I soldered everything on a perfboard just like in the diagram. At least I hope I did, it's my first time using a perfboard.
Just for testing, I tried connecting it to an led with 300ohm resistor, and the 12V 1A PSU. The Arduino was programmed to turn on one side for 2 secs, turn off, delay, and then turn on the other side. It worked great. The led was actually lit only at on side's turn because of it's polarity, but I was able to measure 12V across when it was the other side's turn and the led was not lit.
I then tried to connect the motor instead of the led and the resistor, and instantly there was a tiny spark and now it's not working at all. I think the Arduino is burned because there's still voltage around the circuit. Do you have any clue of why did that happen?
Thanks