gjs31
Posts: 28
Joined: Sat Nov 04, 2017 2:42 am

Servo jitter

Fri Mar 27, 2020 4:37 am

I need some help with servo jitter/shaking.

I’m running 3x MG996 servos off a PCA9685 board on a raspberry pi 3b+. The servos are powered separately from a dedicated 11.1v Lipo, stepped down to 5v.

Movement with nothing attached to the servos seems relatively smooth, but as soon as there’s any load (I’m building a lightweight robotic arm) they jitter, sometimes to the point of violently shaking.

Have spent time googling it, and seen solutions ranging from ferrite donuts to capacitors, but I’d prefer to have a better idea of the cause before buying anything.

Are ferrite/capacitors likely to fix the problem? Or is there something else I may be missing?

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joan
Posts: 14765
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: Servo jitter

Fri Mar 27, 2020 6:28 am

Would need to see a software listing and clear photos of the connections.

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mikronauts
Posts: 2750
Joined: Sat Jan 05, 2013 7:28 pm
Contact: Website

Re: Servo jitter

Fri Mar 27, 2020 4:48 pm

Put a scope on the power supply for the servos, and take a look at the power levels.

Odds are it is caused by the monentary current requirements of the servos being more than your power supply can handle.

Ofcouse it could also be poor quality servos.
gjs31 wrote:
Fri Mar 27, 2020 4:37 am
I need some help with servo jitter/shaking.

I’m running 3x MG996 servos off a PCA9685 board on a raspberry pi 3b+. The servos are powered separately from a dedicated 11.1v Lipo, stepped down to 5v.

Movement with nothing attached to the servos seems relatively smooth, but as soon as there’s any load (I’m building a lightweight robotic arm) they jitter, sometimes to the point of violently shaking.

Have spent time googling it, and seen solutions ranging from ferrite donuts to capacitors, but I’d prefer to have a better idea of the cause before buying anything.

Are ferrite/capacitors likely to fix the problem? Or is there something else I may be missing?
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