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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.

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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.

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  • \$\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

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