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Topic: Servo twitch on startup (Read 2 times) previous topic - next topic

zoomkat

Have you double checked your servo wiring? Make sure you have a good ground connection between the servo power ground and the arduino ground.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

ticklechicken

Good idea.  I just checked all the wiring and the grounds look good.  When I was going over my breadboard, I realized that I was assuming the two grounds on the UBEC were grounded to each other.  I just verified this with the multimeter, but I added a ground circuit across the UBEC grounds just to be safe.  Still twitching...

zoomkat

I've done some tinkering with servos controlled by the arduino and never had this issue.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

oric_dan


I've done some tinkering with servos controlled by the arduino and never had this issue.


As noted, some servos, such as GWS, twitch much more than others on power application.
Other than finding servos that don't twitch, it may work to use a Mosfet to apply power to the
servo [p-chan Mosfet on high-side power], and start the incoming pulses before power is applied. 
Maybe.

ticklechicken


As noted, some servos, such as GWS, twitch much more than others on power application.
Other than finding servos that don't twitch, it may work to use a Mosfet to apply power to the
servo [p-chan Mosfet on high-side power], and start the incoming pulses before power is applied. 
Maybe.

This works with the servos I have.  After I power on the Arduino, I manually connect the servo to power and there's no twitch.  So I know the P-chan Mosfet circuit you describe will work.

I swapped my Uno boards and the twitch is still present.  When swapping servos on the new Uno, one thing that was interesting is that different brand servos twitch in different directions (ccw vs cw).  I'm ordering some other servos today.  If that doesn't do it, I'll do the Mosfet design.

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