ground wires with separate power sources

Iv’e read on an old forum post on here about the {ground wires needing to be connected to the ground pin on the Arduino board.}, is is true in my project, (see photo) as Ive been having trouble with this one for along time, though the first solution was to provide more amps…

The servos are powerd seperately to the arduino board.
The 4-6V servos still disagree and tend to struggle and have a mind of their own after a few minutes of running. ?

thanks

I don't see a ground to the arduino. All grounds should be connected.

All input and outputs need a reference. Gnd so the reference used.

Your car has a battery but until you connect both sides it does nothing. Or when you want to test a lamp with your car battery, it will not work until you connect both sides.

With the Arduino being connected to your board in multiple pins, you may be getting a Gnd though other pins (IO pins) and so getting some signal to Gnd via those pins.

Weedpharma

the ground wire did resolve this a fair amount, plus i put a capacitor on each servo.

thanks

Ground link should kept in safe path.