geared stepper motor - VERY LOW speed

Other Hardware Motors, Mechanics, Power and CNC
1

Hello guys

I m completely new in arduino and now I m trying a project where I need very low speed for 2 to 30 rpm max. I bought a Gear Ratio 19:1 Planetary Gearbox With Nema 14 Stepper Motor 14H for test.

However, although the step level is 1.8' degrees (when motor is NOT geared) the manual does not say what is the new step after geared.

I will use this motor to rotate a camera head and thus i need low speed which will be between 2 to 30rpm max.

I m using an L298N driver (this one : https://www.amazon.com/Controller-Module-Bridge-Stepper-Arduino/dp/B00HNHUYSG)

I tried this very simple sketch to understand how it works since i m new in this :

#include <Stepper.h>

const int SPR = 200; //I keep the 1.8' angle step

// initialize the stepper library on pins 8 through 11:

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

void setup()
{
myStepper.setSpeed(30);
}

void loop() {

myStepper.step(SPR);

Now I have some question:

I played with the values with red color, SPR and speed.

First question is, what is the right value for a geared stepper motor at SPR ? I suppose it is still 200 (360/1.8) or I m wrong ?

Second question is, Lets suppose we need the motor just spining (rotating) what is happening if I change
the SPR to 400 or 600 and adjusting the speed accordingly ? Do I loose in torque ? do I decrease the performance ? or what ?

Third question. with SPR 200 and speeds lower than 10-12rpm I think motor is not working properly. Do I bought a wrong geared motor ? (perhaps more geared needed ?)

thank you and sorry if my questions are silly :slight_smile:

2

The speed of a stepper motor is determined by the interval between steps. There is nothing to prevent you writing a program in which there are 2 or 3 days between steps.

I have not used the Stepper library and I don't know what is its slowest speed. AFAIK you can tell it to move one step and take as long as you like before telling it to take the next step.

You might want a reduction gear on the stepper motor if you want slow continuous motion rather than steps.

And smooth slow motion will be much easier to achieve if you use a specialized stepper motor driver such as a Pololu DRV8825 as it can make the motor move in microsteps. That might remove the need for the gearbox. The code in my examples is for that type of stepper driver.

...R
Stepper Motor Basics
Simple Stepper Code

3

gspir:
I m completely new in arduino and now I m trying a project where I need very low speed for 2 to 30 rpm max. I bought a Gear Ratio 19:1 Planetary Gearbox With Nema 14 Stepper Motor 14H for test.

However, although the step level is 1.8' degrees (when motor is NOT geared) the manual does not say what is the new step after geared.

The clue is in the phrase "Gear Ratio 19:1".

However the subtlety is that the ratio may not be exactly 19:1 (in fact it unlikely to be exact). So its actually
best to measure it.

4

2 rpm is pretty quick - think about stellar telescopes which track at 1 rev/day. and resolution <<1 arc-second ..

generally worm drive.

Allan

5

gspir:
Second question is, Lets suppose we need the motor just spining (rotating) what is happening if I change
the SPR to 400 or 600 and adjusting the speed accordingly ? Do I loose in torque ? do I decrease the performance ? or what ?

Nothing happens - the steps per rev to the library is solely used to map commanded speeds to step rates,
so if you set SPR twice as large and set a speed twice as large they cancel out.

Look at Stepper.h/Stepper.cpp files for documentation on what the limits to various function parameters are too,
the code is there to be consulted.