I want to use a servo motor and control it by an Arduino Duemilanove (or a Leonardo). It seems to work fine when I connect it directly to Arduino's VCC, GND and an PWM pin. But I am a bit worried if this is a good idea. The multimeter shows that it draws up to 0.6A which is about 10 times of what I'd expect that the Arduino can provide. Is this correct or does this apply only to the digital out pins? Would it be better to power the servo using an external power supply?

I thought it would be a nice and easy solution to power the Arduino using a USB power supply and to cut the USB cable and connect the servo directly to the +5V of the USB. But is there even a difference in powering the Arduino via USB and connecting the servo to the VCC of the Arduino? Is it a problem to connect GND and UGND?

(After first tests, I think that the Arduino led is pulsating less using the hacked USB cable, but still a pulsating LED shows that the servo is drawing a lot of power from the board.)

Bonus question: does your answer apply to all Arduino models? (I am interested especially in Leonardo and Duemilanove.)

Similar discussion: http://forum.arduino.cc/index.php/topic,22132.0.html

  • What kind of servo are you using? PWM pin isn't providing any current. USB only rated at 500mA. So your best bet is to use an external power supply. You will indeed need to connect the ground of the arduino and the ground of the external power supply together. Limiting factor is USB not the arduino board (which by itself only uses 20mA). – Gerben Oct 3 '14 at 19:59
  • USB 2.0 is normally only rated at 0.5A. So 0.6A is already 'border line'. How did you measure the servo current was 0.6A? Was the servo moving, or were you holding it still ('stalled')? If it was moving, expect the servo to have a much bigger 'stall' current; in this case USB will not be enough. If the servo stalls, which is easy to do by accident, the USB power supply may switch off or even fail. – gbulmer Oct 3 '14 at 20:33

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