Using 3 different power supply at same time

Hi guys,
I am doing a project which include 2 stepper motor (control by a CNC shield - A4988 driver), 4 dc motor (control by a 4 Wheel Drive Motor Driver Module - L293D) and some sensor module.
I have connected a DC supplier (80 W) to the 4 wheel drive module , another DC supplier (5 W) to CNC module and finally Arduino is powered by USB connection.
One of the DC motors just comes on when machine is working and its working time is when the stepper motors are disabled.
As test of the sketch,I can turn of the power supply of DC motors and the machine works perfect, but the problem is, when I turn the DC POWER supply on, the Arduino reset by itself randomly on different position of CNC.
I have connected VCC and GND to both module.
Would you please let me know why there is the issue?
Thanks
Amir

I'm not sure, because I don't know your circuits exactly, but I would connect ONLY the GND's. I think there are voltage differences between the power supplies, perhaps they have these side effects.

-richard