Two arduinos, each one powered by a battery. Each arduino is connected to a piece of metal. When pieces of metal from both arduinos touch each other, the arduinos have to realise the event.
The problem: by having a different ground, they cannot detect each other electrical signals. Is it there any workaround for this?
I've take a second guess: each arduino uses the piece of metal it is connected to as a capacitive sensor. This way, both arduinos are able to "detect" that the pieces of metal have come together. But, this has the problem that if a human grabs both pieces of metal at the same time, the arduinos will believe that both pieces of metal have make contact.
The problem is: how to make the arduinos able to detect their respective pieces of metal touch each other, without giving a false positive when a human grabs both metals at the same time.
Any ideas about how to resolve this problem?
Edited: About the strength of the signals each arduino takes when the metals as capacitive sensors touch each other, it is of the same intensity and as such non-differentiable from the signal the arduino gets when the human touches the metal.