This might be a very stupid question but please bear with me. So I am using an HC-SR04 Ultrasonic sensor model (5 V) and I want to connect it to Arduino Uno. Do I have to use an external power supply for the ultrasonic sensor (just like with the motors) in order to connect it to the Arduino? Or can I just use the 5 V pin?

  • 2
    It is a low current device so yes you can connect it to the 5V pin, also consult the datasheet for setup stuff and current draw.
    – RSM
    Apr 25, 2015 at 14:32
  • spiked3.com/?p=6021 - includes code without using libraries for arrays of SR04s
    – user6569
    Apr 26, 2015 at 19:50

1 Answer 1


From the question I assume you power your Arduino via USB in which case you don't need an external supply. The HC-SR04 draws 15 mA with is far below the specifications for USB. I did this myself some time ago:

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