Take the 2-minute tour ×  I'm currently trying to build a small
independent rover from my old Lego Technics set. Currently I
power two 9v DC motors (2838) using an Arduino motor shield R3
in combination with an Arduino Uno. I connect the motors
independently to the two outputs of the motor shield and use an
external 9V power supply to power the Arduino via the barrel
jack. All this worked fine in the beginning with both motors
doing their job at full speed. (The software should be OK - I
did set all needed pins on their desired values (brakes off,
directions on, PWM to 255)).  Now here's the problem: After
having tinkered around a bit with my design it seems to me as if
I have broken the motor shield. As I said, the software worked
in the beginning. I also double checked the motors by directly
connecting a 9V battery to them, they both work just fine. Also,
the Arduino board itself is unharmed; I checked it with other
designs just to make sure. But the motor shield does not supply
enough power to the outputs