Hi,
I used my Arduino Uno clone for 7 months and it worked fine. Today I started to upload a code on the wrong port so I interrupted uploading and selected the right port and tried to upload but it doesn't end. I thought it is because of the interruption and I pressed the reset button on the board few times and also long pressed and no result. I switched the USB cable (even if I know it is working), the laptop, the ports, updated Arduino IDE and nothing. I also want to mention that there are no jumper wires or anything at all plugged into Arduino. And at some point, while USB was connected, I put an 11.1V power supply at Vin and since then, whenever I connect the USB cable, the RX and TX LED's are always on and my computer doesn't recognize my Arduino anymore (not in Arduino IDE and also not in Device Manager).
Thank you in advance!
I put an 11.1V power supply at Vin and since then, whenever I connect the USB cable, the RX and TX LED's are always on and my computer doesn't recognize my Arduino anymore
Don't you think that maybe something bad happened here? Was the Uno plugged into USB and powered up when you connected the 11 volt supply? Was the 11 volt supply on when you did this?
Exactly what kind of 11 volt supply was this? DC I hope, AC would probably have made something smoke. But in either case, unfortunately, it certainly sounds like something was damaged. The USB interface chip sounds like one casualty, with both led's being on. With Uno clones going for less than $4 on eBay, it doesn't make sense to attempt repair.
Yep... now I realise that I put 5V through USB while 11V through Vin. So I think that the board is broken. I wanted to supply some motors but I forgot to unplug the jumper from Vin. And yes, I paid around 3$ so I'll buy another one.
Btw, it was a lipo battery 11.1V 2200mA 30C (of course DC).
Thank you for replying 
Купил arduino uno R3, у меня Виндоус 8.1, скачал редактор и по инструкции хотел поставить дрова, но диспетчер не видит драйвера (файл не найден, говорит), хотя сказано что это Arduino UNO REV3.inf и он у меня в каталоге есть. Чем исправить ситуацию?