I have two polystyrene balls wrapped in copper tape. When the balls touch, the tape completes a circuit from a digital pin on an Arduino inside one of the balls to an Arduino inside the other (both powered by 9v batteries). This allows them to send information to each other via the copper tape path.
I was testing the balls out, and they were working too well. Even when the balls weren't quite touching, the signal was getting through! Turns out that's because the signals were travelling via my body. Even if I held one ball in one hand and the other ball in the other hand, digital reads on one Arduino were correctly reading the digital writes from the other.
This is actually great for my project!... unless it's not safe. So I'm looking for two things:
A reliable reference on what is and isn't safe in terms of voltage/wattage/amperage travelling from hand to hand.
A second opinion on the voltage/wattage/amperage that two Arduinos will actually pump through me (from digital pin to digital pin).