I have a 12v relay but I just can't figure out how to use it. I went to tech support, but they just waved me away. So, my problem is that I have an 8 channel relay, but can't get it to work. I did try a shared ground (I know, bad idea) but disconnected that after half a second.
So the board has 10 pins, VCC GND IN1 IN2 IN3 IN4 IN5 IN6 IN7 IN8 and two linked ones, COM-GND. So, the relays require 12v in to move the coil (already have a power supply) and requires 5v logic to move the coils. What I can't figure out is how I'm supposed to use the logic and 12v input at the same time. Shared ground... didn't work. I'm lucky I was just touching some male jumpers and it scared the life out of me and I disconnected them.
But it's basic electronics: there's no flow if the ground isn't connected. The Arduino doesn't have a ground for its 5v logic, and there's no ground on the board that won't blow something up.
So, how do I provide enough power to work the relays and get the 5v of logic to switch them, without setting something alight?