I'm making a self balancing robot and wondered how could I power both the Arduino and the motor with one battery. I know it's not optimal to have a common power source but due to weight and space issues it's not really possible for me to have a different battery just for the Arduino. When I switch the power on the voltage jumps above the configured 7.5V to over 12V but after the arduino boots it goes back to 7.5V. The problem is that this short voltage spike bugs the arduino and I need to press the reset button after every time I power on the device. After that everything works like normal, no problem even after hours of continous working. Can you tell me what's wrong with my wiring or how could I solve this issue?. Thanks in advance!