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R/C Servos Dying left and right!
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

R/C Servos Dying left and right!

by gplatek on Thu Feb 03, 2011 1:58 pm

Hi Kids!

I have used the standard servo offered by Adafruit in a couple of projects. They keep burning out!
I'm using the servo as a replacement for a analog meter. I add a very lightwieght needle to the servo and mount it in a case. There is basically no load as the needle wieghs very little. All the needle does is rise swing from left to right.
Are there better servos to use?
Could it be the code that's burning them out?

Thanks,

GPlatek
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Re: R/C Servos Dying left and right!

by adafruit_support_bill on Thu Feb 03, 2011 2:19 pm

Are you running it into the limit stop on one or both ends? Sometimes the feedback pots are not quite perfectly calibrated and the 0 and/or 180 degree signal positions are beyond the physical stops. This causes the motor to work hard, trying to reach an unreachable position. In extreme cases it can even strip the gear-train. You can tweak those endpoints in software.

This problem can affect even higher quality servos like HiTec and Futaba. Most RC radio systems have calibration adjustments to compensate for it.

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Re: R/C Servos Dying left and right!

by gplatek on Thu Feb 03, 2011 3:51 pm

Yeah, I just started opening them up to find a little chunk of plastic which used to be a stop. It actually broke the plastic stop. That explains a lot.
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Re: R/C Servos Dying left and right!

by westfw on Thu Feb 03, 2011 4:24 pm

It actually broke the plastic stop.

Ah. "Modified for continuous rotation" ! :-)

Is there an easy way to tell whether you're driving a servo past its physical limits? Presumably if it is sufficiently tough, it just silently stops? I've never heard of a servo with a clutch (if that's the right term; designed to slip under overly heavy load.) Or with stall detection.

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Re: R/C Servos Dying left and right!

by adafruit_support_bill on Thu Feb 03, 2011 6:51 pm

Is there an easy way to tell whether you're driving a servo past its physical limits?

The easiest way to tell is when it strips the gears (I lost a whole array of brand-new HS-81's that way as soon as I powered them up and had them seek to 0)

Otherwise, there is a difference in how it sounds when it seeks to a mid-range position versus when it is pushing against a stop. If it is at a mid-range position with minimal load, you can usually hear a faint noise from the controller as it actively holds the setpoint position. If it is blocked from reaching the setpoint, the sound is different.

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Re: R/C Servos Dying left and right!

by richms on Fri Feb 04, 2011 11:02 am

Also currentdraw will give it away if the motor is driving into the stops, a stationary servo will take minimal current unless it it chattering, moving will take more, stalled at the stop will take the most.

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Please be positive and constructive with your questions and comments.