Stepper Motor Power Supply

Question

Just a quick question. Picking up some stepper motors, but confused at what voltage/current things are running off.

Ordering:
2 x Stepper Motor
2 x EasyDriver

An article says

You need some 12V source to the EasyDriver (the motor in this article is 12V) - This will be powering the stepper - Im using a 12V adapter - similar to the one in the illustration. Just make sure it is rated at least 750ma - A higher rating is better, and just means it wont burn out.

So does that mean if I got a plug which is regulated 12V 1A and powered the Arduino from that I could power a rail with VIN pin and that would safely supply the EasyDrivers? And I could then use the 5V pin to power everything else?

Just don't want to break anything! Thanks

Answer 1

As generic rule: avoid powering one device through another. It can cause strain on the middle-man device and it will be inefficient. The only few cases where this might make sense are when it's topologically inconvenient to connect everything to the centralized power supply. Or if the cascaded device requires a voltage that is not available from the power supply.

In your case you can power both the easy driver and the Arduino from the regulated 12v.

And you won't risk drawing too much current through the Arduino.

Answer 2

Stepper Motor Control - one step at a time

This program drives a unipolar or bipolar stepper motor.
The motor is attached to digital pins 8 - 11 of the Arduino.

The motor will step one step at a time, very slowly. You can use this to test that you've got the four wires of your stepper wired to the correct pins. If wired correctly, all steps should be in the same direction.

Use this also to count the number of steps per revolution of your motor, if you don't know it. Then plug that number into the oneRevolution example to see if you got it right.

#include <Stepper.h>

const int stepsPerRevolution = 200;  // change this to fit the number of steps per revolution
// for your motor
// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 8, 9, 10, 11);
int stepCount = 0;         // number of steps the motor has taken

void setup() {
    // initialize the serial port:
    Serial.begin(9600);
}

void loop() {
    // step one step:
    myStepper.step(1);
    Serial.print("steps:");
    Serial.println(stepCount);
    stepCount++;
    delay(500);
}

Answer 3

The V_in pin is after the M7 protection diode, so you won't get quite 12 V out of V_in. Also, depending on the load, the diode might get warm.

I've also found that powering an Arduino from 12 V input (the maximum recommended) tends to get the voltage regulator hot.

Your other issue is that the motor power will be going through the Arduino board, to an extent (in the plug, through the diode, and out V_in) so any noise generated by the motor will be close to the processor.

I don't think your idea would break anything, it just might not be particularly reliable.