I have a RAMPS 1.4 with Arduino Mega 2560 with 2 steppers connected to an external power supply using Polulo stepper drivers. The steppers are for X and Y axis movement. This external power supply is set to 12 volts and power is applied. I have configured the marlin firmware also.

Can I connect my setup to my PC using USB when the external power is also on? If i connect the USB while the external power is off, do the motors take power from USB? Will this will burn my board?

  • $\begingroup$ Is possible that you can burn the USB port and or your steppers can't work due lack of power of the same port. $\endgroup$ – Fernando Baltazar May 11 '19 at 16:51

The motors are powered from 12/24V external power supply, so the motors will not be powered. the ramps Schematics shows the connection diagram and the power is provided via the VMot pin/12V.

Stepper diagram

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  • $\begingroup$ Is it possible to select V in pin on arduino in place of 5 volt pin as logic power supply for motor driver?for how many drivers ,the 5 volt pin can be used as logic power supply on arduino? $\endgroup$ – sandeep kumar Apr 9 '18 at 12:29
  • $\begingroup$ is possible, but you need a driver (switch) to change the source from 5V USB to External 9-24V. $\endgroup$ – Fernando Baltazar May 11 '19 at 16:53

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