Help me with bipolar stepper motor..

[bashok001]

I am devising a knock lock for which i used a bipolar stepper motor using a mosfet driver..I have four terminals coming out of motors! I connected them all with four mosfets...Now it doesn't move...so I did a small research on internet on bipolar stepper motor drivers and i got these circuit diagrams in which they connected the motor with MC driver as I did but the coils are also coonected to 12 v from their middle...
From where should this connection be made..??? We have four terminals coming out of motor which are all already engaged completely... So how will this 12v battery connection to motor made?

 

[Resqueline]

You'll need 4 half-bridge outputs, 8 transistors in all, to make 2 full-bridge drivers to drive that motor. The top 4 transistors would be connected to +12V. Granted, it's a little more complex than using a 6-wire motor.