ULN2003a with Arduino for a step by step motor

Discussion in 'Embedded Systems and Microcontrollers' started by Yokad912, Jan 2, 2016.

  1. Yokad912

    Thread Starter New Member

    Jan 2, 2016
    2
    1
    Hello!

    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!

    Christian

    20160102_124858_Christian.jpg
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    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

    uln2003_ErnieM.jpg
     
    Last edited: Jan 2, 2016
  3. Papabravo

    Expert

    Feb 24, 2006
    10,136
    1,786
  4. Yokad912

    Thread Starter New Member

    Jan 2, 2016
    2
    1
    I understand now! It works! Thank you all!
     
    ErnieM likes this.
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