So I got some chinamen servo motor. However, if I set it below

>>1196168
a servo is just a feedback loop.
controller commands motor, motor moves encoder, encoder informs controller.
you tell controller what to do and it compares the target with the actual to do its dirty business.

ok so.

first of all what most people imagine doing the encoding is a potentiometer, a variable resistor used as a voltage divider or something and the wiper gives you the position. if you have played with a potentiometer you know mostly they don't rotate 360 never mind past that.

ok so either there is some kind of clutch/slip/voodoo allowing the pot to overrun or its a special pot. or it could be something like a rotary encoder perhaps.

fine.

so why does it spin? well the logic in the controller is simple, if the commanded position is > actual position then turn the motor one way otherwise turn it the other way.

you can also have some element of error to stop it hunting or trying to find a position more acurrate than it is capable of doing but thats not important.

so when you say <90 i would expect that possibly it is set up as 90 degrees being actually 0 and 270 being whatever high number the encoder can output. that is scaling to get most accuracy. precision? no accuracy. yeah accuracy. some smart guy will post the archery targets or some shit dont worry.

so when it is set to below 90 and tries to move there the encoder probably rolls over to the highest number possible (its just how computers do maths - google overflows) so the servo is still trying to get to <90 but now it thinks its at fucking 270 or whatever. so it will go down to 90 and guess what? happens again. forever and ever.

so yeah.

but also you can get servos to rotate any angle with a potentiometer by use of gears to ratio the number of output shaft turns to the encoder turns. more turns for a reduction in precision if you think about it right?

most hobby servos do that set angle because thats what you need for rc cars and planes and shit.
big servos can turn all day long

>>1196174
So.. to summarize, 0-89 degrees is out of bounds and it spergs?

>>1196176
i guess?, check the spec!

>>1196168
I bet your 270 is in fact 255.

>>1196168
One or more of the gears is broken.

>>1196225
Why? Isn't 90-270 (or +/-90) degree range normal?

>>1196242
0-255 8-bit intiger precision

>>1196174
>>1196257
I think these cheap servos are generally analog. It's just a comparator hooked into an H bridge. The infinite spinning could be caused by the lower portion of the potentiometer contact being corroded or otherwise fucked. When the wiper makes it to that spot it will go high impedance and default to whatever value the parasitic resistance sets. It will then continue spinning until it reaches the desired value, which it never will. Most servos have stop switches so when it gets to the end it will stop turning, but I guess they left that out to reduce cost.

>>1196168
If those are the Chinese SG-90 servos, they are flimsy as fuck. Pull on the axle a bit too hard and you'll pop the shell off.

Also never turn them by hand (I don't know if you are even supposed to do that) as I broke a few by trying to align them.