Author Topic: Gutless Servo  (Read 462 times)

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Offline The_Welding_Library_Guy

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Gutless Servo
« on: February 26, 2019, 09:10:03 am »
I was needing a 360 degree servo for a project but just had a few MG996r's in the random bits drawer. I did a bit of reading and set out to modify one to turn 360 degrees. While I was mucking around in the servo though. I had a sudden desire to mutilate this poor motor by ripping the control circuitry out and clipping the motor to my bench power supply. So I did and exclaimed EUREKA! Now I didn't need to tie up an ardiouo just to turn a servo left or right when a button is closed. The power source for this project is a 12v lead acid batt. I originally was planing on dropping the voltage down to 7v with resistors for the servo. But the more I think about it. The more that 7.2v max seems like its to protect that now lobotomized control board. What do  y'all think about running the motor at 12.6v outright? Do you think the little DC motor would handle it just fine? I have tested it in short burst under load and it seems to work fine. Just wanted to see if anyone might no something I didn't before I decided to make this the permanent plan.

Offline Psi

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Re: Gutless Servo
« Reply #1 on: February 26, 2019, 10:54:13 am »
Hard to say.

Run it for a while and keep an eye on the motor case temp.
If it doesn't get hot it's probably fine.
If it's going to fail from over voltage it will be through heat.

Also keep in mind that while it may work fine at 12V it may not work fine if stalled at 12V.
At its proper voltage the motor may survive a constant stall.
Handling a stall maybe part of the design requirements for a servo
« Last Edit: February 26, 2019, 10:56:31 am by Psi »
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Online Brumby

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Re: Gutless Servo
« Reply #2 on: February 26, 2019, 12:57:04 pm »
What Psi said ^  ^  ^  ^

Offline tsman

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Re: Gutless Servo
« Reply #3 on: February 26, 2019, 01:10:27 pm »
Sounds dubious to run it at 12.6V. The servo is designed to run off a 5 cell RC battery pack which is nominally 4.8V but may be up to 7.2V straight off the charger. I'd expect the servo manufacturer to spec a motor that operates in that range for maximum torque instead of trying to run a 12V motor from 4.8V.

Offline Psi

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Re: Gutless Servo
« Reply #4 on: February 27, 2019, 11:21:22 am »
It's not uncommon for a DC motor to have quite a wide acceptable voltage range.
No real way to know what spec motor they used.
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