I'm trying to control stepper motor using ULN2804 and a pic.
I want to use 2 outputs on pic cause i need to drive 2 motors and i have only 8 outs
so I have constructed one of the circuits, but it seems to not work(it worked when i made it in my PC(simulator) but not in real life... :x )
Try inserting a 12V zener diode between (cathode here)pin 10 of the 2803 and the 12V supply (anode here). This will increase the rate the current decay rate which should improve motor performance.
Since you're using just 2 pins, the motor is forced to run in full-steps only which will increase the chance of resonance.
Lastly make sure you've got the motors wired correctly.