polgia0:
2) Why I cannot use a H-bridge to control a bipolar motor? See:http://arduino.cc/en/Tutorial/MotorKnob
It looks like that with a single H-bride you can controll a bipolar stepper motor. They use a Texas Instruments SN754410NE and I thought LMD18200 was its big brother.
3)It is the example wrong ? If the esample is right, there isn't a chip instead of SN75441ONE that can run stepper motor with 3A per phase?
4) If I have to use two H-bridges (I have 2 LMD 18200) can I sincronize them by the arduino board ?
You can use a H-bridge to control a bipolar motor. You can also use a 1 inch paint brush to paint the walls of a house.
Stepper motors are very different from DC motors and they need specialied drivers to get the best from them. With a H-Bridge you are limited to using a voltage that doesn't cause excessive current in the motor coils. But that low voltage becomes a problem as the motor speeds up and the inductance of the coils prevents the coils from reaching their full current. A proper stepper driver can control the current so the motor is not damaged and thus can use a much higher voltage to overcome the inductance and get the coils to full voltage quickly. Also most of the proper driver boards include arrangements for microstepping if you need that. And they just need simple step and direction signals so the Arduino software can be much simpler.
...R