Multiple Steppers driven by the same Uno pins

Other Hardware Motors, Mechanics, Power and CNC
1

Hello! I am a beginner at building things using the Uno. I am carrying out some experiments using a basic Stepper motor (28BYJ-48) and driver (ULN2003).

I was able to easily hook this up to digital pins 2,3,4 and 5 to step the motor. I have an external power supply (5V, 1A) to power the driver. My laptop's USB port powers the Uno.

Next, I tried to run three motors synchronously. To do this, I connected three ULN2003 driver boards in parallel - the IN pins of the driver board to the to the same Uno pins (2,3,4,5) and power and ground of each board to the external power supply. I also connected the grounds to the Uno's ground.

I would like your help to understand why this isn't working reliably. In some attempts, two motors would turn and sometimes, only one would run. Only rarely would all three run. The ones that weren't running would vibrate and would start turning when I gave it a push. Is this because the drivers are drawing too much current from the power supply? Can the digital pins be used this way, to drive multiple steppers?

2

You wrote:"To do this, I connected three ULN2003 driver boards in parallel - the IN pins of the driver board to the to the same Uno pins (2,3,4,5) and power and ground of each board to the external power supply. ".

Why did you not connect the grounds of the driver boards to the Uno ground?

Paul

3

Hi Paul. Sorry I didn't mention it. I did this as well. I have modified the question to reflect.

4

Appears to be time to use your test equipment to begin measuring the voltages when running one motor and when running more than one and report the voltages.

Paul

5

Thanks, will do.