The engine doesn't run but vibrates



I have this stepper

Motore passo-passo 12 Vdc. 350 mA. 200 steps
Specifiche tecniche:
200 steps for turn
1.8 degree;
stepper bipolare,richiesto un ponte ad H;
connessione a 4 fili;
tensione di alimentazione 12V;
corrente 350mA;
resistenza per avvolgimento 35 ohm;
Coil 1: red and yellow
Coil 2: green and brown/gray

I put 12V external alimentation and I have set “EXT” with jumper

I try your Arduino sketch example but:

The stepper motor vibrates but doesn’t work
LEDs light up simultaneously when the shield sends the impulse to rotation

Where I have mistaken?



Maybe there is a wiring problem with the stepper motor?