I have Arduino Uno and Arduino Ethernet Shield. I have four sensors. I am reading sensor values and post it to an ip address. Everything works fine. But my problem is about power supply. When i plug usb cable from any PC to Arduino Uno usb port as power supply, everything is fine. But i want to feed my boards with adaptor that outputs 9V, 1A and available for Arduino Uno. When i use adaptor as power supply, my http post method is not working. I measure all the outputs and inputs of all components, then everything is fine again. The problem is about Ethernet Shield i think.

What is the difference between feeding from usb and feeding from adaptor? Codes are the same just the feeding is changed.


The problem is that when you are using the external 9V plug pack, you are relying on the Arduino's on-board regulator to provide the 5V power supply to both the Arduino and the Ethernet shield. This regulator has very limited current capacity — much less than the 500 mA that's available from a PC's USB port — and you're overloading it.

To avoid this problem, you should use a 5V plug pack with a USB connector to power your system.

  • \$\begingroup\$ What should be the ampere value? Did you mean that, i should power my system with connecting adaptor to Arduino's usb port? \$\endgroup\$ – BatuhanC Sep 3 '14 at 13:28
  • \$\begingroup\$ Obviously, it should be at least 500 mA, but must 5V plug packs (a.k.a. "USB chargers") are at least 1A. Yes, you connect it to the Arduino's USB port. \$\endgroup\$ – Dave Tweed Sep 3 '14 at 13:35
  • \$\begingroup\$ I will try that and tell you sir. \$\endgroup\$ – BatuhanC Sep 3 '14 at 13:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.