I have got a RaspberryPi powered by a 5V 2A power supply. The Raspberry Pi has got a wifi dongle that works perfectly. Also I have got an Arduino connected to the Pi by USB (Raspberry USB port to Arduino USB input). This configuration works ok, the Arduino is recognized by the Raspberry Pi without problem (I see it using lsub).

The problem comes when I connect one servo (http://www.servodatabase.com/servo/towerpro/sg90) to the Arduino. The servo is powered by the 5V pin of the Arduino (there is not other supply).

When I do that the wifi goes down and it is disconnected from the WAN.

What is the problem here?

The Raspberry USB port does not provide enough power?

  • It certainly sound like a problem with the supply voltage. Unfortunately the linked database does not list the current of that servo but it's probably safe to assume that it might easily exceed a (few) hundred mA. I don't know how the Arduino handles that, but is there no way to directly attach the 5V power supply to the power circuit of the arduino bypassing the USB ports? – Ghanima Nov 18 '15 at 20:31

It certainly sounds like a problem with the supply voltage. According to this the current of the towerpro sg90 could be as high as 500 to 1000 mA. That's definitely too much for the USB port of the Pi.

Recommendation would be to directly power the Arduino and the respective power stage that connects to the servo from the power supply and bypass the USB connection (and all the trouble that comes with it).

  • That was I think, The servo must be powered independently. – dlopezgonzalez Nov 19 '15 at 16:26

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