I have a pretty complex setup in my robot; several Arduinos powered from two 12V7Ah batteries in parallel. The 12V are stabilized by a ATX car power supply. They also power a PC over a 12V to 19V DC-DC converter. The PC is connected to one of the Arduinos over USB, receiving status messages from it, and the Arduinos talk to each other and to the motor controller over i2c. Here's a schematic:
Now my problem is that whenever the robot starts to move the USB connection drops (meaning the Arduino disconnects from and re-connects to the USB stack on the PC). Everything else is still working though, i.e. the i2c connection is still on, it's just the connection to the PC that breaks.
This happens on full batteries which should (according to the data sheet) be able to supply 140A; nothing in my robot pulls more than 10A in sum. Also the power supplies should stabilize out any spikes, and the motors have denoising capacitors (came with them). I'm at a loss here.
Anyone have an idea what I could do?
Thanks a lot in advance!