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Powering servos continuously for e months
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Powering servos continuously for e months

by Kimevil on Thu Mar 14, 2019 11:19 pm

Hello,
I am about to place a kinetic sculpture controlled by 6 servos, a motion sensor, and an Arduino with an external power supply. I am concerned that the servos may fail having power running to them for so long as they hum when idling and holding position. I have had it going for 3 weeks without an apparent problem but maybe I was just lucky. Do I need to use a fan to cool the motors or drill air flow holes in the casings to help? How about the voltage regulator that plugs into houshols current? Is it likely to overheat and fail? Any ideas would be appreciated.

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Re: Powering servos continuously for e months

by adafruit_support_mike on Fri Mar 15, 2019 3:19 am

It depends heavily on the operating conditions.

The first step would be to measure the temperature of the servos for a while and see how well they can dissipate heat. If they get higher than about 50C (120F), adding some venting and airflow will probably be useful.

Of course, with any mechanical system, it's a good idea to make the things that can fail as easy to replace as possible.

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Re: Powering servos continuously for e months

by adafruit_support_bill on Fri Mar 15, 2019 6:32 am

The two most common failure modes for servos are: motor burnout and gear-train damage. Any servo will have a finite lifetime, but you can postpone the inevitable by choosing the right servos and operating them well within their capability limits.

Most RC servos are rated for 4.8V-6V operation. Running at too high or too low a voltage can put stress on the motor and shorten its lifetime.
For moving heavier loads, look for servos with metal geartrains and ball-bearings.

And, as Mike says: It is wise to design things so that components are easy to replace when they fail.

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Re: Powering servos continuously for e months

by Kimevil on Fri Mar 15, 2019 8:20 am

It would be possible but tricky and tedious to replace motors during the exhibit. I have had it run for 3 weeks without issue. I will let it run overnight and check temps. When the project is not powered the servos will still hold their position with a load....no slipping. Do you think it would help to have 2 extra pulleys at each motor to make the work easier or will it still get hot from the sheer fact that it has power running into it non stop ?

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Re: Powering servos continuously for e months

by adafruit_support_bill on Fri Mar 15, 2019 8:34 am

When the project is not powered the servos will still hold their position with a load....no slipping.

That is a very good sign. It indicates that the servos are not overloaded or straining to maintain position.

With most servos, you can effectively de-power the motor by stopping the control signal. If you are using the Arduino Servo library, you can do this by calling 'detach' on the servo when you are done moving. Simply call 'attach' when you need to move it again.

Unfortunately, this strategy won't work with some of the recent servos from Tower. They will continue to actively hold a position even when the control signal goes away.

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