– Schematic created using CircuitLab
I'm hoping you could shed some light on the causes of my computer's power supply units recent demise. I'm working on an Arduino robot. I decided to add a Raspberry Pi running a simple OpenCV computer vision code that spots a ball of a certain color in a camera feed and tells the Arduino which way to go to follow the ball. I'm using I2C for communication between the Arduino and the Raspberry Pi. So the SLC and SDA pins on the Arduino are connected to the corresponding pins on the Raspberry pi, via a logic level converter.
It is my understanding that the grounds on the Pi and the Arduino need to also be connected. So I did so connecting the grounds directly with a jump wire. The Raspberry Pi is powered from a USB hub connected to mains power. For a while I hesitated to connect the Arduino to my computer's USB port for power and serial communication since I don't really understand common grounds and I thought something very negative might occur. I powered the Arduino from a battery pack. But then I really needed serial communication for debugging so I said to myself 'its probably ok, nothing bad will likely happen'. Nothing happened for a while. And then, after about 5 minutes or so the lights went out. My PC's PSU had failed and was apparently shorted since it kept blowing a fuse.
Could someone explain what went wrong? I believe I had no other connections on the Arduino or the Pi at the time, except that on the Arduino side of the I2C connection I had pull-up resistors connected to the Arduino's 5 v supply (this was instructed for a sonic range finder module which is also connected to I2C lines but wasn't at the time).
EDIT: added schematic. It includes everything I have, but I'm pretty sure that at the time I didn't have the ultra sonic range finder nor the Bluetooth module connected.