ULN2003a with Arduino for a step by step motor

Thread Starter


Joined Jan 2, 2016

I'm trying to control a step by step motor with my arduino Uno. I added a ULN2003a between them to have more current in my motor.
I wanted to test the ULN2003a a bit before I use it on my motor. I made a little circuit with a switch and a LED. (picture joined)
But the ULN2003a is not responding as I was expecting. The tension between A and B is -0.5 V without the switch OFF and
4.4 V when it's ON. The LED is not on. (I tested it, everything except the ULN2003a works).

Is the chip dead?
Or have I made a mistake?

Thank you for your help!




Joined Apr 24, 2011
You have made a mistake, the chip acts like a switch to ground, so at minimum the LED is backwards and should go to the +5 volts.

When I get to my pc I will check a few more things I can't see on my iPad.

Edit: That should be it. I doubt your mis connections damaged your part.

View attachment 97676

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