Unipolar stepper, bipolar driver

[Artlav]

Greetings.
I got an unidentified 6-wires stepper motor, which i suppose is unipolar.
But, the motor drivers i have is for bipolar ones.
As i understand, a bipolar driver can drive a unipolar motor, by plugging in the ends of the coils and leaving the middle wires hanging.
Is it that simple or are there some caveats?

Second problem, how can i identify which wires do what?
There are two trios of interconducting wires, in each one there is a pair that gives the most resistance on rotor when shorted, but when i plugged these two pairs, the motor does not work in a consistent way - either vibrate in place or starts moving back and forth. i tried swapping one pair and different step rates to no avail.
What can be wrong?

 

[Bob S]

Read:
http://en.wikipedia.org/wiki/Stepper_motor#Bipolar_motor
Yes, an H-bridge usually can be used to drive a unipolar motor by driving the two ends and leaving the center-tap wires hanging. Read about various types of steppers in above URL. Based on stepper motor voltage and current ratings, set up the two H-bridge drivers, with series resistors if necessary, and drive the stepper at 1 or 2 Hz with the two H-bridges in phase quadrature. My experience is that many H-bridge drivers are not full-rated below ~ 6 or 8 volts, which may be too high for some steppers.
See the schematic on page 2 of:
http://www.ozitronics.com/docs/k158.pdf
for two 5-50 volt H-bridge drivers using P-type and N-type mosfets.
Two popular integrated H-bridges are the L298N and the LMD18200.
Bob S