With this power source: 20000 mAh 5V 2,1A (Powerbank)
And this driver:
and Arduino Uno
Can i run this stepper motor: Nema 17 Bipolar 36Ncm 1.68A 2.8V?
Do you think the motor can run smoothly at 4rpm?
That doesn't describe the stepper motor very well. Its datasheet does.
Please define "smoothly"!
All stepper motor works, as the name tells, step by step. There's no smooth running, only shaking, step by step. Go for a geared DC motor for smoothness.
Depends on the driver. The more microsteps the smoother it is running. The TMC drivers can run a stepper very very smoothly - and most of them can run at 5V ( datasheet says min. 4.75V ). But I never tried with that low voltage.
The datasheet for that motor:
I am trying to make a barn door tracker, so I need a constant and smooth rotation because the camera is taking long exposure photos. For smooth running, I will make a gear reduction, to increase the speed of the motor and not be so shaky.
I will utilize the motor at around -5ºC up to 10ºC with a power bank, won't the geared DC motor reduce speed depending on the ambient temperature or when the power bank is running low on battery? (newbie question)
So a TMC2209 will do the job?
The datasheet says, up to 2 A per coil.
Normally you'd use microstepping for smoother and more reliable operation, x8 or x16 are good microstepping ratios to try first.
Steppers are very power inefficient, for battery operation they are a poor choice unless you need the precise position control.
Very similar project here : Building a barn door mount, part 1: arduino stepper motor control | f/138 - Daniel Berrangé
For the "smoothness" requirement, it seems that movement several times per second is sufficient. Manual trackers are moved every few seconds. However, precise tracking over time is important, so if a geared motor is used it needs to have position feedback (assuming AC mains not available). A stepper might be better in this case.
To reduce power, the stepper can be disable but at risk of losing position, especially if using microstepping. However, at 4 RPM that is only 13 steps per second, so I think you could use full stepping. If driving a threaded rod, then the stepper should hold position when disabled.
Microstepping won't affect the risk of losing position if the motor's powered down, once power is reestablished the motor will snap to the correct position so long as it moved less than 2 full steps since power was removed. In general full stepping is annoyingly loud and never used these days in commercial products (its a hang over from before cheap microstepping driver chips were available).
I don't think that is true, the stepper driver does not remember the previous position.
In this application, moving 13 steps a second the noise is simply not an issue.
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