So today I’ve continued hacking an ATX PSU into a power supply for my laser cutter, and I thought I’ld give the stepper motor a try on the 12v bus.
I used the same code as in http://crazy-logic.co.uk/archives/314 but this time I managed to get it rotating with 2ms between steps, as opposed to 4ms on 5v supply. I have 200 steps per revolution so
1/200*0.004 = 1.25rps = 75rpm for 5v,
1/200*0.002 = 2.5rps = 150rpm for 12v.
This is an obvious improvement. This will be further improved I imagine after trying a different driving arrangement for the stepper motors with micro-stepping. I did try 1ms, however the stepper motor didn’t really appreciate the speed.