I don't know if It's a good branch for this problem. Feel free to switch it.
In my project, I use an Arduino Mega 2560 to control the state of electrical valves (8) like this one. To switch on/off, I use this relay (sorry, it's in french).
It works well for the moment but I suppose a future problem due to the kickback energy from the coil. Moreover, the constructor of the valve said to me that my system needs freewheeling.
I found this Mosfet Relay which can be equivalent at my relay + the freewheeling, but It exists only whit one way, so it will become a mess (place and wires) if I use 8 of this chip.
A second way to do it is to create a board between the relay and my valves with only freewheeling but it's more experimental than industrial.
The relays should be just fine if you have them. I could not determine which relay you are using but I do not think they will draw more then the relays can support. The freewheeling diode is need if a non protect device such as a MOSFET or Transistor is used to drive the valve. You could add them to the relay contact if you want but the kick back is stopped at the relay, the relay coil is driven by the onboard driver which is protected. If this is a high cycle design then best go to a solid state solution.
Les relais devraient être parfaits si vous en avez. Je n'ai pas pu déterminer quel relais vous utilisez, mais je ne pense pas qu'ils tireront plus que les relais peuvent supporter. La diode de roue libre est nécessaire si un dispositif non protégé tel qu'un MOSFET ou un transistor est utilisé pour piloter la vanne. Vous pouvez les ajouter au contact du relais si vous le souhaitez, mais le rebond est arrêté au niveau du relais, la bobine du relais est entraînée par le pilote embarqué qui est protégé. S'il s'agit d'une conception à cycle élevé, il vaut mieux opter pour une solution à l'état solide.
The free-wheel diode is always used for DC solenoids, to prevent huge voltage spikes that will blast EMI around, and damage whatever is switching the solenoid, be it semiconductor or mechanical relay/switch. Some solenoids have diodes built in, so check for this as in this case the polarity matters.
No, the diode goes across the solenoid, not the relay.
It belongs to a bioreactor. Imagine a tank full of water where we control the in and out of it. Some are used as a drain or to fill the tank for example. One relay is used to control an air compressor.
The compressor is systematically ON in normal mode. For the valves, it depends, but the state doesn't change fast if it's the question. ==> 24 V solenoids