I was trying to find a cheap geared stepper motor and found the 28BYJ-48 a number of places online and from the specs it seemed to fill the bill. 64 steps to the motor and 64X gear reduction 4096 steps per revolution. I received it and wired it up and ran it for the better part of three days with various programs. I kept finding that a full revolution was somewhere between 4072 and 4080. Maybe I was slipping with acceleration and deceleration??? Slowed everything down. No change. Finally I cracked the geartrain open and found the following gear teeth counts 9, 9, 10, 11, 22, 26, 31, and 32. If you calculate this out it is: (22X26X31X32)/(9X9X10X11) = 63.68395... Multipied by the 64X motor that is 4075.7728.. steps per revolution not 4096!!! I was expecting an integral number of turns to return to zero. If you reduce this to the lowest common denominator ( 283712/4455) it means I have to go 4455 revolutions to get back to zero degrees! I'm disappointed that it's not an integral number of steps to get 360 degrees. It was cheap but now I'm looking for a stepper motor that is actually an integral number of steps per 360 degrees. I'd like to find a stepper motor that's >1000 steps/revolution and returns to zero every revolution. Any ideas?

Thanks,

Dave