Ihave an arduino uno board and have a project i have been working on. i connected and LCD diplay, an ultrasonic sensor, two servos, a few switches and a couple of LEDs. i connected them all and programmed my board and i saw only my servos werent moving. So i connected a 12V 1.5A DC external source to my board and after a while i couldn`t find my board on my pc through my usb cable. Although my code still works, except for the servos, on my board. Did i blow something up??? Should i get a new board? i have checked the regulator and it is working properly. Please advise...
Assuming you connected the 12v to the barrel jack it should not have caused a problem - provided the polarity was correct.
You should NOT be powering servos through the Arduino. They should have their own power supply with a common GND with the Arduino. The servos and the Arduino could both be powered from the 12v supply (with a suitable voltage reduction for the servos.
If the servos are drawing too much current through it they will cause the Arduino to malfunction and may damage it.