I have a working sketch running on Arduino Uno+Wifi shield, this sketch measure electrical power using emonlib and current sensor.
I send consume values on thingspeak cloud through wifi shield connected at my home wifi.
Until now I had always connect my Arduino directly with pc usb cable, and it works.
Now I try to plug from external power source using same usb cable but with my smartphone power supply (5v output like pc usb) .
With this connection I not see the green link led on wifi shield and data is not sent. I don't know what happens becouse I can't see serial monitor.
I try a direct power supply too with same results, this is the power supply model :
Manufacturer & model: Ideal Power Ltd. 77DE-06-09
Input: 230-240V AC 50Hz
Output: 9V AC
2.1mm barrel jack