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Pololu Maestro Mini 12 not always finishing the moves

Hi,

I have 2 robot arms with 4 micro servos each (channels 0-7 on Mini 12) and I set them in operation by having configured the channels 8,9,10 as inputs that are getting signals from Raspberry Pi.
I have a script which is scanning the inputs and call the appropriate sequence when the input is triggered.
The movement sequence for the first robot is always running properly but the sequence I have for the 2nd stops without completing.
This happens when the Mini 12 isn’t connected to PC through USB. As soon as I connect the controller to USB port all sequences run perfectly even if the Maestro control center isn’t running.

What could be the problem?

Link for my setup:

Hello, kallileo.

That’s a neat project!

Since it does not happen when the Maestro is connected via USB, I suspect your operating voltage might be dipping too low and causing the Maestro to reset sometimes when the servos move suddenly and draw a quick spike of current. What are you powering the Maestro’s logic side from? If it is the same supply you are using for your servos, could you try powering it from a separate supply to see if that fixes the issue? If it does, you might be able to power them from the same supply if you add a capacitor to your supply voltage to prevent the voltage from dipping.

Brandon

You were right, Brandon.
I was suspecting something like this but I thought a 5V, 7A power supply would be more enough than enough to run 4 MS90G micro servos.
I added a 2200uF capacitor and it works now.

Thank you for the help.