Review on Relay Module Channel Opto Isolated Trigger by Matt Kucrud

Made exactly as it should be. Would buy again. A bit confusing with jumpers, 3.3V input and trigger pin. I found that VCC was the power supply for the relay, the 3V command pin was the enable pin, and ground naturally acted as ground. After understanding this part for my project, they worked fine for what I was using them for (low voltage application). I think the seller explains this in the product documentation as well, but I'm not sure I read it until I tried to use it.