Stepper motor full stepping

74194 bipolar stepper motor driver

Hey Everyone.

I'm trying to get more torque from my unipolar stepper motor.
I'm using a circuit similar to this
**broken link removed**

Except I'm just using the 74LS194, 555 timer (not the same resistances for the frequency), and a ULN2003 transistor array.

What I want to do is change it from single stepping to power stepping ( 2 coils charged up per time )
Its a 6 wire motor, black and brown pair 1; orange yellow pair 2.
I tried putting pin 3 and pin 5 high and 4 and 6 as low.
But the motor goes back and forth.
I tried pin 3 and 4 high, 5 and 6 low; but no movement at all.

How would I make this do power stepping with this shift register.

If I cant do this, if I turn this into a bipolar motor ( ignoring the centre taps) and step it in full mode; roughly how much torque would I get versus single stepping a unipolar?

Thanks in Advance!

As I can rmember, the vector will be on 45 degrees with the same force in x and y direction, so I think it is about 1.4 times the torque.

Consider the inductance of the winding, if you drive the windings with a constant voltage, the current will rise according the inductance of the windings (V = LdI/dt). At higher stepping frequences, you do not reach the nominal current anymore, and you loose a lot of torque. When you put the two unipolar windings in series, you get a higher inducance. You can use a chopper circuit to have enough current at higher steprates (sinde the initial voltage is much higher, the slope of the current will also).

Stefaan