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defwheezer
08-10-2010, 01:02 PM
How does one deal with a situation where you have external forces pushing a servo off of its holding position- in particular, would this lead to servo motor burnout (or wiring meltdown)?

Since the servo will try to maintain its set position as long as power is being applied, does having an external force opposing this inherently cause problems with the servo because it is constantly "pushing" against this external force to maintain the servo set position?

Would setting the servo at its "neutral" position overcome this? Or would one have to power off the servo altogether?

Example: here a rubber band is applying external force on the servo. Does the servo need to be "parked" (either positioned, or powered off) at the point of zero resistance to prevent burnout?

http://mental-escher.net/images/servo_rubberband.jpg

DresnerRobotics
08-10-2010, 01:19 PM
You're putting the servo under load. In many cases there are builds where servos are under constant load, which is fine. It does certainly wear them though, so in situations where you can prevent or minimize default load, it's advisable.

Giger for example, is under slight load even standing under his own weight. I've built the leg in such a way that when it stands straight up, the weight load more or less goes in a straight line down the servo axis.

defwheezer
08-10-2010, 04:41 PM
What does a buzzing sound from the servo indicate (when in certain positions, it makes a sound like its trying to get to its set position or being pulled away from its set position)? I was thinking this sound was because the servo was under load, but based on your reply that "many cases there are builds where servos are under constant load" I am now not so sure.

DresnerRobotics
08-10-2010, 04:54 PM
I was just saying that in many robots, servos are under constant load. Most hobby servos make a buzzing noise of some sort due to oscillation of the motor trying to hold position.

defwheezer
08-10-2010, 05:06 PM
"Most hobby servos make a buzzing noise of some sort due to oscillation of the motor trying to hold position."

-OK, I won't worry too much about it then as it sounds like a normal event for hobby servos. Thanks for the info/replies!

Al1970
08-11-2010, 12:19 AM
Hi:

"How does one deal with a situation where you have external forces pushing a servo off of its holding position- in particular, would this lead to servo motor burnout (or wiring meltdown)? "

It can burn out the motor driver in the servo IF there is too much force. If a servo is at a position and the force is so strong that it is able to move it from that position then you are putting too much force on that servo. Also if the servo starts to get warm then I would think about getting a more powerful servo for the job you are trying to do.

Al
http://diyrobots.webng.com

defwheezer
08-11-2010, 12:19 PM
Hi:

"How does one deal with a situation where you have external forces pushing a servo off of its holding position- in particular, would this lead to servo motor burnout (or wiring meltdown)? "

It can burn out the motor driver in the servo IF there is too much force. If a servo is at a position and the force is so strong that it is able to move it from that position then you are putting too much force on that servo. Also if the servo starts to get warm then I would think about getting a more powerful servo for the job you are trying to do.


That was what I thought intuitively- so how much is "too much"? Servos seemed to be rated on the amount of force they can apply, not how much/long they can sustain a given force.

I was thinking that anytime I can hear the servo buzzing "at rest" (in its set position, but under external force) that the servo is on the road to burn out, especially for my application, in which the servo is energized for long periods (many hours at a time). I suppose for short and/or intermittent times it would not be too much of an issue.

DresnerRobotics
08-11-2010, 12:40 PM
Yeah, it does matter how much load you're putting on it. If you're exerting enough load to move it WAY off position, it's too much. If it's just moving slightly off position, that could be heavy load and/or gear backlash. Obviously the more load, the more stress to the servo.