Earlier I had used the USB-C adapter to power my raspberry pi and an external PSU to power the servos. I had to connect the ground of the PSU to the ground of the R-PI so that the control signal from the R-PI is relative to the same ground as the servo.

Now I have my final PSU and am using it to power the R-PI over the 5V and GND PIN and not the USB-C input. The same PSU is also used to power the servos. Am I right, that I no longer need to artificially connect the PSU ground to the R-PI ground because ultimately it is already connected to the same ground as the servo?

2 Answers 2


All the "Gnd" pins, including the USB ports and power connection are internally connected (also the the ground plane of the circuit board).

NONE of these are ACTUALLY connected to ground and float WRT true ground. Technically they should be called "Common" not Gnd.

Whatever it is called, it is essential that all interconnected circuits share a common connection.

In fact it is preferable to connect the common connection of the servos to a "Gnd" pin on the Pi header, rather than a circuitous connection via the power supply, as this would impose any common mode voltage fluctuations in the control flow.

It is generally advisable to avoid ground loops and to have all common connections directly connected to a single point.


Yes, that is fine.

It is important that anything you control with a Pi GPIO shares a common ground with the Pi. They need the common reference so that both sides agree when the GPIO is high or low.

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