Hello Arduino fans 
I am modifying an old rc remote car to control it over bluetooth with Android.
The problem is that when I turn the motors backward the Arduino resets!
It looks like a current problem because if I accelerate very slowly this doesn't happen (sometimes it happens also in this way).
So i measured the current of the motors running forward and backward and it is the same!
So how is it possible that the Arduino resets only when i run it backwards??
BTW by running the Arduino on USB power the problem isn't there...
How are you powering the Arduino and the motor driver? Separately I hope.
The motors are overloading the power supply and causing the reset. The largest current draw in a motor happens when you rapidly switch the direction of rotation, in which case the current draw can briefly be as twice as large as the stall current. It is best to power the Arduino and the motor from separate supplies, with all grounds connected together.
No I'm powering the Arduino from the same powersource. (In fact when I power the Arduino from USB it works) But why do the motors should take more current backwards then forward?? I also measured the continuos current when the motors go at full speed and forward and backwards is the same!
The problem is there even if I go backwards directly (not inverting rotation).
As the project is a RC remote car I need to power the arduino from the battery pack as well as the motors.
Now I try with a cap and a diode between the motors and the cap.