schematic knowledge

This stepper controller circuit shown here can used to control the unipolar stepper motor,which has 4 coils . The stepper controller circuit can drive for a motor current of up to about 500 mAmp/Winding by suitable heat sinks for the SL-100. directsinks In higher currents power transistors seem 2N3055 can be used as darlington pair along with SL-100. All diodes are used to protect back current the transistor from transients.

Stepper Motor Circuit with IC 4027 Circuit diagram :



Remark. 

• You may be able to substitute any standard (2N3055) power transistor for Q1-Q4 or get IC type UL to modify for transistor.
• Every time in move the motor put signal the STEP line is pulsed, the motor moves one step.
• Switch S1 for changes the motors direction