Servo mis-positioning
 

Hi,

My question is; what reasons can cause a servo to loose its center position. I have two brand new cirrus type mini servos and have some problem . They are not enough precise, it is difficult to find the center position of the servo. (sometimes 5-10 degrees far from the center point)

Thanks,
Fatih

RE: Servo mis-positioning
 

I have had the servo arm slip one tooth on the output shaft. then from that point on, the arm is off by about 15 degrees. this is especially likely if you use a servo arm from one servo on a servo made by another manufacturer

RE: Servo mis-positioning
 

I think DMcQuin answered your question, WRONG SERVO ARMS!. It is important to not mix brands of servo arms unless you are 100% sure they are compatible. One other remote possibility is that the servo motor buried inside the servo is slipping in its mount. This a a very rare happening but remotely possible. Most modern ones are glued into place but some are just friction fit and some have a screw you need to tighten down to fix its position. I have seen one instance where the fault was in the transmitter. If the fault always occures only on one channel it is possible that the potentiometer on that stick position is slipping in its mount in the transmitter. If you have an oscilloscope, you can check that out yourself, just monitor the input to the servo being effected and make sure it is 1.5 milliseconds long with the transmitter stick and trim centered.

RE: Servo mis-positioning
 

I have tried the servos at all channels and with another transmitter as well. Nothing has changed. I have one Futaba 9 CAP and the old one is Hitec Focus 6. The servos are strangely getting off the center.Sometimes can find the center with a small touch from the transmitter. (behavier is same under load and without load) I don't have any wrong servo arm.I think there is some kind of incompatibility or some mistake inside the servo.
I don't understand how can this happen at the same time for both brand new servos...

Thanks,
Fatih

Servo specs : Cirrus CC-22BBMG Mini Servo 2.2 kg-cm (30 oz-in), 0.15 seconds/60 degrees (@ 4,8 V)

RE: Servo mis-positioning
 

This is not uncommon for low-cost servos though 5-10 degrees is rather extreme -- sure your not exagerating here? Some servo brands center better than others. Some servo models within the same brand center better than others. I was once told the quality/design of the motor plays a large part in this. 5-pole motors are much more accurate than 3-pole motors and coreless motors are even more accurate. Digital servos tend to be more accurate than analog servos because they typically have a smaller deadban and their neutral update cycle is significantly higher than analogs -- ever hear a digital servo whine, that's the servo seeking neutral/center across a slop boundary.

Hope this helps -- can't think of anything more distinctive given the very general nature of the question.