have some suggestions on how "isolating" better the Arduino power supply?
Applying a snubber on the contactor solenoid could help?
The disturbances are generated by arc effect in power contacts I gess.. so the snubber doesn't help. It's correct?
Using a solid state contactor could help?
In case I will replace the contactor and let's it..
Any other suggestions? Filters.. for example a couple of zener diodes can help to discharge overvoltage on gnd it the voltage is greater the 5.1 Vdc for example?
Thanks in advance
Andrea
In my part of the country, many people have wells for domestic water supplies. Older wells used a magnetic contactor just like you are describing. When ANY well problem happens and the well service company comes, the very first thing they do is replace the contactor with a completely solid state control box. That sometimes fixes the problem and always stops the clicking and sparking.
I encourage you to do the same, rather than fighting the contactor problems and avoid future control problems.
Paul
Thanks very much because your message doesn't leave any doubt to me.. 
I saw some contactor solid state supplied by Crydom and the price is not crazy.
Do you have some additional hints? I mean, I consider a contactor with same power and current max,
the issue is that I have also a thermal protection for pump and I have to find a model with same
add-on. Or I will search for a protection not from the same supplier.
I don't know if the same thermal protection is compatible with new contactor because the input is not
done by wires but it has 3 rigid pins with same gap of existing contactor..
Ok, I will search also for it.
Thanks so much!
Andrea
Explain the thermal protection you are concerned about. If the controller has some temperature sensor, it is not measuring the temperature of the pump motor, it is measuring the temperature of the wires in the control box. If it's just in the control box, a solid state controller will not need such temperature control.
Or are there a separate set of wires going directly to the pump motor that carry a temperature sensing back to the controller?
Paul
No, I'm speaking about a thermal overload relay. I attached the image of the component I'm using now.
For sure it make sense to find the same kind of protection because if the motor stuck, the current raise and it's easy to burn motor and/or cables...
Looks like the overload relay is separate from the contactor. In any case, use a 3-phase solid state contactor and a regular overload relay. All the match what you have.
Paul
I'm looking to the right model and I have a doubt:
"Available with Zero Voltage Turn-On (resistive loads) or Random Turn-On (phase control or inductive loads) output"
There are two possible configurations for open/close actuation, in the catalog seems clear that for inductive loads like a motor the best is Random Turn-On.. but in this way it's the same as before, right? I was preferring the model that switches passing from zero so the arc effect and disturbances are minimized.
I know that with inductive load the current is not phased with voltage so when the voltage passes to zero the current for sure not not zero but maybe it's small.. and for example closing the current is zero, maybe opening there is a minimum.
With random.. I risk to have same behavior as now with mechanical.
Does it make sense? Or "random" mans something more intellingent than "random" as word means..
This random means the turning on of the three phases will not be identical and will not even be predictable. Pure restive means the zero crossing turn on is not effected by stray voltages.
If this was a problem, they would not be selling the device because no one would buy it.
Paul