Using water drops as switches/conductors with the digital inputs

Hi,

I am planning an interactive artwork that will use small streams of water to randomly turn on and off sounds. I would appreciate some help on how to handle this.

My initial tests was a simple circuit with a pull up resistor (to the Arduino 5v) and two wires going into a small vial with water. Then I did some larger probes with copper foil. Then I poured a lot of salt in the water. Not working, not even with a 12ohm resistor.

DC in water may be a problem I understand, but I was hoping to get some kind of reaction.

I will need several switches so I prefer to get the digital inputs going before using analog.

(FYI: I am using Arduino with the Firmata firmware as an interface to control computer software (PureData), and changing the Arduino code will be awkward.)

How can I do this in the most simple way? The solution should hold for two months of usage. The water should be safe to touch.

Thanks a lot!

brodbord:
Not working, not even with a 12ohm resistor.

Seems very low ! I would have expected a much much higher value was needed.

brodbord:
My initial tests was a simple circuit with a pull up resistor (to the Arduino 5v) and two wires going into a small vial with water. Then I did some larger probes with copper foil. Then I poured a lot of salt in the water. Not working, not even with a 12ohm resistor.

I presume you mean a 12ohm pullup resistor.

If you anticipate a very small current (through the water) then you need a very high value of pullup resistor so that the very small current is capable of pulling the I/O pin LOW. Try 100k for the pullup.

...R

Robin2:
I presume you mean a 12ohm pullup resistor.

If you anticipate a very small current (through the water) then you need a very high value of pullup resistor so that the very small current is capable of pulling the I/O pin LOW. Try 100k for the pullup.

...R

Hah, I was thinking backwards... Thanks a lot. Now it works as I imagined.