[SOLVED] Calculation of step angle in stepper motor

[jjzai123]

Hi guys, recently I've been studied about the stepper motor and I found 28-BYJ-48 motor is widely use in any application. According to the datasheet, the stride angle is 5.625 degrees / 64. Means it need 64 steps to reach 360 degrees, what if I make it to half step? Is the step angle become 2.8125 degrees and required 128 steps to complete a rotation? The datasheet is attached here.

http://robocraft.ru/files/datasheet/28BYJ-48.pdf

 

[FvM]

This is a geared motor, the step angle is only 5.625° /64. Respectively you need 64*(360/5.625) for a full shaft rotation.

 

[rho-bot]

I don't think it's that easy... Usually there is a lot of confusion & translation bugs within vendor chain.
- Speed Variation Ratio 1/64 => gear ratio, output shaft is driven via a 64:1 gear ratio
- Stride Angle 5.625°/64 => motor has a step angle of 5.625°, and the resulting output shaft (gear ratio 1/64) movement will be 0,088°

But the big question: What is a motor step?
Here marketing begins to involve. Usually they specify using halfstep mode (8 halfsteps, 1-2 phase excitation), to make the motor look nicer.
Phys. fullstep resolution is based on fullstep mode (4steps, as you have 4 coils), resulting in 11,25° per fullstep.
The motor has 32 poles (360°/11,25°), so you need 2048 fullsteps, to make a full shaft rotation (32*64)

Dependent on the torque you need, you may go with 1-1 or 2-2 phase excitation (both 4 fullsteps) or 1-2 (8 halfsteps)
All of them have pro&con, so it depends on your application needs & driver capabilities.

 

[FvM]

Usually there is a lot of confusion & translation bugs within vendor chain.

"Usually" motor vendor supply clear, unequivocal data sheets, at least that's what I'm used with professional products. Unfortunately no clear datasheet seems to exist for 28-BYJ-48.

The motor has 32 poles (360°/11,25°), so you need 2048 fullsteps, to make a full shaft rotation (32*64)

Might be, full or half step isn't specified in the data sheet. Do you know from own tests or is it a conclusion?

 

[rho-bot]

"Usually" motor vendor supply clear, unequivocal data sheets, at least that's what I'm used with professional products. Unfortunately no clear datasheet seems to exist for 28-BYJ-48.

Yes, agree. But these cheap motors are cloned that much, therefore impossible to find out manufacturer/supplier. And this vendor datasheet is missing some basic details & has strange translations.
And as a professional, you know that even supplier datasheets have bugs/ are missing essential data sometimes ;-)

Might be, full or half step isn't specified in the data sheet. Do you know from own tests or is it a conclusion?

During Web search, I found some supplier drawings and other vendor specs, which had the clear description:
step angle of 5.625° (8-step 1-2 sequence)

My post was meant as a hint to OP. Although I think my description is closer to reality, nobody can say for sure, how the motor is really working.