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Unipolar Stepper Motor Driver (need assistance)

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New Member
Hi guys,

I need assistance from you all in driving my unipolar stepper motor. The stepper motor requires around 1A of current through their coils. The Vstepper should be around 12V. I planned to build two drivers, for my bigger and smaller stepper motor (2A and 1A coil current).

What I have now on my table:

-L297 chips
-TIP110 NPN Darlington 1A
-TIP120 NPN Darlington 2A
-ATMega 8535

I googled some designs and found this one:
Unipolar Stepper Motor Driver Circuit - Mechatronics Wiki

I wish I could drive my unipolar only with L297 (without L298) and TIP110/120 according to my motor size. Is it possible?

What should I feed on the CLOCK pin? I read the similar thread in this forum and some guys fed up with 555 timer IC, I need to interface with microcontroller so what is the best approach here?

I have tried the schematics at that website (given above from wiki), but my stepper motor doesn't run at all. The high pitch sound is generated and I couldn't turn the shaft of the motor with my fingers, say it has holding torque in it. I don't know why, maybe you guys could figure it out?

Help me.

Best regards,



Well-Known Member
i would guess that either you have incorrectly connected the stepper motor wires, or the stepping frequency is too high.


New Member
i would guess that either you have incorrectly connected the stepper motor wires, or the stepping frequency is too high.
Dear dougy83,

I have done the coil resistance checking by using digital multimeter. I have found the COM and coil wires. I definitely sure about this though.

The stepping motor wires are done well without any doubt of having those wires improperly connected.

Now, about the stepping frequency. I will try to use 555 timer and see if it goes right, I choose the 555 timer parameter about this:

R1 = 1.2kOhms
R2 = 6.8kOhms
C1 = 100uF

that will give me:

T1 = 554.4ms
T2 = 471.2ms
Frequency = 0.973Hz

Please do comment about this asap, I am doing it now with my protoboard.

Thanks anyway for your comments and hypothesis! I will work on it now...


New Member
IT WORKSSSSSSSSSSSSSSSSSS!!! The problem is only the CLOCK!!! damn it works man!!! I am so happy! Thanks GOD! Thanks a million guys!


New Member
I have another question.. The motor is running per step, according to the CLOCK given, but why my motor is hot? I tried to drive it with 5V now, see if it is cooler in some ways?


Steppers tend to get warm, when they're not moving the coil is actually drawing more current than if it were rotating quickly. You could alter your code so that it sends short pulses to the coils instead of continuously drives them, steppers tend to cog so as long as it's very lightly loaded it will stay in position by itself. If you need the holding torque or you are spinning it fast you can try a lower voltage but it will lower the torque.
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