stepper motor controller circuit
I had immediately into my document. I do not know where it came from, but it seems that I photocopy a few years.
I think it should be very helpful, so I decided it here. The circuit is very simple and inexpensive. It is a good thing, since most lines step motor controllers are very expensive. The circuit is made of standard components and can easily be adjusted by a computer. If you cheap surplus transistors and stepper motor, the price of the circuit can be less than $ 15.
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. 
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.
*** 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
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what are the resistor values wit 2n3055’s? can u use BC547’s to “darlingtonize” the 2n3055?
yes that should also work . try 1k ohm resistors w/ 2n3055 1/4 watt or so. Also note the hookup for this is coil 1 signal is from pin#14, coil 2 is from pin#1 coil 3 pin#15 coil 4 is pin#2. Also remember this circuit logic is
on on off off
off on on off
off off on on
on off off on
so the stepper has higher power but will heat up if run for a while.
Good luck!
does 2n3055 can handle a current up to 3A?what should i do for the over heated transistor?
I think,you can change the transistor number which more than 3A.
but 2n3055 npn transistor is Max currrent at 15A.
I have a stepper motor with the rating 5 v,1.6 amps. What modifications I need to do in the circuit so as to drive the motor. One is definitely replace the 12 v supply with a 5 v one. Do I need to use other transistors