Hi @Paul_B .
I've been trying the modules in the picture, which are high level trigger, as well as a 4 channel module which is a low level trigger. I did not know it made a difference, and to be honest, the 4-channel module was giving me a bit of trouble, so I've switched it back to the individual modules.
What needs to be done for the low level modules to work?
Also, I don't think it's an issue, but I have a question. I'm using the 5V output of the power supply to connect all 3 relay modules and also the 5V pin of the micro, to power it. This is correct, right, since that pin can also be a 5V output? but I guess that's only when it's plugged in via the USB, and it's never both powered by the two sources. When it's installed, it's only powered by the PSU, and when I'm testing/programming it, it's only powered by the USB.