WalkItOut:
Couldn't you just use a servo motor, attach a pipe and code it so it points to each plant?Something like this?
i'm planning on hooking up 16 plants to this (or more) and want to have it so that i can basically have as many plants hooked up as i have shift register outputs for it... basically each plant would use 2 shift register outputs, one to detect moisture level in the soil and another one to kick on the solenoid valve that feeds water to that particular plant... the lines go straight to each plant so there is no spilling or anything... i noticed with the method that you suggested that some water gets spilled on the floor during delivery to the plants, and i definitely want to avoid messes and waste in my system. i'm making this to use for industrial and commercial indoor or outdoor farming, or for personal botanical projects that people might have... but the idea is to make something that can water as many plants as you need with precision.
PaulRB:
I don't know for sure the idea will work at all, that's why I suggested experimenting with it before abandoning your multiplexers.If it does work, you could extend the idea to a matrix. 8 rows could be driven by 8 shift register outputs, and 6 columns connected (via diodes on each sensor) to 6 analog inputs, giving 48 sensors. Again, experiment needed to see if this works well, especially if the sensors are close together in the soil.
i like this idea of a matrix... i see how that could potentially work out very well... sensors being close together won't be an issue considering each plants soil will be isolated. I like all these ideas alot, they will make the project alot simpler to start coding... I'm thinking perhaps what i should do is use the analog multiplexers to switch to each column of the sensors, so that i can switch between which column is being read without using up any more analog inputs/outputs on the arduino...