Hello again Diego,
I got my SPDT relay and I'm working on wiring it up, but I'm not entirely clear on your instructions. Could you look over this schematic for me and let me know if anything seems out of place?
(The relay in the schematic has six pins for some reason. My actual relay is identical to your diagram with only 5 pins.)
The part I'm most concerned about is that you have "from power supply cable output" labelled on two of the relay pins. I'm interpreting that as two inputs both from the + of the barrel jack. And then the "to GND" I'm interpreting to mean all the grounds should come together as in my diagram. I'm not at all certain on these things, so if you could clarify it for me, I'd really appreciate it.
Thanks again!