ITS URGENT! Arduino not working with external power supply?
I have made arduino uno u3 robot, i have used 2 geared motors via a l293d using one 9v battery and tried power the arduino with a 9v battery, then with 9v adapter but it did'nt work, I also tried powering the board via the Vin pin, also through the usb cable using the 9v batterg and adapter, but it didnt work either.when i plug it to the laptop with usb everything works very fine. Please give me a sol. soon urgent i hav the exhibition after 3 days!!