My understanding of the H-bridge is, that activating in1 or in2 will direct the 12V current to the motor, so it either spins right/left. Not that in1 or in2 is the actual current passing through to the 12V motor.

These are the schematics.

I am trying to activate the H-bridge and the 12V motor by powering In1 with digital 2 from my Arduino.

The power outlet is an universal adapter connected to my wall outlet, which then goes to a breadboard power supply.

I don't have a functioning multimeter, so I cannot measure the exact current going through, but I do know, that if I place in1 in the power outlet's Vout the 12V motor spins.

Other than that, I do not have much information, and I would like to ask you guys for help as to why, the 12V motor doesn't spin when I power in1?

enter image description here

  • 1
    You don't have a ground connection between the Arduino and the H-bridge?
    – Majenko
    Commented Jun 10, 2020 at 11:26
  • @Majenko This is about the dumbest mistake I have made in a long time. Thank you, it needed a common ground. Commented Jun 10, 2020 at 11:35
  • 3
    It's not a dumb mistake. It's a common mistake. So common I wrote an entire blog article all about it. majenko.co.uk/blog/importance-sharing-grounds
    – Majenko
    Commented Jun 10, 2020 at 11:47
  • 3
    George, you should post a self-answer with the solution and then accept it so the question is marked as answered. (Or @Majenko should post an answer, since they're the one who identified the solution.)
    – Duncan C
    Commented Jun 10, 2020 at 12:34
  • @DuncanC Will do, I can accept it in 2 days. Commented Jun 10, 2020 at 21:22

1 Answer 1


There was no common GND between the H-Bridge and the Arduino.

The question has been solved.

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