When scanning a low-voltage motor like the XL-330, do I need to also connect it to a 5V power source, or can I use a higher voltage 12V power source just for the purposes of setting its ID (and not actually running the motor)?
Sorry if this is a dumb question, thanks.
The XL-330 is rated for 5V for any purpose. Using 12V on them would most likely void their warranty.
The XL330 is only rated for 5V, so do not connect a 12V power supply.
Basically, you can use USB power to scan and set the ID for up to one unit of the XL330.
In the official e-Manual, it is noted that if you run it at high speeds or with high torque, there is a possibility of damaging the PC, so use a 5V power supply (such as the Terminal VIN of the OpenRB-150) instead of USB bus power.
Reference URL
ROBOTIS e-Manual OpenRB-150 5. 4. 1. When running 5V DYNAMIXEL with the USB power