Hello, I've just received my shiny new Uno and I'm attempting to run a stepper.
I'm using a L293D to drive a bipolar, 12V, 4 wire, 400 step/rotation motor (it looks just like this one: http://www.ebay.com/itm/Applied-Motion-Products-Stepper-Motor-12VDC-5016-852-/260508343789)
Wiring is according to datasheet and a few tutorials I've found around: Enable pins 1 and 2 and pin 16 connected to arduinos 5V 8 hooked up to positive lead of a rather old 9V adapter 2, 7, 10 and 15 connected to 8, 9, 10 and 11 on arduino 3 and 6 connected to one pair of motor wires 11 and 14 to the other pair 4, 5, 12 and 13 connected to negative of 9V adapter and GND on arduino.
Running the example code found in Examples/Stepper/stepper_oneRevolution turns the motor one way and then the other, however, increasing the RPM makes the motor not turn the full revolution. Maximum is around 30 RPM, anything higher makes the motor not turn 360 degrees. Another thing is lack of any serious torque. It could be that's it's a weak motor (I believe it's from a very old HDD), but what about lost steps at not-so-high RPMs?
Thanks for any help.