Sketch won't run with non-USB power supply

I'm having the problem where my arduino sketch won't run when I power the arduino with anything other than a USB connection to a computer. I've tried a 9V battery, I've tried a 5V input to Vin, and it simply will not run the sketch. I tried connecting RX and TX directly, also tried a 10k resistor between RX and ground, as suggested in various posts in this forum, and nothing seems to be working. The board is an Arduino Uno R3 with a SeeedStudio ethernet board on it, the sketch I'm trying to run is just the blink sketch (pin 13 high, wait 1 sec, pin 13 low, wait 1 sec, repeat forever).

Can anyone suggest any other solutions?

9v batteries are not able to supply much current. Try another power source in the power connector.


How did you determine that your sketch is NOT running compared as running? The blinking of the LED at 1 second interval? Feeding 5V to vin will not power your arduino. How did you connect your arduino and the 9V battery? Which pins and where?

The shield may use pin 13 for something, perhaps connect an external resistor and LED to pin 8 and modify your sketch to blink that pin instead of 13.