16mm projector and seral port

Hello,

I've been working on a 16mm projector that I want to control through a computer. So far it works fine, but I have an issue with communication and power. I am powering the Arduino and the circuit that controls the motor of the projector with a 12v power supply, and I am using the USB port to communicate through serial port. However, when the power supply is disconnected the Arduino gets power from the USB port, and when I turn on the power supply I have to somewhat re upload the program for it to work. Either that or reset the Arduino, but since I'm going to leave it out of reach the reset button won't be an option. What is the best approach to solve this? Thanks a lot!

Cut the red wire in the USB cable and the Arduino will no longer receive power from the USB-port.

It sounds like you have a damaged chip in your Arduino if the sketch gets corrupted upon power loss.

// Per.