My Robocat is planned to purr when petting.
Petting means humans touching his "fur" = capacitive touch sensor => purr (loudspeaker + EEPROMs).
The touch capacitive sensor is this one:
Command is via Arduino Uno. For the time being, the Arduino board is connected to a Desktop PC, to transfer the code. To feed all sensors and memories, there is a separate power source.
According to the reference section in this web-site, the capacitive sensor shall be connected to earth somehow in order to properly work.
The cat is going to be on batteries alone when the project will be completed.
For practical reasons, is there any other possibility to "earth" the Robocat, besides sticking a wire connected to the water supply network in his mouth?