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floppy bipolar stepper motor driver? Answered


i wanted to salvage my old floppy drive , and take the small bipolar motor from it

after i removed it , i looked around and i found small ic (  LB1838M  )

its data-sheet is here


i found somethings (pins configuration) in the data-sheet that i don't understand

like :  IN1 ,  IN2  ,  ENA1 , ENA2

so , what this pins represent for ?

and , can i remove this ic from the board , and make a circuit like this one in the data-sheet and use it to control the stepper ( independently ) ?

if yes , i need to know how to make controlling buttons or something .

English in not my 1st language btw , so ...
thank you :)


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Jack A Lopez
Jack A Lopez

Best Answer 10 years ago

This chip, LB1838M, does not do much, except translate binary inputs (IN1, EN1, low or high) into the 3 states possible for a single motor coil (current forward, current reversed, current off).

It's all in the truth table on the second page of the data sheet.  IN1 and EN1 control the first coil via OUT1 and OUT2.  IN2 and EN2 control the second coil via OUT3 and OUT4.  The letters EN stand for "ENable". Setting a EN input high enables a coil to turn on, either forward current or reversed current, depending on IN.  Setting a EN low forces the coil off; i.e. current =0.

Anyway, this IC by itself will not make the motor turn, you still need to figure out the sequence for actuating the coils.  I don't know what the proper sequence is but,   these links might help with that:





8 years ago

this is the sequence for a bipolar stepper motor which is the most common type used in floppy drives.

Step 1: coil A1 = ON, coil B1 = ON, coil A2 = OFF, coil B2 = OFF.
Step 2: coil A1 = OFF, coil B1 = ON, coil A2 = ON, Coil B2 = OFF.
Step 3: coil A1 = OFF, coil B1 = OFF, Coil A2 = ON, coil B2 = ON.
Step 4: coil A1 = ON, coil B1 = OFF, coil A2 = OFF, coil B2 = ON.

Hope this is plain and easy to understand.
It should help with the step sequence.
to get it to run the other way, just reverse the sequence.


10 years ago

I'd suggest that you look for application notes for the IC, although my experience has been that finding anything in that respect is difficult or near to impossible for Asian rim IC mfgs. Either they want to make it difficult or they're ... well never mind. I suspect they just want to make it difficult as part of their program of keeping the technology we originally provided to them from us..

IN1 and 2 are likely inputs, possibly feedback.. ENA1 and 2 are likely enables. I really can't say for sure though and I hate reading Japanese datasheets. they're too often full of unreadable gobbledeegook.

It's also possible that contacting Sanyo directly might reveal more info, although my experience in this regard has also met with dismal failures in the past, even when using my once upon a time NASA credentials as an "in".


Answer 10 years ago

thanks man 4 ur answer , it helped