Making sure not to blow anything up before testing.
I have an adafruit motor shield and an arduino Uno. The arduino uno has a power input and I was hoping to use it to power the motor shield, a nema-17 motor, and an I2C connection. Currently I'm using the power connection on the motor shield to power the nema-17 motor and a serial connection to power the arduino.
Can I just connect a power supply to the input port on the ardiuno uno and power the motor shield and nema-17 step motor?
You should not power the motor shield (and thus the motor itself) through the Arduino. The motor draws a high current (depending on the exact product - there are many versions of the nema-17 - I found current in the range of 1 - 2A) and the voltage regulator (or the diode in the path) are not rated for this much current (for the Uno the absolute maximum is 200mA, including the Uno itself). You will fry these components, if you try to draw more than the rated current.
But you can use the same power supply and provide the power to Arduino and motor shield in parallel. This way the current for the motor does not have to pass through the Arduino.
