So I am facing a problem and I might have an idea on what is going on but i would like to get some help. So I am driving a 5V 4 channel with and arduino in order to control 4 solenoid valves that are utilizing 110VAC.
As of now I have the AC common(White) connected to the 4 common channels of the relay - The AC hot (black) connected to one side of the solenoid valves - The other side of the solenoid valve is connected to the NO of the relay.
Now the arduino digital 9 to 12 are connected to the IN1 - IN4 of the relay via a transistor connection as such:
The digital pin connected to a 1K resistor to the base of the transistor. The emitter of the transistor connected to the INX of the relay. The collector connected to the cathode(-) of a diode. and finally the anode to 5V vcc.
The programming side of things are fully working and I am sure of that because without the solenoid valves connected the system and the relays does just fine.
BUT the moment I connect the AC my system starts to have a lot of noises, where sometimes it works but sometime the relays has sparks, sometimes it turns of a channel that was not touched.
After some research I found out that a rc snubber might be needed on the solenoid contacts, although I am not familiar on how to calculate it and also how to place it on the system.
That relay board already has driver transistors for the relay coils, the ones you have serve no purpose, you need RC snubbers or bidirectional TVS diodes across the solenoid coils. How are the relay coils being powered?
Sadly, much of this problem relates to "lead dress", keeping all the connections to each part grouped tightly together, avoiding any open loops in the wiring and keeping the AC connections to the relays completely separate from all the connections to the digital logic.