Unipolar Stepper Motor Resistors

Thread Starter

stoopkid

Joined Mar 3, 2011
146
I just got a 28BYJ48 stepper motor from ebay. I don't have a ULN2003 yet so I thought I would just test it with four pushbuttons or NPN transistors. The thing is, every URL2003 driver schematic I find have no resistors. It it okay to drive the motor directly off 5v? And when I DO get the ULN2003, do the bases not need to be limited like transistors' normally are?

Thanks
 

Potato Pudding

Joined Jun 11, 2010
688
The Darlington array ULN2003 that I believe you are referring to has internal bias resistors.

You might be able to click the motors a bit back and forth but it will not run without pulse sequencing.
 

Felo

Joined Feb 20, 2012
91
The datasheet states 12v rated voltage I doubt it will move on 5v, ULN's are logic input so no biasing res required.
 
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