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Asked — Edited

Servo Makes Buzzing Sound When Under Load


I have a small arm on my robot and when it extends outward the servo makes a slight buzzing sound from the weight of the arm. Is this bad for the servo?

No, Digital servos are very noisy under load. This is common and causes no problems or harm other then to your nerves. There are a few ways around this. You can use analog servos that run very quiet, add a servo helper to keep the load on the serve down (a simple spring works nice) or wrap sound proofing around the servo like Dynamat/ sound proofing wrap. I've used Dynamat and this works great.
It's possible that the servo is attempting a load that is heavier than it's designed for. Over time it may fail. Can you lessen the load or use a stronger designed servo ?
Well it's a pretty light light, a little plastic piece and another servo. Can a servo carry its own weight?
As @dschulpius has more experience with these servos than I do it appears that your servo is working as it should and it can support its own weight. Most pan and tilt cameras have a similar arrangement.
Well, Robot-Doc could be correct also. If your servo is overloaded it will fail.
Also, I'm no expert. ;) This is just what I have read in this and other forums. Just passing along learned info with a tad of personal experience behind it. :)

I did add a helper spring to my High Power Servo. It's lifting about 15 lbs and it stopped buzzing.
Thanks Dave!....Helper spring or bungee cord ! ..and you can measure the torque with a SCALE...fish or DIY.:)
I'd go with analog servos for shoulder joints.
Near all servos are loud... It's how they work - and you'll never really be able to stop it. Unless you wrap it in some sound dampening material.

Servos are loud because of their design. A servo is a little motor. And the little motor has gears. The gears add torque to the motor's output. If you turn the motor a few rotations, the output shaft of the servo will turn a tiny little bit. This allows the servo to move heavier objects with precision. The servo circuit knows what position the servo is in by a little potentiometer. When the output shaft moves, the potentiometer does also. The EZ-B sends a signal to the servo and tells it what position to hold the potentiometer in. When you apply load to the shaft, the potentiometer notices and sends a pulse to the motor. The motor moves to attempt and hold the position. The motor will move back and forth rapidly to hold the position.

And voila, your buzzing noise:)
Out of the mouth of our Guru.
If you have room in your robot, get some Dynamat off of eBay and give it a try.
@feroze if you can't do dynamat then I would look into high torque analog servos. In areas where I simply didn't have extra room I found analog were quiet in comparison. Here's a video of two that I had to modify for continous rotation for gearboxes and also a video comparing analog vs digital.

Here's a video comparing accuracy but you can use this as a reference of what difference analog vs digital makes.

Here are two analog servos close up and you can hear about how much noise they make ( not much)

I can understand your concern , my hitec 5995 ltg servos make a loud buzzing that would drive me nuts even under the lightest load so I found they would not be what I want for my robots shoulders. I went with a analog servo and a gearbox to multiply the torque. You can usually search YouTube by model to see how a servo performs and sounds. Digital will always buzz at least a little and is part of how they work but a analog in some cases can make much less noise. Its all preference.