Big trouble alimentation of a stepper motor


I'm using an arduino uno, a motor shield from adafruit, and one stepper motor (3.3V, 3.3A).
I burnout a 5v transformator (connecting to the Arduino jack, jumper of the motor shield off) while the installation was working for 20 mn.
Then I burnout the motor shield itself!!!! yes I did!!!! (connecting a 5v transformator to the Arduino jack, and a 12v transformator to the motor shield PWR) after a few second working!!!!

So now I'm looking for help to be safe for my next try!!!!!

If someone can understand what and where is the error, this would be wonderful!!!


Even though it seems obvious to you, a picture or diagram of your circuit would help.

Which motor shield? Which motor? These are questions answered best by a link to the datasheet or other
informative webpage.

A 3.3A stepper motor is almost certainly a powerful bipolar stepper motor requiring a chopper drive
controller board, certainly not anything based on a darlington motor drive chip such as the L293.

For that current level there is no one-chip solution that I’ve found, one-chip motor drivers use darlingtons
or DMOS output transistors, just not up to handling motors with 1 ohm windings.