Stepper needs more torque

Using Arduino Motors, Mechanics, Power and CNC
1

Hey guys, you have all helped me so much and I thank you.

I finally got everything to work. However, my stepper needs more torque, I think, because it doesn't like to spin up. If I use my finger to get the platform spinning, the stepper will engage and keep it spinning.

Now online I have read that I could up my voltage. But I am already using a 12V wall adaptor and don't want to use more unless I absolutely have to.

Is it possible to use a "tone" function, or some other way, to get the motor to slowly and steadily spin up? I'm pretty steppers have more torque at lower RPMs. The RPM is specified currently by:

 tone(stepPin,300);

I will need to be able to adjust the final frequency and resulting stepper RPM within the range of about 100-400hz

Also, what about changing the duty of the tone?

I previously used delay but it was buggy:

  //  digitalWrite(stepPin, HIGH);    //pulse the motor high then low 400 times to achieve one spin
  //    delay(15);
  //  digitalWrite(stepPin, LOW);
  //    delay(15);

Here is what I use:

Nema 17 (unknown model - if you know how I could Identify it, that would help with current limiting)
A4988 driver

2

HunterHunter:
I finally got everything to work. However, my stepper needs more torque, I think, because it doesn't like to spin up. If I use my finger to get the platform spinning, the stepper will engage and keep it spinning.

That strongly suggests that you need to accelerate it up to your desired speed. Either use the AccelStepper library or implement your own acceleration code. This simple acceleration code may give you some ideas.

Here is what I use:

Nema 17 (unknown model - if you know how I could Identify it, that would help with current limiting)
A4988 driver

Measure the coil resistance with your multimeter.
Where did the motor come from?

...R
Stepper Motor Basics
Simple Stepper Code

3

I figures out a way to accelerate the stepper, and it works now, mostly.

My stepper has six wires and two coils. The coils are both divided in the middle by one of the wires to make 0.4 + 0.4 = 0.8 ohms per coil. measured using multimeter. I do not know the origin of my stepper nor does my boss who gave it to me. It is black with a 5mm D shaft. (pretty generic)

Do you know anything else I could do to figure out how much current I should allow the driver to deliver?

4

Are you confident that your multimeter can measure low resistances accurately?

If the coil resistance is only 0.8 ohms it suggests to me that the designed working current is unlikely to be less than 1.5 amps and could be a great deal higher.

An A4988 will probably struggle to do more than 1.5 amps so my suggestion is to set it for that current and see if the motor gets very hot. If it gets quickly gets too hot to touch then 1.5 amps is too much. If it only gets warm my next step would be to try 2.5 amps with a more powerful driver.

But don't blame me if the smoke escapes :slight_smile:

...R