ULN2003 and steeper motor not working

[mapmaker]

I am trying a simple stepper motor example using the ULN2003 with a 28BYJ-48 steeper motor. I have set the speed to very slow so that when i connect the ULN2003 without the motor I can see the LEDs flashing in their correct order: CD, BC, AB, DA. However when I plug the motor in the LEDs all turn off and the motor does nothing. I have tried four different motors and four different ULN2003 boards. What am I doing wrong?

#include <Stepper.h>

const int stepsPerRevolution = 2048;

Stepper myStepper(stepsPerRevolution, 8, 10, 9, 11);

void setup() {
  myStepper.setSpeed(15);
}

void loop() {
  myStepper.step(1);
  delay(500);
}

[ruilviana]

@mapmaker

What am I doing wrong?

Hi,

"What am I doing wrong?"

Using a 9V battery.

Look at the figure below which is the battery voltage per elapsed time as a function of the drained current.

Using 9V with motor for 12V.
Look engine datasheet.
" 28BYJ48 pdf, 28BYJ48 Description, 28BYJ48 Datasheet, 28BYJ48 view ::: ALLDATASHEET :::

These batteries do not supply enough current that the motor needs.

Use an external 9V source.

[mapmaker]

Ruilviana,
Thanks for the useful response. However the motor is a 5v motor, I'll see if I can find an external power supply but the battery was a fresh one, so i'm still puzzled.

[jim-p]

If you remove the battery you can plug in a usb 5V adaptor into the USB port. That should power the motor

[mapmaker]

Jim
Thanks. That fixed it.

[jim-p]

You are welcome
Have fun

[ruilviana]

Hi,

@mapmaker

However the motor is a 5v motor,

true,
in this datasheet it is 5V.
https://www.mouser.com/datasheet/2/758/stepd-01-data-sheet-1143075.pdf

Oh my goodness, you can't even trust datasheets anymore lol