Stepper stops working when Arduino is connected to USB and works fine when not

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,
I have two Nema 17 motors, each connected to a L298N driver, they are all powered by an 300 W ATX. Both work just fine when the arduino is not connected to my PC and is powered by the ATX, but as soon as the USB conection is made one of the steppers stops working (the other one keeps working just fine).

#include <Stepper.h>

const int stepsPerRevolution = 200; 

Stepper stepperX(stepsPerRevolution, 8, 11, 12, 13); // Correa
Stepper stepperY(stepsPerRevolution, 4, 5, 6, 7); // Tornillo

void setup() {
  stepperX.setSpeed(60);
  stepperY.setSpeed(60);
}

void loop() {

  stepperX.step(200);
  stepperY.step(200);
  stepperX.step(-200);
  stepperY.step(-200);
  delay(500);

}

Do you have any idea what could be wrong? I wouldnt think that it is the conections as they work fine as long as the USB is not connected

2

Do you have the motors powered thru the arduino board? If so you will need to power the motors directly from the power supply itself.

3

Both L298N drivers are connected to the ATX power supply, and both motors work perfectly fine as long as the Arduino is not plugged to the USB, as soon as the USB is plugged one stepper stops working (always the same one). The situation doesn't change if I change the pins each motor is connected to. I am increadibly confused as to why it stops.

4

When the arduino is not powered from USB port, how is the arduino powered, from the ATX? The arduino has an auctioneered power setup for the board. When the arduino is powered from the USB port, that should take some preference over the barrel jack. Could be just lose wires or similar. You might check the voltages various points under the different conditions and see if there are any differences.

5

Yes, the Arduino is connected to the ATX by the barrel jack when not connected to the USB. Although the problem presist when the USB and the barrel jack are both connected. I checked the voltage readings on the A+ A- B+ and B- pins on the driver and the give readings only when the USB is not conneted, else, the LED flash (I suppose it is getting the signals) but the readings on the output pins is 0.