hello
my arduino is leonardo
last week i had a servo motor which works on 7 volts , so i connected it to an external power supply 12 volts and it didn't work, then i connected the 5v pin in arduino with the positive terminal of power supply to the motor and it worked
yesterday i had a servo motor which works on 5 volts, and i connected the 5v pin inaruino with the positive terminal of 6 volts power supply to the motor , it worked at first, but after a lot of tries (because i control it using accelerometer so i tried many times) the usb interface stopped working so it disappeared from device manager
i plugged out the usb cable and plugged it in again, then it appeared for about 10 seconds and disappeared again, and now it doesn't appear at all
does anyone has an idea to how to fix it ? or should i buy a new one ?
When you were trying to use an external power supply to run the motor did you connect all your power supply - (grounds) together?
Using the Arduino power pin to drive more than LEDs or 1 servo is certain to pull too much current. Trying to drive a stepper was probably enough to damage the board.
You could try connecting your Arduino (just the Arduino board) to a USB port on another computer. You might have damaged your USB port, or more likely you damaged the Arduino board.
Look on the bright side - if your Arduino has the 20 pin DIP on board you can use it as a second chip for your replacement board. Or you can use it in a breadboard.
yes i connected the grounds together
i think the arduino board was damaged because i tried it on other computers and it also didn't work
is there any way to repair it ?
and what do you exactly mean with "you can use it as a second chip for your replacement board. Or you can use it in a breadboard"
can you tell me more about this ?
Just to be sure, try connecting your Arduino with another cable. Coincidentally, I had problems today with an Arduino dropping off the USB connection all the time all of a sudden. Since I was working with servos and had made a wrong connection on top of that, I assumed I damaged either my Arduino or my USB port. But with an other cable everything worked fine again.
I actually find my Arduino (UNO) surprisingly indestructable. Made quite a few stupid errors over the time, but it survived them all... 
Good luck,
David
I had a similar problem with my Uno driving a servo. All of a sudden, when USB-connected to my PC, the connection started dropping and the functioning became erratic. When I disconnected from the PC and powered the Uno from a 9V DC battery it worked fine.
In desperation I swapped out the USB cable for another I had and now it's working fine with the new cable.
I have no idea what happened, and it makes no sense to me, but it works.
If there's anyone out there who can explain what might have happened I'd sure like to know.
Thanks.