I've built a circuit to control a motor with arduino/L293D and everything works as expected connecting a 9v/1A wall wart to L293D pin 8, but when I connect a 12v/2A wall wart to pin 8 the motor does some jerky movements and then stops moving all together. If I'm powering arduino through my computer's USB, it actually crashes the computer at this point (12v but not 9v connected to L293D pin 8).
If I power arduino with the 12v wall wart and pin 8 with 9v the motor works as expected. In all cases L293D pin 16 is powered by arduino's 5v output.
My layout is similar to the below example: https://learn.adafruit.com/adafruit-arduino-lesson-15-dc-motor-reversing/breadboard-layout
Thank you in advance!!