Strange design of the Arduino version about astroeq HOT 1 CLOSED

The VIN pin is connected to the power supply by design. It's intended that the whole circuit be powered off the 12V supply so that if you are using a laptop it doesn't drain the battery as fast.

Genuine Arduino Mega boards are rated for a nominal VIN of 9-12V, of which 12V is in that nominal range. There absolute max rating on VIN is 20V. I recommend 9-15V supply range for both the Arduino and ATMega162 versions.

If powering the VIN pin with 12V fried your Arduino, it either means you are using a clone board which was not built with the same specifications as the genuine boards, or if you are using a genuine board then the board was defective anyway and should be returned.

from astroeq.