Can someone help me understand steps for 28BYJ-48 stepper motors? I purchased this set of steppers with drivers and have been playing with them. I continue to be confused about the number of steps per revolution. While I read that this combination should give me 2048/4096 steps (dependent on full or half step), this example has 64 half steps and appears to work correctly with these devices. Can anyone explain what is going on relative to steps/half-steps for these devices?
There are a number of variations of that motor on the market, with different gear ratios. The only way to know what you have, without disassembling the motor, is to count the steps that make one full revolution.
Please post the code (with code tags) that you have actually tried and wish to discuss.
64 steps/revolution does not make sense. The ad you linked claims the following, which would be 64 full motor steps per revolution geared down 1:64, for 4096 steps/revolution of the output shaft (common for those motors).
Step angle: 5.625 x 1/64
Consider opening one up and checking the gears, or check the code.
These motors are 32 steps/revolution (they are 8-pole-pair steppers), followed by a gear-train that's nominally 64:1, but the actual ratio varies.
Mine is 32/9x22/11x26/9x31/10 = 64 x 403/405 = 63.68:1
BTW half-steps-per revolution is best ignored, its confusing, these are nominally 2048 steps-per-revolution gear-steppers. If you happen to drive it with half-steps, thats x2 microstepping, so the step count is 2048x2 = 4096.
The reason they are only approximately 64:1 gearing is that the application allows some spread in gear ratios - these gear motors are for moving flaps inside car heater/air-con trunking - they never have to rotate more than 180 degrees in that application so accumulated error over multiple rotations is not a factor in their design.
They were never designed for hobby use, but because they are in high-volume production they are very cheap and multiply-sourced (hence the variation in gear ratios).
Thanks to all of the responses. I think I've maybe figured out my confusion. I think I've read about both the motors steps without gearing as well as the steps with the gear train. Dependent on the conditions, I guess both are valid.
Just so you are aware, the gearing on these motors often does not give a "workable" number of pulses to give exactly 360 degrees. I have one that says (in the specification) it rotates 360 degrees every 2038 pulses. But it doesn't. It rotates once every 2037.5 pulses (yes I did say .5).
These motors are fantastic for some applications (like moving air vents in air cons). but if you want precise angular movement then a NEMA stepper is good. They are usually exactly 200 steps per 360 degrees - i.e. exactly 1.8 degrees per step.
If you really want to use a geared motor like this then setup a test rig and run it for a days of so in order to calibrate your code for the movement you want.