Currently, I have an uno hooked up to an ultrasonic distance sensor and an ardafruit motor shield (I will edit this and upload a wiring diagram soon). The ultrasonic distance sensor requires 5V, Ground, and two GPIO pins, I am choosing pins 7 and 8. The ardofruit motor shield requires the SCL, SDA, 5V, and ground pins to operate (as well as an independent power source). Note: I am not stacking the shield onto the board at the moment because I am doing prototyping and don't want to solder yet.
The problem is that whenever I connect the common ground to the motor shield, the processor chip on my distance sensor heats up very hot - why is this happening? I don't have any power going into the motor shield - its acting like when i connect the ground pin a lot of current is flowing through my distance sensor, which I don't understand why that would happen.
**Edit - Once I stack the shield on top of the uno everything works fine, its only when the shield is not stacked that the sensor heats up... odd