I'm using the 5V onboard power to provide power to all 3 DC motors by shorting all relay load(power) ends together in a breadboard.
I am connecting each ends of a DC motor to a relay and the relay is connected respectively to a load and PWM signal.
Ive tested with 1 dc motor and a relay connected with the arduino
and it worked perfectly
Using Arduino with other software (Processing, Flash, PD, MaxMSP, etc.)