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I plugged a BLDC gimbal motor in to my Arduino today, and it made a very small jitter. I tried to set an analog pin for the signal pin of the motor (motor had three pins, I assumed one was power, one was ground, and one was signal/data/position) but the motor barely moved. I wanted to see my motor spin at some constant rate determined by that signal pin, or maybe move to the position specified in the signal pin.

Upon further research, I find many pages advising me to use "controllers" or other complicated setups to manage a motor. I am confused as to why it is so complicated. Can't it be simple to plug a stepper motor into an Arduino and get some constant revolutions based on Arduino control?

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    the arduino is not a power supply ... its output current capacity is very limited ... it cannot drive a motor directly ... you are lucky if your arduino output pins are still alive after your experiment
    – jsotola
    Commented Nov 4, 2021 at 22:39

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Not only is the available current limited, but a stepper motor in particular is not capable of running just by supplying power.

It's drive coils must be energized in sequence to "pull" the rotor around, and sequenced at a rate that drives the rotor at the desired RMP. The circuitry to do that is external to the stepper, usually a combination of logic signals from a micro-controller (typically) and hardware to translate those signals into drive currents sequenced to the stator-coils. This is what makes steppers so flexible - controllable in direction and speed, down to the single-step level (subject to the rotor's interia) - at the cost of more complex drive circuitry. In short, steppers need to be programmed, continuously, to drive them however the mechanical system requires.

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It is a power issue. By that I mean Power = Votage x Current.

Put simply, the 5V supply regulator IC on the Arduino is only designed to power the microcontroller(s) and a handful of other electronic components.

The Arduino has a little 5V regulator that is capable of delivering 100mA to 500mA depending on your Arduino. Don't forget that the microcontroller itself uses roughly 20mA. The remaining current is capable of runing very low power items such as sensors, switches, LEDs etc but not parts that require more power. Unfortunately motors require a lot more power than what the regulator on the Arduino can provide.

I suggest that you use a second 5V supply. For example you could use:

  • Benchtop power supply
  • Plugpack or phone charger type power supply
  • An old computer power supply
  • A DC/DC converter (like this one)

These are just a few. There are many more options.

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A brushless DC motor consists of three coils of wire wired in a Y (wye) or Δ (delta) configuration and a magnetic rotor. The coils are evenly spaced around the 360 degrees of the motor. There can be multiple poles, or "copies" of each coil, so it's not necessarily 120 degrees from a coil A to a coil B - e.g. it could be ABCABCABC to go around the full circle with 40 degrees between coils. There are no power or ground or data wires, just electromagnets.

Anyway, when current goes through one of the coils it forms an electromagnet and attracts the rotor to that position. We say the coil is energized. By repeatedly energizing and de-energizing different coils you make the rotor spin around in circles. If you energize A, then B, then C, then A, then B, then C it spins one way; energize C, then B, then A, then C, then B, then A and it spins the other way. The current direction also matters because an opposite current produces an opposite magnetic field. Of course you also have to get the timing right - so the magnetic force is always pulling the rotor ahead of where it currently is. When the rotor catches up with the magnet coil you switch to the next one. I'm oversimplifying.

To use one you can buy a controller which does have power and data and ground wires, as well as the 3 wires for the magnets, and you tell the controller to go, and it handles all the switching and timing for you. You could design your own, but good luck.


Steppers are the same basic idea but optimized for low speed and precise movements instead of big movements. Because you don't care about timing so much for a stepper - you're moving it one step at a time and not really trying to use its inertia - you can write your own control algorithm if you want. Note the Arduino's digital pins still can't output enough current so you still need some circuitry. Or you can buy a stepper motor controller.

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