So I was trying to build a basic Sumobot using 2 motors and 3 HC-SR04 ultrasonic sensors (no edge sensors yet). I used an L293DN dual H-bridge motor driver, and supplied each of the voltage pins of the motor driver with a 9V battery. I tested that setup before connecting the sensors and it worked fine. Then I connected the sensors and tried some tests but found that I forgot to connect each of the sensors to the 5V pin of the Arduino. As soon as I did, poof! Micro-controller stops working. I looked over all the electronics to see what could've went wrong but I can't find anything. I have done this setup with one ultrasonic sensor before and it always worked fine. All the wires are as they should be and the Arduino was powered by the USB jack - not the power jack or Vin. Can someone suggest what might have happened? Is this some kind of overload on the micro-controller? Or what? Thanks in advance.
Have you disconnected the thing that made it stop working when you connected it? If so, do that. Does it work again?
Does the power light come on?
My guess is most likely the +5v going to sensors you connected was/is shorted to ground (arduino lives once you remove the short), or connected to the +9v (not looking as good for the Arduino).
Was there any smoke? Burned circuit smell?
Yes it worked! Thank God! When I disconnected the sensors, it came back to life :'). In fact, after testing with each sensor separate, it was just one of the sensors that caused problems. Thank you man!