Good Morning,
My question regards the ‘Small size and high torque’ bipolar 5V stepper motor 24BYJ48S Digikey part number [1597-1203-ND ].
The digikey description of the part says it has 2048 steps/rev and a step angle of 0.176 degrees.
The datasheet from the manufacturer the step angle is 5.625°/32 which agrees with the above and I assume the reason for putting it in this form is because the motor has a 1:32 reduction gearbox.
I have taken the motor apart to find that it has 2 coils, each of which has 16 positions on it, making a total of 32 steps for a complete revolution. The gearbox train then appears to result in a 1:32.86914 reduction. 32 X 32.86914 gives rise to 1051.8 steps/ revolution. Driving this motor I also find that nominally 1024 (32 x 32) steps will move the spindle through a complete revolution, rather than the 2048 steps described in the datasheet and the product description.
Is the datasheet wrong, or am I?!
Many Thanks
Greetings,
On a point such as this, I would trust your direct observations; the product listing on the website does indeed show 2048 steps/rev which would appear to be incorrect based on the datasheet which claims 32PPRx32:1 reduction, (1024PPR overall) which would appear to constitute an error in our listing of such.
However, if you’ve counted gear teeth and determined that the reduction is actually closer to 33:1, I wouldn’t be surprised if that was the case. It’s certainly possible to mis-count gear teeth, but documentation standards for low-cost products aimed at hobby markets such as this is commonly of a lesser standard than that of products intended for industrial use, and I’d not be surprised if the actual ratio were fudged a bit for documentation purposes. 27 steps out of a thousand and change doesn’t make a lot of visual difference after one rotation, but it’ll stack up after a while. Try counting teeth again, check the math, and double-check by running things through something like 10240 steps to see if the angular position ends up at its original position or not when done.
It is conceivable, though misleading, that they are including half-stepping in their calculation of step size. If they were including half-steps, then there would be 64 steps per revolution, before including the gear reduction. Then, including half-steps, you would have roughly 2048 (2103.62 by your count) total steps per revolution.
As Rick alluded to, unfortunately, it’s not uncommon for hobby-grade products such as these motors to have vague, and less than reliable documentation.
