Im connecting a servo to my Arduino Uno Rev.3. The general recommendation is to put a 7V -12V power supply for servos as far as I understand. However I’d like to combine it with an USB to a computer since I use it to flush data from a different probe on the Arduino to my PC.

  • Will it be safe to use both a AC/DC adapter and serial bus?
  • Will it use the USB for power draw even if adapter is connected?
  • Arduino Uno supports external power supply and USB at the same time. There is automatic switch will re-direct the power feed. so, your answer to your first question is YES. and the second, if you connected the external power supply, USB part won't be used for power feeding through your servo motor. But, this won't still guarantee you can feed you servo motor safe and sound. Because, you are again limited to some current around 1A. It is still up to the specs of your motor.
    – Sener
    Sep 3, 2018 at 14:14

1 Answer 1


You will see that the Servos have 3 wires [GND, Power, and Data/Signal]. You can connect your external power supply to GND and Power of the servos, and connect the GND and Signal wires from the Servos to the Arduino.

By connecting the Grounds of the Arduino and Servos together, they share the same 0V reference and you will not damage either by powering the Servos from a higher voltage and the Arduino from USB.

It is not necessary to connect the Arduino Vin or barrel jack to the external power supply. Look at the Servos+power supply as one independent unit, and the Arduino+USB/Computer as a separate independent unit, and the only things connected between them should be GND and the servo signal/data wire.

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