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I was working on a project to make a bedside night light out of a stuffed butterfly or bird. I was making a mechanism to make the wings flap with a servo motor and some small gears. The servo motor was very loud as it moved. And this was whether or not the servo was moving large amounts, small amounts, fast or slow.

I've worked with small servos before and realized they usually are pretty noisy machines, but I can't really explain why.

Why are small servo motors noisy when they move? Is it backlash in the internal gearing?

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    $\begingroup$ Amusingly, I've found that a lot of people like that sound. It sounds like robots! $\endgroup$
    – Joe Baker
    Dec 23, 2012 at 1:09

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They aren't. The word servo refers solely to a device that uses negative feedback for control.

Gearboxes or cheap brushed motors can be noisy. You can get very quiet systems if you are willing to pay for it.

Cheap hobby grade servos can sometimes chatter if they do not settle in a stable state. This is normal and is caused by poor tuning, a lack of a deadband, and backlash between the motor and the encoder (potentiometer).

Gearbox noise is caused by the spur gear teeth hitting eachother. You can use heavier grease or quieter gear geometries such as helical gears which mesh smoothly.

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There are also piezoelectric or memory wire based servos which are completely silent.

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    $\begingroup$ well this was during travel not while holding a position. So it must be the gearing inside that is making it noisy. Thanks for the input. Where does the term servo come from? I know a servosystem is something that relies on feedback for control, but where does the term come from? $\endgroup$
    – Michael
    Dec 21, 2012 at 1:17
  • $\begingroup$ Wikipedia suggests that the origin of the word servo is slave, so a servomechanism is a system whereby a motor, for example, is a slave to its encoder. $\endgroup$
    – user65
    Dec 21, 2012 at 5:22
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    $\begingroup$ I would argue that if there is a master to the motor, this master would be the controller and not the encoder. The encoder is merely the means by which the master witnesses the wrondoings of his slave... :) $\endgroup$
    – georgebrindeiro
    Jan 11, 2013 at 4:00

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