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I want to run a 9g servo off of the pins from an arduino nano board, using only the 5v USB connection.

The servo specifically is a SG90, which I have measured a stall current of ~250mA - I don't intend to stall it, just have it run with almost no load

I am not sure which pins to power it off of from the arduino itself - do I use the VCC or the +5v? does it matter which ground I use? should I use a breadboard to help me place any other components that may be needed, i.e. a capacitor or something? does the arduino nano negotiate to get more than the default of 100mA from a USB power connection?

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The max current of the Arduino-Nano 5V Pin is 200mA. So if you draw more than that it might damage your Arduino.

Here is an interesting summary regarding the Maximum Ratings of the Arduino Nano: https://electronics.stackexchange.com/questions/67092/how-much-current-can-i-draw-from-the-arduinos-pins

The 5V pin of the arduino is not connected through the microcontroller. As such, it can source significantly more power. When you are powering your arduino from USB, the USB interface limits your total power consumption to 500 mA.

So yes, it actually seems you can draw 250mA out of the 5V PIN.

do I use the VCC or the +5v?

You use +5V, because VCC is for powering your Arduino with an external Power Source. It allows you to use up to 7-12V (recommended), or up to 6-20V (limits).

does it matter which ground I use?

Doesn't matter

should I use a breadboard to help me place any other components that may be needed, i.e. a capacitor or something?

A breadboard makes it easier for you, to test your circuit. But you can do it without if you like. Then you possibly have to solder some connections

See also the offical Arduino Page for the Nano.

  • Thanks - might I ask a few more details - does the arduino negotiate for more than 100mA with the computer when connected to one, and also what would happen if more than 200mA are drawn - would it just lower the voltage and become temporarily unstable, or would something overheat? (does it even go through anything, or is it directly connected to the USB port?) - the breadboard was for if any extra components would be helpful, i.e. a capacitor or diode or something to keep the signal "clean" for the arduino – user2813274 Feb 3 '16 at 18:49
  • Isn't the 200mA limit only for when the board is power via VIN and not USB? – Gerben Feb 3 '16 at 19:35
  • @Gerben Thank you. I researched it and you're right. Actually the USB-current-limit is much higher then 200mA. I have updated my answer. Source electronics.stackexchange.com/questions/67092/… – Michael B Feb 3 '16 at 21:53

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