Hi,
I have a similar setup but another problem.
I'm controlling multiple valves in the same way by using an UNO board and a MCP23017 to control 2 8xRelay modules.
Then each relay control a 12V solenoid valve. Powered by a separate 20A power supply.
Positive wire going through the relays and all ground connected back to the power supply.
note: valves wires are not polarized.
My problem is when I'm turning on 5 relays in the same time (this is the maximum I need to turn on simultaneously), all leds on modules turn ON and some others valves also.
It seems that there is a kind of "bleeding" of current through the common GND who turn on other solenoids.
So I want to :
- connect a secondary 5V power supply for the modules, connected on the jumpers, as described earlier here.
- add some diodes in there, to block this "overflow" (I don't know how to call that) but where?
I have some 1N4007, and I feel to put them between the coil and the GND terminal block I'm using, so nothing can come back on the coil.
Should I add two diode /coil?
or the one to protect the relay should be enough?
